Tài liệu biodrainage principles experiences and applications docx

Biodrainage relies on vegetation ater than mechanical means, to remove ‘excess water The driving force behind the biodrainage concept is the consumptive water use of plans Biodrainages e

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International Programme for Technology and Research in

Irrigation and Drainage

BIODRAINAGE

Principles, experiences and applications

Albertus F Heuperman Department of Natural Resources and Environment Agriculture Victoria, Ist of Susanable ligated Agriculture- Tatura Centre, Tatura, Australia

Arjun § Kapoor IPTRID Consultant, India Harry W Denecke Theme Manager, PTRID

IPTRID Secretariat

Food and Agriculture Organization of the United Nations

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Preface

A primary requirement for sustainable apriulture isthe maintenance ofa satisictory balance of water at and salt inthe rootzone favourable for plant grvth, This lance ean be achieved by adeguate drainage Drainage canbe ether natural or areal Mest land has some natural sure and subsurface drainage When natural druinage i inadequate, arficial drainage is required to increase the drainage capacity Ansifcial drainage is essential to sustain gated aprculure Often, subsurface drainage is nedodn ington schemes contol the rising water table and avoid waterlogging and salinization Conventional subsurface drainage systems ate of to types, vertical (tubewells) and horizantal(deainpine) systems, When propery slesigned, installed and maintained, these systems are efficient in lowering the water table and preventing salinization of ieigaed lands, However, they have nwo drawbacks, namely, they ae costly and they generale drainage eMuens, which ill have tobe either carefully geused wr safely disposed of

An option is biodrainage, which can be less costly and more envtonmentlly friendly Its @ combined -drinage-cuft-ieposal system Biodrainage relies on vegetation ater than mechanical means, to remove

‘excess water The driving force behind the biodrainage concept is the consumptive water use of plans Biodrainages economically atracive because it requires oly an ial investment ar planting the vegetation,

nd when established the system coll produce exonorc retums by means of fodder, wood or ibn harvested

“There is consensus that biodainage, when properly implemented, can lower the water tale, It could solve woblems associated with waterlogged areas an canal seepage, Whats not clears the ability ofthe biorainage system to maintain a salt balance

This publications compilation of existing information both formally published and unpublished literature aims to inform water professionals in general and drainage experts mn particular of curent knowledge of

IPTRID

Acknowledgement

Biodainage has remained a provty topic for knowledge synthesis on IPTRID senda for quite sometime

Jn February 2000, the Interational Commission on ligation ad Drainage (ICID) convened is 8h Intemational

‘Workshop on Drainage in which a special session on biodrainage was organized, It as at this Workshop that IPTRID identified experts in biodrainage andthe idea was bom to write a synthesis on the subject,

“Mr Alfred Heuperman’s interest in biodrainage started inthe early 1980s when he became involved ina project investigating the impact of tees on shallow saline groundwater ables in nonhem Vitoria, Australia,

“The numberof co-workers and technical assistants he has worked with on related issues since that time are

‘0 numerous tobe listed but their asisance over the years is gratefully acknowledged,

“Mr Arjun Kapoor's intrest and motivation to work onthe subject of biodrainage was bor through his work

‘on the Indira Gandhi Canal projet (IGNP), a major irigaton projet in the desert land of Rajasthan, Inia

‘The help received from the personnel working onthe project in collecting some of the data used inthis document has heen invaluable,

IPTRID’s Theme Manager on “Drainage and Sustainability", Mr Harry Denecke, symhesized the views of

‘contributors and managed the final preparation of the document

Special thanks are 1 be expressed to Dr Vashek Cervinka fr reviewing the final draft ofthe document nd suggesting a numberof improvements

ns hoped for thatthe initiative taken by LPTRID to publish and disseminate this document will enable a

‘rtcal examination ofthis relatively new technology by fllow-professionals and hat it will result in further slscussion on how to best use Vegetation t9 manage the drainage of our agricultural and ina sustainable

‘The text was language edited by Ms Rosemary Allison and prepared in final form for publication by Ms

~

Biodvainae:prineiples, experiences and apleatons v

52 Idi: Channel seepage inthe India Gandhi Nahar Project, Rajasthan ai oS

55 lam: Biodrainage for water table control

554 Pakistan: Stud of biological cont] of woterlossing in Bhawalnavar Punib, 68 5.5 Paraguay: Saliizaton resulting from deforestation in the Cental Chaco 65 5.6 USA: imeprated management of saline drainage effluent 65 BCC

“| E7] Salinity and tees and galrloleranteros 7

LABBEonIX 1 SaLE 1OLEBAXESEECIES AGED OS HESEARCIS PAST

Sr Webnites providing information on biodrainage and biodiaponal ystems 2

List of tables

1 Comparison of deinage methods

Average composition of iver saters around the world

‘Surary of soi solution salinities and concomitant leat salt concentrations

(Mineral (cations: Na, K", Ca”, Mg”) content in tee and crop biomass

Suitability of toe species for saline soils

Relative tolerance of tee species t oil

kanity Development of irigationin GNP

\Watertogged area in [GNP command areas

Inita Gandhi main canal Section km 228-416; areas with groundwater st surface

10, Distribution of ree species in 25 ha plantation area

List of photos

1 Recharge conto planting

2 Break-of slope planting of wo-yearold blue gums (Eealyprs globuts n norte

Victoria, Australia

3 Deforested hil in northern Victoria, Australi, salinity problems in lower parts of

the landscape

4 casured using the heat pulse

5 Five-year irrigated variable spacing tral site at Kyabram, Victoria, Australia

6

‘Tree water use ca bế n

‘Seepage interception plantings atthe Boor ste

‘Seepage intereption plantings atthe Boort site with sain discharge in the foreground

8 _ Five-year interception planing a the Boor site

‘SBC site at Undera with sal-affected land inthe foreground

aused by leakage alongside JGNP main irigation canal

11 Eucalypascamaldulensis

12, Trees in background are te biodrsnage systom that dried the inundated areas

long main eanat

13, Biodrainag in Rajasthan, India

” 6

Biodrainage: principles, experiences and applications

1 Dryland plantation scenarios (schematic) 9

2 Flow towards depressed water table under “

3 Combined bio-and conventional drainage management options l6 4 - LeaFsueCl, Na, K, Ca an Mg concentrations for ve salinity

tweatments, averaged across five Atriplex species ”

5 Observation bore nerwork layout in the Kyabram plantation 6

6 Typical water table and piezometric pressure level transects through

7 Piezometicwate table (D-S) hydrographs ®

8 Diagrammatic presentation of hydraulic gradients and water table drawdown under

9 EC,, sol profiles at Site 21 inthe Kyabram tee plantation (1983 and 1992) ”

10, Water table and piezometer hydrographs at site 21 in the Kyabram see plantation ”

11, Kyabram irgate variable spacing tial layout 4

12, Water table and piezometric pressure hydrographs under the Kyabram irrigated

13, Layout and observation nenvork for Sites | and 2 “ 1Á Site L, water table and sliity levels under east observation section 4

15, Site2, water table and sanity levels under north observation line 46

16, Average 0-2.7 m soil chloride concentrations under Site 1 4

17, Average 02.7 m sail chloride concentrations under Site 2 7

18, Deep chloride proiles under wee line and in adjacent pasture a Site 2 a

19, Root distribution under tree line Site2 4

20, Cnose-seelion tthe light and heavy sol type channel seepage interception sites 0

21 Disgrammatc representation of serial biological concentration 3

23, Layout ofthe Mount Seobie Piet Site = 24 Pie:omeiecros>sccionthtoughbiodainaeeplaningatRD953-909 0

25, Farm layout of integrated on-farm drainage management system %

26, Inegrled on-Tarp đoidge managomenLđidgrim, o

International Furd for Agricultural Development Integrated on-farm drainage management India Ghali Nabar Project

International Programme for Technology and Research i Irigation and Drainage Institue of Sustainable Irrigated Agriculture

Mega hectare {ha 10°) Mega lites (Lx 10%) Mii Motar(mo??) Ministry of Agriculture and Cooperatives, India Non-governmental organization

Nuclear Institute for Agriultur and Biology Pakistan Overseas Economie Cooperation Fur, Japan

Sovtum asorbion saio Serial biological concentration Salinity conto and reclamation project

‘United Nations High Commission for Refugees

‘World Food Programme

Biodrainage principles esperences and appivations bx

1 Dewatering inducing water low through the sil towards the subsurface drain tubewell pipe or open đan)

2 Transportation ofthe drain water through the Interal, o field drain, te collector drains and thercaer 10 main nôn

3 ORenpamp ling the druin waters higher elevations in he evacuation system andor furher conveyance

by gravity outflow to disposal sites

44 Final disposal at selected sites (by evaporation pends)

5: Salinity coniro: dewatering ofthe rootzone and leaching of salts happens atthe same ime,

Biological systems make us ofthe evapesranspirative oscer of plans, especially of tes, to lower grounvater tables Functions 1, 2,3 and 4 are performed together Saliity contol function No, 5, is mave dificult to achieve and this requires addtional means inthe long-zem, However, biodrainage systems may delay the

‘salinization proces,

‘Conventional drainage systmashave perfonmed adequately, but lack of inancig ofen mpc their instalation,

“The disposal ofthe poor-quality elfluent generated by conventional drainage systems may cause proberns Where drainage effluent is reused for rigation, salts are redistributed inthe landscape Where effluent is spose int iversystems, pollution of natural water results

Low eost technology such as biodrainage could bean slteratve providing several advantages asthe negative side effects of conventional drainage systems are reduced and, as they require less investment, may find {quicker application Biological systems provide forsuch an alterative although the availabilty of and sa

<ecisive factor inthe eventual establishment of biodranage systems However, in most cass, in developing

‘ours water seaeity isthe predominant feature and not land scarcity

Apart from being a tnanciallyatactive eltemative, there are many other advantages for rural livelihoods

‘sing biodrinage systems They are environmentally friend, provide fuelwood, timber its sade and shelen (mon as windbreaks and yield organic matter For ftilize In addition, they eonttbute to the cehancement of biodiversity as lors and fauna lourish, ar pollation i diminished and they contribute to

<arhon sequestration

Applicability of biodrainage systems isnot restricted to the simple substitution oF pipe dan or bell

‘Canal leakage always ours in inrigation projecs, Tre planations have effectively drained the ponds formed Alongside canal embankments, as compared wit larg aeas that have been inundated and became saline A

‘urter aplication of tee plantations is that they can eTaetitgly don mturdlinudaled depressions, oF teas where efuent i produced by conventions drainage techniques where wate is disposed of in evaporation ponds

“Much researc as been completed, more is required Not ll questions have been answered concerning the precise design ofbidrainage systems, even in thse areas where biodrsnage systems have proven adequacy

in imtegrated water management of iigation and drainage seems Examples fom several countries have been documented inthis paper, where vegetation, especialy tees and sal-olerant plants hs been used (0 achieve environmentally safe and effective drainage and disposal systems,

‘Convention desinage design includes many safety factors to compensate forthe possible malfunctioning of the drainage system ot compensation for spail variability in soils, selection of the next Iggest available ameter pipe sizes, pay use cost sting aa redaction faetors au over -sign related train Requencies,

Iv is fair that biodrainage sysemis should be allowed such safety mechanisms im the design and thi implementation be inivared

Drainage engineers shocld ne longer ignore the opportunities that biodrainage systems can offer When planning for projects the agricultural selo increasingly feels pressure from other users ofthe environment For example it is becoming increasingly unacceptable fo set ase land exclusively for outinely designed iigaion and drainage projects This strates the possible advantages of biodrainage systems

Biodvanage: principles, experiences and apteations

Shallow groundwater ables and associate salinity

problems have become dominant features in

agricultural areas around the world These prablems

have been caused by increasing pressures on ind

resources eaused by rising populations, especially

in irigation areas, Increasingly, lange areas of land

having historically deep groundwater tables are now

inneed of some form of water table contol In many

places management strategies have heen developed

to address this problem These often focus on

‘engineering approaches such as deep open ditches,

vertical drainage (groundwater pumping) oF

horizontal subsurface drainage,

‘Conventional physical drainage works require

‘expensive capital investment, operation and

maintenance Physical drainage measures also

generate drainage effluent Disposal ‘often saline, and sometimes chemically contamin- to rivers ofthe

ated fluent is increasingly considered unacceptable

boss downstream users inthe catchment rely ot

these river systems for their water supplics

Greenhouse emissions caused by enerey-hungry

jpurps may also be disapproved afin a world that

fs becoming more aware of isis related to global

‘warming Any positive alternative, preferably

cheaper, addition to our arsenal of drainage

‘echniques would beextremely weleonie in out it

to keep groundater bles in our agricultural arzas

under conto, Biodrainage, i the use of vegetation

tomanage water fluxes ip the landscape sone sich

technique that has cecently atacted interest in

<rainage and envionment management crces

Biodrainage relies on vegetation, eather than

cegincering mechanisms to remove excess soil water

‘ough evapotranspiration I is often considered

attractive because i requires only an initial

investment in site development (planting of a

“bodrainage crop") and (potentially) rtuens a

Chapter 1

Introduction

benefit when the bioerop is harvested for fodder,

‘wood or be In addition, under some management scenarios, iz certain cropping systems and slightly saline conditions, it might offer limited scope to schieve nutrient andr sal-balane through removal

‘of biomass, this alleviating the problem of the isposal of polluted drainage elfiuent from the biodrainage crop area by reducing volumes and Jmproving the quality of he effluent

‘The concept of leaking landscapes, caused by clearing and adoption of inappropriate land use proces, as recently become topical, especially

‘in Australia, This has resulted in iereased efforts dimetel towards the development of wgriculural systems (bot rainfed and irigted) with improved water use efficiency that minimize groundwater recharge, inadtion attention is being pad to direct management ofthe and afte by sallow saline ater tables, Drainage is generally neither econo

‘ically nor practically Feasible in these areas, especialy in anfed agricultural systems Enhancing groundwater discharge has become popular to ose increased recharge in adjoining parts of the landscape, through planting salltolerant trees or

‘oader crops However, there are concems about salt aveumulation that might restrict the long-term viability of enhanced iechưưy

The current status of biodrinage research and applicaions are described in this document Much ofthe research information is based on Australian work presented in a special review issue of the Incernational Journal for Agricultural Water Managemen Inadktion work done in Asia, notably

tn Rajasthan, India, has also Been draven upon Literature fom other counties, nshuding workshop Proceedings and technieal repors is examined and Tisigation-based biodrainage case studies are

——

Blodeaie:prncoes experiences and pphcaions

Chapter 2

Background - traditional drainage techniques

and the need for alternative approaches

All agriculture erops need water to grow, Naural

precipitation does not always meet the full plant

‘water requirements and, wherever possible

inigation is introduced to overcome this problem

FAO (1989) reported hat 15-4 percent of the 1474

Ma of cutive lad in 1087 was erate This

Felatvely small area produced one-third of the

‘world’s Food supplies Average agriculture produce

froma unit of irigated areas more than ewo times

that from average rainfed lind, The World Food

Summit (1996) estimated tha 60 percent ofthe extra

ood requir to sustain the world i the Flue must

come from irgated sgricutre

Irrigation of agricultural land husalong and well-

documented history ligation will, withost doubt,

ply’an important roe in keeping the future world

population supplied with their food, fibre, bio

‘ergy and biosindustril feedstock needs lerigation

hhswever has negative impacts on whats called our

natural esource bas’, which often include shallows

water tables, Waterlogging and increases in soil and

grounavater salinity ate associated with lack of

¬

‘Changes in land use, and especialy iigation

development (which is one ofthe most drastic land

‘se changes conceivable), nerly always upset the

‘natural hydrologieal balance: Indylandagrculure,

‘he introduced plans and ers rarely have the same

rooting dep and snnwal evaporative potential as

the natural vegetation they replace Inthe case of

irigaion, the eomponent of applied water tat is

not used by dhe plants further adds t0 the water

‘entering the water table, The hydrological changes

‘cused by land use moulification lead to changes in

the sat-blance Under rainfed conditions his often

results in a lateral redistribution of salts in the

landscape; exampes of this will be discussed

sti 3, Salt baanes Under iigted conditions,

the extra sls imported vio iigation water have tobe

removed fiom the rootzone to avoid Tong-tem

socumlation; this proces fs offen referred to as

esching

Int pst, deuinage has often been neglected It

is now widely accepted tht itis essential Io eny

inigaion system desigo The history ofthe Assyrian

<iviizaion in Mesopotamia presents an example of the cares epond case where a whole population vas forced 10 abandon 2 region because of sing roundvater ables and salinity Oacobsen and Adams, 1988), Other examples ate quoted in Ghassemi er a (1995), pp 23 and Ritzema (1998), pp 24-26 Presetlyaboutone-tind of the word's iigated

eo aces the thea of waterlogging ts estimated that 60 Mth s already waterlogged and 20 Ma salt affected, About 30 Mha of land has been provided with subsurface drainage systems For example in

‘westem Europe, agricultural! intensification has led

to the reclamation of more than $0 percent af waterlogged ateas through the use of subsurface Arainage measures The proportion of drained land 's largest in Europe and North America (20-35 percent of total enltvaied land), moderate in Asi, Ausralia and South America (S-10 percent) and lowes in Africa (0-3 percent

Recenily, some of the detsimental impacts of drainage on the ensironment have been esognized,

ln some circles “crsinage” has hecome a “éiety

‘word and its implementation has een restricted, for even prohibited, especially in environmentally sensitive wetlnd regions The very high anneal ate

of installation of subsurface dsinage ofthe 19805

3001000 ha year) hạt fallen 1 about 150 000 ba _year during th 19904 (Lesadf and Zimmer, 1995),

‘The range of drainage techniques presently

‘employed to manage the hydrological balance i agricultural areas hasbeen describe inthis chaper, which includes some alternative approaches 10

‘engineering-based drainage designs

‘Surface drainage is described by the American Society of Agricultural Eayincers as “he removal fof exeess wate from the soil surface in time to prevent damage 10 crops and to keep water from

ponding on the suriee" (ASAE 1979), The tem

surface drainage applies to situations where

‘overland flow isthe major component of the excess-

water movement o major drains natural streams

“The technique nomaly involves the exeavation of

‘open trenches'dains 1 could also include the

construction of broad-based idges or beds, as

grassed waterways, with the water being discharged

Theough the depressions between ridges Surface

ainageis most commonly applied on heavier soils

‘where inflation is slow and excess reinfall cannot

percolate freely though the soil profilo the water

table The technique has also been applied in more

‘permeable soils to de-water areas having ashllaw

[groundwater table: under those conditions itsbould

"be considered as part of the eatogoy below: Iisthe

‘most important drainage teenie inthe humid and

sulbhumid zane,

Horizontal subsurface drainage involves the

removal of water from below the surface The field

deainsean either be open dices, or more common!

‘network of pipes installed horizontally below the

ground surface These pipes used to be manu

factured of clay tiles, with the water entering the

Pipes through the leaky joints (hus the term sie

rains), Iv 1968 flexible corrugated plastic drainage

Pipe was introduced and this products ow widely

sed around the word Inspit ofthe diffrent material

sod, the term le drains itil in common use

Mote drains are unlined circular channels

‘nstalled at depth in the sil profile; they Function

‘mila t ie drains, The technique can be applied

in heavy soils as an alternative to surface drainage,

In those soils the very close drain spacing needed to

achieve water tebleconeot would make tie drainage

excessively expensive Mole drains are mest

‘commonly used forthe control of perched water

tables The technique is described by Nicholson

(1942) forthe United Kingdom and by Hodson et

4al (1962) and Bowler (1980) for eanditions in New

Zealand Rivema (1994; pp 915-927) presents @

good overview of the principles and applications

Horizontal subsurface drainage has been found

to be an effective technigue It controls the rise of|

groundwater tables and enables productive

Agriculture, Drawbacks are that i is relatively

‘expensive 1 install, operate and maintain, Also the

cdeposdl of drainage water that ean contain high

‘concentrations of pollatants (nutrients andor toxic

lements such as boron) can ereae problems

Vertical subsurface drainage involves te teva

of groundwater through pumped boreholes or

Background madtona drainage tchnigues and the need fr alternate approche

tubewells, either in single oF multiple-well configurations, The common problem with this

‘echnique is tha deeper, often more saline water san be mobilized which can cause disposal problems Also, asthe water is commonly used for irrigation eather than disposal, salt is recycled

‘though the sol profile and inevitably groundwater salinities will nerease overtime,

Low-yielding, large diameter open weils, or skimming wells, explore lenses of fresh water

‘overlying deeper, more saline groundwater The system has been applied in the Indo-Dutch Operational Research Project on Hydrological Smudies The final report of the project (Agarwal and Roest, 1996) presents information on the

‘concept an lists «numberof research papers

Allthe above-mentioned conventional drsinage techniques requite disposal of drainage eMMuent, management of which has become an important issue around the world Where he drainage eMuent isoFa reasonable quality itiscommoaly re-used if nvcessary afer blending ith good-quality surface supplies, However, after extended periods of irigation (in Some eases more than (00 years), soil salinities in oreas with arid climates have often approached level that require sal export maintain production Commonly drainage effluent has been disposed of int vers This practice is progressively becoming peflemate as drained nuns, salts and residues of agro-chomicals aect water quality, because downsteeam users (both itrigators and urbawindustril populations) rely on these rivers for water supphet In addition, environmental consideraionsassoraled with iver eslth are now receiving more atenton

Problems associated with eMMuent disposal are

‘widespread The salinity of most inland seas is knows to increase over time because of the continuing inflow of saline drainage water Ix California's Imperial Valley deainage water from Tergated los is discharged ino the Salton Sea,

‘whose salinity is on the inerease, Discharge of frainage water fom ierigated Tands in the San Soaguin Valley in California into the Kededon Reservoir has resulted in problems of selenium toxicity inthe biota (Cervinka et at 1999)

The Aral Sea Basin today faces ersis similar

to the one that destroyed the Mesopotamian cegilzation 4 000 years ago, as the discharge of polluted and saline drainage efuent ito the ver systems has reached hazardous level, Similarly the Indus basin in Pakistan, various river systems in

Plodrainage:

rinclpes experiences and pplication

India and the Murray: Dasting Basin Catchment

Australia are suffering the consequences of river

‘water pollution 98 result of the discharge of

polluted drainage eMuent from ingation, Where irrigation areas are in closed basins

Without an oalflow to rivers or the sea, disposal

offers even greater challenges to sustainability In

this ease various techniques such as evaporation

ponds, solar evaporators, solar ponds and salt

harvesting could provide a solution othe disposal

problem

In many counties disposal into rversis restricted

asthiserestes major ecological problems, Bodainage

systems combined with the above-mentioned

techniques should be envisaged to deal with the

fen fom te irigated and drained teas

33 ALERSME sernonctes

Vertical drainage with reuse of the extracted

groundwater for imigation is effective where the

gzoundwateris of good quality and easily accesible

(ell-developed aquifers) However, tis approach

‘docs nat remove silts from the region, The long

term sustainability of vertical drainage without

drainage disposal for salt-balance is therefore

«questionable

Horizontal drainage also has a proven record,

4s it controls the rise inthe groundwater table and

‘enables productive agriculture However i is

relatively expensive to install, operate and maintain

Another serious drawback i he iste of drainage

fluent disposal that can pollute surface water

bodies, especially where a direct outlet wo the seais

notavailable, Water quality usually restricts the use

for irtigation Even the disposal to evaporation

ponds can create environmental problems

‘The limitations and shortcomings of the

conventional drainapetechiqus eal foraterative

approaches toeip keep agriculture sustainable over

of natural fand and water resources Biodrainage is

ne of these alternative options The absence of fluent makes the system attractive However, for biodrainage systems to be long-term sustainable, careful consideration is required ofthe salt-halance under the biodrainage erops This issue will be

‘discussed in detail in section 3.4,

‘The term biadrainageis relatively new, although the us of vegetation to dry out sol profiles has been

‘known fora long time The fist documented use of the tem biodrainage can be attributed to Gath (1994), Prior to that date Heuperman (1992) used the term bio pumping to describe the use of ees for wate table contol Another term relating the io” aspect of sail water removal is Bioispasa, Which refers to the use of plants for final disposal

‘of excess drainage water (Denecke, 2000, IPTRID: FAO: personel communiation).In his publication all these Biotechnologies are considered under the common heading of iadrainage

fn response to the increased interest in bio- drainage, a special session on the topic was

‘organized at the Eighth Drainage Workshop ofthe Tmtersaional Commission om irigaton and Drainage

‘(ACID in anwaryFebrary 2000 in New Deli, ni

“The six papers presented by Austealia, India and Pakistan ae in chapter 4 oF his publication

‘The need for drainage is not restricted 10 irrigation areas In rainfed areas without iigation,

‘water (and sal) balances, disturbed by land use changes, often need to be managed to minimize negative environmental impacts, As the land use in

‘these aroass often Tess tensive han in those using irrigation, economic considerations prevent the adoption of expensive engineering inputs This fet makes the biodrainage approach especially atractive for the management of drainage problems

.Miadrdnusv:prinjpl cpoitncsy an apphetue

Chapter 3

What is biodrainage, how does it work?

Issues related to its implementation

{A range of issues is presented inthis chapter

associated with the design and management of

biodrainage systems In considering thei longer

Viability, biodrainage systems will have to be

subjected tothe same sertin as other plant-based

biological ystems with regards to quien and salt-

balance, si considerations et, Moreover as arge-

scale adoption of biodrnage crops could include

considerable traets oF land, socio-economic

‘considerations will have 1 he taken into account

when considering the adoption ofthis technique

3M Scieynine masts oF toonasser

In natural environments the components of the

‘hydrological system, ic rainfall, evapotranspira

tion, change in soil-water storaze and drainage, are

{on average) in balance Periods of high rainfall

‘might temporarily resultinineteased drainage flows

{risen the groundwater tale andor soil moisture

storage, then over a petiod of about 3-10 years

“Squitbrum i established Vegetation plays vital

rol in the evapotranspization and soil-wate stra

‘components ofthis balance

‘When natural vepotatin is cleared and replaced

by erops or tre plantations, the seepage loses to

the groundwater able under the new land use sytem

arcether higher or lower than under te pre-learing

The ineeased sespageSeonaro prevails and the

‘development of land for either rainfed or iigated

‘agriculture generally increases groundwate

recharge fates the new landscape systoms “lak!

Where this incteased recharge results in shallow

water tables evaporation atthe sl surface eases

sroundwatr to move upward through the soil and

consequently salts accumulate inthe rootzone,

Timiting plant growin Although this process has

‘ocurred gradually throwehout histor i iscurently

adversely alecting extensive ares of the North

American, Asian and Australian continents For

example in Australia, the area of shallow, saline

water tables s expanding rapidly Robertson, 196:

‘Western Austrian Government, 1997) in response

to widespread agricultural development over the past

An example of increased recharge flr clearing

is presented hy Allison and Hughes (1983), They showed that in a semi-arid region in southern Australia (average rainfall 250-200 myn) the recharge rate beneath native Eucalypmus spp Was

<0.1 mm’yt, Recharge was found to increase signifcanlyto between Sand 30 mmr following searing and subsequent cropping Management Solutions to the problem of excessive recharge are being developed, based om improved water use ficiency of the agricultural systems

The reduced seepage scenario, although less publicised, does also occur Vertessey eal (1996) Stdcd the hydrology of mountain ash (Eucalipiux regnans} forest in a ighrainfall environment in southern Australia and analysed relationships henseen forest age and runoff volumes Old-grossth forest yielded up to ice as much annual runotT as younger re-gtowth forest, The same process was

‘observed in a mixedsspecies Forest in a drier athnent www atchment ropa), The diving

‘mechanism behind this process lea area index,

‘hich was highest berween the ages of 30 and 40 years, The Findings have important consequences for the management of the catchments, which are used for water harvesting for urban water supplies, Forthese ares, ong harvesing ation are obvi prefered to obtain masimu runol yields, Plantations of Fst groin tee species such as couealyps, when grown on previously eleared land

‘oul also result in strongly reduced accessions to the groundwater and inthe drying-up of wells and sings

The driving Forse behind the bodraimage concept isthe consumptive wateruse of plans, Early sties

in Australia (e Greenwood etal 1985) sygpested thatthe rites of transpiration and groundwater uptake by trees underlain by relatively shallow (58

1 below surface) water tables, were very hh, exceeding the annual evaporation from pasture {C400 som) hy a Factor 36 (1 200-2 300 mmyn

‘These results, coupled with a growing interest in timber production in Australia led othe popularity fof the tee-based water management stratezy for agricultural areas However, results obuained bythe

measurement techmigue used by Greenwood

(eatilted chambers) have been challsnaed and

Tater work suggess more modest water use Figures

with potential stand water use approximating

stun Css A pan evaporation Forexampe, Moms

eral (1998) foun that Fuca camalddensis and

E grandis grown on a shallow saline water table

hot used appeoxinetely 300 mm pe year Th

Stated that the plantaton’s ability t sranspice

sroundwateris reduced where the groundwater table

‘sdaundovinin soils of ew hy dale wondctvity:

Potential water use ferences hetwoon species are

sso tic of discon, Hatin ea (198) ec

rized the noel 1 generalize water se behaviour of

Eucalypts wo faeilitate landscape management

racessesina wide range Austaan envioaments

Thay coc thatthe lea eiieney of synpattic

Eucalypr species i soil waterliied systems is

similar, ie, there was a stone linea felsionship

tween re ea are and mean diy water use foe 3

‘wide range of Eucalypt species grown under similar

climatic conditions Meyers etal (1996) arrived a

the sme conchision for non-watr lite sitsaons,

stating that sposies (iclading Pinas radiata) ith

—

tse a similar sages oF eanopy development,

‘One of the major factors determining the

sustainability of pant produetf (an this pant

-wgler use) provesses 18 salt ance If the sas

othe roctzane are mo either) ake ty

bythe vegetation andharvested or(2) removed Fo

the rootzne by lvching the vepeatin x doomed

to succumb o salinity: Te general concept of salt

balance is deseribed in a large number of ization

textbooks, These mostly foeus.on the water and sat

Ihalances and do not take into account nutrient

bolances and whatever sal uptake may take place

with raps, Therefore as salt lance consierations

are erucil to the viability of biodrainag

detailed discussion of the issue as Ht relates to

biodrainage will be presented in Section 3.4

‘the deep-rooting characterises of trees make

them extremely efficient users of water While

shallow-rooted grasses and crops fave limited

sccess to underdying water tables, deep-rooted tres

team access water tables downto several metes, The

tase stuies in Chapter § present « number of

scenarios, No, it recharge situations with deep

‘wate ables, de deep root systems of tees greatly

reduce the opportunity for rainfall rigation

sovessions to the water tale

"he water tablecan be defined as “she upper surface

of a zone af saturation, where the bods of groundwater 18 not confined by an overlying impermeable formation” The depth af the sater

‘able is measured n observation wells In contrast, precometors record pressures ata specie de in

‘the soil profile: they are often installed in aquifers for faster response to changes in pressure, Where

‘he water table, as measured in abservation wells,

is perched, leakage through an wnderiying slowly

a micas of salt export

erched

pemeable layer can provide

to deeper formations in the profile

_roundvater ate rypicaly shall, small in extent and often fesh (618, George tal, 1997), The tistinetion Derween water tables and ple7omerie Pressures should be Kept in mind when analysing

8 PoSSiiE MGPRAIXAG SETSAMOS drainage processes can he classified based on Jand use contest Inthi publication the authors hase distinguished between dryland rainfed and iigated land use systems considering the following biodainaae management mechanisms:

Dryland ninfad systems

oR + Groundater int + Discharge enhancement

charge contol

pion

Insigated systems Water table osteo + Channel seepage inesception + Bhodrsinage cum conventional dinagesystems Roinfed systems

A major problem with biodrsinage (as apposed to conventional drainage) in rainfed conditions is that plant water requirement is generally low dering

‘ole winter periods with high rainfall So theres delayed drainage response to rainfall inputs with the son reserve filling over winter and being depleted by vegetation water use over summer, thúc creating a storage bur to acconsmodste the next rainfall season,

Non-irrigated biedrsinage plantings can be

“designed for different purposes as describe in the following sections (Figure)

Recharge controt (Figure 1a, Photo The sustainability of natural environments relies on the balance between recharge and discharge oF Indra Balance: water fines passing beneath

Biodrainage: principle, experiences and applications

Figure: Dylan plantation seenario(schamati)

theootzone of vegetation communities are laterally

điacharted through regional subsurface aquifer

systems Where vegetation ischanged by agricultural

“develope (clearing) and crops widower annual

‘water use and/or shallower root systems ae planted, recharge increases As the conveyance capacity of the underground aquifer system is often not high

‘enough to accommodate the inereased recharge volumes, groundwater tables rise and cause

‘waterlogging andsalinization, (Often the clearing of vegetation in the higher teas ofthe landscape results in inetease recharge, followed by the formation of shallow water tables

‘nthe lower areas ofthe landscape, Water tables in the recharge areas are too deep to be accessed by

‘vegetation root systems, and plants in these areas rely on rainfall for their evaporative requirements

“The process to minimize deep seepage losses the higher pars ofthe landscape to minimize discharge problems downslope often refered tos recharge

‘contro Revegetation of recharge areas isa major

‘oo! in the fight against dryland salinity in Australia, Often only relatively small proportions of the Tandscape have tobe planted to achieve the objective

of reducing localized salinity discharge problems

in he lower part of the landscape (see Photo 1) However, e-vegetation of recharge areas can also have negative effects Where the evaporative Capacity of the new vegetation exceeds the pre- clearing evaporative demand, the landscape ‘dries

‘out’ Ths scenario i often encountered incalchments covered by newly established fast-growing planta- tions Itisan example ofan overdesigned recharge control biodrainage system and could cause problems such as reduced river flows, the drying-

‘up of wells and inreasing groundwater salinity

10

‘Photo 3: Deorested hi in nonhem,

Victoria, Australia with salinity

‘probleme In the lower part of the —

Groundwater flow interception (Figure 1)

Break-of-slope, (where the slope “breaks? from

convex to concave) plantings have been promoted

8 flow interceptors for areas where groundwater

flows through permeable layers overlying low-

permeability stata, By tapping these layers at some

point down the slope, where the quality is sil

felatively res, the res are considered to intercept

these flows and thus reduce discharge problems

further down the slope Location of the tree

plantations, based ona thorough understanding of

‘the underlying stratigraphy, is extremely important

if this concept isto work Photo 2 shows a break-

of-slope planting of two-year-old blue gums

(Eucalyptus globulus) in northern Victoria,

‘Australia,

MeJannet er al (2000) discuss

site in northern Victoria, Aust

‘geography is dominated by ái

raped with thick collvial deposi

‘rial planting

ia, The local igneous lavas, which under

‘What is bodrainage, tow does it work?

Photo 2: Break-f-sope planting of

‘wo-year-old blue gume (Eucalyptus {globulus) in northern Vieterla, Australia

the plantation are about 10 m thick, with thinner

‘deposits upslope and thicker ones down-slope A fresh shallow aquifer system flows through the colluvium The water table under the plantation was

‘deep (about 9 m below surface upstream of the site and increasingly shallow downstream from 6 to about 4m below surface) The authors conclude that under the site's deep water table condition, the broak-of-lope tee plantation didnot behave inthe prodictod manner They highlight the need to design such systems carefully, taking into seeount factors such a5 up-slope catchment area, net recharge, profile stratigraphy, water table quality and depth

to water table Discharge enhancement (Figure te)

‘Low-ying landscape units with shallow water tables often serve as local discharge areas Where these

5 have drainage outlets and seepage flows discharge into rivers, salt balance is provided

Biodeaiase: principles, experiences and pplcaions

‘Where the depressions ar land Jock (losed basins)

and percolation 10 deeper aquiters is inhibited,

‘linization of dhe landscape units inevitable

‘The wse of biodrainage in waterlogged dschary

areas is based on the concept af enhanced

‘evapotranspiration, The long-term sustainability of

bodranage inthis environment isa topic of intense

ehae Seder 1997) highlghs thin is shoxt

opie paper He suggests that biodrainage could be

considered for waretlogged landscape depressions

and canal seepage interception, and could be applied

in “parallel field drainage” arrangements as an

alerative to conventional field drainage systems,

Ín Australia it is now widely accepted that in

lischarze situations, enbanced evapotranspiraion

biuetinage sites will eventually succumb osiniy,

unless some form of conventional drainage i=

installed t0 contol sat balance tothe vegeation’s

roorzone by removal of saline drainage effluent

(euperman, 2000), Phoro3 shows deforested hill

in northern Vietoria, Australia with salinity

problems in the lower parts ofthe landscape

Plans ean use water both from the unsaated

part of the sail profile above the water table and

from he saturated part below the water able Plants

inthe latter cuegory ate called plreatophytes They

often (but no always) grow in (semi) ari climates

‘where they tp deep vater tables Van Hylckama

(1978) reports on mesquite (Prosopis) growing in

sdsert washos inthe southeastem United Staes

‘where the groondwater is sufiiently shallow that

seedlings ean ogcasionally produce deep enough

roots © reach the water table in wet years In that

same area the introduced pheeatophste Taare has

lowered the wate table wo uh ow Level that other

species with shallower rooting depths are being

inated

One special application of the biodrainage

concept is the amelioration of waterlogged soils

‘during the intial reclamation of ripening phase of

“now’land development Vegetation with vigorous,

deep and extensive rot system is used to dry out

‘waterlogged soil profiles For example, in the

Netherlands land tobe recsimed trom the sea i

serra with rod while 0 few conimecres of wake

femain, This accelerates the ripening process

Anotherexample of raining fully wateriogged land

fs quoted by Allender (1990) who states that

Fuealypts were successfully used daring the

rineteonhcontuy to dain the Porne Swarops near

Rome region hat had been a malarial swamp since

oma ies,

Irrigated systems Inlundscapes ith undulating topography recharge and discharge areas are offen relatively easy lo delineate Recharge occurs at the higher pans ofthe landscape and discharge lower down the slope In Jergation areas, with their Nat topography and {often shallow Water bles the distinction between recharge an discharge ses clesrly delineated and frequently’ areas that are discharging groundwater

by evapotranspiration between irrigation events temporarily turn into recharge areas ding and Smmediatly after irrigation

Water table comet Shallow water table levels pose « threat to fagsculural sopsas they often result in salinization

Dt the plant rootzone The management of iigation areas often aims to Keep water tables beiow the ritcalept, which defined as the depth at khích sapilln) slihizalen is neil,

Sustainability of rigation is detemined by the leaching capability of soils To avoid salinity problems the salts present inthe ieation water

‘wll have to be removed (rom the rootzone by Feacking ther either laterally to adjoining non irrigitod areas or streams or verily downto levels below the vegetation roo:zone

Plants can remove water from the sol ether (1) iesdy tem the saturated zone below the water table (2) fom the unsaturated capillary Fringe above

th water table or 3) from unsaturated tepsoil layers for rainfall ot irigation Seonarios (1) and @2) result in water sable comma scenario (3) recharee conte Insoenatio(3) leaching is uninypeded: when water application exceeds plant water demand Teaching wil ‘ake place Ip scenarios (1) and (2) leaching becomes restricted and salt accumulation processes begin to occur, This happens especially

‘where water tables are shallow, asi often the case

in rigation areas final equilibrium salinity fev will establish, depending on applied water salinity, soil hydraulic conductivity, hydraulic gradients (vertical and lateral) and vegetation type (salt tolerance)

Tn Chapter there are a selection of biodruimage case studies that describe water table control in irrigation areas

Chonnet seepage interception Chante! seepage ean hea mj contributor to water table accessions in iergation area High seepage rates will result in groundwater mounds beneath

2 ‘hat is bedrainage, ho des it work?

chanel, causing watslogging and salinity problems

inthe adjoining land, Water quality n supply channels

‘snormally good andthe seepage water, ifnot eto

evaporate and inerease in salinity, can be

productively used by vegetation and commercial

‘rops The ssue of salt balance although lesscrtical

than for more saline groundwater situations, is stil

‘matter of long-term concera, The issue is discussed

Jn detil in some of the literature references in

(Chapter 4 and the casestudies in Chapter 5 and in

Section 3.4,

Bindruinage cum conventional drainage systems

Biodrainage cops are no exception tothe basic rule

‘that irrigation, oF fr that mater plant growth, is

‘ot sustainable without some form of rotzone salt

balance Where biodrinage resus in salt accurula-

tion, engineering assistance is needed to make the

system sustainable, The issue of salt balance is

siscussed in detail in Chapter 3.4 and a number of

Diodrainage eum conventional <rainage scenarios

is presented in Section 3.3 and Chapter 5,

33 Pause

‘The aim of biodrainage is to remove excess

groundwater through the process of tanspiratin by

vegetation, This is achieved by enhancing the

transpiration capacity of the landscape by

inyoducing high-water use vegetation types in lange

‘enough areas to balance recharge/dischat

processes to maintain groundwater balances below

the rotzone ofthe agriculture crops The following

‘anaes should be considered inthe development of

biodrainage systems:

i, Water balance: Biodrainage plantations should

be able to extract groundwater volumes equal 10

the net recharge The water balance isto be

‘malotained sch thatthe water tables kept below

the rootzone

li, Plantation area: The biodrainage plantation area

should be kept as small as possible Agriculture

(particulanly isgated agricutre) is practised

primarily to produce high-value crops

Conversion of high-value eropping land

‘relatively low-rerum forestey may be dificult

‘Often good quality waters in shor supply while

Jandisnota limited resource Patculasly nar

and semi-aré region, dryland areas surrounded

by irrigated land could be earmarked for tee

plantations without loss of productive resources,

Til Salt tolerance: Biodraingge crops need tobe salt

‘tolerant Groundwater qualities can vary greatly

spatially, normally they havea higher slinty than imigation supplies, The water use capacity of

‘ees and other crops decreases with inerease in water salinity he ease of Eucalypt species, i seduces to about one-half of potential when the

‘water salinity increases to about 8 dSim (Oster eral 1999),

Drawdown of water table: Crops, including

‘wees, act as biopumps they depress the water table directly underneath planation areas and

‘consequently lower the water table in the surrounding azea, The drawdown effect under treescrops depends on the tee!eop's water use, the rate of recharge inthe surounding area, the hydraulic conductivity of substrata and the depth

to deeper barrier layers Biodaingge plantings should be established in blocks oF strips and spaced o keep water table levels inthe irrigated farmland in between the plantings below the rootzone, The harvesting of the biodrainage plantations would need tobe planned in such &

‘manner that the “drainage” function is net lost (Ghinning regimes)

Salt balance: The inttoduetion of irrigation allvays upsets the salt Balance Although gi tion supplies often have relatively low salinities, the large volumes of water that are intoduced

in the landscape increase salt imports signi ficantly Drainage ofeMuentt export these salts

Js therefore generally considered a necessity To achieve salt balance without conventional drainage, the irrigated crops, along with interspersed biodranage plantings, would have

to accimulate the salts inode by ierigation,

‘and would subsequently have to be harvested and removed from the region, This is only (potentially) achievable in situations where very Tovsalnity water i available tothe plans, Economic aspects: The growing of biadrainage trees and crops requires a different operational

‘management approach than the growing of agricultural crops Up-font costs associated with planting and maintenance precedes the income from harvesting by many years, Some form of contract growing, based an annual payments

‘might have to be considered to make the system aveeptabl to landholders,

fi Social acceptance: The introduction of new

‘cops such tree plantations affects rural social societies New markets might have 0 be developed, security arrangements differ from

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4 Exbropomtremayse —« Soaremapomremayon + Nout edoo pmstimgesyiem” * perel neurone ger dnhamase— + Beeman camo cPoeemlongl esa of waged ee 4eaarsgee `.“ reggrlvee 1 Na rap cơm

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7 Feioce means

ni

TEReaunremb

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Stara ers wut (i Gant sty water THE

Tô mem, * Pampa iam amass

aa

« Braun pons can

thse for normal crops (llega pruning or euting

fr fuelwood) and fires could destroy the results

fot many years of labour ina single day Active

Participation of focal communities in the deve-

opment of tre plantation-based biodrainage

systems is extremely important to overcome

problems and ascertain thatthe benefits ofthe

biodeainage systems ate reaped tothe maximum

Some of the issues related to the design of

biodainage systems ate discussed in more detail

hiện

Design considerutions for biodesinage

Comparison of drainage methods

‘A range of issues has to be considered before an

appropriate drainage technique can be selected, tn

‘Table I biodrainage is compared with conventions!

<rsinage techniques and various factors that should

+ Poet stp

Sane trary

ty tare orcaa men dip

Ho ‘lec son 0% orgies

‘na panof standard size suchas a Class A pan which

fs generally 1.15 to 1.20 Gimes of Es, (Allen et of, 1998),

‘Troe plantations often use water at higher rates than shorter vegetation types This is for three feasons: (1) the high aerodynamic roughness of forest leads to greatly enhanced evaporation rates,

‘which on an annual basis can be as much a tice that for grass; (2) this effet may be even more pronounced because of the so-called clothesline cect prevailing in rows of wees, substituting for tonventional drsin pipe; (3) deep root system of

‘tees with access to good-quality groundwater leads

Whats bodanage, how does it work?

to high annual transpiration rates The wate use by

tree plantations is not less than 1 times that of

agriculture ers or about 1.25 times of Class A

‘an A conservative re water se Figure of 10 Class

A pan could therefore be assumed to estimate the

potential biodraining capacity of tree plantations

under conditions of good water quality For design

purposes this must be eorected for future estimated

salinity levels

Reported research data on tee water use under

waterstressed conditions are not relevant 0

Diodrainage scenarios under conditions of

wwaterlogging where water is in ample supply

However, where tees are used to dry ou so stata

40 create a storage buffer for a subsequent rainfall

season, water-stressed tee water use information

can be highly relevant,

Maer table drawdown by plantations

‘The water table under vegetation falls when

Aischaree (evapotranspiration, surface runofT and

groundwater outflow) exceed recharge (infiltration

and groundwater inflow) and stabilizes when they

are equi A depressed water table beneath a tree

plantation induces groundwater flow from the

surrounding areas (where the wate able is higher)

towards the planation area thus providing water

table conteo to these areas Ire plantations were

Planted in parallel strips the water table profile

Would be similar to the profile found between

parallel, open drainage ditches (Figure 2) The

relationship between depression ofthe water table,

rate of recharge, hydraulic conductivity, depth to butt layer and distance between plantations can bbe described using equations developed by Hooghoudt (1940 in Dutch, and later applied by Donnan (1946, in English as follows:

ydaulic conductivity of substrata (day) ead difference tn)

Asan illustration, for R=0.0005 miday, Y,=10 m and h=10 my, the distance between tre plantations (L) would be 1 $00, $00 and 150 m for K-values of respectively 1, 0.1 and 0.01 miday, Low-hydraulic conductivity soils require closer-spaced plantation strips than sols with more permeable substrata, However, often higher intake rates occur in the high Permeability profiles and this would require larger larger areas to be covered by biodrainage crops to balance the increased accessions The plantation strips in areas with high hydraulic conduetvity could potentially cover large areas of the landscape Site= specifi eld data should be collected to estimate the size of and spacing between plantation strips

Biadrainage: principles experiences and apptcations

“The lateral extent ofthe impact of the water table

<epression beneath plantations on the surrounding

land obviously depends on the vertical and Inter

size ofthe tres" s001 system Ront systems have &

remarkable ability to expand to access water and

nutrients, The selection of appropriate species is

important in the design of efficient biodrainage

platuatons

“Zohar (1985) measored roots up to 20: from

the trunk of individual eucalyptus seas

Kolesnikoy (1966) reportson root measurements

‘on apple trees in the Crimea (Ukraine, formerly

USSR) He found a total length of al tree seaold

and fibrous toot of2.7 km under a5 year-old Sary

Sinap’ apple tre, with the vertical rots accounting

fr 1.6 kim and the horizontal rots 1.1 kan, tn the

same orchard, ona site with shallower water table,

excavations under a 25 year-old *Reinotie de

Champagne" apple tce revealed axoot depth of only

1.3 mand total root length of $23 m, the vertical

rots accounting foe 77 m and the horizontal rors

fr 456

In the Indica Ghandi Nahar Project, Rajasthan,

India, a perched water table along a seeping

irrigation canal resulted i the development of pots

in the borrow pits Plantations of (mainly)

Fucalypmus camaldulensis and deacie nilotica,

established stound te waterlogged ares, transpired

enough water to lower the water able by 15 m over

a period of 6-7 years Open pits excavated inthe

plantations down to a depth of 10 m, showed that

tree ropts were extending at least fo that depth (see

case study in Chapter 5.2)

Theiveyanathan and Benyen (2000) compared

water use of Flooded Gum (E grandis} and Spotted

Gum (Corymbia maculata) ona sallow water table

sive in sutheastem Australia, E grandis wsed 300,

sm groundwater per year while C maculata used

(675 mm over the same period atthe same ste The

researchers atribue the difference tothe tres" rat

systems Both species showed dense rot growth in

the top half mete of the soil, Spotted Gum hada lot

‘of roots inthe capillary fringe ust above the water

fable and seemed better equipped to tap water at

depths of around 3 metres

Quality of groundreater

In (semi) ard regions, the groundwater table is

normally quite deep before irigation is intwduced

and groundwater s commonly sine and unsuitable

for iigation, Aer intodtion of irgation, with

good quality water Brought in ffom outside the

*eglon the deep percolation losses increase and wo

‘things eam happen:

+ there is a barter layer above the groundwater

‘able, most ofthe deep pereoating water may collet over the barser layer and forma perched water body The perched water table will rise and will eventually cause wateriogging Since

‘the quality of water in the perched waterbody is

‘generally good, the groundwater can be purnped

‘ut, either directly by conventional drainage or via biodrainage crops

+ Where the percolating water infiltrates down to the saline regional groundwater table, this water lable then rises and causes waterlogging and salinization problems The poor quality of the groundwater limits suse Subsurface drainage resents problems fr disposal Biodrainage can

be practised with certain limitations The tanepiring capaeity of trees reduces progressively as the groundwater salinity increases When the groundwater salinity is, bout Sit, eucalyptus trees may transpire only if as much water as they do under non-

‘saline conditions (Oster eral 1999) However, this tue for many eros, not just tees ater balance shrowgh biodrainoge in irrigation

‘When iigation is introduced, the pre-existing water balance is disturbed; groundwater recharge increases, and causes the water table to rise The echarge to

‘the groundwater occurs by way of) seepage lasses fiom the water conveyance system, (2) irigation

‘water application and (3) rainfall evens, the ater {especially during cold seasons with limited exop

‘growth Seepage losses from the conveyance system

‘depend on constnicion techniques and materials used, Recharge accessions directly from inigaion

‘can be small when appropriate efficient irgation techniques are used Winter raigall events can be significant contributors to groundwater recharge as ops use litle water during chat time of the year and non-cultivated fields are often fallow

biodrainage seppied to obain regional water balance, the total water use of the biodrainage Plantations in a region should balance the recharge processes described above, minus the net regional subsurface drainage flows out of the region through underlying aquifer systems The latter can be substantially different from the pre= irrigation situation when water tables were often manh deeper

+8 hats bodrainage, how does it work? Figure 2: Combined bio- and conventional drainage management options

tree crawdown

giờ Bi water able love

Bl R ent established plantation

‘wi ag: avcumulted sas

‘away tom under the oder pnlalon afer hawest

_Blodvainage: principles experiences and applications

Water balances and recharge volumes are

inhorently dificult to determine, especially at a

regional level, as recharge processes ae extremely

‘atiable, both spatially snd over time, This makes

it more difficult plan regional vel bindrainage

activities Planning should focus at loeal level

implementation such as seepage intereption or

break-ofslope plantings

Sustainability and combined biodrainage and

‘conventional drainage systems

The long-term sustainability of non-irrigated

biadrainage tee plantations growing in shallow

saline water table areas may be questionable, At

some stage in their commercial life theit growth

performance could be affected by increasing root-

one salinity Aer the tees are harvested, in the

thsence of subsurface drainage to provide salt

balance, the accumulated salts in he rotzone will

move tothe sutice by eapllaity and impact an

successive land use A number of management

options could be considered 10 minimize, delay or

even avoid this problem (Figure 32)

Trees adjacent to groundwater pump (Figures

ja and 38)

Groundwater pumps are used extensively for water

lable contre, While trees lawer water table eves

pumps actually lower piesometric pressure levels

Inthe aquifers from which they pump Ths way, a

ddvenvard recharge gradients created which allows

salts to Teach out of the ootzone from shallow

rooted irrigation crops and pastures

Figure 3a presens seonario where tees ate

planted in close vicinity toa gromawater pur

The tees see itrigated with groundwater and the

Planting seis a5 a biodisposal area, The pomp

provides protection 1 a larger area, which can be

used 10 grovr any salt sensitive crop if suitable

quality itigation supply is available, Inthe Jong

ten, groundwater quality will deteriorate unde this

‘management option ad salt export from the area of

influence of the pump will have to he considered

Figure 3b shows where tees are planted a the

periphery of a groundwater pump's area of

influence, The tees are not irrigsted and live on

rainfall and groundwater As the piezometric

Arawvdown impact ofthe pump a shat location is

nly small Ge between O.1 and 0.3 m), the tees

‘would draw the water table down below the

Piezomsetrc pressure level ereated bythe pump and

thas accumulate sls in thei rootzone during theit

commerealifespan of around 30 years, During this

”

time the wees would (marginally) ealage the water table-proection area, a the trees would provide water table contol in stip of about 50-00 m round the plantation, ARer the sees are harvest,

‘he pump would subsequently leach the aecumalaed salls down the profile towards the aquifer thos providing salinity protection forthe successive shallow-roted ageicultural erop Tree plantings

‘oll moved progressively around the periphery ofthe area of influence

“Watking" plantations (Figure 30) Where toes, afer harvesting, are replaced by shullow-rooted isgated erops, wate table eonca) could be provided by 2 new plantation established

‘onan adjacent site This second tee erop should be planted about five years before the planned harvesting date of the original planation so the new tees would be old enough to have an inspact

‘onthe water tableand protest the adjacent paddocks from shallow water table induced salinity problems The tree plantation width would depend on its drawdown impact, Under tis system tree planta- tions ‘walk’ through the landscape, each new planting providing water table and salinity protection tothe preceding site

is important to note that neither ofthe thee options destined above is sustainable in the long term inthe absence of some form of salt expor, esther from the mee roaizane (user the "walking planation” scenario) or from the groundwater body, tapped by the groundwater punap, after salinitios have risen to unmanagenbly high levels Crees aujacent 1 groundwater un scenario),

[As described in previous chaptots, changing vegetation cover in a landscape is fraught with danger as it normally results ina reistnbution of salsin he landscape, bth verically and o laterally

‘This chapter sets out salt balance processes and their smpacton the sustainability of biodrinage systems Tio sat balance mechanisms ean be ennsdered in plan systems: (1) salt balance through removal of| Suits from the vegetation ootzote by leaching and (2) saltapplied othe plants taken up and removed through grazing or harvesting of plant matter, The

+ ĐWhul it inhuge, to does it work?

‘able 2: Average compositions of river waters of he world

former neds litle discussion, sits well understond

snd covered in maay texthooks on irigation

technology, The latter mechanism however needs

some elaboration as itis often mentioned in

Diodrsinage related information,

“There appcars to bea general consensus thatthe

salt uptake by plant is eligible compared to the

total salt applied in irrigation supplies Hoffman

(1990) mentions that under most agricultural

conditions where salinity isa concern salt removal

by crops can he ignored in the sal balance equation

The United States Salinity Laboratory (1954)

suggests disregarding of salt emoved from the soil

inthe harvested crop Chhabra and Thakur (1998)

‘of the Central Soil Salinity Research Institue ia

Karnal, Inga, mention that wes do not bio-harvest

the sali nd thus donot remove the salts from the

sol Heuperman (1999) mentions that the tee roots

‘exclude salts during water uptake; the tees skim

water ofthe top ofthe saturate part ofthe profil

causing the formation of a saltwater Jens The

‘Nuclear Institue for Agriculture and Biology (1997)

reports that when res tke up water, most ofthe

dissolved sats remain in the sol

Although in igh-salnity environments plat salt

uptake might be negligible in relation to the salts

present in the system, under low-salinity scenarios

‘his might not be the ease and salt balance by plant

uptakeand removal might be wchievable This option

eds tobe eitcally reviewed, Important aspects

to be considered in the salt balance analysis are (i)

‘mineral content in supply (ergation oF ground)

‘water ani) mineral content in plant biomes,

Plant water supply

James (1982) presents an overview ofthe average

‘composition of river waters ofthe world as shown

fn Table 2

Total dissolved solids (TDS) in irrigation

supplies in IGNP inthe Indus Valley i India ison

average 125 mglitre more than three decades afer the reservoirs were commissioned

Saltloads in rivers generally increase inthe lower reaches Tiss tue for natural river systems, even more so for river systems where irigation is practised with discharge of drainage water from agricultural fields being one major source of contamination Many examples are given in the Titerature Saivat Abdel-Dayem (2000) report hat

ân Pakistan about nine millon tones of sas are sischarged annually with drainage water into the river Indus The Amu Darya ver in Urtekistan receives an average of 6 billion 1m per year of drainage water eausing an increase of 1000 mg! Five salt in downstream river water during normal flows and 2 000 mine salt during the low flow season, Kitamura et af, (2000) report that in the Tower river basin of de Sy Darya, drainage water fiona irigated agriculture of ree-based cropping systems increased the salinity in ver water om 400-600 maine to 1 300-2:000 mili during the last three decades Xie eof, (1998) report that 1.1 bilionm afaitape wafefconaining L2 milion

*onnesof sa js£cbarged annually fromthe Yinebi ingated ara inthe Yellow Riser basin, Chin,

‘A distinction must therefore be made beoween inigation systems using “natural” river water from

‘the upper par ofthe catchment and those using polluted water Commonly ‘natural iver water is

‘Stored in reservoirs andi used for migation through iverson canals The quality of such water is not affecied by drainage pollution For example, imigaien water with a TDS load of 125 mele used at an overall annual water application of S00

‘run would add 625 kg of salt per hectare, Biomass harvesting could potentially evacuate this quanHly

‘fsa from th soil, However the exported biomass saks will end up somewhere in the landscape, for example in the fora of ash (after Burning of crop

‘residue or fueled}, animal or hunan exererents

Blodranase: princes, experiences an opteatons

{after grazing o rom sewage tearment plants) orn

fod processing plant outlets as pyimary-oF waste

praxis The care management of wiser anspor

ows through the fandseape importa toavoid ocal

cumulation ze,

Salinity mitigation drainage measures adopted

in the upper reaches f catchments merely transfer

the salinity problem from one region to another In

downstream reaches of river systems where

irrigation is based on more saline river water,

agricultural crops and tee plantations willbe unable

to bioharvest imported sls Management of river

systems should ain: at minimizing the discharge of

drainage eluent Systems based onthe us of good

‘quality river water for iergaton and dischaeye of

the saline drainage eluent ack ini the river are

not sustainable Biodrainage can play a role

{although relatively minor in the management of

the sltebalance in river catchments,

Salt uptakelexctusion processes in plants

‘Water taken up by plans carries some sol solutes

that, following transpiration, are eventually

deposited in leaves so that salt nthese leaves buds

up gradually over time For this reason olde leaves

generally have a higher mineral salt content than

‘yung leaves, The mineral content in plans largely

depends onthe species and (to a lesser extent) the

mineral composition of the soil elution The

‘inerl contents maximum in ety vegetabies The

‘venige dry weight content of minerals is rou (5)

leafy veges ~ 14 percent, (2) other vegetables

X pereent(3}roessandubers 6.8 percent (4) pulses

tnd legumes ~ 3.5 percent and (8) cereal grains

2 perosnt (ICME Indi, 1989),

Depending on prevailing climatic conditions,

plants transpire from 30-70 times more water than

they retain Consequently any soit solutes not

excluded by the roots, will end up in leaves in

concentrations 30-70 mes that ofthe water taken

up a he rot tps (Atwel eta, 1999, p S51),

For plants to achieve masintum growth rates,

hey should exclude most of the soil salts a theit

pointof uptake For example, fa plant is transpiring times more water than itrerains, should admit

only a0 oF 2.5 pereent of soi salt and exclude the

other 97.5 poreen If this was achieved, laf salt

feoncentation auld stay comparable 1 soil salt

concentration and the plant would survive

indefinitely povided sls remained compastment-

alized, If salts were not excluded at all, shoot

‘concentatons would soon be 0 times the externa

to regulate xylem salt concentration once the soil solution exezeds about 125 mM (7 2S0 marlieoe EC fabout £2 100 dem (Atwell eal 1999, p $82) Lambert and Turner (2000) present good overview of tee crop physiology issues related 10 salinity They deseibe the mechanisms behind the ability of plans to survive in saline environments

by salt exclusion a the roots, transper prevention

to the leaves, sl elimination by lea shedding and salt excretion ate eaves Plans ake up inorganic chenlcsls fom the soil solution and these include those essential for growth plus others whieh are non-essential oF even toxic, such as salts At felatively lowe concentrations of salt ons in the soil solution many plants can resiet their uptake This

Js called the single phase uprake At higher concentrations, there #8 more tapi, less restricted uptake possibly related to mass flow This uptake

‘equivalent tothe quantity of nutrients inthe water taken up in the transpiration seam and is less coniclled This is the second phase in the dual

‘mechanism uptake process, With tres there is evidence tht in the fist phase they generally use exclusion, while the second phase of rapid uptake they uslize compartmentation of elements through for example eccumalation in bark The concentra tien t which the Phase-2 mechanism occurs varies for each element, The authors quote an example oF

he uptake by E camaldulensis where NaC ions are excluded up to about 100 mM NaCl (S 800 mp! Tie oe EC of about 9.7 dS) soil solution: at about

200 mM NaCl there was rid uncontrolled uptake

of sal by the re ross

Aaiplex spp, (saltbush) are wellknown fr their salt uptake capability Schultz (1994) reports on salt

‘ptake by halaphyticsripler spp as measured in field experiments under a range of saline conditions

‘Yields ranged from about $ tomes dry Weightha (4 tensormis) to nearly 10 tonnes dry weight a (1 mummularia and A- undulata) a a plan density

‘f 10-000 bushes/ha, ater one-year sublshment

‘with flesh water ivigation and seasons of saline inigation The highest yield of 10onnes dry weight yrlha was achieved with the highest applied irrigation salinity of 10 000 mire Al treatments showed reduced yields in the third year of saline irrigation Higher iigation salinities resulted in

Wate biodrainge, how does it work? Table 3: Summary of sol solution salinities and concomitant lef salt concentrations

higher Na and Cl concentrations in the leaf: K

shossed no trend with inereased salinity nd Mig and

CaleaTtissue concentrations actually deereased with

increasing itgation salinity Data and salt balance

calculations based on these figures are presented in

Section 3.4

‘Most trees and shrubs are classified as non

hhalophytes; they show growth reduction with

increased salt concentrations Some trees and shrubs

are halophytic;, hey commonly require some salt 0

‘chieve maximal growth, Whilst they exclude sls 0

‘cern extent, these plants are much beter adapted

‘© managing salt accuroltion in thei eaves,

‘Table 3 shows soil salinity versus lea salinity

anges for halophytic and non-halophytie plans in

‘NaCl-dominant environments Concentration

“eo forthe non-halophytes (about 3x) are higher

than for the halephytes (about 2x) Cleary the

halophytes (especially the dicotyledon species)

accumulate ugh hghersalt concentrations in their

leaf tissues and are ths able to live in much higher

salinity environment than non-halophytes

‘of bodainage technology in situations where plants Ihave access to relatively fresh water supplies such

as for example channel seepage Van Reuler (Applied Plant Research, Agricultural Research Department, Ministry of

‘Agriculture, Nature Management and Fisheries, the

"Netherlands, personal communication) onthe issue

‘of salt uptake states that plants do not need Na and CCl however, e.sugarbeet reacts positive on some

Na present inthe soil The amounts of Na and Cl taken vp by plants are very low: the straw of wheat

«contains about 0.6 pereentCland about 0.01 percent

‘of Na, With a straw yield of 2tonnestha the total mount taken up by the plants is 12 kg Cl and 0.2

‘kg Naper a, For sugar beet this is 0.08 percent Na

in the (root) beet in the leaves this i even less

‘Biodeanase: principles experiences and appieations

More interestingly on grassland Cl coment is about

| percent and Na content about 03 percent, oF 10

‘kg Cland 3 kg Naperha respectively, When several

‘os of the grass take place every year the toa]

harvested grass may be several tonnes (dry weight)

and then the salt removal somewhat increases,

Salt storage in vegetat ments

Halophytes survive in saline environments by

absorbing salts Most halophytes accumulate

(relatively) ange amounts of satin thet leaves For

‘example, Atwell eal (1999) eepor that Atriplex

-nunmmutaria (OM Man Saltoush) grown near ts

“optimum saiity of 200 mM NaC (1 600 mete

‘oF EC of about 19.5 68m) contains about 10 percent

NaCl on a dy eight basis,

Schulz (1994) measured average yields of A

‘nummudaria 00.6 kg dry weight per plant per year

across range of applied irigaion sdiniies (100

10.000 mglltre; NaC/lominant water) overa three

year period At planting densities of 10 000 bushes!

ha this translated t0 6000 kg dry weight ha year

He also measured leat fons forthe range of applied

Water salinities for five sriplex species, 6 4

animenicoka A cinerea A entiformis, A mammidaria

and 4 undulata, On average across the five species,

leat Na and C1 inerasel with increasing iigation

Sslintes, K showed no tend and Ca and My shoved

decreasing tends, Figure (Schulz, 1994) shows the

results With the average leaf component of dry

weight production being 43 percent (ranging

between 38 ad $1 percent forthe five 1jple sp),

the salt export in the leaves (considering the major

“Tae : Mineral (ations: Ns

21

on in Figure ) would be between 350 and 433g: haiyear for ivigation salinities of 100 mgsitre and 10-000 mg/l respectively, ial leaf mater was harvested and removed fom the sit, The snnwal migdion application of about 10 milion litestha applied | tonne’hayr and 100 tonne’ta’yr for respectively thelow and high salinity treatment This suggests that with the low salinity irgation water the plants mde a sigificnt contribution to sal removal, but with the higher salinity values, salt balance contol by vegetation was not possible In

‘his experiment only the salt uptake inthe leaves

‘vas considered, probably to simulate grazing his

‘only marginally affects the total salt uprake 3s the plants’ stems accumulate only minor quaaites of salts

Caleulatng salt balance based on tral sts ts risky Plants take up ions ftom the soil solution selectively different species take up diferent ions

at different rates depending 08 climatic conditions

an grvin tage, Sal alance calculations based on lant matratremavl will have to be made on an

‘vidal ion basis ater than atonal bas Salt content in ierigation water is generally assessed by measuring the EC of a sample and converting this to the gravimetric weight of sll

‘mineral compounds (eories, sulphates and (bi) carbonates of ealeum, sodium, magnesium, ee.)

‘sing an empirically developed conversion factor

‘The “total sats’ (expressed in mice) include the sulphate, (bi)eatbonate and phosphate anions Thus the carbon, hydrogen and oxygen components of | the anions are included in he oll salt measurement

2

“The mineral conten in plans is determined by

<ither ash analysis by wetucid digestion methods

Inthe shing method omganie matenal is comple

destoyed by burning ina ceucible toa tempera

‘oF 00", Ashing techniques can eause vaporization

and sublimation of some ofthe clemens, resulting

innmineral losses, Wet digestion methods determine

individual clement content; samples ave washed

wih hydrochloric acid, treated and heated with

nitric acid and then with perchtorie acid The

method produces weight values of individual

elements (caleiue, sodium, magnesium, chloride

sulphus, nitrogen, phosphorus et.) ine plant asa

percentage ofthe plat dey biomass weight Anions

such as NO, , 50," and PO,” are not measured but

‘heir element contponents N, S, and P (sometimes)

are, Chlorine when analysed using this method

‘would volatize and escape on heating and should

be determined by, for example, tiation Bosh the

sshing and the wer digestion method can result in

‘av under-valstion ofthe mineral conten in plans

Microwave assisted digestion using closed

containers, reduces these losses and gives more

complete digestion

‘Where salts are NaCl-dominant (as in the

saltbush example above), the limited number of

elements measured, including thechlrides, willbe

only slightly lower than the actual! ota sxineral salt

content ofthe plan samples

‘The above suggests that calculations based on

analysis of plant material often underestimate the

total salts taken wp hy vegetation The oer of

‘malgitude of the under-estimatinn depends on the

sshing method used and on the composition of the

Salts It seems that this aspect has often been

‘oxerlooked by pactsing engineers and researchers

Non-halophytic recs are salt exetuders The

relatively small amounts of saltsutrients that are

taken up hy tees ate recyeled by folie dop The

‘only export of salts takes place dough removal of

‘invber during harvesting and throups seepage lesses

‘where trees grow on deep ater ables that ean not

be accessed by roots,

Ecalyp species are not known for their sal

‘uptake capabibty Lambert (1981) discusses the

resulls of large numberof batk and wood studies

for Australian tre species grovn in forest envion-

ments Sbe found very high variability between

species and belvcen the woody components inthe

same te (sapwond-hearwood-bark), However the

‘mineval ash content af the Beart-ocds (he major

bulk: ofthe timber removed in lagging operations)

‘was quotedas generally being less than 1 perce

Hát: hùndnihuge nu diệt nie?

"vi somMe spgglet showing highe levels vực E mackløt L4 preew)

Mineral content in plants rowing in the Indira Gandhi Nahar Projet, Rajasthan Indi, determined

by the diacid wet digestion method are presented

in Tabled Stemevvood percentages forthe re sp areofthesame order of magnitude as mentioned by amber (1981)

Halophytes with thet high leat salnties, on Hist sight seem to offer the Best seope fo achive salt- balance tough expor: of plant marer from sites However, experimental Feld dts do not sopport this A yield of 1 S00 ky dry matter per a (Schulz 1994: NaC dominant envionment) Would translate

to 150 ky of salt per hai the foliage was removed fom the ste H water applied 0 the site contained shout § 000 mg sale li0e, and the saltbush would lise around $ million lites'yr (conservative),

25 tonnes of salt would be added tothe ste and nly

130 kg (oF 16 %) would be exported: hat a sal balance scenario,

‘ proctcal challenge would be the development

of technique harvest the slush plants, Grazing

‘would be the most convenient system although this

‘would result inset of most ofthe salts hack 10 the site, Cut-and-cary systems tht do not rm the reductive capacity of the saltbush would have to

be developed The five species in the Schulz tral

‘were harvested by euting hack at about 20cm from aground level using 2 flail mower The bushes showed excellent re-growth during the frst and second year Yields destined in he hid season and continuis heavy cutting back can be expeeted 10 result in dghack of th saltbush

For Eucalypt plantations the prospects for salt balance in saline environments through harvesting sand expor are not much beter Following dal rom Lomiper (1981) and using the highest recorded ash percent forthe heartwoedof4 percent for E rss fan annual growth increment of say HO tonnes (high forsaline environments) would result in an average sal removal through harvesting of 400 yh per {year Following the ste caleustion for saltbush above, with an asumed applied water quality of

3000 mg salsite and annual water use of LO milion ies'yt, 30 tonnes of salt would be added

to the site of which only 400 kg for 1.3 persent)

‘would be exported Lambert and Turner (2000) present data on sodium and ehtoride accumulation in different components of five and 22-year old & grandis Consequences for bier

Biodrainage:prncpes experiences and epplicatons

plantations For five-year old plantations, 35 kg/ha

"NaC was stored in otal wood pls 17 ka in bark;

for 27-year old plantations the figures were 186 kg)

ha in total wood and 170 kg/ha in bark This means

that over the 22-year period the uptake in both the

wood and the bark was about 7 kpha/y oraotal of

11 kghhaie for the combined components These

«quantities are small in relation tothe salt inputs in

the plantations, even under some rainfed scenarios

‘where annual inputs of sodium and chloride in

coastal areas canbe as high a 65 kghaly (eg Cofls

Harbour, | km from the coast in easter Asta

Lambert and Turner, 2000) Leaching would stil

have to take care af considerable salt export from

unde tree plantations grown at these sites also

has to be noted that bark and leaves and wigs are

normally not exported from plantation sites at

harvesting

In conclusion, the potential for export of salt

through plant harvesting does not lok promising

Salt balance through the removal of vegetation has

‘only been teported fr situations with very low salt

inpa/esh water supplies suchas channel seepage

‘More detailed information on this scenario is

presented in a case study in Chapter 52 Other

etailed examples of salt balance seenarios are

included in Chapter 5,

A8:

Selection of species fr biodrainage purposes will

‘depend on the environmental conditions for which

they are planned, Sat tolerance will bean important

criterion for (potentially) saline discharge

‘environments, water use considerations wil prevall

in recharge contol situations where salinity is of

ro concer and in channel seepage scenarios with

loy-saliniy water supply

Crop selection

Literature on salt tolerance for agricultural crops is

commonly based on Maas and Hofiman (1977) For

‘non-agricultural tree and bush species, reliable

information is mote difficult to obtain Marcar et

a, (1995) provide detailed information on the use

(0 30 tee species for use on salt affected land and

less detailed summary desriptions for an additional

30 species Schulz(1994) provides comparisons for

five saltbush species grown on a range of saline

irrigation regimes and other authors have

investigated water use of different tee species under

range of saline conditions (Slavih eral, 1999;

Cramer et al, 1999; Mortis and Collopy, 1999; Benyon eral, 1999),

Shah e a (2000) bring together salt tolerance information from research in Pakistan They present data on crops, salt tolerant tees, grasses and saltbush (set Aphendix)

‘Khanzada e al (1998) monitored the water use

of Acacia nilotica, A ampliceps and Prosopis pallida on 3-S year old plantation sites with

‘contrasting soil and groundwater salinity inthe Indus Valley in Pakistan, Annual water use by A nilotca was | 248 mm on a severely saline site and

2225 mm on a moderately saline site This was considerably higher than the annual rainfall, indicating that much of the water was taken up from the saline water tables underlying the sites (20 dS/

‘mat L-LSm below surface at the sine site and 1.5 dSim at 2m below surface atthe moderately saline site) The other species used less water, this

‘was considered to be a result ofa lower planting density The authors concluded that trees can

‘evaporate larg volumes of saline groundwater but

‘they warn against the dangers of salt accumulation

as observed under the wal sites Roatzone salt-

‘lance might he achievable in the long term, but at

‘much reduced tree water use and thus shallower

‘water table, Photo 4 shows the he measure te water use

pulse method used to Photo 4: Tee water use can be measured with the heat pulse method

"1

What ix bndvaine, ow does itor?

Table 5: Suitability of tree spp for saline sole

‘marae rove Fata, Posspa ators Pins cesta en, Painaona sa, Aaa à

The Central Soil Salinity Research Institute

(CSSRI) at Karnal, India, presents data on the

tolerance of tee spocies to sil salinity a shown in

Table 5 (Tomar and Gupta, 1999),

Reported salt tolerance data Tor the same mee

species vary widely Deep root systems make

measurement of average rotzone-FC dificult and

sometimes meaningless; the trees develop active

roots in the lest-sline part of the rootzane For

example “moderately tolerant is defined as EC,

8 dSim by Marcar eral (1995) but is eporced as

15.25 dSim by CSSRI Karnal (Table 5)

ucalypus species are generally considered to

be effective for biodrainage purposes Eucalypius

camaldulensis ts hardy tee that prows under á

‘wide range of climatic conditions and sol types

Some provenances of the species tolerate saline

conditions quite well They grow fast when good

ly water is available Ina study in IGNP,

Rajasthan, India (Chapter 5.2), five-year old

‘subirigated plantations (channel seepage} produced

sry biomass of 185 tonnes/ha, The utilizable

‘iomass prodetion was 29 tonnesha/ysa

Acacia nitotica, Dalbergia sissoo Tecometa

undulata ao Ziziphus mauritiana are ober species

that have performed quite wel in plamations along

leaking canals in arid conditions Species suitable

for non-irrigated conditions are Acacia tori,

Prosopis einevaria, Prosopis juliflora and

Parkinsonia, Poplar and tarvarix trees are also

reported to perform well for hiodeainage (Bhuta

Improvement of alhall soils by tree plantations

‘Alkali soils ate characterized by high DH (8210.5)

And high exchangeable sodium percentage (ESP

> 15), High pH and ESP primarily occur asa result

‘of the presence of measurable amounts of soluble

sexu carbonates an bicarbonates in these soils

“Thetolerance plants is yovermod by several actors such asthe Na rato of shoots and the capacity 0 take up K under strong Na competion, selective absorption or retention of cations (mainly Nain the Foliage, roots and shoots ability toexerste soi throu leaves, tolerance to oxygen stress in the shizosphere and rutrtionalsiresses

‘Available research information on the soil alkalinity tolerance of important fuelwood timber and uitzees as compiled by Gil ea (1990) and Singh and Gill (190) is presented in Table Exporimentsat the Cental Soil Salinity Research Institute, Kamla (Gill and Abro, 1985), have demonstrated that special tree establishment techniques in alkali soils requite the planting of tree saplings in 0.18 - 0.25 m diameter, 2 Lm deep post-hoes filled with ether good non-alkali soil oF alkali soil amended with 2-3 kg gypsum and 6-8 ke 1m yard manureieompest pot posthole Use of teypsum is a must for achieving desired establish

nhe tran Pheơn mem ‘ene mameos

8200 Nove ats DaBggg<ep —punce garanun Pins bo

Asoractannats đương pade Popaus does Sym crnml Bao htt

Biodraiae: princes experiences and plications

‘ment (comme ria survival ates) an boosting aly

growth of trees im the inhospitable alkalt soil

environments Troe growth hy itself initiates

Diolagial amelioration onee a good cinapy over

is developed Significant decrease in soil pl

clectrical conductivity, and inerease in organic

cearbon and ether nutrients (N, PK, ete) Was

‘observed to result in seeyeling of mutients through

lier production, Gill eral 0987) Nirogem-tsing

trees doexceptinally well inthis respect leization

promotes root development and decreases soil

sodicty: Pruning and lopping hep wee grosth

‘Close spacing of wees (1 Lor 2.2 m) produces

less biomass vield per tee but more biomass per

ho, Grossing of tees hasbeen report to ameliorate

alkali soils by improving physical, chemical and

biological properties, Tyagi (1989)

Tree cropping sestems managen

Selection af species fr biadrainage purposes will

have to be based on currently prevailing and

expected folie ensitonmentsl and veononiie

anions, rather than natural conditions as they

existed before agricultural clearing and

development For example, in regions where water

tables were deep before agricultural development,

clearing andthe intodhction ofigation have often

rele in the formation of shall water tables

Under this scensrio tree species selected for

Diodrainage should beable to survive and grow in

shallow-water tableenvironments rather han nthe

pre-clcusing dep-water ble environmen

“The management of forest plantations in saline

‘waterlogged environments deseribed in detail in

[Lambert and Tumer (2000), Chapter 8, and M:

erat, (1995) sues sch 3 site preparation (deep

"ping imine, eypsum application weed eontro

sil mounding: mulching an Fetzer application

all need tobe considered if tree vegetation sta be

established suceessllly a sites with unfavoursble

characterises On sites with high sol salinities,

(Cemporary} remedial drainage might have to he

applied betore bidrainage plantings can be

‘established

‘On-going management issues, sueh spring

and pest control are dependeat on the purpase ot

‘the inal pratt (timber or Fueovoad a Toca

e0numc cunsileradions, Generaly seleston af a

‘ni af species father that a monocuTtuee tee

plantation minimizes the risk of severe insoet or

‘isease aac,

“Animal and young tees do not mis wel, Youn

seadings might have 0 be protected from small

25

hative wildlife spovies suchas vadents or rabbis Individual se guards sight herequred toss oid major losses Whonanisaltreimtaoduos for prving'keat contol at later tage, elose supervision i intl esd to prevent damage o bark

Theplanting of eps between widely spaced roe rowan be considered, especially at an early Sage before competition fr light becomes am sue Crops such as wheat, mustard, lent, berseern and gram forpastre species ca be grown However, the main gbjestite of biodainage plantations isthe peoven- tion of waterlogging and salinity management The

‘scot plantation pts forthe growing of nlersraps may diver landholders’ altenion from the tres in favour the erp and fortis reason inter<ropping

‘snot commended until the water able and sani conditions ull and inl stabilize Tn generat itis recommended o assign a certain function tot certain area to avvid eonihict of interests negatively ateoting the bladramage function

“Monitoring of pant heals and soil salinities at bielalinaae sie s extremely imporant tbe able

‘o.adjust management of perennial (re)creps ez

by occasional srrigation, pruning oF dinning t© reduce water use) and avoid tre crop losses

"`

Landscape biodiversity is cumemly nthespetight

‘cultural aces ofthe developed word Inthepast, biodiversity was olen neglected issue,

‘especially initrigation areas, Lack oF aware shor-sghtedness of previous generations of policy makers regional resource managers and landholders has often resulted in landscapes with very li le

‘of the original native vegetation and fava

‘Conalions in agricultural emeonments often vary considerably Irom thse ofthe original landscape For example water ble regimes are changed, there are higher water andr nutrient inputs and intensive

“topping practices impact mative flora and fauna

‘The “mangpolizing” of the landscape by the sgrieultralsetor alone is inercasingly challenged boy other landscape users, including promoters oF more natural environmen development, Howevet Tanhing anl landeeaping tay cumpably cecxi Adoption of biodrainage proctces rather than conventional ninsge can conibut to diversities thn in the agricultural andseape, However, fen the tree crop selected for biodrnage will ote teste the indigenons species for that locality a8 the

‘agricultural practices will have changed the

‘ensitonmental conditions tthe site

essand

Manocultue Blocks af land have an inherently

pon biodiversity and biorainage plantig

signed for daalsparpose draina

‘purposes, they should incorporates mixture of tee,

shrub and grass species An example of the

biodiversity value of a small hiodrainage block

atactng lange mrbers of bird species is presented

incase study in Section 5.1

"hodainage planings will often insomporate (or

even he filly composes of) Euealypt species The

logical effects of Evealypts are reviewed by

Pore and Fries (1983), Eucalypts are often

perevive as environmental bands because they

arcalleged io ave adverse impacts on sil nutrient

Status and encouraging erosion), on hydrolog

(arying up aquifers) and on the esosystem (poor

labial for fauna) n ther discussion on the impact

of Eoelspb on the water evele, Poore an Fries

fonsider Euclypts as anier “crop and otside

{cir natural ecological region, Euctlyptspeobaby

have little value as habitae providers However,

eucalyptus trees provide wildlife habitat in

Calfortia and especially when, apar for toes,

other salttolerant erops are intraduced, the

‘ecological value mereasesremirkabl:

3.7 Maer tim oF Prooice,

“The adoption of new production systems, such as

biadrsinage plantations, by private landholders is

so some extent linked 10 the market value o sera

frelets, which n tum depen asa onions,

In fae, the biodrainage plantation is needed

sustain igh yields ofthe main commercial eros

Studies carried ut in different parts ofthe work

indcatethatanincressein incomes always associat

with an inewease in comet and industrial ood

consumption in rust aeas in developing countries

suchas India, fuelwood isa basic ne Idea durin

the past decades the rte fee in pri af ash

timber and char ha been much pester than tht

‘of gricohune commodities, The nen i continuing

(Dsived, 1992),

In several parts of iia frm Frese has shown

penomtenal growth rates in the past an good

3s0n0miereturtv Rasenly however market pices

have collapsed heeause of the lack of marketing

facilites, Obviously macket research should form

the basis of any là

scale mave towards the duction fnew crops, inluding tees However,

the situation might he completely differen foe ral

‘communities in developing countries where other

hy the Indian Corporation L988) inthe catchment of the Mail reservoir, the henetivcost ratios for diferent investment sectors were assessed! a soil conservation 1.6

‘sine om several research farms in Inia

‘Oser time conditions may change considerably For insange a ee-groeine projeetim California look! at the market value of Eucalypt wood for fuelwood prosiction Based an a net value of LUSS3-50 per ord (2.3 m' he annual sustainable sles 0.2-0 Seo peracre 0 5-1 89h) were

‘ot considered hizh enough to enerat the level of nnd income thot would exceed the annual

‘operating costs of USS Mũ hạ and ở hú share of| the development cost of about US$3 000 ha However, its reported that there would currently

be a large profitable market for evealyptus chips sed in landscaping

Timber vields oF tees grown under saline conditions can be reasonably i

ocientais arom with 9 US tigaton Water on saline site in northem Victoria, Australia, showed nnugl growth inerements of nearly 17m during

‘ts four vero saline gation, However

ff poor tee shape the timber wasnt stable fe anything except fuclwood Breeding efforts co Jimprove form and timber quality have trađiiofally Fcused on high yielding species in more beni

astare and ater perennial forage spaces such

fs luceme are gener easier to incorporate in existing ayriculral systems than tree plantations They can he either gnzed directly or harvested, AS with trees, breed

forts have traditionally focused on more productive no-saline eironments, Mare salt taerant species are being Aleveloped and production systems ate presently being tested in the USA (Oster etal, 1999),

Biodrainage: principles, exerence and eppiatons

‘Wetlands are areas tha ate covered with water fr

at least part of the se a dep of ss than 60

metres The values of wetlands are now widely

recognized as reseres of native plans and wild

water quality improvers(nrtent filters} and flood

protection bffes ntheirnataal envionment the

evgpotranspiation ofthe vegetation ofthe wetland

sysiem si balange withthe throvgh-flow and

seopage tues Where either the vegstation or the

Watering regime is changed, these finely tuned

hulanees are disturbed and habitat changes axe

inevitable

Water balance changes in wetlands are

‘mentioned by Poore and Fries (1985) who sat that

tece plantations, especially Euealypts, have bees

used to lower water tables im swampy ees either

to dry out the soil or fo contral mosquitoes,

Dbviously this practice clashes with the

‘management of wellands for ecological vals,

3.9 Bonnar Vi: so ces 1A0 v0

Unan salinity is an issue associated with Fsing

water table levels Water use i arid urban

environments can be high ad leakoge from water

Pines substantial, Urban areas often have relay

ood surlace drainage but subsurface drainage is

rarcly considered Onlin places where grounsvater

‘spumped for water supplies is subsurface drain

provided This practice isnot feasible in urban

Jandscapes overlying saline water tables, In some

eases, ok and leaking seage pipe systems might

have been providing some orm ofsal-balanee by

Jnerceping shallow saline groondater however

‘where these old systems are being upsraded and

Teak ived, sgiaus waterlogging andor salinity

problems can be expected to develop

In Aostnli, urban salinity hs Bown idee’

ss erious problem The ety of Wag

caste Australia suffers from extensive damage 0

ld brick structures (Spennemann, 1998) The

sratepies involved in managing this poem elude

biodrainage Uougt planting of deep-rooted

vegetation species adapted to the local ard climatic

conditions her tan the commonly wed tiparted

exotte species requiring ivigation to survive

Commercial tree plantations are grown to yield

seonemie returns Plantations developed for

biedrainage potentially offer an extea protection

benctit free of cost, and improve the regional seonomy, However, looking at the level of the findividallandhotder who nosds anna returas to survive, the aim should be © produce economic retums comparable at leas othase om agri The planting of large areas of new crops, expecially ee ers, will havea sinificamt impact

‘regional economies and social stuctures, Casson (1997) discusses these issues i a working paper based on to case slidies in South India and Thailand During the 1980s, social protests developed in Asia and ebewerein the word) over alleged adverse effets of Evealyptson soi nutrient Status, soi water depleting, sil eosin aa willie Casson argues tha the evtieism against Encl

‘often conceals here reasons for ansetes 4 the Jack of consideration of community needs

Tn the Inia exse study timber production ws

‘the main driver forthe foresey projet Issues such

es (1) loss of grazing opportunities forthe focal fiumers, (2) the use of public, ‘communal’ land for tree rowing, and (3) insofieient involvement

‘of cal communities inthe planning esablishent snd management of the plantations all complicated the implementation ofthe project,

Inthe Thailand example the two main objectives ofthe projest were to (1) improse the standard of Jiving of the rural popolation; and (2) improve Fesource management through tee planting in eehatge aes to protest downslope sal affected sgnedltual land The main problems encountered

‘were that (1) village wells dred up asa result ofthe ucalypts lowering the water table, 2) communal raring land in ocharge areas was replaced by lose- fcinopy plantations without understorey aad (3)

‘ownership af the new trees was not clear

‘identified Therefore, by focusing on saving the salinity problem the community inadvertently

‘flere fom hood, Rader and water sora The lessons lear! fom the two dryland case

developing countries, especially when thereare new

projects and the choice is berween (1) bindrainage,

(2) instalation of a conventional subsurface

drainage system using a closed horizontal pipe

drainage system, by open drains, of by vertical

drainage, and (3) a combined system of biadrainage

and conventional drainage Often the rural

livelihood benefits heeause hiodrainsge provides for

fuelivood, fru, timber, fodder, windbreak, ora

and fauna, biodiversity, pollutant removal,

RAV Osernay senses REGIONAL mUDRAINAGE

“Themostimporian factor a consider when deciding

where to establish biodeainage plantings is the

hydrological process underlying the catchment

water Balance, Accurate identification of recharge

(intake) and discharge (seepage) areas in the

landscape is @ major requirement forthe proper

planning of hiodeinage activites

In_non-ittigated, undulating areas the

identiicavion of recharge-discharge relationships is

fle relatively’ easy with the lower areas of the

Jandseape venerally servings discharge land unis

Exceptions do atou whore impermeable layers in

the sil profile ean cause discharge to occur higher

up deslope Bidrainage plantings in dryland areas

‘whereslts are sored inthe soil profile shoul focus

‘on recharge areas and thus prevent the development

of sane seeps further down the slope Innon-sline

areas, recharge plantings cold result in the drving-

‘up of springs of wells futher down the slope ad

thus have negative socal impacts

hat bdr, oe does i wor

Ân relatively fat irrigation areas, recharge: discharge interactions are offen Tess ele, On the same land unit recharge sonar immediatly ater Snrgaton can rm ino & discharge situation at the end ofthe itgation cycle when vegetation starts to tap te shallow water table

The planning scale of biodrsinage plantings depends on large numberof factors, Where fara holdings aresinal, obously landholders are unable

fo set part of their farm aside for biodrainage activities Therefore any application of this technique will have 6 focus on public land Where farms are large, landholders might be able 10 Inegratebiodruinage plantings in thee farm layout

‘Where lage-scale recharge plantings ae pla ned, cos-shanng arrangements might have to be developed to asure that (par of he implements tion costs af the works are eerie’ by the bene ficiarcs fy Australi, where regional tee-planting activities are widely supported by volunteer sonmmanity groups, there have been examples of saltatfeete ination farmers in the bottom-end of catchments actively participating in tee planting activities inthe top-end of tie extchment, or more Kilomeres tay

mà are now Being considered in icrigation areas, especially 10 use poor-quality drainage water Simi othe small-scale scenario described above, the socio-economic impact of the intreduetion of large-scale plantations ean be ether positive (new industry offering employment) ornepatve(spional restructuring with industy buying out small farses ain causing social change)

Biodraiage: principles, experiences and applications 29

Chapter 4

Synthesis of recent biodrainage

The status of biodrainaye related research is

presented inthis chapter by country of origin

4 Aosaia

‘Much ofthe information inthe first section of this

chapter is based on papers presented in special

issue ofthe Dnernational Journal for Agricultural

ater Management, whieh focused on Australian

work in this area (Thorburn, 1999),

‘Areas with shallow saline water tables in

Australia have been rapidly expanding in response

to widespread agricultural development over the past

100 years (Robertson, 1996), Ia response to this

alarming tend, Regional Management Plans have

been developed over the past 10-20 yeas for many

areas around the country, both for dryland and

inrigated areas

The processes of interaction between vegetation

and soil water are dificult © quantify; soils are not

uniform, water fuxes are often smal, vegetation is

often perennial and trends in soil and plant

Parameters are affected by seasonal variability In

addition, work in this area covers a range of

disciplines including agronomy, hydofogy soil

science and forests, however communication

between the specialists working in these feds is

‘often lacking,

‘Much of the work descried in this section is

related to trees, either in natural stands or in

plantations few examples of other crops such as

lucerne (Medicago sativa) and saltbush (Atriplex

spp.) are presented Research will e discussed

under the headings ‘dryland’ and irgation’

Dryland seenarios

Dryland salinity resulting from ever-elearing, has

‘only been recognized in Australia since the late

seventies Average accessions to the water table in

wetter parts of Australia (rainfall > 750 mm/year)

have increased from <5 mmear to >20 mm year

following clearing; in drier regions deep drainage

increased from <0.1 mmiyear 19 >10 mm/year

(George er al, 1997), Inthe Murray-Darling Basin

about 0.5 milion km’ of mative vegetation had been

related literature

totheremoval ofabout 12-15 thousand million trees (Dryland Salinity Management Working Group, 1993), In Western Australia the removal of about

50 percent of the perennial, deep-rooted native forests end woodlands over an area of some 20 million ha and its replacement with predominantly shallow-rooted annual erops and pastures has resulted in salinization of about 1.8 million ha of previously productive cropping land (Ferdowsian tal, 1996) Atthecurentrate of expansion, about 2-3 times this ares can be expected to become salt flected unless counteraction is aken to restore the hydrological recharge-discharge balance (George et

al, 1997),

‘Because of the large areas involved, the high costs of drainage engineering works and the relatively low returns from the agricultural production systems, management ofthe clesring- induced salinity problems is based on agronomic measures The objective is to move toa plant water use sbenario that more closely approximates that of the pre-clearance situation (Dryland Salinity Management Working Group, 1992) This could involve a range of plans, including deep-rooted Permanent pastures crops and trees

‘The question of where o plant tes fr control

of dryland salinity” is addressed by Strzaker et al (1999) The paper presents simple rules and analytical expressions to optimize the number and location of trees required 19 control rising water tables on relatively flat cropping or pasture hind, Deep water table often recharge areas) George eta (1999) analysed data from some 80 sites in the medium-rainfll ($50-700 mmyear) southwest of Wester Austria, for which data were collated to asess the impact of ees on water table They distinguished berwoen discharge and recharge areas withthe late, being higher inthe landscape, generally having deeper water tables Only two Satistcally valid relationships were found: (1) significant lowering of groundwater tables were highly correlated tothe area of revegetation and (2) only the proportion planted (%) was necessary as

an explatatory variable for water table response

a0

Both proportion plant and “age of the ees were

ede to explain the rate of water table response

“The papor also concluded that ees ae best planted

insecharge areas for fongsterin hydrolopcal benefits

and that extensive plantings, covering as much as

70-80 percent ofthe catchment is neoded i achieve

significant water table raductions

Strzake ral (1999) discuss the scenario where

the water tae is below the dep of tho re rons,

and distinguish “comperition zones” anal “capture

ones’ beeen tre plantings and suroundingerops

bor pastures fu the competition zone, tee 001s ard

trop roots compete for moisture: inthe epture zoe

the tees provide deep drainage tothe surrounding

cxops without competing est or moistre The

absolute maximum width of the capnite zone

depends on the tre Foot depsh and the fexture oF

‘he soil In coarse sads capture zones would be

Tess than I m wide, in lay soils they could be up to

3m wide The paper quotes Zohar (1988) who

‘measured roots up to 20m fram the trunk of

individual Euealyp ees Basen this igure about

ten trees per ssould potentially be enoueh lo

intercept recharge tothe water tale, ass that

tree waler use was high entgh,

‘Sharma {1984) found monthly evaposranspiea-

tion rates up 16 3 x Class A pan in Ewcalyp

‘dominated forest in Wester Australia daring rainy

winter periods He argued that diese high values

‘were the esll of canopy interception and direct

evaporation fom de leaf surface, During the os,

‘ry summer months much lowe evapownspiration

rales of0.1-0.5 Class A pan were found, rlesting

the lowe water asilaility during that pen

Shallow water table (often discharge areas)

‘Shallow water tables commonly are associated with

iseharge ares, they nay be also perched shales

water fables Thisisthe casein rechange areas where

‘hey are often shallow an elatively fresh, George

‘ra (1989) reposted that recharge sites planed over

perched local aquiters had better response dan

‘hose oerrogionl stems, tho ater penal having

deper wate ables Rss of tatsical analyses oF

theta oFtreeson water ables att sitesn discharge

areas were higly variable A significant coreation

‘between the proportion ofthe revegsttedcatmnt

potceatage and water table response was observed

For every 10 percent increase in planted ate, the

water table was Fsvered by about 0 m, Howexer,

the planted atea at most sites was less than

30 percent ofthe eatehment, so The toes had only

relatively small and localized effet

Shes of en hhahaiuge nued nga

George etal (1999) als reported that sites with

Jo stoundwate salinity shossed the greatest water Table response to tre planting in discharge areas Thorbum (1997) who hypothesized that tees are more c tables in lower salinity environments supports this The study

‘onchided that in dish areas water table con)

by wee planting might only bo a meslum-tesm Solution and tha imay Be more appropriate plant

fo reasons such as reducing the visual impact oF salinity and te risk of ewson

Strzaker et af, (1999) describe the use of wee belis grown over shallow water tables using the Dupuit-Forehheimer theory as developed for engineering apen-deans ¢Kiekham,D, 1957), They stole that for tree belt spacing intervals of 40 m considered t0 be the minimum for eropping situations) drainage values of upto 100 mm year ould be accomodated for soils ith a saturated conductivity of S mmiday Por well-srucmred clay subsoils and deep san they calculated that 4001 spacings would be feasible Wide tee bells woul

be needed to keep the water ble a sae levels balReay between the belts The problem of salt build-up athe capillary tringe above the water able

is also discussed in the paper The ase of Old Man Saltbush (41ripley -numnmdaria) wo eootrt sallow saline groundwater tables was described by Slavieh eal (1999) Saltbush has been widely planted on salt affected land in tsemi)and southeast Austatia, The study indicated that the transpiration ate of saltbush was very low (= 0.3 mum day) relative 1 the recharge Fate thoughout the monitoring period Up 4 bal the tanspration during the driest time of the year

«Maeh) was derived fam groundwater The authors

«concluded tat saltbush plantations are kelytohave

4 neglvible hydrological impact However the Abit of saltbush provide soi cover and produce Fixer on severely saltfected lad makes it am important erop in the management of dischange

‘Cramer eta (1999)deserbe three field studies

‘onthe aby of Casuarina slau and EueofNpfue ceanaldulemaix to use sallow saline groundwater They used naturally occurring isotope signatures oF soilwater, groundwater and toe xylem and spose measurements o determine tee water sources The studies concloded that C.glanew had a greater impact on groundwater discharge then

E camalulensis, panied at similar densities elaue sovreed moc of its water from the saturated groundter zone deeper in the prof

bi rama: prncples experiones a pico

while E, cumatdutensiseelied on the shallower

unsaturated zone (Soil water), the former thus

showing a greater potential © eonsunie saline

_roundvate,

Morris and Collopy (1999) compared E.camaldaensis and C.cunninghamiana fr tele

water use under shallow saline water table

conditions, using a water halance monitoring

approach Tei duy se wasin nonbem Visto,

Ausualia, wih an average annual afl of about

“480 mim and average Class A pan evaporation of

11350 mimiyt Evaporation eveceds rainfall inthe

area over nine months of the year between

September ang May Si Cramer al (199%,

they found thatthe Casuarina

adapted to the saline site conditions than the

Eucafypnus genus, however this depends on the

species The sll dynamics measured at hesite Were

‘complex; oil solution sani was measured using

Soil salinity sensors (Soi Moisture Equipment

Corporation, Sana Barbara, United States) at four

des down the profile (1, 2, 3 and 4 m) at wo

locations, The measurements showed large

fluctuations with sos! solution salinity in the

‘ootzone singor falling by 10 Sim over apetid

fof several months This suggested that capi re

stribution of salt as aking place inthe clay sil

However, the authors suggest thatthe sol slinity

sensor data might have to be interpreted with some

‘areas the sensors might only measure sais in

ain poresize range and wetting and dryin teyeles preferentially occur in te larger pores, The

authors also note the need for ang-team monitoring,

unr plantations to quantity fn slow fo

trends,

The use of lucemne (Medicago sativa) as a boodnsinage crop was svestigted by Zang ea

(1999), Luceme is a deep-rooted, relatively sal

tolerant eens thai believed abe ale to bath

rece recharge and use sallow groundwater They

used lsmeterso investigate capillary uplow fom

shullow water tables and the associated processes

fof salt accumulation, water use and growth

response Stable isotope techniques were used to

<etermin the components of wpfow resulting fom

the luceme plant cover Inthe presence ofa shallow

(1 mbelow surface) and saline (EC 16 dS) water

table, luseme did not appear to derive eh of is

‘water divey fom the water table, preferring to

use fresher water stredhighor up ine oil proie

‘Theauthors highlighted the prt hat over tine

cil slinities wil start to build wp, plan water use

will reduce, water bles will start t rise an salts

tw make the system sustainable ever the tong ter,

“Te ability of saltbush niptex ypp.)t0 provide water table control was investigates by Barcet {Leanard and Malcolm (1999) They looked at he soil profiles beneath sands of salbushes, growing

‘nastalow (0.1.21 saline water table ina plant spacing trial conducted in Western Australia at a

‘ite with average annual rainfall of 330 mmm, They Found a substantia inerease in soil chloride seenation beneath the plantings over the two

‘sear tial period The increases were ropontional

ta the saibash “Tea density" (weight per unit oil surface aca} and insersely proportional othe ital Concentration of corde the soil, They arg that

nity under

the inereases in sil and wer table

the planation wore a result of theuse of round

hy he plants, Tes also suggest tha the ower water table cou! oxide opportunities for salfowsrooted legumes toe establishod inthe saltbush stands Irrigation scenarion

Daring the 1980s, when salinity problems became more prevalent in the eastern irigation areas of Victoria te management plats deveinpd io contin the problem were based mainly on engineering approacies, such as groundwater pumpiog, sure sdsinage, channel sealing and system management insprovemen irigation efficiencies

In response to suggestions that vegetaion could riay an impontantroleinthe management o shallow water tables, a symposium in T991 đctssedl the role tees could play in the management of the salinity problem in rgation areas Two views were presen (1) es eopld be used to manage the shallow water tble‘alnty problem (Alexa, 1991) and (2) tees ean lower water tables to be Jong erm sustainable hey have tobe provided with asa bulance mechanism (drainage) to manage salt aceumulation i their otzone Heuperman, 1991) Although initially received! with some septicism bythe ores industry theater sie se widely accepted and the management of the salt aaceurmulation process fs becoming sn issue ol increasing interes and concern)

‘One ofthe earliest documtented abservations oF water table lowering neath ate plantation was recorded by Heuporman era (1984), A water table Crawdown of 24 m was moasufed in a seven-year old non-iiguted planting surrounded by iigated land with ushallow (2-8 mp water table The ators