Estimation of water quality trends in thua thien hue coastal zone, vietna

Intensification of agriculture and extension of aquaculture is increasing thepressure on the natural resources by introducing fertilizers, nutrients and pesticides into thesystemThis stu

~~~

M.Sc Thesis HE 164

April 2004

Nguyen Thi The Nguyen

Estimation of Water Quality Trends in Thua Thien-Hue Coastal Zone, Vietnam

UNESCO-IHE

This research is done for the partial fulfilment of requirements for the Master of Science degree at the

UNESCO-IRE Institute for Water Education, Delft, the Netherlands

Examination committee Prof Bela Petry (UNESCO-IHE), Chairman

Dr Randa M Hassan (UNESCO-IHE) Drs Mindert de Vdes (WL) Drs Robbert Misdorp (RIKZ)

Supervisors Drs Mindert de Vries (WL)

Dr Randa M Hassan (UNESCO-IHE) Drs Maarten Scheffers (RIKZ)

Master of Science Thesis

by Nguyen Thi The Nguyen

ESTIMATION OF WATER QUALITY TRENDS

IN THUA THIEN-HUE COASTAL ZONE, VIETNAM

The findings, interpretations and conclusions expressed in this study do neither necessarilyreflect the views of the UNESCO- IHE Institute for Water Education, nor of the individualmembers of the MSc committee, nor of their respective employers

The coastal zone of Thua Thien Hue encompasses 34% of its total area and about 81% of itspopulation are concentrated there It is largely dominated by the Tam Giang-Cau Hai lagoon,the biggest of its kind in Southeast Asia The socio-economic developments together withnatural disasters are causing pressures on the coastal zone in general and in the lagoon inparticular Intensification of agriculture and extension of aquaculture is increasing thepressure on the natural resources by introducing fertilizers, nutrients and pesticides into thesystem

This study focuses on quantification of the relationship between agriculture in the drainagebasin, aquaculture in the lagoon and the water quality of the coastal ecosystem Based onextensive literature research the use of fertilizers and some popular pesticides is estimated.Through mapping of historic and present spatial extension and analysis of future planning,the load of substances from agriculture and aquaculture to the lagoon system, are quantified.Implementation of a 2D hydrodynamic and water quality model allows the estimation ofhistoric, present and future concentrations of substances in the water of the lagoon It isconcluded that planned extension and intensification of agriculture and aquaculture will lead

to serious exceedance of internationally accepted water quality standards, indicatingoverexploitation over resources and increasing risk of serious problems with ecosystemfunctioning The study result shows promising potential to develop this tool for optimization

of land-use planning and for delivering relevant information to the policy-making process

ABSTRACT

UNESCO-IHE, Delft, The Netherlands

April 2004

Nguyen Thi The Nguyen

Thank you all!

Finally, I am grateful my parents and my brothers for their encouragement and for the way they overcome the difficulties during the time I was away.

I also wish to express my gratitude to all other members of UNESCO-IHE, especially the Department of Water Engineering, Prof Bela Petry, Ir Ronald de Heer and Ir Mick van der Wegenfor their academic guidance and thoughtful encouragement in everyday life I thank all Vietnamese, Dutch,foreign friends, and my colleagues at WLIDelft Hydraulics.

I am thankful to the Hanoi Water Resources University, especially Prof Dr Le Kim Truyen,

Dr Vu Minh Cat, Dr Do Tat Tuc, Dr Le Dinh Thanh, Mr Nguyen Van Bao, Mr Tu Van Hai and all my colleagues at Section of Chemistryfor supporting my study in many ways.

I would like to deeply acknowledge Drs Mindert de Vries,for his supervision, significant technical assistance and encouragement I wish to thank Mr Gerben Boot for his kindly help

on the modelling part during the time I worked at WL IDelft Hydraulics Greatly acknowledgement must be given to Assoc Dr Randa M Hassan for her constant support and encouragement during my studies in the Netherlands Moreover, my sincere thanks are extended to Drs Robbert Misdrop, Drs Maarten Scheffers, and Dr Joost Stronkhorst for their kind advices and support.

This work is completed with assistance of a number of people and organizations, all of whom

I gratefully acknowledge I would like to express my sincere thanks and appreciation to all people who directly or indirectly contribute to the complement of this study.

-lt)('.1~~lt)('.1 -Acknow ledgment

2.1.4 River system , 2-62.1.5 Soil 2-6

2.2.1 Demography 2-72.2.2 Economic sectors 2-7

2.2.4 Infrastructures 2-8

2.3 Water quality in the Thua Thien Hue lagoon 2-9

3 LITERATURE REVIEW AND DATA ANALISIS ON CHEMICAL USE AND LANDUSE INVIETNAM AND THUA THIEN HUE PROVINCE •• • • ••.• • • • • •

3.1.1 Introduction 3-1

3.1.1 Fertilizers 3-53.2 State of rice culture and aquaculture in Vietnam and TTH province 3-7

3.2.3 Rice culture and aquaculture in Thua Thien-Hue province 3-93.3 State of chemical used in Vietnam and Thua Thien-Hue province 3-10

1-11-21-31-41-41-6

2 DESCRIPTION OF THUA THIEN - HUE PROVINCE AND ITS COASTAL ZONE ••••

TABLE OF CONTENTS

Appendix 1- Lists of some allowable pesticides in Vietnam

Appendix 2 - Water quality monitoring records of CCP 2003

Appendix 3 - Waste load calculation

Appendix 4 - DEFLT3D-FLOW model

Appendix 5 - Model sensitivity analysis, calibration and results for future situations

Appendix 6 - Impacts of dam river construction and global warming on lagoon water quality

Appendix 7 - Total coliform bacteria simulation

APPENDICES

REFERENCES

4.4 Loss coefficients of selected substances to water bodies 4-4

4.6 Loads of selected substances according to administrative units 4-5

4.8 Loads and concentrations of selected substances into the lagoon 4-64.9 Estimation of the loss factors for agricultural loads using monitoring data 4-7

5 WATER QUALITY SIMULATION S • •.•• • •.• •.• • •

5.2.1 Grid outline and bathymetry 5-15.2.2 Boundary data 5-1

5.2.4 First order decay and dispersion coefficients 5-35.2.5 Setting other parameters 5-4

5.3 Sensitivity analysis and model calibration 5-5

5.3.1 Introduction to sensitive analysis and model calibration 5-55.3.2 Sensitive analysis and model calibration 5-5

6 MODEL RESULT INTERPRETATION AND WATER QUALITY ANALYSIS •

6.4.1 Ongoing monitoring program of CCP on water quality 6-9

6.4.3 Proposal for additional monitoring 6-11

3-l3

3-143-143-194-24-34-54-64-64-74-75-25-35-45-65-116-1

The lagoon geometric features of the Tam Giang-Cau Hai lagoon system

The lagoon geometric features of sand barriers

Meteorological data at A Luoi and Hue weather stations

Monthly average climatic data in Thua Thien-Hue delta

The flow characteristics of the rivers

Statistics of land uses in 2001 in Thua Thien-Hue

Partition coefficients of some typical pesticides

Expected expansion of the aquaculture area for the coming period

Number of pesticide species registered to use in Vietnam from 1991-1999

Statistic figures of insecticides, fungicides, and herbicides (Year 2000)

Pesticides imported and used, 1991-1999

The state of pesticide application on some crop plants in 1995

Pesticide using level in regions, 2000

Rice area, pesticide and fertilizer uses in some communes of Phu Loc district, 1996

Selected substances in agriculture and their input amounts

Rice and shrimp culture area according to administrative system (ha)

Distribution rates of loads (%)

Input loads from rice culture into the lagoon (kg/season)

Input loads from aquaculture into the lagoon

Average concentrations for agricultural waste load input into the lagoon

Nitrogen and phosphorous calculated and measured concentrations (mg/l)

Open sea boundary conditions - Tidal components

Open sea boundary conditions at the present situation

Decay rates of pesticide

Final calibrated coefficients

Input data for water quality scenarios

Water quality standards

4-84-94-9

5-25-75-75-75-85-85-85-95-95-105-106-26-26-26-36-36-36-36-56-56-56-76-76-7

Location of the study area

Flow chart for methodology and approach of the study

Administrative map of Thua Thien - Hue province

The tidal inlets in the Thua Thien Hue lagoon

Rice field

Shrimp pond in Phu Loc district

Rice, paddy production and cultivated area, 1992-2002

Aquaculture yield in Vietnam, 1991-2001 (tons)

Annual average yield of rice crops in Thua Thien-Hue

Shrimp culture in Tam Giang-Cau Hai lagoon area

Number of active ingredients registered for use in Vietnam from 1991-1999

Pesticides usage in Vietnam, 1991-2000

Farmer spraying rice field with insecticides

Fertilizer ratio used in 1998

Local fertilizer produced and foreign fertilizer imported, 1990-2000

Hydrological system in Thua Thien-Hue province

Rice area

Aquaculture area

Model schematization and boundary locations

Salinity simulation (Sal - 0/00) - Dry wet seasons

The change of salinity (Sal- 0/00) in Tam Giang-Cau Hai lagoon - Dry season

The change of salinity (Sal- 0/00) inTam Giang-Cau Hai lagoon - Wet season

Calculated TN and TP concentration for wet and dry seasons

Measured TKN concentration (mg/I) in Tam Giang - Cau Hai lagoon - Dry season

Measured TP concentration (mg/I) in Tam Giang - Cau Hai lagoon - Dry season

Measured TKN concentration (mg/I) in Tam Giang - Cau Hai lagoon - Wet season

Measured TP concentration (mg/I) in Tam Giang - Cau Hai lagoon - Wet season

Scenarios for water quality simulation without dam river & global warming effects

Scenarios for water quality simulation with dam river &global warming effects

The change of TN value with and without aquaculture load (mg/l)-Present dry season

The change ofTP value with and without aquaculture load (mg/l)-Present dry season

Contribution of agriculture and aquaculture loads into nutrient contents

The change of TN value (mgll) - Dry season

The change ofTP value (mg/I) - Dry season

The change of 'Total' pesticide value (ug/l) - Dry season

The change of Formalin value (ug/l) - Dry season

The change of TN value (mg/I) - Wet season

The change ofTPvalue (mg/I) - Wet season

The change of 'Total' pesticide value (ug/l) - Wet season

The change of TN value with and without aquaculture load (mg/l) - Future dry season

The change of TP value with and without aquaculture load (mg/I) - Future dry season

Areas exceeding standard values (ha) compared to US standard

Ministry of FisheryThe National Environment Agency (Vietnam)Ministry of Agriculture and Rural Development (Vietnam)Plant Protection Department (Vietnam)

Total nitrogenTotal phosphorus

Farmyard manureWorld BankADB

ABBREVIATIONS

4 Theo sl! phan tich sO'lic$uhic$nco, dic$ntich da"tcanh tac nong nghic$p co xu hudng giam

nhy, nhu'ng dic$ntich da"t sil' dl;lng trong nuoi tr6ng thllY san se tang mQt cach dang k€.Nong nghic$p va thllY san se dUQctham canh hoa nh~m ml;lc dich tang nang sua't va thunMp Hoa cha"t sil' dl;lng nong nghic$p va thllY san kha nhi~u va phong phu, nhu'ng ph§:nldn dUQc sil' dl;lng theo kinh nghic$m va chua tuan thii to't cac hUdng dftn khoa hQc Sosanh vdi mQt sO'trong vung (Nh~t, Han QuO'c va Thai Lan), IUQnghoa cha"t (phan bonhoa hQc, cha't dinh duong, thuO'c bao vc$thl!C v~t) sil' dl;lng hic$n ~i d Vic$t Nam khongcao Tuy nhien trong thai gian tdi, IUQnghoa cha"t sil' dl;lng se ldn hon do vic$ctham canhhoa tang nang sua't trong nong nghic$p va thii y san

Ke't qua nghien CUll

3 Luan van dU(1cthuc hien thong qua mot phuong phap nghien ctru Mthong, bao g6m 5budc: (1) Nghien cuu tai lieu co ban, (2) Thu tMp va phan tich sO'lic$u,(3) Tinh toan vaudc hrong hrong phan bon, cha't dinh dirdng va thuoc bao vc$thuc v~t thai vao vung d§:mpha, (4) Thanh l~p so d6 toan va me phong cha't IUQng nudc b~ng chuong trlnhDELFT3D-FLOW, va (5) Phan tich ke't qua mo hlnh phan doan di€n bie'n cha't IUQngnudc va d~ ra mQt sO'kie'n nght

Phuong pha p nghien CUll

2 Muc tieu chinh cua luan van nay la phan tich va dinh hrong mO'i quan M giii'a viec sil'dung da't trong nong nghiep va thiiy san de'n cha't hrong mrdc vung d§:m pha Tam Giang

- C§:u HaL Luan van dii danh gia, tinh toan hrong hoa cha"t thai vao vung d§:m pha Xu

hirong ciia cha't luong mroc trong vung cling duoc mo phong va nnh toano Tit do, lu~n

van dua ra mot sO'kien nghi cho chirong trlnh quan tr~c cha"t hrong nude trong thai giantdi, cling nhu nhii'ng thong tin c§:nthie't cho viec quan 19.

M\lC tieu nghien CUll

1 Thira Thien Hue' la mot tinh mi~n Trung Viet Nam, n~m each tM do Ha NQi 660 km vaeach Thanh phd H6 'Chi Minh 1060 km Vung duyen hili Thira Thien Hue' chiem 34%dien tich va 81% dan sO'toan tlnh, bao g6m vung d§:m pha Tam Giang - ch HaL He

thdng d§:m pha nay la mQtMthong phuc tap, d~ bien d5i va nhay cam vdi stf bien d5icua moi tnrong E>§:mpha Tam Giang - C§:u Hai la mot h~ sinh thai da dang, dQc dao covai tro quan trong trong viec phat tri€n kinh te' xii hQi cua tinh, Tuy nhien, Mthdng d§:mpha nay (cling nhu toan bQ vung duyen hai) dang dung tnrdc cac nguy co de doa, catrong hien tai va nrong IaL Nhii'ng nguy co do la: Khai thac qua mire cac tai nguyen thiiysinh, thieu quy hoach phil hop cho viec sit dung da"t,0 nhiern ngudn mroc, Ili Iut nghiemtrong, chuyen dich cac cita d§:m va xoi Id bo bi€n, mau thu~n trong viec sil' dung tainguyen da't - nude giii'a cac bQ phan kinh te'

Gidi thieu chung

TOM TAT (EXECUTIVE SUMMARY)

Dien bien chit ilf(fng nude trongtuangiai:

• Ke't qua tinh toan ciia mo hinh chi ra rang h~ thong dffm pha se bi 0 nhiem cha't dinhdudng mot each nghiern trong trong mua kho, vdi ngudn 0 nhiern chinh la cha't thai

tu nuoi trong thiiy san Khoang 90% dien tich dffm pha co nguy cdbi 0 nhi~m (sovoi tieu chu~n hi~n hanh cua Hoa Ky va Nh~t Ban) Cac vuong, ao tOm la ndi bi 0nhi~m n~ng n~ nha't Nhln t6ng th€ ciih~ thong, ham lU<;1ngc\l'c d9i cua Nitd va Ph6tpho dU<;1Cghi nh~n t~i pha Tam Giang va d§m C§u Hai, trong khi do d§m ThanhLam co gia tr!trung blnh cao nhfft N6ng dQ cha't dinh duong trong mua mtta trentoan h~ th6ng cling ra't cao

• Ke't qua tinh toan cua mo hinh cling chi ra rAng, phan bO'cua du IU<;1ngthuO'c BVTVtrong tUdng lai cling tudng tt;lnhu hi~n t9i ThuO'c BVTV dung trong nong nghi~p bixem la vi ph9m tieu chu~n cua Vi~t Nam Gia tr!0 nhi~m cao nha't du<;1Cghi nMn ~ivung cii'a song trong mua kho song trong mua mtta, di~n tich 0 nghi~m se Ion hdn sovoi mua khO Tuy ham IU<;1ngformalin v~n nha hdn so voi tieu chu~n cua WHO,nhu'ng khoang 50% di~n tich d§m pha se bi anh huO'ng cua formalin va mQt vai loaithuy sinh co th~ bi tieu di~t

• Nhln chung, d§m C§u Hai va pha Tam Giang bi 0 nhi~m bai cha't dinh du6ng vathuoc BVTV trong ca mua mua va mua kho B§m Thanh Lam bi 0 nhi~m cha't dinhdu'ong trong mua kho va 0 nhiem thuO'c BVTV trong mua mu'a Trong mua kho, d§mThuy Tu bi 0 nhi~m cha't dinh du'ong, trong khi do ham 1u'<;1ngthuO'c BVTV khongvu<;1tqua gia tr!tieu chu~n

• Bffm Cffu Hai va Thanh Lam bi anh hUdng nhi~u bai di~u ki~n bien ngoai bi~n,thong qua cii'a Tu Hi~n va Thu~n An Vi the', cac h09t dQng kinh te' cua cac vung Ianc~n h~ thong d§m pha cling co anh huO'ng nha't dinh de'n cha't IU<;1ngnuoc cua Mth6ng d§m pha

Dien bien chit Iuang nude hien tsi:

• Vung d§m pha dang bi 0 nhiem nhe bO'i cha't dinh duong (Nito va phot pho) trong

mira kho Khu vue bi 0 nhiern nang n~ nhft la tai cila song va nhii'ng vung nuoitr6ng thiiy san Cha't thai nong nghiep la ngudn gay 0 nhiern chinh,

• Du IU<;1ngthuoc bao v~ tlnrc v~t (BVTV) dung trong nong nghiep diroc xem Ia cha'pnhan du<;1cdoi vdi nuoi tr6ng thiiy san trong vung d§m pha Dir hrong cao thuocBVTV voi ham IU<;1ngcao dU<;1Cghi nhan tai vung cira song Thuoc BVTV t~p chungchii ye'u 0'cii'a song trong mua kho, nhung trong mua rmra chting Ian rQng va co mat

0' h§u he't h~ thong dffm pha, d~c biet la a pha Tam Giang va d§m C§u Hai Hamhrong formalin kha nho so vdi tieu chuan cho mrdc sinh hoat cua WHO, tuy nhien susii' dung formalin lam nhiem d9CMsinh thai mroc quanh vung nuoi tr6ng thiiy san

6 Cha't IU<;1ngmrdc trong vung nghien cttu du<;1cmo phong bang chirong trlnh FLOW Nhln chung, ~e't qua mo phong ttl mo hlnh (v~ n6ng dQ cha't va s11phan bO'cha't)kha phu hop vdi so lieu thuc do cua du an CCP trong nam 2002 va 2003 Sii' phan tichcac ke't qua mo phong da dua ra dU<;1Cmot so ke't luan nhir sau:

DELFT3D-5 T6ng hrong thai tu nong nghiep va thiiy san du<;1ctinh toan vdi S\l'tham khao so lieu ciia

BQ Nong nghiep va Phat tri~n Nong then va nhieu tai lieu khac, Ke't qua tinh toan chotha'y rang, ngoai cha't thai tu hoat d9ng nong nghiep, cha't thai sinh hoat co th~ anhhuang mot ph§n de'n cha't IU<;1ngnude, d~c biet la cha't IU<;1ngmrdc song

10 Kie'n nghi v8 nghien ctrueha't hrong mrdc

• Trong nghien ctiu nay, hai ngudn 0 nhiern chinh (tai hrong thai tu nong nghiep vathuy san) du'<jetinh toan va phan tich Tuy nhien, eha't thai sinh hoat cling dong vaitro quan trong va cftn duoc dua vao trong cac nghien ciru sau nay

• Hien nay, tai lieu v8 du hrong thuoc BVTV trong vung nghien ciiu hftu nhir khong

co Trong khi do, loai 0 nhiern nay co anh hirdng ra't IOn de"n con nguoi va moitnrong Trong thai gian tdi, 0 nhiern hoa cha't BVTV eftn phai diroc xern xet, d~e biet

la hoa eha't BVTV trong thiiy san

• Cac nghien ciiu phai d\l' bao va danh gia du<je s1;fthay d6i ciia eha't hrong nude ungvoi stf bie'n d6i co th€ co trong tudng lai eua Mth6ng (Vi d\l: Thay d6i v8 su d\lngda't, thay d6i hlnh thai song va yen bi€n, thay d6i di8u ki~n bien h~ th6ng bdi hi~uung nha kinh lam trai da't nong len )

• Nghien euu nay eho tha'y rhg rno hlnh toan la m9t eong e\l hii'u ich trong vi~c danhgia va phan tich cae di~n bie'n moi tru'ang trong tudng lai Ben e~nh do, mo hlnhtoan co th€ eung ea'p nhung thong tin cftn thie't eho vi~e ho~eh djnh cae ehinh saeh.Vi~e thie't l~p rn9t mo hlnh toan mo phOng dung eha't 1u'<;1ngnuoe khu v1;fedftm phaTam Giang - Cftu Hai la di8u ra't eftn thie't Mo hlnh nay se dong vai tro tf\l e9t trongvi~e phan tieh, danh gia va giam sat eha't lu<jng nuoe eua toan b9 h~ th6ng S6li~uthtfe do cftn phai dfty du nbarn bao dam stf ehinh xae eua rno hlnh

9 Kie'n nghi v8 quan trac eha't hrong nude va thu tMp s6li~u

• Cftn thie't thirc hien chuong trlnh quan trac moi tnrong cho toan b9 vung duyen haiThira Thien Hue' Co sd ciia chirong trlnh nay d§ diroc nghien ciiu bdi Pham H6ngNga (2003)

• £>6i voi va'n d8 eha't hrong nude, cftn co s\l' thong ke h~ thong v8 chung loai, li8uhrong, thai gian va phuong pha p sil' dung cac hoa chdt BVTV su dung trong nongnghiep va thiiy san Du hrong thuoc BVTV trong mroc cftn phai diroc quan trae trongthai gian tdi

Kie'n nghi

8 Hirdngtiepcan ciia lu~n van nay co th~ eung ea'p nhieu thong tin eho cong tac quan 19b8n virng vung ba Nhimg thong tin do la: Tai hrong thai lien quan tdi viec sil' dung, tacd9ng ciia quy hoach de'n eha't lirong vung dftrn pha, nhtrng vung nhay cam, rmrc d9 sudung cue dai tai nguyen vimg dftm pha

7 Ke't qua mo phong di~n bie'n cha't hrong nude cho tha'y rhg trong thai gian tdi, cha't dinh dirdng nen du'<jc t~p chung quan trdc quanh vung nuoi tr6ng thuy san vao mua kho Du hrong thuoc BVTV cftn du'<jcdo tai vung cua song trong thai vu nong nghiep, d~c biet

vao mua rmra,

The coastal zone of Thua Thien Hue encompasses 34% of its total area and about 81% of itspopulation are concentrated there Itis largely dominated by the Tam Giang-Cau Hai lagoon; thebiggest of it's kind in Southeast Asia The lagoon does not only affect the socio-economicdevelopment, but also plays a very important function in coastal ecology and environment of thearea In 1997, a proposal to establish a national wetland protected area at Tam Giang-Cau Hai wasprepared The total area of the wetland protected area defined in this proposal was 4,189 ha,comprising a core zone of 1,286haand a buffer zone of2,921 ha In 1998, Thua Thien Hue lagoon

Figure 1.1 Location of the study area

Thua Thien Hue is located at the latitudes 16°14'- 16°15' North, longitudes 107°02' - 108°11' East

Itis 127 km long and 60 km wide on average, with mountains and forests accounting for up to 70%

of the natural land Some of the main rivers are Huong, Bo, Truoi and 0 Lau, running eastwardacross the province Geographically, Thua Thien Hue borders Quang Tri Province to the North, DaNang City to the South, with Laos P.D.R., separated by the Truong Son range, to the West, and over

120 km of seacoast to the East (Figure 1.1) Thua Thien Hue Province covers a natural area of 5,009km',and has a population of 1,091,000 in 2002 - accounting for 1.5% of the land and 1.4% of thenational population respectively

1.1 Brief description of study area

Chapter 1:Introduction

of biodiversity In the ICZM Strategy Report elaborated by IT-Hue People's Committee in 2002,the most emerging threats and constrains that limit the sustainable development of the provincehave been clearly addressed (Nga P.H, 2003) One of the most emerging threats is environmentalquality degradation in the lagoon and nearshore zone, especially due to receiving of pollution from

Generally, there are three types of communities living around the lagoon - farming, fishing andaquaculturing Conflicts in demands for the use of space and natural resources arise betweendifferent users In Thua Thien Hue province agriculture is the main production activity and it will beintensively farmed Over the last decade, fishing capabilities have rapidly increased in term ofnumber of boats as well as each boat capacity Aquaculture has become a priority of the provincialgovernment, especially shrimp farming Recently, shrimp culture has increased significantly Itistriggered by economic demand of the Thua Thien - Hue Province and has improved the livingconditions of many villagers (Nam D, Thu L.V, 2002) The creation of fish and shrimp pondsaffects protective spawning grounds for lagoon and sea species and causes disturbance of thenatural hydrodynamic functioning of the lagoon wet land Therefore, sustainable developmentplanning should be of concern to reduce the impacts on resources in the coastal zone

The Tam Giang-Cau Hai lagoon system is considered as the biggest lagoon in Southeast Asia,which has an area of 220 km2 stretching about 70 km Approximately 300,000 inhabitants from 31communes live around the lagoon in 236 villages and earn their living by directly or indirectlyexploiting natural resources in and around the lagoon The growing urban population of Hue isexerting more and more pressure on the lagoon system, through increased agriculture, aquaculture,fishing, transportation, and cargo handling, in a limited and confined area Moreover, the lagoon isstrongly influenced by both marine and freshwater inflows Most rivers in the province flow into it,but discharges into the sea with only two tidal inlets along the entire length of70 km, leading floods

in rainy seasons The lagoon is a dynamic and sensitive environmental system ruled by a complex set ofinteracting components, which are controlled by dynamic processes varying in time and space Shiftinginlets and coastal erosion have been dramatic recently Hence, there are difficulties to manage such acomplex system for sustainable use and development (Nam D., ThuL.V., 2002).

1.2 Problem analysis

was included on a list of the 16 proposed marine protected areas compiled by Ministry of Science,Technology and the Environment On this list, the area of the proposed marine protected area wasgiven as 24,876 ha ADB (1999) has proposed to establish a marine protected area at Tam Giang-Cau Hai, comprising entirely of the marine component In 1999, Thua Thien Hue ProvincialDepartment of Science, Technology and the Environment nominated the Tam Giang-Cau Hailagoon complex as a Ramsar Site

Chapter 1: Introduction

In the framework of the CCP2002, an initial monitoring program on biodiversity, water quality andcoastal dynamics has been conducted since August 2002 This monitoring program is a great helpfor ICZM However, effects of pesticides on water quality have not been considered yet At the

The Coastal Co-operativeProgram(CCP) 2002 is an extra-supportto the VN-ICZM project Itis mainlyfocusedon strengtheningthe ICZM activitiesthe Thua Thien-Hue province.The CCP2002tasks focus on(i) Awareness rising,(ii) Remote sensing as a management tool, (iii) Monitoring lagoon environmentquality and coastal hydraulics, and (iv) Development a GIS water balance(STREAM), being a usefulinputto the VN-ICZMLagoonmodel

On the basis of the VVP project documents and discussions, recommendation for the long termICZM Program were formulated, leading to the Vietnam Netherlands (VN)-ICZM project 2000-

2003 Through the VN-ICZM project, the concept ofICZM was officially and fully introduced inVietnam The project operated both at a national level in Hanoi and at provincial level in VN-ICZMpilot provincesNam Dinh, TTHue and Ba Ria Vung Tau It focused on strengtheninginstitutionalframesfor ICZM, awarenessraising,transparent data managementand data accessibility,and produced nationaland provincialICZM Strategiesand Action Plans (MisdorpR et al, 2002)

In response to a request from the Director General of the Hydrometeorological Service of Vietnam

1992, the Project "Vietnam Vulnerability Assessment and First Steps Toward Integrated CoastalZone Management (VVA Project)" was conducted in Vietnam from 1994-1996 by joint Vietnamese

- Polish - Dutch team, sponsored by the Netherlands Ministry of Foreign Affairs As a part of thisproject, the first steps towards ICZM in Vietnam were conducted by setting up an initial database,developing and implementing tools for database management and (GIS) presentation and trainingstaff in dealing with these matters

Integrated Coastal Zone Management (ICZM) is a cycle process for achieving sustainabledevelopment of the coastal zone resources.Inother words, the purpose of ICZM is to maximize thebenefits provided by the coastal zone and to minimize the conflicts and harmful effects of activitiesupon each other, on resources and on the environment (FAa, 1998) In Vietnam, several initiativeshave been taken in order to ensure sustainability of its coastal resources

1.3 Background on Integrated Coastal Zone Management in Vietnam

In conclusion, the problems arising in the Thua Thien - Hue coastal zone are serious floodingevents, shifting lagoon inlets and coastal erosion, land - water use conflicts, and water pollution.The main objective of the study is to investigate the water quality problem with special emphasis onnutrients (nitrogen and phosphorus) and toxic chemicals (pesticides) The study gives an overview

of landuse impacts on the lagoon water quality This is done by estimating/predicting input wasteloads from agriculture and aquaculture into the lagoon, and modeling water quality The result ofthis study will, therefore, contribute to water pollution control and ICZM of the Thua Thien Hueprovince Moreover, the model application, which provides a preliminary analysis for the impacts ofdifferent landuse scenarios on the water quality in the study, can be considered as an ICZM tool ifimproved with relevant data

inland Waste loads from agriculture and aquaculture becomes an increasing issue of concern for theThua Thien-Hue coastal zone and requires studies and regular monitoring Until now the extent ofsuch pollution has not been documented

Chapter J: Introduction

• Defme the real problems in the study area and the objectives of MSc study to solve theproblems

Data collection and analysis

• Collect data on the use of chemicals in aquaculture and rice-culture in Vietnam andThua Thien-Hue province;

• Collect data on the area of rice-culture and aquaculture in Thua Thien-Hue;

• Use available Internet sources of comparable land uses to estimate missing data forselected substances;

• Analyze the data to get a first and global insight on the type, quantity and season ofuses of chemicals in aquaculture and agriculture in the Vietnamese situation

Problem definition and objectives

• Review literatures related to chemicals used in aquaculture and agriculture, water qualitymodelling, and management

Literature Review

In order to achieve the objectives of the study, a systematic methodology is proposed as illutrated

in figure 1.2 and decrised below:

• to provide relevant information for management

• to propose recommendations for additional monitoring to Thua Thien - Hue province;

• to estimate the water quality trends in the lagoon due to changed intensity of agricultureand aquaculture;

• to estimate the use of pesticides, fertilizers, nutrients in aquaculture and agriculture thatinfluence the water quality in Thua Thien - Hue lagoon;

The objectives of this study are:

1.4 Objectives of study

November Workshop CCP2002, CCP activities for the following years were proposed A number ofthe suggestions indicated the necessary of making an inventory on the type and amount of pesticidesused in Thua Thien-Hue and to develop a first 2D coastal hydrodynamic and water quality models(MisdorpR.et al, 2002) The present study focuses on these issues

Chapter I: Introduction

Figure 1.2 Flow chart for methodology and approach of the study

Development of the mathematical model inDELFT3D-FLOW to simulate water quality

Estimation of waste loads

Development of a mathematical model for water quality

• Prepare an input dataset for the water quality model that links land-use to quantities ofused fertilizers and pesticides and calculate the total amounts of pollution produced.Select the locations where the pollution load enters the lagoon;

• Extend the Delft3D model, which has already been developed for the Thua Thien Huelagoon, to simulate and estimate water quality trends

Estimation of input waste loads into the lagoon

• Select a few most heavily used and best known substances for further study;

• Establish trends and reference values of selected substances that can be used formodeling water quality in Thua Thien Hue lagoon on the basis of educated guesses offuture land-use or of changed use of selected substances Find reference values onallowable concentrations in literature;

• Calculate total loads and concentrations

Chapter 1: Introduction

Introductions to projects and program on ICZM in Vietnam, objectives and general outline of thestudy approach are presented in Chapter 1 followed by a brief description of the study area inChapter 2 In Chapter 3, a description and analysis are given to pesticides, fertilizers usedVietnamese agriculture and aquaculture as well as in Thua Thien Hue province based on availableinformation In Chapter 4, some pesticides and fertilizers are chosen for water quality modelling inthe lagoon and their loads are estimated A mathematical modelling approach including adescription of the model set-up, extension, calibration and sensitivity analysis is presented inChapter 5 In addition, several scenarios related to different landuse situations and waste loads aresimulated The results of the model simulations are discussed in Chapter 6 The last chapter,Chapter 7, includes conclusions and recommendations

1.6 Outline of the report

• Analysis of present situation in relation to distribution of selected substances in wetand dry seasons;

• Analysis of calculated water quality in relation to applied standards;

• Analysis of future trends on the basis of predicted intensity of aquaculture andagriculture;

• Proposal of future monitoring locations, monitoring period and selection of substancesResult analysis/interpretation by using Excel spreadsheet and GIS-Acrview

Chapter 1: Introduction

Ingeneral, the largest lagoon is Cau Hai, in the southeast of the site This lagoon is connected to thesea via the Tu Hien inlet The other three lagoons are not directly connected to the sea Tam Giangand Thanh Lam lagoons, which open into the Huong River, flows into the sea via the Thuan Anchannel The water body (lagoons) is separated from the sea by a large sand dune system.

(Source: Cu, 1995; Hoi, 2001 as cited in Lam N.T, 2002)

1121.2

1011

362

24

Thuy Tu lagoon

16.2

1.5Thanh Lam lagoon

Cau Hai lagoon

Table 2.1 The lagoon geometric features of the Tam Giang-Cau Hai lagoon system

With a length of nearly 70 km, the water body system of the Tam Giang - Cau Hai lagoon spreadsover an area of 220km'.The average volume of this system is 300 million m' However in case offlood water discharging into the system the volume can increase to over 400 million m3•There arefour different components in this system, namely: Tam Giang, Thanh Lam, Thuy Tu and Cau Hai(figure 2.2) Based on some studies on Thua Thien-Hue and its coastal zone, a brief description ofthe lagoon geometric features is summarized below:

2.1.2.1 The waterbody

The Tam Giang-Cau Hai lagoon system includes series of coastal lagoons, located to the North andEast of Hue city The lagoon complex occupies 4.3% of Thua Thien Hue province area and 17% ofthe province plain area This system can be divided into four structural morphology types: (1) waterbody (lagoons), (2) sand barriers dunes, (3) inlet, and (4) inland lagoon banks

2.1.2 The structure of the Tam Giang-Can Hal lagoon system

Thua Thien Hue province is located in central part of Vietnam The province is 128km in lengthand 60 km in width on the average The topography consists of forests, mountains, hills, coastalplains, lagoons and seas, etc The features show a gradual variation from west to east Westwardsare hills and mountains with the highest point around 1600m, occupying about 70% of the naturalarea, and next are the basins of Huong, Bo, Truoi, 0 Lau rivers To the east the dominantgeographical feature of the coastal area is the large group of lagoons that lie behind the coastal sanddunes (Figure 2.1)

2.1.1 Thna Thien-Hue province topography

2.1 Natural conditions

Chapter 2:Description ofThua Thien Hue province and its coastal zone

::$

::

E-c (+ j

0 p

~

N

~,

The existence of the lagoon depends mainly on the sand barrier and dune system (Tung T.T., 2001).The sand barriers comprise sand dunes, sand bars and beaches with a total length of 102 km fromCua Viet to Loc Thuy inlet The maximum height of this system is 30m at An Loc and Dong Ha.The sand barriers can be divided into four parts as follows:

2.1.23 Sand barriers and dune

Figure 2.2 The tidal inlets in the Thua Thien Hue lagoon

According to Cu N.D (1996) and Thanh T.D (2000) as cited in Lam (2002), the Thua Thien Huelagoon system has two tidal inlets namely Tu Hien and Thuan An Before 1404 the system had only

Tu Hien inlet Thuan An inlet was opened in 1404 and became the main tidal inlet Under action ofwaves, littoral drifts and river flows, the Tu Hien inlet has been regularly changing to amorphological cycle This inlet has gradually declined since one more inlet had been opened Themain inlet, Thuan An, is rather dynamic and changeable It has been located at different placesfrom Hoa Duan, Tan My, Thai Duong Ha and Thuan An with different moments and differentnames The distance between Tu Hien and Thuan An inlet is 40 Ian A brief description of theseinletsisshown in figure 2.2

2.1.2.2 Tidalinlets

Chapter 2: Description of Thua Thien Hue province and its coastal zone

• Precipitation: Due to the effects of the monsoons and topographic conditions, Thua Hue province has the highest amount of rainfall in the country The rainfall regime sharplychanges from wet to dry seasons The monthly average rainfall can vary from 50mm inMarch to 740mm in October The amount of rainfall in the wet season holds 70-80% of theannual rainfall The annual rainfall in the mountains and hilly areas is 3000-4000mmlyear

Thien-In Thua Thien-Hue coastal zone, this value is 2500-3000mmlyear (Tuan N.D., et aI, 2002)

• Temperature: The average annual temperature in Thua Thien-Hue province ranges from

24 to 25°C Winter is cold and humid, due to northeasterly winds In the highlands (over400-500m), average winter temperatures drop below 20°C and during December andJanuary the average temperatures can drop below 10°C In contrasts, summers experiencehot and dry westerly winds The average temperature is over 25°C from May to August Thehottest months of the year are usually June and July, with the temperature of 29°C Peaktemperatures can reach 39-40oC (Trai L.T et aI, 2001)

• Solar radiation: The solar radiation in Thua Thien-Hue province varies from 120-140kcal/cnr' The maximum and minimum solar radiation ever observed are 15.58 kcal/cm' (inMay) and 6.12 kcal/cnr' (in December) respectively (An Q.N at el, 1996)

Vietnam's central region is characterized by distinct tropical wet and dry seasons, variable winterand summer temperatures, and eastern tropical monsoons The influence of the eastern monsoon incentral Vietnam is experienced during the months of September and October, slightly later than innorthern Vietnam

2.1.3 General climate

The inland banks of the Thua Thien Hue lagoon have a total length of 183 km, of which granite andgabbros occupy 23 km, including tidal alluvia (2-3m high) and coastal shore alluvia (4-6m high)(Tung T.T., 2001)

2.1.2.4 Inland banks

The shoreline in front of the sand barrier system is 102 km long extending from Cua Viet rivermouth to the cape of Chan May Tay The beaches are mainly formed by cross-shore sedimenttransport (Lam N.T., 2002) Within the first 5 m the beach has a gentle slope, but from 10 m to 15

m the slope is quite steep The distance of the 10-m depth contour to the shoreline is 1.2-1.5 km,

(Source: Lam N T, 2002)

2 - 2.53

2.50.3

From Thuan An to Linh Thai

4.560

22

From Linh Thai to Tu Hien

1037

From Tu Hien to Loc Thuy

Table 2.2 The lagoon geometric features of sand barriers

Chapter2:Description of Thua Thien Hue province and its coastal zone

(Source: Trai L.T et al, 2001)

Table 2.3 Meteorological data at A Luoi and Hue weather stations

Meteorological data from A Luoi and Hue weather stations indicating the climate on themountainous and delta areas are shown in table 2.3 The average meteorological data in ThuaThien-Hue delta is the summarized in table 2.4

• Wind: Thua Thien-Hue province is affected by monsoon systems From May to August

there are SW monsoon with an average speed of 1.4-1.5mJs and an occurrence of 65% The

occurrence of SE wind is about 35% From September to April the dominant winds are NE(70%) and NW (30%) TheNE monsoon has average speed of 1.8-1.9m1s and maximum

speed of 40mls

• Evaporation: The average evaporation of the study area is 1011mm (An Q.N at el, 1996).High monthly evaporation occurs in June, July and August with values such as 138mm,149mm, and 133mm respectively Lowest monthly evaporation is 43mm in November,December and January

• Humidity: Relative humidity for the area averages between 85-88% During the rainyseason (December, January, and February), relative humidity is about 90% Minimumrelative humidity during the hottest months (June, July, August) is around 72%

The very high rainfalls in the wet season usually cause floods and inundation in the coastalplain There was an extremely serious flood even in the area in 1999 However, the areaalso has experienced draughts and salt intrusion during dry seasons

Chapter 2: Description ofThua Thien Hue province and its coastal zone

The Thua Thien-Hue province has typical soil characteristics as described below:

• Mountains and hills: yellow and red alpine humus and feralite soils developed onsedimentary rock with rude soil composition, or yellow and red alpine humus on effusiveacid rock

• Basins and river washes: river and stream alluvium

• Beach: sand with particle size from 0.05 to 2 mm

Table 2.5 The flow characteristics of the rivers

As a result of the uneven rainfall distribution, the flows of the rivers sharply change each year Theflow is rather high in the flood season and holds 70% or more of the yearly flow The flow data ofthe rivers at some gauging stations are listed in table 2.5

The river system in the area includes Truoi River, Nong River, Cau Hai River, Dai Giang River,Huong River, and 0 Lau River Almost all rivers originate from mountainous area inside ThuaThien-Hue province at an elevation of 200m and discharge into the lagoon The total catchment ofthe rivers is about 4000km2 of which the Huong River with three tributaries occupies 75% of thetotal catchment The riverbeds are quite steep with slopes ranging from 20 to 29%

2.1.4 River system

(Source: An Q.N at el, 1996; Tuan N.D et al, 2001)

Met~.rol.,giealdata • Jail . F~b · ·· ·.- l uar • Apr > > . l U?IJ'. 'I • ~UI ;;,; • , •• I • Jill A'UI·.·•·•·iSep • > • • ' N()~ > /

Mean temperature (0C) 20.1 20.2 23.0 25.8 28.1 29.4 29.5 29.1 27.1 25.1 22.8 20.8

Table 2.4 Monthly average climatic data in Thua Thien-Hue delta

Chapter 2: Description ofThua Thien Hue province and its coastal zone

Agriculture is the leading economic sector in Thua Thien-Hue but the yield is low and unstable, due

to the effects of natural condition (flood, drought, salt intrusion ) In 2000, agriculture and forestrymade up 17% of gross provincial output (ICEM, 2003) The annual average rice yield recently was0.39 tonlha or about 22,000 ton/year For the last few years, fisheries and aquaculture have becomeone of the most important contributions to the province budget (Nga P.H, 2003) One third of thepopulation of the province have been involved in aquaculture and fisheries activities This year thetotal aquaculture areas are 4458 ha, increasing by 17% compared to that of last year The TamGiang-Cau Hai lagoon is an area of important economic activity bringing high income with its seaproducts Yearly thousands of tons of sea products are bought from here (fish, shrimps, and others)

In recent years, the cultivation and a rising of sea products, mainly the raising of shrimps andcultivation of "gracilaria" has developed in this zone of the lagoon The provincial authority ishaving the policy to improve shrimp intensive farming (or industrial shrimp farming) In agricultureand aquaculture, chemical fertilizers and pesticides are used to increase the production; manure israrely used Consequently, expansion of the agriculture, aquaculture and fisheries activities have thepotential of causing pollution like eutrophication, pesticides residue in the lagoon With naturaland historical potentials, tourism is also an important sector in the economy of Thua Thien-Hueprovince Besides agriculture, aquaculture and fisheries, there are some other economic activitieslike industry, craft industry, service, and forestry, etc

Together with the development of the country, living standard ofThua Thien-Hue people has beengradually improved for the past years In 1995, the annual income was recorded at 179USD perperson But so far, it increased to 376USD It is a higher rate compared to other provinces in theregion It is, however, still low in comparison with the average rate of the whole nation

2.2.2 Economic sectors

In 2002 Thua Thien-Hue province had a population of 1.091million, and 300,000 people reside in

or around the capital city, Hue (DPI, 2003; ICEM, 2003) The population is evenly distributed overthe province's territory, but mainly centers on city, towns, seaside and riverside Much of theinterior of the province has a population density less than 50 people per km2while this figure for thecoastal zone is higher thari 1000 At present, urban population occupies about 29.7% of theprovince's total population The natural population growth rate decreased from 2.3% in 1995 to1.5% in 2002 There are 24 different ethnic groups including the Ta Oi, CaTu and Van Kieu, themajority being Kinh, the main Vietnamese group The 2002 labor resource is 607,000, making up55.6% of the population The labor force in the economy is 458,200, accounting for 75.5% of theentire province'S labor This includes 8.5% industrial labor, 77.6% labor working in agriculture,aquaculture, fisheries and forestry, and 14% labor involving in service and tourism According toNga P.H (2003), the growing population is one of the driving forces that cause the environmentalproblems in Thua Thien-Hue lagoon

2.2.1 Demography

2.2 Socio-economicconditions

Chapter 2: Description ofThua Thien Hue province and its coastal zone

Much of the infrastructure and industry in the province lie in the coastal plain The main north-southhighway and railway line linking Hanoi to Ho Chi Minh pass through Hue city and effectivelybisect the province Additional road access is provided to the district centers, including a road to ALuoi - the relatively isolated westernmost district The province is also severed by Phu Bai airport,which permits daily flights to Hanoi and Ho Chi Minh as well as other domestic destinations Thuan

An seaport, which is situated 12 km East of Hue, can accommodate vessels of 1,000 - 2,000 MT.Chan May deep water seaport is 49 km South of Hue City, a key project in developing deep water

2.2.4 Infrastructures

(Source: Report on land planning and utilization in 2001 ofThua Thien-Hue)

Table 2.6 Statistics ofland uses in 2001 in Thua Thien-Hue

In the coastal plain the dominant land use is agriculture, primarily paddy rice Aquaculture mainlytakes place in the lagoon bank Forestry and livestock predominate in the remaining lowland areas

In the highland areas the main land uses are forestry, and subsistence agriculture The forests andthe protected areas lie more in the mountainous interior of the province Land is utilized as follows:

Figure 2.4 Shrimp pond in Phu Loc district

2.2.3 Land use

Figure 2.3 Rice field

Chapter 2: Description ofThua Thien Hue province and its coastalzone

Water quality status of the lagoon is reviewed based on result of the integrated environmentassessment ofNga P.H (2003) and the latest record ofCCP monitoring program (see Appendix 2).

In general, the water quality of the lagoon is not bad and is considered still suitable for aquaculturepurposes However, suspended solid, nutrient and coliform pollutions have been observed at somelocations of the lagoon Organic, nitrogen and phosphorus contents are often higher in ponds foraquaculture than outside and the lagoon Relatively high sediment concentration occurs during thedry season Data of toxic substance concentrations in the study area are non-existent so this kind ofpollution is unclear An analysis on nutrient and pesticide pollutions will be given in detail inChapter 6 A rough analysis on coliform bacteria is presented in Appendix 7

2.3 Brief review of water quality situation in the lagoon

In Vietnam's development master plan for the coming period, Thua Thien-Hue is one of the fourprovinces in the key economic complex of the Central Area Based on the socio-economic analysisduring the period 1991-2000, and in terms of advantages of and restrictions to the developmentprocess in the forthcoming time, Thua Thien-Hue plans to achieve an annual average economicgrowth rate of9-10% from 2001-2005 and 12-13% from 2006-2010 The new economic mechanismfocuses on small industries and handicrafts, tourism and services, agriculture, forestry and fishery

In future, industry and construction will be the important economic sectors Up to the year 2010both industry and construction are expected to contribute 43.3-44% to the economic growth,employing 24-25% of the labour force Aquaculture and agriculture will be gradually intensifiedand industrialized with new technical farming Thua Thien-Hue's government also has policies toimprove the tourism and services sector so that they can contribute 40% in 2010 to the totaleconomic output of the province (DPI, 2003)

2.2.5 Socio-economic development orientation by2010

seaport of Vietnam for the period of 1996 - 2010 calling for investment According to the masterplan, this port will have the receiving capacity of 40 MT per year and will provide easy entrance for50,000 - 70,000 MT vessels all year round This will make Chan May one of the most importantcommercial ports in the Centre undertaking the shipment of goods through the commercial East-West trade corridor connected with Mekong sub-region

Chapter 2: Description ofThua Thien Hue province and its coastal zone

Pesticides can be classified and grouped in many different ways (lmpthailand, 2003; Ritter W.F et

aI, 2001) Regarding to pests they control, "Pesticides" is a general term that includes: insecticides,herbicides, rodenticides, fungicides, miticides, wood preservatives, disinfectants, products thatcontrol algae etc Pesticides can also be synthetic or organic pesticides Synthetic pesticides aregrouped by their active ingredient This refers to the chemical class to which toxic componentsbelong Major chemical groups are: organchlorines, organophophates, carbamates, pyrethroids

Each of these chemical families is known to cause certain general health effects Most pesticidesproducts will have more than only active ingredient Pesticides are again grouped as broad spectrum

or selective pesticides Another way of grouping pesticides is according to the potential risk tohuman health The World Health Organization (WHO) has developed the following classes forchemical pesticides: class I (Extremely hazardous), class II (Moderately hazardous), class ill(Slightly hazardous), class IV (Product unlikely to present acute hazard in normal use) Besides theabove classifications, there are other numerous ways of grouping pesticides according to pesticideformulation (Liquids, powders, granules, baits, dusts ), the way they move to the plant (these

A pesticide is a poisonous chemical or mixture of chemical that controls, prevents, or kills pests oraffects plant or animal life (Groundwork, 2003) Pests are living organisms that occur where theyare not wanted or that cause damage to crops or humans or other animals as insects, mice and otherrodents, unwanted plants, fungi and microorganisms (bacteria and viruses)

Pesticides used to be products from natural sources such as (nicotine, pyrethrum ), and inorganicchemicals (sulfur, arsenic ) before the 1940s During and after World War II, with the discovery

of 2,4-0 and DDT, phenoxy herbicides and organochlorine insecticides were widely used In themiddle 1960s, the use of these classes of pesticides declined They were replaced by amide andtrazine herbicides, and carbamate and organophosphate insecticides Some pesticides have beenbanned from use mainly due to toxicities Recently, the use of trazine herbicides, and carbamate andorganophosphate insecticides has decreased They have been replaced by other classes of pesticidesthat have shorter half-lives and are used in smaller amounts (Ritter W.F et aI, 2001)

3.1.2.1 Pesticide definition and classification

3.1.2 Pesticides

During the 20th century, industrialization has influenced agriculture and aquaculture directly bymodifying the way farming·activities One of the most important impacts of industrialization onagriculture and aquaculture was chemical development Chemical products have been used widely inalmost all agriculturaland aquaculturefields all over the world in order to improvethe yield and protectthe crops.Inagriculture, chemical products usually are pesticidesand fertilizerswhile in aquaculture,thefarmer can use antibiotics, disinfectants,vitamins, soil and water treatment compounds, feed additivesbesides pesticides and fertilizers However, synthetic fertilizersand pesticides have played a dominantrole in both agriculturaland aquacultureintensificationfor decades

3.1 Chemicals used in rice culture and aquaculture

3.1.1 Introduction

LANDUSE IN VIETNAM AND THUA THIEN HUE PROVINCE

Chapter 3:Literature review and data analysis on chemical use and landuse in Vietnam and Thua Thien Hue province

• Pesticide resistance and pest resurgence: Pesticides almost never kill 100% of a targetspecies even under the most ideal conditions Every population contains some diversity intolerance to adverse environmental factors The most resistant members of a populationsurvive pesticide treatment and produce offspring like themselves with genes that enable them

to withstand further chemical treatment Because most pests propagate rapidly and produceoffsprings, the population quickly rebuilds with pesticide resistant individuals Thisphenomenon is called pest resurgence The United Nations Environment Program reportedthat at least 500 insect pest species and another 250 or so weeds and plant pathogensworldwide have developed chemical resistance

• Effects of non-target species: It is estimated that up to 90 % of the pesticides we use neverreach their intended targets Many beneficial organisms are poisoned unintentionally as aresult For instance, about 20% of all honeybee colonies in the United States are destroyedeach year and another 15% are damaged by pesticide spray drift or residues on the flowersthey visit

While synthetic chemical pesticides have brought great economic and social benefits, they alsocause a number of serious problems As explained previously, pesticides are poisons and seldomselective in their action Harm can arise in several different ways, but two basic types of effects can

be distinguished: the toxicological and ecological effects (Rice R, 2003) Many pesticides areacutely toxic They can, and do, kill within days of exposure They are also "slow" or chronicpoisons, causing sickness in people who are regularly exposed to small doses over long periods oftime The possible impact of pesticides also has to be considered from an environmental andecological point of view It is estimated that 90% of an applied pesticide is "lost" to the surroundingenvironment (50% in soil) (Rice A, 2003, Khoa L.V, 1996) Some of worst problems of usingpesticide are as follows (Cunningham W.P, 2003, Rice A, 2003):

With the demand for food security when the farming land is getting smaller and the worldpopulation is increasing, it is necessary to intensify agricultureand aquaculture Intensification willincrease the potential for epidemic diseases In this case, pesticides play an important role Thebenefit of pesticides lies in their ability to manage a pest (weed, insect or disease) that becomes out

of control Crop protection products prevent crops and lands from being ravaged by insect or fungiinfestations, thus minimizing the risk of related disease or damage, and allowing essential foodgroups to be harvested for consumption Although reliable data on crop losses are difficult to obtain,

it is thought that plant diseases, insect and bird predation, and competition by weeds reduce cropyield by at least one-third (Cunningham W.P, 2003) Post harvest losses to rodents, insects, andfungi may be as high as another 20 -30% Without modem chemical pesticides, these losses might

be much higher A commonly quoted estimate is that farmers save $3 to $5 for every $ spent onpesticides.InVietnam, the benefits of pesticides are quite clear Since 1993 Vietnam has become arice-exporting country instead of rice importing This development is not only due to increasedfarmed areas but intensification with the application of pesticides (Anh D.T, 2002) For a majority

of farmers, pest control products have become a necessary part of life

3.1.2.2 Pesticide benefits and problems

products are taken up by plant through roots or leaves or not), the mode of action (stomach orcontact poison or fumigants)

Chapter 3: Literature review and data analysis on chemical use and landuse in Vietnamand Thua Thien Hue province

The fate of pesticides in the environment is not determined by a single property but by acombination of their properties Chemical characteristics of pesticides that influence transportincludes water solubility vapour pressure, and partition coefficient (Ritter W.F et aI, 2001) Adirect measurement of how much of an organic compound is likely to be present as a solute in water

is given by its aqueous solubility Chemicals with high solubility have a tendency to be leachedthrough the soil to ground water and to be lost as surface water runoff from rainfall events orirrigation practices Pesticide vapour pressures are extremely low in comparison with other organicchemicals such as alcohols or ethers Pesticides with high vapour pressures are easily lost to theatmosphere by volatilization Some highly volatile pesticides, however, may also move downward

Once applied to a site, pesticides may reach surface water through a number of routes such asrunoff, leaching, spray drift, or even direct application to water bodies for weed control (Ritter W.F,2001) The concentration, behaviors, and fate of these organic contaminants in aquatic environment

is then dependent upon their physical-chemical properties, as well as the various physical-chemicaland biological transformation processes that they may be subjected to The main transportationprocesses of a pesticide, which are of interest, are adsorption/desorption,sedimentationJresuspension, biodegradation as well as photochemical degradation

3.1.2.3 Fate and transport processes

• Human health problems: Pesticide effects on human health can be divided into twocategories: short-term effects and long-term effects The World Health Organization (WHO)estimates that between 3.5 and 5 million people suffer acute pesticide poisoning and at least20,000 die each year (Cunningham W.P, 2003) At least two-thirds of this illness and deathresults from occupational exposures in developing countries where people use pesticideswithout proper warnings or protective clothing

• Persistence and mobility in the environment: The qualities that make DDT and otherchlorinated hydrocarbons so effective are stability, high solubility, and high toxicity Thesealso make them environmental nightmares as they persist for years, even decades in somecases, and move freely through air, water, soil, and often showing up far from the point oforiginal application In agricultural areas where these compounds have been heavily usedwithin the past few decades, mother's milk often contains levels of these persistentchlorinated hydrocarbons that would make it illegal if sold on the market Pesticides canbioaccumulate through food chains or increased concentrate in successive steps of the foodchain The term "food chain poisoning" refers to the process whereby organisms, includinghumans, high up in the food chain feed off pesticide -contaminated organisms, which feedoff smaller prey even lower in the food chain (Rice A, 2003) In doing so, the large animalssuch as humans and domestic animals can accumulate pesticide residues in their own bodytissues, particularly body fat Although the amount consumed is hardly enough to kill in thecase of humans and domestic animals, the pesticide may still be present in sufficient amounts

to lead to poor reproduction and fertility and general ill-health

• Creation of new pests: Often the worst effect of broadcast spraying a pesticide is that it killspredators that previously kept a number of pests under control As a result, it allows anothergroup of pests to flourish In other words, another emergent species may become a pest in itsown right, leading to what is known as a "secondary pest outbreak"

Chapter 3: Literature review and data analysis on chemical use and [anduse in Vietnam and Thua Thien Hue province

The term 'transport', representing advection and dispersion, is always present when two or morewater and sediment compartments are considered When a micropollutant partitions amongparticulate and dissolved phases, this term affects all phases equally, except for sediment layers It

is obvious that all other specifically particle related transport processes disappear from the equationfor non-adsorbing (i.e dissolved phase) micropollutants

Ct =total concentration of a micropollutant (g/m'')

Table 3.1 Partition coefficients of some typical pesticides

into the groundwater Partition coefficient (Koc), otherwise known as the solid-water distributionratio, is the ratio of pesticide concentration (or any substance) in the adsorbed-state and solution-phase The smaller the partition coefficient value, the greater is the concentration of pesticide insolution For example, 2,4-D, Fenobucarb, Methamidohphos have small partition coefficients(Table 3.1) and readily transported as free substances dissolved in water On the other hand, Methylparathion with high Koc value is typically not very water-soluble and will preferentially adhere tosoils than be dissolved in water This means that, it is unlikely to be carried off-site in runoff asdissolved substance; instead, it is transported on sediment particle

Chapter 3: Literature review and data analysis on chemical use and landuse in Vietnam and Thua Thien Hue province