Luận văn numerical simulation for the assessment of groundwater safe yield in red river delta viet nam

Tn the northern areas of Nam Dinh Province, duc to the the high concentration ol” contamination in the groundwater aquifers, surface water is used as the main source of water for the r

during the last decades, which is based on the availability of water resources, and

the extensive exploitation have strongly increased the pressure on this finite and vulngrable resource Since surface waler is unevenly distributed and increasingly affected by human activities, groundwater has become the majar source of potable

water

This thesis therefore focused on contributing to the improvement of groundwaler management in RAD by determining groundwater safe yield using modelling

method Nam Dinh Province was selected to be the study area

Tn the northern areas of Nam Dinh Province, duc to the the high concentration ol”

contamination in the groundwater aquifers, surface water is used as the main source

of water for the region Groundwater usage in these areas is mainly for other

purposes [han domestic use Small scale groundwater extraction can be found near the main rivers with shallow wells in the uppermost aquifer due to the high level of comlamination Deeper aquifers are the main subject for extensive extraclion im the province Significant extractions are found in the south of Nam Dinh, where large

freshwater lens in Pleistocene aquifer are located ‘herefore in this thesis, the

Pleisincene aquifer is the main arca of interest

it was decided to use the Visual MODFLOW for the setting up of a numerical

model of the Nam Dinh Area, The 3D hydrogeological structure for the model was

created from strata data of 83 boreholes, including 27 boreholes fram Nam Dinh, 15 boreholes from Ha Nam, 17 boreholes from Ninh Binh, 23 boreholes from Thai Binh and I from Thanh oa Natural neighbors method was used to interpolate the

elevation of surly 6 and bottem of the layers

‘The 3D structural model was built with 5 layers, representing 4 aquifers and 1 aquitard, inchiding Upper Holocene aquifer (qh2), Lower Holocene aquifer (qh), Pleistocene aquilard (qp2), Pleistocene aquifer (qpl) and Neogen aquifer (n) with

the order from top to bottom sespectively The finite difference grid used for the model has the size of 181 x 160 (181 columns x 160 rows, the size of each cell is approximate 400m x 400m)

Observed water heads from 19 wells were used to calibrate and verify the model The normalize root mean squared of the calibrated model is 6.296%, which

is considered to be good cuough to simulate the fulure uses of groundwater for the study area

To show the impacts of groundwater utilization on the qp aquifer in Nam Dinh

Province, scenarios of future silualions were simulated using ihe calibrated model lixtraction rates were extrapolated until 2050 and three versions were considered: 1)

Extraction rises constantly until 2050 in the same manner than from 1994 to 2012;

2) Extraction stays on a 2012 level, which means thal no addifional water is going

to be extracted; 3) Extraction gradually declines to 0 by 2050

The simulation results of these scenarios were used to estimate the groundwater

safe yield for Nam Dinh Province Tt showed thal the sale yield lor the aren is

estimated to be 70300 m'/day.

River Delta, Vict Nam” in partial fulfillment of the requirement for the award of the Master of Science in Integrated Water Resource Management, is an authentic record of my own work carried oul under supervision of Associate Professor Dr Vir Minh Cat and Dr Bui Du Duong

The matter embodied in this thesis has not been submitted by me for the award

of any other degrees or diplomas

Date: 28" November 2014

First and foremost, 1 would like to thank my advisor, Assoc Prof Dr Vu Minh Cat for his invaluable guidance I am deeply grateful that I had the opportunity to learn from his knowledge

1 would like to thank Dr Bui Du Duong for his helpful contribution to the hydrogeolopy field and his supervision of my study

Tart very grateful to Assoc Prof Dr Pham Quy Nhan, MSc Dang Tran Trung and MSc Tran ‘Thanh Le for their valuable advices and help with the preparation of

spreadsheet data for the boreholes and well logs

To Ms Mancelie van Tilburg, T am very thankful for the English corrections,

suggestions for my thesis and for providing me useful writing resources

Lastly, a word of thanks is extended to NICHE-VNM-106 project team for

providing a 18 months MSc scholarship

Again, 1 would like to express my sincere gratitude for all these valuable help!

1.2 Objective & scope of study

1.3 Previous studies & state of knowledge

1.31 Tn the world

1⁄42 In Viet Nam

14 Methodology

1.5 Structure of thesis

CHAPTER Il — CHARACTERISTICS OF NAM DINH PROVINCE

2.1 Physical settings of Nam Dinh Province

2.11 Geographical lecation

21.2 Topography

2143 Climate conditions

2.14 Surface water bodies

2.1.5 Soils and land use

2.1.6 Population & Socio-Ecemomy

2.1.7 Water supply and groundwater utilization

2.2 Geological characteristics of study arca

44

44

47

GROUNDWATER SAFF, VIELP IN NAM DINH PROVINCE,

3.1 Introduction of MODFLOW model

411 Extraction rises constantly

41.2 Extraction remains constant

41.3 Extraction gradually reduces

41.4 Estimation of groundwater safe yield

4.2 Discussion of model results

CONCLUSIONS AND RECOMMENDATIONS,

REFERENCES

APPENDICES

NAWAPL National Center for Water Resources Planning and

Investigation NDWRPT Narthiem Division of the Nalional Center for Water Resources

Planning and Investigation

NSEW North, South, Last, West

UNICEF United Nations International Children’s Emergency Fund

‘Technical abbraviations

m bgl Meter below ground level

mash Meter above modern sea level

TDs Total dissolved solids (mg/L)

Figure 2.2: Monthly averaged data for temperature, precipitation and potential evaporation

in period from 1959 to 2007, measured at Van Ly station, coastal area of Nam Dinh .23 Figure 2.3: Land use disinbulion m Nam Dinh provimee, status 2007 25

Figure 2.4: Bar chart showing official data for communal and private water supply (ws) in

Figure 2.5: Quatemary geology and topography of the Red River delta and adjacent

Figure 2.6: Geological Sketch map including major structural features and basis

bourdanes of the Holocene, Plastocene and Neogene sediments (Source: NAWAPE) 30

Figure 2.7; Sketch map showing location (orange line) of typical hydrogeological

Figure 2.8: Cross soclon from Vu Ban to Hai Hau (1 40x vertical exaggeration,

modifled aRer Ho et aL., 2003) 31

Figure 2.9: Tine-series of monthly averaged Grounihwater level of Holocene (qh),

Figure 3.3: Finite difference grid and extent border of the model 48

Figure 3.4: 31D hydrogeological structure of Nam Dinh Provinee "—.

Figure 3.6: Hydraulic conductivity (m/day) for each aquifer: 2) Upper Holocene, b) Lower Iolocene, e) Upper Pleistocene, đ) Lower Pleistocene, e) Neogone 53 Figure 3.7: Distribution of antificial well locations ini siudy sres 58 Figure 3.8: Estimated groundwater withdrawal rate from 1994 to 2009 in Nam Dinh

Figure 3.9: Sketch map showing the locations of groundwater monitonng wells in

Nam Dĩnh PT@VIHEE nh tr eerrrree see GL] Figure 3.10: Calculated versus measured water heads in Q108, 109 and 110 62

Figure 3.11: Best (it simmulalion water level contour m gp aquifer (December 2012)

Figure 3.13: Calculated versus measured waler heads in Q221-Q229 from 2010 ta

Figure 4.2; Sketch map showing the groundwater level contour in gp aquifer in

December 2050 with a constant rise of extraction as postulated until 201 2 67

Figure 4.3: Estimated groundwater level until 2050 at Q109 with a constant level of

extraction as Im 2] 2 cành re ¬—

Figure 4.4: Sketch map showing the groundwater level contour in qp aquifer in

December 2050 with a constant level of extraction as 2012 68

Vigure 4.5: Lstimated groundwater level until 2050 at Q109 with a constant decline

Table 3.2: Table for siatistic paraeters of calibrated model result G5

Table 4.1: Estimated safe pumping rate in Nam Dinh Provinee v71

coastal areas ‘he growth of both the economy and the poyulation in these areas

during the last decades, which is based on the availability of water resources, and

the extensive exploitation have strongly increased the pressure on this finite and vulnerable resource Since surface water is unevenly distributed and increasingly affected by human activities, groundwater has become the major source of potable water #1

Understanding and quantifying groundwater resources, especially m coastal areas, is a very complex and difficult task considerably more problematic and uncerlain Chan surface water bydrology Various stustics have bean comducled using different types of models, including empirical, probabilistic and deterministic models Since empirical models are limited in scope and probabilistic models yoquire large dala sets and carmol be used to solve mary problems ini pravtice (e.g,

effects of a future pumping) !"), numerical deterministic models are increasingly

applied, especially within GTS environments However, in contrast to the developed

countries (¢.g., Europe, Australia, Japan, and North America), where a vast majority

of projects have been carried out due to the availability of a wide range of

information and where Lechnical and financial resourees are available /?]) few

projects have been in Viet Nam with very limited results This has led to an inadequate understanding of the aquifer system characteristics as well as to unwise

groundwater management in Viet Nam, especially in RRD_

‘This thesis therefore focused on contributing to the improvement of groundwater management in RRD by determining groundwater safe yield using modelling

method However, with the limiled time, it is not feasible to construct the model for the whole Delta In this study, Nam Dinh Province was selected to be the case

study There are 3 reasons for this selection:

SW border is where clastic sediments of the Cenozoic meet the Mesozoic

graben shoulders of the clongated Red River graben; and 3) Agriculiure

dominated land use with an extensive system of dykes and canals constructed

to irrigate the paddy fields with river water

« Nam Dinh Province is facing the same groundwater problems with RRD,

including: 1) Continuous declining of groundwater tables on a regional scale;

2) Potential salinization of coastal groundwater resources by seawater intrusion; 3) Potential pollution by unsuitable handling of domestic, agneullural and industrial wasle, waste waler and sewage, and 4) Urowise management and inadequate understanding of the aquifer system characteristics leaded to serious problems, such as the drying up of shallow

wells, land subsidence, cle

¢ Nam Dinh is the province which has the highest proundwater drawdown rate

compare to the other provinces/cities in Red River Delta "I

(For more details, see Chapter 2)

Nam Dinh Province is principally endowed with a subtropical climate and

abundant surface water resources However, economic and social developments,

combined with the population growth over the last decades, have strongly increased pressure on available waler resources Surface water is the Iraditional water source

and still used m Nerthem and liastern areas of Nam Dinh In South and West of

Nam Dinh deeper groundwater resources has been increasingly exploited for

domestic as well as ceonomie ulilvation

Monitoring data since 1995 showed that the groundwater extraction exceeded

the recharge resulting in drawdown of groundwater tevels in Pleistocene and

Neogene aquifers up to 0.6 m/year A regional abstraction cone las developed in

Pleistocene as well as the underlying Neogene aquifer In this area, the natural

from the ocean towards the fresh groundwater area Ihe consequences are that nowadays hand pumps must be replaced by electric pumps in order to pump the groundwater to the surface and, thus, ineroasing the costs for water supply

Groundwater will be increasingly important for Nam Dinh’s future water supply strategy, since surface water is vulnerable and increasingly affected by climate

change, urilreated sewage waler and mdustrial waste waler Thus, sustainable

groundwater exploitation and management is crucial for life, development and the

environment in Nam Dinh

1.2 Objective & scope of study

The overall goal of this thesis is to provide a rough assessment on the safe yield

of groundwater far Nam Dinh Province on the basis of numerical medeling method

To achieve the overall goal of the rescarch, these following specific objectives have

been addressed:

«Clarify the spatial characteristics of groundwater in Nam Dinh

& Trvestigate the impacts of pumping aclivitics on the flows and hydraulic heads of groundwater in Nam Dinh

« Roughly estimate the safe groundwater yield for Nam Dinh

«Proposing recommendations to improve groundwater management for Ihe province by analyzing the simulation results

Tn the northern areas of Nam Dinh Province, due to the the high concentration of

contamination in the groundwater aquifers, surface water is used as the main source

of water for the region Groundwater usage in these areas is mainly for other purposes than domestic use Small scale groundwater extraction can be found near the main rivers with shallow wells in the uppermost aquifer due to the high level of contamination Deeper aquifers are the main subject for extensive extraction in the

province Significant extractions are found in the south of Nam Dinh, where large

groundwater pollution and salinization process were not taken into account due to

the limitation of time and collected data Furthermore, detailed evaluation of

alternative groumdwaler management strategics was also included in this research

1.3 Previous studies & stale of knowledpe

231 inthe world

Worldwide applying of modelling methods to study the subjects of groundwater

began in the 19th century, especially in industrialized countries like the former Soviet Union (Russia and others Republic countries now), the US, France, Canada, Domnark History of groundwater modelling can be divided into two stages

The first stage lasted from the 19th century to the late 50s of the 20th century At

this stage, modelling method was applied to study the basic seepage problem

Several laboralories, which suuhed soit permeability, were formed in the Soviet Union as VNUG, VODGHO, MGRL ‘his stage is characterized by a strong

development of EGDA method (Analogue RGDA), which was developed and used predict groundwater dynamics, balance of groundwater in ungated areas in

Davogia, Dovongie, North Keprad, Central Asia, Ukraine

The sccand stage extended from the 60s of the 20th century to the present Ta this stage, modelling method was strongly developed and applied to interpret many complex problems as: Assessment of exploitable reserves of underground water,

Prediction of groundwater dynamics in irrigated areas, ete Developed countries like

the United States, Russia (former USSR), Denmark, Canada, Australia have used

numerical models to serve the integrated management of water resources, Countries

in Asia, Southeast Asia have also applied the model to assess and manage waler

resources in their territory

For the last decades, several methodologies for groundwater management and vulncrabilily assessment have been developed to deal with groundwater problems

spatially dense geophysical/hydrogeological mapping, dense perforation grids as well as numerical modelling, GIS and advanced database technology for

groumdwaler management and protection in Denmark El Other advanced

approaches include quantitative aquifer modelling, for entire catchment areas using numerical groundwater flow modelling as a basis for sustainable aquifer exploitalion and vulnerability assessment [th 61 However, in contrast to the availability of data in developed countries, the reduced availability of the necessary input data in developing countries require that a significant part of the basic input

variables has to be oslimaled As a result, these approavhes lean towards a growing,

uncertainty |"?!

13.2 In Viet Nam

In Vietnam, several studies have dealt with groundwater problems Mirh, (2004) used weak Galerkin finite element method to simulate the movement of saltwater

wedges inlo the coaslal aquifer in Hoa Khanh, Tien Giang 5) Postma’s research in

2007 under the Damda Enreca Project provided a sct of sources a3 well as

mitigations for arsenic contamination in the groundwater of the Red River Delta "%1,

Nguyen (2011) used finite cloment modelling for the assessment of scawaler intrusion into the ground aquifer in ‘Thai Binh province Hrban (2013) provided an extensive study on arsenic releasing into deep groundwater in the Mekong Delta, which is linked to pumping-induced land subsidence ®! However, there has been

less unprovement in groundwater management in Vietnam, since growidwater

problems were still reported to happen in many areas of Vietnam according to 'MOKRE, 2013 I4!

Previous studies in Nam Dinh Province:

Since the 1990s groundwater resources in the Red River Delta (RID) including

Nam Dinh area were subjovt of mapping and exploration projects carried out by

studies and information sources are namely

“Characteristics of geology, natural resources and geochemical environment of sediment on tidal estuary of Xuan Thuy and Nghia Hung, Ha Nam Province” —

report by staff's at Hanoi University of Mining and Geology, 1995

"Geological mapping for Nam Dinh area ratio 1:40.000" — project by Division

47 of Hydrogeclogy — Geology Bngineering, 1996 In this projecl, 27 boreholes

were drilled, including 8 boreholes in Iotocene aquifer (qh), 17 boreholes in Pleistocene aquifer (qp) and 2 boreholes in Neogene aquifer (n) Strata data eaHleoted [rơm the borcholes was used for the mapping process Slug Lesls were also conducted in 26 boreholes to determine the hydrogeological parameters of the

aquifers and the chemical composition of water I“Ì

"Planning of walar supply and sanitation in Nam Dirh provines in 1999 — 2010 period” report by the Center for Water and Sanitation, Nam Dinh Department of Agriculture and Rural Development, 1999

“Assessment of groundwater potential and prediction of depiction and salimty

instrusion in [lai lau Giae ‘Thuy, coastal areas of Nam Ding Province" report

by the Department of Waler Management and Trigalion Works, Ministry of

Agriculture and Rural Development, 2000

"Evaluation on characteristics of natural conditions and non-biological resources

in coastal areas of Nam Dinh province" — report by Marine Natural Resources &

Environment Survey Center, 2001

"Assessing the sustainability of the exploitation of groundwater resources in Visinam territory Strategic orientation for rational ulilivation and protection of

groundwater resources by 2020" _ state project by Bui Lloc et al, 2003 "1

"General survey of groundwater resources in Nam Dinh province: planning for

vational and sustainable uses” —reporl by Doan Van Canh and Te Thi Lai, 2003 21

Van Dan - NDWRPI, 2009 4,

In 2010, within the framework of the project “Improvement of Groundwater

Protection in Viel Nam” in Nam Dinh Province, 10 additional grourrdwaler

monitoring points were constructed, In total of 23 new monitoring wells, there are 4 wells in Tolocene aquifer, 14 wells in Pleistocene aquifer, 1 wells in Neogene

aquifer, and 1 well in Triassic aquifer Slug tests were conducted in 2011 by

National Center for Water Resources Planning and Investigation (NAWAPI) to

determine the hydrogeological parameters of the Pleistocene aquifer in Nam Dinh

Based on principle of waler balance this research used the waler balance

equation to detcnmine the groundwater safe yield Numerical sinrulation of a hypothetical case was used to demonstrate the natural groundwater balance, effects

of pumping and the dynamic development of the caplure

In this thesis, as a systematic evaluation tool for groundwater How, GIS program and the groundwater modeling program MODILOW were integrated and used (Figure 1.1)

At fst, related information available in print or published on the intemet were gathered and analyzed, To simulate the groundwater flow, regional hydrogeclogy,

topography, hydrology, soil, land use anc well data during the period of 1995-2012

were collected from NAWAPI under the Ministry of Natural Resources and

Environment (MONRE), Vietnam The aquifer system was identified and characterized to construct the 31) structural model

Groundwater safe yield

determimation & assessment

Figure 1.1: Steps of study

Tn order Lo use MODFLOW, initial conditions, hydraulic properties, and stresses

wore specified for every model cell in the finite-~difference grid Measured heads

from the field were assigned directly to inland constant-head boundaries

Afer setting up the model as well as calibrating and verifying, different pumping schemes were used, based on which, corresponded simulations were executed The results were analyzed to determine groundwater safe yield for

diferent, arcas of Nam Dinh Province Finally, recomunandations were given 1o

improve the groundwater management in the area.

1.5 Structure of thesis

‘This thesis consists of 4 chapters

Chapter I - Introduction: This chapter is Ihe mtraduction which contains the

background, importance, objectives of the stidy and short description of the study area A comprehensive review of literature and a description of study scope were also presented in (his chapter

Chapter Ll - Characteristics of Nam Dink Province: ‘This chapter provides a

comprehensive description on the natural conditions as well as socio-economic

characterislics of the shuly area This chapler also describes the current status of

groundwater and the utilization of groundwater in Nam Dinh Province

Chapter Lf - Construction of numerical model to assess groundwater safe

yield in nam dink province: Tn (his chapter the numerical model set up will be presented, The simulation results will then be analyzed to estimate the impacts of pumping activities on groundwater flow and hydraulic head

Chapter TV - Simulated results and recommendations: This chapter prosenls the results of several pumping variations Finally, overall conclusions,

recommendations were given Cor improving groundwater management, im the sludy area as well as possible works for the future studies.

CHAPTER IT —- CHARACTERISTICS OF NAM DINH PROVINCE

2.1 Physical settings of Nam Dinh Province

2.1.1 Geographical location

Nam Dinh is the province in the Red River Delta region of northern Viet Nam It

has a border adjacent to Ha Nam Province to the north, Thai Binh Province to the

east, Ninh Binh Province to the west and East Sea (South China Sea) to the south-

east, The province has a NW-SE extension of 46 km and a SW-NE extension

of minimum 16 km in the central part and maximum 60 km at the coastline to the

Gulf of Tonkin and an area of about 1652 km? The province comprises one city

(Nam Dinh city) and nine districts (Giao Thuy, Hai Hau, My Loc, Nam True, Nghia

Hung, True Ninh, Vu Ban, Xuan Truong, Y Yen) (see Figure 2.1)

[J Provinciat Boundary

Figure 2.1: The outline map of Nam Dinh Province

Nam Dinh represents the southernmost edge of the RRD, which is located on

the western coast of the Gulf of Yonkin Therefore, its physical setting is

connected lo the subsidence of the Red River basin and development of the della

system

212 Topography

Nam Dinh terrain is relatively Mat, tend to lower from NW io SE with

common elevation from Om to 6m The province can be divided into two main

regions:

The low-lying delta region - Vu Ban District, Y Yen District, Nam Truc

District, ruc Ninh District, Xuan Truong District and Nam Dinh cty Thu

region is characterized by flat plains with favorable conditions for a high development level of agriculture, textile and manufacturing industries

The lowland coastal region - is home to districts such as, Giao Thuy, Iai

Hau, and Nghia Hung This region has a relatively flat terrain with a coastline of

72km long, whicli is heavily divided by the large estuaries of Ba Lal (Red River), Day (Day River), Lach Giang (Ninh Co River) and Ha Lan (So River)

The coastal plains, with fertile land, have favorable conditions for raising

livestock and fishing This region also locates Kuan Thuy National Nature

Reserve

213 Climate conditions

‘The northern pat of Vietnam has subtropical monsoon climate, with humidity averaging 84% throughout the year This typical North Vietnamese

climate dominates the microclimate of Nam Dinh province with bit cooler

temperatures and a higher humidity due to its vicinity to the sea

During the winter or dry season (November - April), the monsoon winds

usually blow from the NE along the China coast and across the Gulf of Tonkin,

picking up considerable moisture Consequently the winter season in most parts

of the country is relatively dry in comparison to the rainy or summer season Lowest daily average temperalures are met in January and February wilh 10 lo

130C and average humidity can be “relatively low” with 94% (November-

December), but also reach highest average humidity with up to 98% (January- March) The monthly average rainfall varies between 25 and 220 mm

The summer monsoon from May to October is associated with hot

temperatures and heavy rain falls Maximum daily average air temperature occurs generally in June and July varying from 29 - 31.20C The lowest relative humidity is 86.5% and the highest relative humidity is up to 92% in July, while

the monthly average rainfall lies between 175 and 330 mm (Figure 2.2)

The climate data from Van Ly station close to the sea shows the development

of the potential evaporation throughout the year Where open surface bodies,

such as channels or irrigated paddy fields exist, the evaporation is quite intense throughout the year In other areas, evaporation is limited in the dry season

(November —April) by lower rainfall

Figure 2.2: Monthly averaged data for temperature, precipitation and potential evaporation

in period from 1959 to 2007, measured at Van Ly station, coastal area of Nam Dinh The total number of hours of sunlight per year averages out about 1650-1700

hours Additionally, being next to the Gulf of Tonkin, Nam Dinh is normally affected by tropical storms and monsoons, with an average of 4-6 attacks per year.

21.4 Surface water bolies

The hydrologic network is very dense, including more than 16 small and two tain river systems (the Red River and Day River systems) with density of 1.5 jan/km’, occupying 3 percent of the natural land area ‘he channel network is increasing in density towards the coastal Nam Dinh area and has crucial relevance lor irrigation of paddy ficlds and other agricullural areas with river water as well as discharge of sewage and waste waters to the sea Four major rivers are located within or at the border of Nam Dinh, the Red River along the

NW border of Nam Dinh with its river mouth af the Ba Lat Fstuary, the Dao

River connecting the Red and the Day Rivers (SW border of Nam Dinh) and the Ninh Co River with its river mouth to the sea at Lach Giang estuary

The Red River is the natural border (low between Nar Dink and Thai Bink Province, The Red River bed has $4 lan lengths and is estimated to be 400-500

m wide and about 10-15 m deep The water discharge of the Red River varies strongly in lerms of the season The disvharge at Ha Noi slation reaches a maximum in July-August (about 23,000 m*/s) and a minimum during the dry season in January to May with Lypical flow of 700 m/s During dry season and

tidal high stand, clevated salinity has been observed up to 4.5—5 km inland from

the Ba Lat estuary

The Day River is a tributary of the Red River, which flows from NW lo SE, winding ina W shape along the SW border of the study area for about 70 km before flowing to the ocean Maximum flow rate has been observed in August with 3110 m’/s; lowest flow rate can be almost zera (no flow) in December and January, yearly average is 813 m/s Although this river is tidal influenced, salinity monitoring has shown that total salinity is generally <1g/1 Day River is

considered Lo be the western atural boundary of the fresh waler Jens ia the

southern coastal districts of the province

The Dao River, with the length and the average width of about 35 km and

$0010 correspondingly, is one of the major rivers in (he region The river

originates from the Red River to the north of Tan De Bridge, flowing through the

city of Nam Dinh to The Day River in Nghia Minh commune before joining the

ocean

The Ninh Co River is a tributary of the Red River, located near the center of

the southern districts of Nam Dinh The river originates from the north of Xuan

Truong district (Hanh Thien commune), flowing through Lac Quan to the South before discharging to the ocean at the Lach Giang estuary The river is very

winding with the average width of 400-500m and extimated length of 35-40 km

2.1.5 Soils and land use

The soils of the RRD are generally fertile and have been utilized since ancient

times for intense agriculture with predominance of rice paddy cultivation

Traditionally, the repetitive flooding events regularly added nutrient rich silt and

clay to large areas of RRD Dykes and other flood prevention measures result in the

increasing use of chemical fertilizers Large areas of the RRD including Nam Dinh

province are covered with alluvial fluvisols, moreover with saline soils and acid

sulphate soils

— / Thai Bin

Nam Dinh is an agricultural dominated province More than 58% of the whole

area is covered by paddy rice I'ish and shrimp aquaculture using fresh and brackish walor is widespread wilh almost 5% arca coverage Olher armuat crops have only less than 2% coverage Urban and village area represent about 16% of the total area (Figure 2.3) In total about 74% of the province area is temporarily flooded by paddy irrigation, aquaculture farming and olher water bodies which are expected to

shave relevant unpact for the subsurface water balance

21.6 Population & Socio-Economy

Latest slatistical dala published by Nam Dinh province slale a total population of

1,826,300 (2009) persons and a population density of 1,105 persons per km”, About

16 percent of population live in Nam Dinh city and 84 percent of remain population live in 9 olher disiriels with an average population densily of <1000/ km? Since

2005, the fertility rate is reported to be quite stable within 15-16 %, corresponding

to a mortality rate of 5.8 %o The Viet people represent by far the majority of

population in Nam Dith, only less than one por cent belong lo 3 other minorities, the Tay, the Muong and the Hoa

During the French occupation, the province was famous for textile industry and ananufacturc Recently, Nam Dinh has cstablished 7 industrial zones which arc located along the main roads and ports ‘hese industrial zones accelerate the

ceonomie development of Nam Dmh and have an enormous need of natural

sescurces such as fresh water and waste water disposal ‘[herefore, the industrial

zones enormously increase the pressure to the environment given the fact that water consumption as well as waste water treatment and disposal is not sufficiently segulated

247 Water supply and groundwater utilization

Official slalistical dala about centralived water supply demonsirale the increasing water demand in Nam Dinh province (igure 2.4), in both communal as

well as private water supply The majority of the communal water supply is based

on surface water using simple treatment techniques The private households often

take their water from tube wells screened in 50 to 130 m depths

Figure 2.4: Bar chart showing official data for communal and private water supply (ws)

in Nam Dinh from 2005 to 2009

Currently, there are 3 water supply systems in Nam Dinh city: an old system

operated since 1924 and the two other systems constructed by the French

government Total capacity of three water supply systems is around 50,000 m‘/day

using water from surface rivers in the region According to 2009 statistics, these

systems have supplied freshwater for 24960 households, 365 offices, factories and

83 public taps with the coverage of 92% According to the Provincial Health Center,

the water quality is quite meets the standards

In rural areas, centralized water supply is very limited due to the difficulties in

capital rising for creating new connections, There are two options for water supply

in these areas:

+ Water supply systems in communal scale with the average capacity of 600-

1800 mỶ/day The water here is mainly taken from surfaces water sources Acording

to the collected data, there are only 12 systems of this kind in Nam Dinh province

+ Small scale water supply on the basis of groundwater extraction

In the past, groundwater in Nam Dinh was rarely utilized, only a few extraction wells drilled in Nam Dinh City for the service of industrial hygiene I'rom 1983, wilh the help of UNICEF, “Clean Water for Rural” program has been implemented with thousands of small boreholes constructed to supply water for domestic use Until 2009, the total amount of boreholes constructed with under this program was

more than 166000 (sce Table 3.1)

UNICEF boreholes are often drilled at the depth of 50-130m in the Quaternary

sediment with 40-50mm diameter PVC casing The water is extracted using

tandpump or small electric pump wilh small rate of 0.4-0.5I/s The extraction

depends on the water demand of different areas and households In some communes

in Hai Hau and Nehia Hung districts, 100% resident area has the access to clean

waler from these boreholes:

However, there was no regulation and/or appropriate operation for the extraction

of groundwater in the province Therefore, the boreholes were constructed without

amanual or guildance (location, depth, otc.) This may lead to contaminant, Icakages between aquifers and the risk of depletion of groundwater resources This also

cansed difficulties for the morelling process dae to the lack of proper pumping data aucantioned in chapter 3 It is recommended that more data should be collected to help the improment of groundwater resources management in Nam Dinh Province

2.2 Geological characteristics of study area

221 Structural characteristics

The Red River (Song Ilong) is about 1,200 km long, originates in the mountains

of Yunnan Province in China and enters Vietnam close to the Laos border Its twa

anain tributaries, the Song Lo, also called the Lo River or the Clear River, and the Song Da, also called the Black River contribute to the high water volume of the Red River The river course and the narrow dre

aligned Red River fault system

The pre-cenozoic basement of the NW trending Red River basin began to

Wage area are regulated by the NW-SE

subside in Neogene time, iniliated by the strong uplill of the Prolo-Himalayan

mountain chain High erosion rates resulted in the mobilization of huge amounts of material, which was collected by the tributaries of the major receiving river systems and transported to the Gulf of Tonkin; recent erosion rates reach approximately 130

Million tons of sediments per year (TANABE et al 2003b) During millions of

years, deposition and accumulation at the river mouth in combination with ongoing

subsidence of the Red River basin finally resulted in the formation of the huge

River Delta complex

The axis of the Red River basin is marked by the Red River fault which splits

into two branches, the NEern Song Chay fault, and the SWern Song Hong (Red

River) fault These two faults bound the Ailao Shan-Red River shear zone The

central basin axis contains more than 3 km of Neogene sediments along a narrow 30-50 km wide graben The graben is thought to have subsided totally about 6 km

over the last 50 million years resulting in a maximum long-term subsidence rate of

the 0.12 mnva of the central part of the basin

[a] even nes tasrocenemarnatarace [1] ttt anaree)

Figure 2,5: Quaternary geology and topography of the Red River delta and adjacent

areas (Source: Tanabe et al 2006)

The tectonic features of the Red River basin are a major driver for the

development of the RRD Therefore, especially in close vicinity to the adjacent Mesozoic bedrocks, tectonic structures and features are quite complex This is also

the case for Nam Dinh province which is indicated in the sketch map in Figure 2.6

Nam Dinh lies above the Ailao Shan-Red River shear zone within the Song Chay

and Song Hong fault Previous tectonic studies characterize these major faults as normal fault with dipping 72° NE Further minor parallel faults displace the Mesozoic hard rocks One major structural feature in the subsurface of the Nam Dinh province is the uplifted Vu Ban block (Nguyen Van Cu et al 1996), indicated

by few Proterozoic outcrops in the NW of the province Another important

structural feature is the incision of the paleo Song Hong (Red River) valley, which

is, surrounding the Vu Ban Block and crossing Nam Dinh province to the sea

Recent Ouateriary

‘Sediments 32

Bathymetry (mbsi)

QP boundary

— ,.,,, maior

— tauits, minor cana estimated

~~ Stream, River

=~ + Prownce boundary

ap boundary (9),

Figure 2.6; Geological Sketch map including major structural features and basis

boundaries of the Holocene, Pleistocene and Neogene sediments (Source: NAWAPI)

The cross sections in Figure 2.8 provides a clearer picture of the 2D-Geological

structure (location see Figure 2.7) This provides insight into local and regional

hydraulic connections within the hydrogeological units.

Figure 2.7: Sketch map showing location (orange line) of typical hydrogeological

cross section of Nam Dinh Province

{| Ton Wal sion, ator: Doth FS} conning ape a eer

‘gh ] Upper Holocene aquifer [BRET Upper Pleistocene aquiter

SE] Lover locene ater [ead] Lover Peistocen aguler

Figure 2.8: Cross section from Vu Ban to Hai Hau (140x vertical exaggeration,

modified after Hoc et al., 2003)

in vieinity to the adjacent bedrocks such as it is the case in Nam Dinh area, active faulting and repetitive transgression and repression events have resulted in a helerogeneous structure of inlersceling aquifers and aquicludes Geologic formations in that area with relevance for groundwater supply last from ‘Triassic bedrocks and late Neogene (Pliocene) semi-consolidated sediments up to unconsolidated sediments of Pleistocene and Holocene time Table 2.1 presents a stratigraphic overview of Nam Dinh Province

Table 2.1: Stratigraphy and Hydrostratipraphy of the strata in the Nam Dinh area

Middle [Q2"ln HaNoi am, a

Lower | Qi'le Le Chi am

Neogene Pliocene Ny vb Vinh Bao am

* Note: (a) - alluvial; (m) - marine, (b) - swamp, bog; (v) - colian

Paleoproterozoic - ed River Complex (PI sh)

The ancicnL metamorphic rocks of the Red River Complex mark few clevaled

hills in the NW of Nam Dinh, which are scattered along a 4 km’ area in NW-SE direction Outcrops can be found in Goi, Le Xa and Ngan mountains in the Vu Ban

district, as well as Phnong Nhi and An Lao mountains in Y Yen districl The

smountains mark the top of the uplifted Vu Ban Complex having a structural

direction of NNW-SSE and NW-SE Strike slip and reverse faults mark the contact

to the adjacent Triassic rocks to the West

‘The Red River Complex mainly consists of

¢ Gneiss with biotite, gamet and sillimanite which is commonly found in the

Vu Jan Glock Rock texture reaches from small to middle mineral size with

spattered large idiomorphic gamet with longths from 0.5 to 0.8 em

« Beside higher plagioclase contents, the Plagiogneis typically found in Goi

and Lc Xa mountains contains also biotite, garnet and sillimanite minerals

The texture is characterized by small te mediwn mineral sizes and

Nengene, Pliocene ~ Vinh Bao Formation (n; vb)

‘The Vinh Bao formation is widely present in the deeper subsurface of the Nam Dinh province, except of areas of the uplified Vu Ban block in the North-West and

West

‘Yop of Vinh Bao formation was met from 70 m bel (in NW of Nam Dinh) down

to 151 m bgl close to the coast in the SE, maximum observed thickness is >65.0 m

The top bormdary of the Virih Rac formation is an expecicd to be an unconformity

with intercalated laminated beds of clay and siltstone The Vinh Bao formation is believed to be deposited in a deltaic-neritic environment

Quaternary, Lower Pleistocene - Le Chi Formation (q," tc)

Le Chi formation was identified at a depth range within 93 to 118 m bel The

maximum thickness is 18 m and the minimum about 4m Le Chi formation has an

unconformity to the underlyimg Vinh Bao formation and to the the upper - middle

Pleistocene sediments of the La Noi formation

The Le Chi formation mainly consists of coarse grained material such as gravel and medium to coarse sand Sporadically, beds of groyish silt are intercalated The

sediments have been deposited in an alluvial to marine environment

Quaternary, Upper to Middle Pleistocene - Ila Noi Formation (q;°? hn)

Depth of the lop of the formation is increasing from NW (62 m bel) to the SE coastal area (96 m bel) Average thickness is about 24 m with a maximum at 49 m The basis of this formation is represented by unconformity to the Proterozoic and Triassic basement rocks, Neogene Vinh Bao formation and the Early Pleistocene Le Chi formation, whereas the top generally is an unconformity to the overlying Vinh

Phue formation

The Ha Noi formation is separated imto an upper and a lower part:

«© The upper part is composed of fine sedimonts such as sandy sill, silt and clay Previous palynological studies indicate that these sediments are deposited in a alluvial to marine environment

«The lower part can be characterized by dominated by medium to coarse grain

size sediments with intercalated silt layers This sub-formation shows fining-

upward characteristics, with a dominant coarse fraction (coarse sand, gravel)

close to the basis and an increasing fine fraction (fine sand, silt, clay) with

The Vinh Phuc formation is found from 35 m to 96 m depth It has an average thickness of about 30 m, with strongly varying maximum of 61 m in the south contral parL of Nam Dinh and minimum of 12m close to the adjacent bard rocks in the south west In the West of Nam Dinh area this formations locally overlies directly the Mesozoic and Proterozoic rocks In other areas of Nam Dinh (and the whole Red River Delia) il typically has a disconformity to the underlymg Ha Noi formation A disconformity to the Llolocene Lai [Jung formation is generally found

at the top of Vinh Phue

The Vink Phuc formation can generally be divided into 3 paris wilh different origins:

¢ Alluvial Vinh Phuc formation: his part can be found locally in Nam Dinh

It is characterized by a coarse grain fraction (fine to coarse sand, gravel)

Dominating minerals are quartz and mica

« Alluvial to marine Vinh Phuc formation: This part of Vinh Phuc formation conlains coarser grain sic fraction as fine lo medium sand and scatfercd gravel, representing sedimentation in an alluvial environment

« Marine Vinh Phue formation, This sediment only exists in the south of Nam Dinh area This part mainly consists of clay and silt of marine origin

Quaternary, Lower to Middle Holocene - Hai Hung farmation (Q;'* hh)

The Lai lung formation widely located in Nam Dinh area and is locally exposed at the surface Top of the Hai Hung formation can be in depths of down ta

37 mm Tho average thickness of this formation is about 28 m, bul varies strongly with maximum of 45 m and minimum of about 8 m in the vicinity of outcropping hard rocks in the west The Hai Hung formation is generally met sandwiched between the late Pleistocene sediments of the Vink Phuc formation at the bottom

and more recent Holocene sediments on the top,

lenses Locally, shell layers occur

‘The lower Llai Llung subformation comprising three facies types:

- Alluvialmarine: Mainly grayish silt and clay wilh intercalated fine sand layers

- Bog-marine: Dark gray silt and clay with varying fine sand and

remarkable cantent of plant remnants

- Marine: Brownish grey fine sandy silt and clay, typically contains

remnants of gaper shell

Generally, the sedimentation environments of the Hai Hung formation reflect the

marine transgression of the Liarly Llolocene by the succession of a prevailing estuarine environment up to a more littoral, swamp dominated and finally a gulf

ervirormertt,

Quaternary, Upper Holocene - Thai Binh formation (Q,' th)

The Thai Binh formation has major impact on the geomorphology of Nam Dinh

and roproscnls the source rock for most of the agricultural soils, The Thai Đình

formation generally overlies the Hai Hung formation with an observed thickness

‘between 37 and 51m (average 21 mm)

The Thai Binh formation is divided into three sub-formations They reflect the transition from a marine dominated to a more alluvial environment:

‘Upper sub-formation comprises marine, alluvial, boggy and colian facies

- Marine: Mainly consist of grey fine sand and silt

- Folian marine sediment: Boach ridge deposits aligned parallel 10 recent coast Due to evlian sorting processes the sediments are dominated by

fine sand

- Alluvial - marine sediment: These sediments distributed widely in Nghia Tlung, Iai Iau District Their composition included grey fine sand

Fining-upward to silty clay

- Alluvial-boggy sediment: Sedimentary composition was mainly silt and clay with fine sand

Middle sub-formation: marine dominated with alluvial influence

- Alluvial - marine: Composition contained brown clay with fine sand and sandy silt layers

- Marine sediment: ‘This sediment is widespread close to the surface with a

range of fing sand and silly sand Typical characlerislic are ramnants of marine snails (operculum)

Lower subformation: marine dominated with alluvial-boggy influence:

- Alluyial - marine: ‘These sediments are found in Xuan Thay and Hai hau area Composition is mainly fine sandy silt and clay

- Roggy - marine: Grayish clay with sand and bigh content of organic

material

Tiydrogeological characteristics

Hydrogeological units

According to Iloc et al 2003, the Cenozoic formations m the RRD can be

distinguished into 5 hydrogeological units, namely Upper Holocene aquifer in Thai Binh formation (qhéd), Lower Holocene aquifer in Hai Hung formation (qhhh), Upper Pleistocene aquitard in Vinh Phuc formation (qpvp), Lower and Middle

Pleistocene aquifer in Ha Noi formation (qpha) and Neogene aquifer (qp-m2) "41

Upper Holocene aquifer - Thai Binh formation (qhié)

This aquifer is widely distributed in the district of Iai Tau Nghia Hung, Giao

Thuy Xuan Truong Nara Dinh aral Nam Truc Main components of aquifer include

on terrain feabures and characteristics of water-bearing lens The IDS has the range

of 0.5-23 gf, freshwater lens with TDS < g/l are rarely distributed near the rivers Major recharge sources for this aquiler is rainfall and surface water bodies in Xuart

‘Truong, Giao Thuy, Hai Hau and Nghĩa Hung districts

In general, this aquifer has a poor potential for groundwater in both terms of quantity and quality, thus less sigreficanl in waler supply However, in some

northern communes in Nam ‘ruc, ‘ruc Ninh and Nam Dinh city, groundwater in

this aquifer is still used in small scale for agricultural puposes

Lower Holocene aquifer - Hai Hung formation (qhi:)

This aquifer is not evenly distributed throughout the study area, and is not

exposed on the surface Components of aquifer inelude sand, silty sand, silty clay of

Hai Hung formation This aquiler has a hydralic conductivity of K 0.05-0.4 mưday,

TDS of the waler changes very sharply The freshwaler lens with TDS < 1g/ are rarcly distibuted ucar the Red River Major recharfe sources for this aquifer is rainfall and surface water bodies in Xuan Truong, Giao Thuy, Iai Hau and Nghia Hing districts

This is a very poor aquifer with low water quality, thus less significant in water supply Groundwater in this aquifer is only used in small scale by households living

along the Red River

Upper Pleistocene aquitard - Vinh Phuc formation (qpvp)

This aquitard is widely distributed in the region with the main lithological composition of clay, silly clay af marine sediment The thickness of this aquilard ts

ranging from 7m to 34m ‘This aquitard has a hydralic conductivity of K = 0,005- 0.07 m/day.

formation, ‘his aquifer has a transmissivity of T = 500-1000 m?/day

TDS in this aquifer ranges from 0,3 to 3 g/l A large freshwater zone with TDS <

igél lays beneath the southern districts of Hai Hau, Nghia Hung, Truc Ninh and a

part of Nam ‘True ‘this aquifer has a very weak hydraulic connection with the above aquifers (see Figure 2.9)

This aquifer is classified as water-tich with high thickness, wide distribution area and good water quality ‘This aquifer is currently the main subject of extensive extraction for domestic use in the southern areas of Nam Dinh Province It is

suggested that there should be appropriate extraction planning and management ko

utilize and protect this aquifer

Neogene aquifer (qp-m2)

This aquifer is widely distributed throughout tie siady area Lithalogical

composition includes sandstone, siltstone, claystone, Groundwater exists in the form of fracture and porosity This aquifer has a transmissivily of T — 16-438

ul /day

‘The chemical composition of water changes vertically l'reshwater can be found

al the depth of 250 m hg] in Nghĩa Hung distriel, However, water at the same depth

in other districts is mostly saline water

23.2 Groundwater dynamics

Operating by NDWRET since 1995, the national groundwater-monitoring

unetwork represents an important ebservation source providing groundwater quantity

and quality data for more than 18 years The national monitoring network in Nam Dinh comprises 5 stations Q107, Q108, Q109, Q110 and QUIT, comprising 10 monitoring wells sereened in the three hydrogeological units qh (5 wells), qp (3 wells) and n (2 wells), Long-term monitoring shows that groundwater level

fluctuation are caused by nalural factors (climate aud hydrological faclors) as wall

as anthropogenic impacts such as groundwater extraction, lake and canal

construction, irrigation and drainage systems

The long-term time series of monthly averaged groundwater level dala iTustrate some major impacts of these factors According to the behavior of level fluctuation, the screened aquifers can be allocated to two hydraulic groups (Figure 6) The

shallow gh aquifer shows a slable (rend sinee begin of data colleclion im 1995,

Deficits in the Holocene groundwater budget are balanced by recharge in frame of repetitive phases of irrigation and mundation The seasonal amplitude of up to one Meter indicales a close hydraulic connection wilh nearby rivers and charmels Q111 even shows a slightly increasing trend, possibly originated in local subsidence or increasing sea level The second hydraulic group is represented by the time-series of

gp and n aquilers indicating hydraulic conmected aquilers Obviously, Ihe inercasing exploitation of groundwater since the 1990s results in a decreasing trend of groundwater levels in both Pleistocene aquifers of 0.4 m/year (Q108, Q107) up to

0.6 m/vear (Q109) The Ulusiraled tine series of groundwater level Muctuation is 4

typical example for the situation in Nam Dinh and shed some light on groundwater

dynamics in this province Shallow groundwater (qh) receives a significant amour!

of recharge duc to hydraulic connection with river, tibutarics and urigation channels It can be concluded that at the transition of the units qh - gp, low permeable aquicludes separate the relatively isolated hydraulic system of unit gh and units qp 1 Assuming the majority of abstraction wells are screened in gp aquifer, the similar behaviour of qp and n indicates a close connection on a regional

scale At the site with the strongest observed groundwater drawdown (Q109), a

selatively high hydraulic head inn is observed indicating a flow recharge of gp from

n aquifer.