By Md. Rezaul Hasan, Md. Shamsuddin, Md. Sohel Masud, Dr. AFM Afzal Hossain (Institute of Water Modelling) Revitalizing the Ganges Coastal Zone Conference 21-23 October 2014, Dhaka, Bangladesh http://waterandfood.org/ganges-conference/

1. Groundwater Salinity Zoning in the
Southwestern Coastal Region of
Bangladesh
Presented
by
Md. Rezaul Hasan
Senior Specialist, IWM
October 22, 2014
A Research Study
Team Members:
Md. Rezaul Hasan, IWM
Md. Shamsuddin, IWM
Md. Sohel Masud, IWM
Dr. AFM Afzal Hossain, IWM

2. Presentation Outline
l Justification of the Study
l Methodology
l Findings
l Conclusion

3. Jus$fica$on
of
the
Study

4. Review of Issues Related to Coastal
Area
l Coastal area covers about 32% of the country.
l Coastal area of Bangladesh has three distinct regions ~ southeast
(Eastern Hilly), central and southwest.
l The southwestern region is characterized by the Ganges floodplains
with low relief and numerous rivers and channels linked with the Bay
of Bengal.
l Salinity exists in the surface water since long but it has increased
significantly over the last four decades due to reduction of upland
fresh water flow.
l Eventually salinity intrudes in the coastal aquifer towards upwards by
each year.

5. Map Showing Coastal Region

6. River
System
in South
Western
Region

7. Groundwater in Coastal Region
l Due to influence of tide in coastal rivers, the livelihoods of the
inhabitants of coast area have to depend on groundwater for meeting
demand in respect of domestic, municipal, irrigation, industrial and
other needs.
l Groundwater can be abstracted from aquifers at varying depths-
shallow and deep. There should be an aquitard or aquiclude
separating the shallow and deep aquifers (DPHE, 2000).
l Inland salinization also occurs due to the presence of paleo-brackish
water entrapped in small areas during the geological period between
12000 and 10000 years.

8. Justification of the Study
l Very few studies on groundwater salinity for southwestern coastal
region.
l Most of the research works to date have been carried out mainly on
irrigation, drainage, flood control and diversion of Ganges flows during
dry season.
l For optimal use of groundwater resource in coastal area, salinity
zoning map is a useful tool for planned development to meet drinking
water supply as well as boost up agricultural production.

9. Salinity Standard
l Salinity is the measure of concentration of dissolved salts in water
such as chloride anions, usually expressed in parts per thousand
(1 ppt = 1000 mg/L = 1000 ppm).
l In Bangladesh, the recommended range of chloride in drinking water
is 150 to 600 ppm (ECR 1997).
l A higher value of salinity upto 1000 ppm for problematic areas
including coastal belt is considered (DPHE 2006) for drinking.
l For rice production in Bangladesh generally salinity upto 3 dS/m
(around 2000 ppm) is accepted (BARC 2013).

10. Study Area Boundary
The area covers Dumuria,
Batiaghata and Paikgacha
upazilas of Khulna district,
and Tala upazilas of
Satkhira district
The area is about 918.3
sq km.
River System:
Kazibacha
Kobadak
Gangrail
The boundary of the study
a r e a m a i n l y f o l l o w s
e x i s t i n g r i v e r s a n d
northern part follows
administrative boundary.

11. ü Aman is the principal crop.
ü Agricultural use of groundwater is limited.
ü GW utilization is limited with domestic use through HTWs.
ü Mechanically driven tubewells are very few.
ü GW remains within suction limit but the utilization is
restricted mainly by salinity and at some places by
excessive Arsenic and Iron.
ü Shrimp farming is being practiced.
ü The study area lies within different polders of BWDB.
Overview: Study Area

12. Methodology

13. Methodology of the Study
l The present study was formulated on the basis of field
activities conducted in April 2013.
l The field activities were carried out from two main
considerations, namely i) hydro-chemical investigation
and ii) qualitative survey.
Although hydro-chemical investigation reflects fairly the degree of
salinity, the relevant sociological indicators are also useful in
understanding the level of impact of salinity from social perspectives.

14. Hydro-chemical Investigation
(Shallow Aquifer)
l Groundwater samples were
collected from 130 SHTW.
l Shallow Aquifer: 35-120 m.
l Field test kit was used for
measuring groundwater
quality parameters.
l GW quality parameters- pH,
temperature, EC, TDS and
salinity as Chloride were
measured.

15. l Groundwater samples were
collected from 115 DHTW.
l Deep Aquifer: 150-340 m.
l Field test kit was used for
measuring groundwater
quality parameters.
l GW quality parameters- pH,
temperature, EC, TDS and
salinity as Chloride were
measured.
Hydro-chemical Investigation
(Deep Aquifer)

16. Hydro-chemical Investigation (in-situ)

17. Hydro-chemical Investigation (lab test)
l Field test kit – not shows high level of accuracy, requires modification
based on relations derived from lab test results
l 28 water samples have been tested at the DPHE laboratory.
l Prior to the selection of the testing laboratory, samples of eight wells
were tested in (BUET), (BCSIR) and DPHE laboratories.
l Since DPHE laboratory analyses matched satisfactorily to those of
BUET results, DPHE laboratory was selected for lab analysis.
l Field values were modified according to relations derived from the lab
test results.

18. Hydro-chemical Investigation
(Field vs Lab)
Relationship curves: EC (µS/cm) -BUET vs Field (left);
and EC vs Chloride (right).

19. Information on FGD and KII
l Qualitative data were collected by FGDs and KIIs using
checklist.
l The FGDs were conducted at six unions with local level
public representatives and people of different
professional groups (farmers, businessmen, service
holders, shopkeepers, teachers, housewives, etc).
l KIIs were held in the study area with Staffs of DPHE.

20. Verification of Qualitative Information
l To verify GW salinity especially at relatively less saline
areas as noticed from qualitative survey, field tests were
carried out at most of the locations.
l Samples were taken from at least three tube wells of
each location.
l Thus, information of qualitative social survey verified by
field test kit.
l Verified information has further been utilized for map
delineation.

21. Findings

22. Public Consultation
l Change in groundwater salinity is not prominently
perceived but there is apprehension of increase.
l During Rabi season, most of the agricultural land could not
be cultivated due to presence of high salinity.
l However, the Boro cultivation is limited in the upper part of
the study area where suitable groundwater is available.

23. FGD and KII
l Mostly of the tubewells belongs to government.
l The study area covers both saline and less saline aquifers.
In Paikgacha, shallow aquifer is less saline at the adjacent
areas of the Kobadak river while in the rest part is not
suitable.
l Shrimp culture by intruding saline water is degrading the
soil quality and poor paddy production.

24. Groundwater Salinity Zoning
l Both quantitative (i.e., hydro-chemical investigation) and
qualitative (i.e., FGD, KII) data were used for proper
evaluation with a specific range of salinity.
l The qualitative information that was verified by field test kit
was superimposed on the salinity distribution map.
l Classification of GW salinity into different zones for various
purposes including drinking purpose and rice cultivation.
l Ranges of salinity is of allowable limits.
l The zones with concentration are <600, 600-1000,

25. GW Salinity Zoning Map-Dumuria
Shallow Deep
<600
600-­‐1000
1000-­‐2000
>2000
12% 21% 57% 10%
<600
600-­‐1000
1000-­‐2000
>2000
75% 5% 3% 17%

26. GW Salinity Zoning Map-Batiaghata
Shallow Deep
<600
600-­‐1000
1000-­‐2000
>2000
1% 5% 89% 5%
<600
600-­‐1000
1000-­‐2000
>2000
68% 8% 18% 6%

27. GW Salinity Zoning Map-Paikgacha
Shallow Deep
<600
600-­‐1000
1000-­‐2000
>2000
20% 4% 35% 41%
<600
600-­‐1000
1000-­‐2000
>2000
0% 4% 26% 70%

28. GW Salinity Zoning Map-Tala
DeepShallow
<600
600-­‐1000
1000-­‐2000
>2000
71% 2% 27% 0%
<600
600-­‐1000
1000-­‐2000
>2000
36% 32% 7% 25%

29. Groundwater
Salinity
Zoning Map-
Shallow
Aquifer
<600
600-­‐1000
1000-­‐2000
>2000
20% 12% 54% 14%

30. Groundwater
Salinity
Zoning Map-
Deep Aquifer
<600
600-­‐1000
1000-­‐2000
>2000
54% 9% 11% 26%

31. Conclusions

32. Conclusions
l The deep aquifer is less saline than that of shallow
aquifer except Paikgacha
l For shallow aquifer that the zone of salinity 1000-2000
ppm covers 54% of the study area extending over
northern, eastern and major portion of southern parts.
l The saline zone with salinity >2000 ppm also lies in the
southern part (14%).
l Fresh zone (<600 ppm) covers only 20% of the study
area in scattered manner.

33. Conclusions (contd..)
l In case of deep aquifer, fresh zone with salinity <600
ppm covers major portion of the study area (54%) with
exception at the southern part.
l Saline zone (>2000 ppm) is prominent at the southern
part covering 26%.
l A strip of three zones (600-1000, 1000-2000 and >2000
ppm) covers in scattered from north to south at middle of
the study area.

34. Conclusions (contd..)
l Change in GW salinity is not prominently perceived by
the local people but there is apprehension of its increase
l During Rabi season, most of the agricultural land could
not be cultivated due to presence of high salinity.
l Shrimp farming has reduced rice production.
l Similar study may be extended covering the entire
coastal belt for proper planning and development
activities.
l Assessment of available fresh water resources in
groundwater reserviour using state of art technology like
mathematical model.

35. Thank You

37. Comparison of Aquifer System
UNDP
(1982)
Aggarwal
(2000)
BGS (2001) JICA
(2002)
GWTF (2002)
Upper/
Composite
Aquifer
1st Aquifer Upper
Shallow
Aquifer
Upper
Aquifer
Upper Holocene
Aquifer
Main Aquifer 2nd Aquifer Lower
Shallow
Aquifer
Mid Aquifer Middle Holocene
Aquifer
Deep
Aquifer
3rd Aquifer Deep
Aquifer
Deep
Aquifer
Late Pleistocene-
Holocene Aquifer

38. References
l Aggarwal, P K, A R Basu, R J Poreda, K M Kulkarni, K Froehlich, S A Tarafder, M Ali,
N Ahmed, A Hossain, M Rahman, S R Ahmed, 2000. A Report on Isotope Hydrology
of Groundwater in Bangladesh: Implications for Characterization and mitigation of
Arsenic in Groundwater. IAEA TC Project BGD/8/016.
l BGS and DPHE (2001), Arsenic contamination of groundwater in Bangladesh,
Kinniburgh, D. G. and Smedley, P. L. (Editors), vol. 2, Final Report, BGS Technical
Report WC/00/19, British Geological Survey, Keyworth, United Kingdom.
l GWTF, 2002. Report of the Ground Water Task Force. Local Government Division,
Ministry of Local Government, Rural Development & Cooperatives, Government of
the People’s Republic of Bangladesh.
l JICA, 2002. The study on groundwater development of deep aquifers for safe
drinking water supply to arsenic affected areas in Western Bangladesh. Final Report.
Kokusai Kogyo Co Ltd., Mitsui Mineral Development Engineering Co Ltd.
l UNDP, 1982. The Hydrogeological Conditions of Bangladesh. Technical Report DP/
UN/BGD-74-009/1.