08
PROMOTING RAINFED POND FOR THE TOWN’S WATER SUPPLY SYSTEM:A CASE STUDY OF THE SOUTH-WEST COASTAL REGION IN BANGLADESH
Md. Zahid Hossain1 and Ghulam Murtaza2
Technical Consultant (Bangladesh Rural Water Supply, Sanitation and Hygiene for Human
Capital Development Project of Bangladesh Government),
Palli Karma-Sahayak Foundation (Government Organization), Bangladesh
2
EX. Professor, Urban and Rural Planning, Khulna University, Bangladesh
Email: zahidho@yahoo.com

1

How to cite this paper:

Hossain Md. Zahid andMurtaza Ghulam (2023)
Promoting Rainfed Pond forTown’sWater
SupplySystem: A Case Study ofSouth-west Coastal Region
in Bangladesh, Journal of
Global Resources, Vol. 09(02)DOI:
10.46587/JGR.2023.v09i02.008

Received: 25 May 2023
Reviewed: 15 June 2023
Final Accepted: 28 June 2023

Abstract: Bangladesh’s coastal area is vulnerable to thechanging climatic condition because of its geographic
location and low-lying topography, and this vulnerability has
been acute due to reducing upland flow during dry periods
and sea level rise contributing to saline intrusion andinundation of coastal freshwater resources. Over the past 25years, salinity intrusion in Bangladesh has increased byabout 26 percent with the affected areas expanding eachyear. According to a study by World Bank in 2014, climatechange is likely to further increase river and groundwatersalinity dramatically by 2050 and exacerbate shortages ofdrinking water in the southwest coastal areas. Because of
the salinity of both groundwater and surface water in theMongla port municipality area, compound river water andrainfed pond water became the main source of drinking
water here. Currently, Mongla Port municipality located inthe coastal belt is supplying water to town dwellers bypipeline with a water treatment system taking raw water fromboth harvested rainwater and a limited period of river water
through ponds. From physical observation, focus group
discussion with water users, and interaction with key
information providers, the study team assessed the quantityof water against the demand and also analyzed the qualityof water both are satisfied. By using secondary data, thestudy team also analyzed the Mongla River’s water salinity
and rainfall intensity for assessing its long-run feasibility ofit. The result of the study on Mongla Port municipality’s watersupply shows that it is a well-functional system, that could be
replicated in another coastal area as it is a nature-based
solution which makes the people and authority adapt it easily
with keeping well-functioning.
Key words: Rainfed Pond, Nature-Based Solution, Salinity
in Coastal Area, Climate Change62

Introduction
The coastal zone of Bangladesh covers one-third of the whole area’s population nearly 40
million. Out of 64, 19 districts are coastal, and the most southwestern five coastal districts, i.e.,
Satkhira, Khulna, Bagerhat, Pirojpur, and Barguna, have been identified as the hard-to-reachareas. People in these districts have been exposed to different types of water security risks,particularly groundwater contaminated with salinity, which is not suitable for humanconsumption. Previous studies conducted by many research organizations have consistently
reported higher salinity, as well as considerable trace and toxic elements in the groundwater
samples from this area. Hoque (2009) estimated that approximately 30 million people areunable to collect potable water and 15 million people are already forced to drink saline
groundwater in this region. This is principally due to the higher degree of spatial variability ofsalinity in both shallow and deeper aquifers. It is a consequence of the complex coastalhydrogeology and land use of the active Ganges–Brahmaputra delta. This water quality
constraint, together with complex hydrogeology, leads to the unavailability of suitablefreshwater aquifer layers limiting the use of tube wells. Therefore, the coastal people ofsouthwest Bangladesh must rely on alternative options. In these five coastal districts, 12–34
percent of the inhabitants are using alternative sources such as rainwater, surface water, andother unimproved water sources.
Climate Impact Stress of South-west Region
The Southwest (SW) region is more vulnerable comparatively than the other 07 hydrologicalregions because salinity intrusion is high here. The green and black lines of Figure 01 (left)show the salinity concentrations 01 ppt and 5 ppt respectively which covered almost all areasof the SW region. Three mighty rivers Ganges (in Bangladesh is called Padma), Brahmaputra,and Meghna (originated by Surma and Khusiyara rivers) came from the neighboring country
and are dominating whole surface water resources in Bangladesh. SW region’s salinity
intrusion is high because Padma’s branch rivers Garai and Modhumoti are being dried up due
to low water flow during the dry season caused by climate change and the withdrawing riverwater from up land. However, salinity intrusion in South-centre and Southeast regions iscomparatively low because up surface flow comes from jointly three mighty rivers-Padma,Brahmaputra, and Meghna, that’s why here backflow from the Bay of Bengal is less than thebackflow in the SW region. The intrusion of backflow from the sea depends on river flow, thatwhy the study team analyzed the Ganges minimum water flow for having an understanding ofsalinity intrusion in the SW region.
Figure 01: Location Map63

Figure 02 on the annual daily minimum flow (m3/s) of Ganges water at Hardinge Bridge is takenfrom a study ‘River salinity and climate change’ carried out by the World Bank in 2014. Thisgraph shows that before the Farakka Barrage minimum water flow of the Ganges to Padma
River was 1920 m3/s, but after Farakka Barrage it started to reduce and reached a minimum
average flow of 425 m3/s in the time of 1990. After the Ganges water treaty in 1996, theminimum average water flow started to move up to 750 m3/s.
Figure 02: Annual Daily Minimum Flow, Hardinge Bridge

Review of Literature, Country’s Strategy, Policy Act
Many works of literature have been taken to review with a view to gathering information about
rainfall patterns and intensity. The rainfall patterns in Bangladesh are governed by theseasonally varying meteorological system of the southwest monsoon, in which monsoon andwinter seasons are separated by two transitional seasons namely pre-monsoon and postmonsoon (Quadir et al., 2006). Several studies (Choudhury et al., 1997; Quadir et al., 2001)
have reported that the precipitation in Bangladesh has been increasing during recent decades.
Hussain et al. (2001) found that the mean annual rainfall was 2387.20 mm from 1975 to 1995.
May to September were the highest rainfall months when the rainfall was more than 300 mm
in over 63.80 percent of the years. Karmakar and Mian (1994) stated, the correlation between
pre-monsoon rainfall and monsoon rainfall over the different stations of Bangladesh According
to Ahmed and Karmakar (1993). Chowdhury and Debsarma (1992) investigated a significant
upward trend of precipitation (by 18 percent) in the north, and west-southwest 11 regions since
the early 70 percent, and a downward trend in the south-east. Quadir et al. (2003) reported
that the average annual over Bangladesh varies from 1429-4338 mm. About 75 percent of theannual precipitation occurred during the monsoon period, about 15 percent in the pre-monsoon
season, and the rest 10 percent occurred in winter and post-monsoon season. In Bangladesh
monsoon, average rainfall varies from 1194 mm to 3454 mm (BBS, 2002). More than 70
percent of Bangladesh’s annual rainfall occurs in the monsoon (June-September) season(Hussain and Sultana, 1996; Matsumoto, 1998). The main rainfall during the monsoon season
ranges from 1000 to 3000 mm in the country. The annual rainfall in the country ranges from1400 to 5800 mm, but its distribution is uneven.
The country’s strategy, the 8th Fiver Year Plan has been reviewed. The country’s policy
regarding water policy (1999), water supply and sanitation policy (1998), national arsenic
mitigation policy (2004), climate change strategy and action plan (2009), national adaptation
64

plan (2023), coastal zone policy (2005), water act (2013), water rules (2018) along withcountry’s 8th Five Year Plan (FYP) were reviewed.
Figure 03: National Adaptation Plan

According to the National adaptation plan formulated in 2023, Figure 03 shows that a naturebased solution is best for adaptation. A rainfed pond is an option for water supply for coastal
areas in Bangladesh where water scarcity is acute. Water Act and Water Rules are giving
support for restoring the ponds for drinking purposes and giving security anyway these ponds
could not be used for other purposes instead of drinking water. 8th FYP has been focusing on
digging rainfed ponds for ensuring safe water for people in the coastal area, especially in theSW region. The national water policy (1999) and national water supply and sanitation policy(1998) are inspiring to adapt rainwater harvesting where possible. Coastal Zone policy andClimate change strategy also give importance to rainwater harvesting for drinking purposes incoastal areas in Bangladesh.
Study Area
Mongla Port municipality is situated under the Bagerhat district in the southwest coastal
region of Bangladesh. This municipality was established in 1990 and became an ‘A’ classmunicipality in 2012. The municipality has 8615 Holding Numbers where 2980 HHs relate topipeline water supply. The literacy rate among the town's people is 53.6 percent.
Figure 04: Study Area

65

DISCUSSION AND RESULT ANALYSISRainfall Intensity of the Study Area
Availability of rainfall data, rain curve in the hydrological map of the country, and 41958 # rain
gauge is the best for choosing as it is situated at Mongla. Data was collected from Bangladesh
Agricultural Research Council (BARC)’ webpage. Monthly and yearly rainfall from 1991 to 2019has been analyzed, in Figures 05 and 06. Yearly rainfall in Mongla from 1919 to 2019 showed
no continuous degradation or upgradation but showed a fluctuation that did not follow a timeinterval. After analysis, it was seen, yearly rainfall was unpredictable from 1991 to 2019. For
example, in 1992 annual rainfall was 1232 mm, and the next year in 1993 it was 1853 mm,
and the previous year in 1991 it was 1997 mm, which means that there was a huge gap inconsecutive two years. In addition, after 10 years it was 2786 mm in 2002. On the other hand,another observation was found, in 2017 annual rainfall was 2100 mm, and since then it wasaround 2000 mm with fluctuation. Rainfall intensity from lowest to highest was 1258 mm to2786 mm respectively, but we can assume an average rainfall in Mongla is 1800 mm basedon analyzed and correlation with literature.
Figure 05: Yearly Average Rainfall, MonglaMongla (Rain gauge station # 41958)
Rainfall, mm

3000
2500
2000
1500
1000
500

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

2014

2015

2016

2017

2018

2019

0Year

Figure 06: Monthly Average Rainfall, Mongla

Rainfall, mm

Monthly Average Rainfall, Mongla
600
500
400
300
200
100
0JanFebMar

AprMayJunJul

Aug

Sept

Oct

Nov

Dec

Month
2015-20192010-2014

2005-2009

2000-2004

1995-1999

1991-1994

From 1991 to 2019, monthly rainfall showed at the figure, there was a fluctuation in
their intensity, but maximum rainfall has been happening from June to July. Monthly rainfall
also shows significant rainfall has been happening from May to October. Rainfall is shortened
than in earlier decades. From analyzing the monthly rainfall from 1991 to 2019, the study teamassumes the monthly rainfall for calculating the effective harvested rainwater for Mongla Port
municipality
66

MonthsRainfall, mmJan0Feb0Mar0

Apr70

May150Jun300July320

Aug270

Sept160

Oct120

Nov0Dec0River’s Water Quality
From published different journals following figure was analyzed for getting an understandingof river water’s salinity passing by the Mongla port municipality area. The river’s water at
Mongla port municipality from where water has been collecting municipality is September toDecember as salinity level during that period is 0.25 to 0.30 dS/m. During interaction withconcern persons of Mongla port municipality and physical observation of water collecting
practice it was seen that Mongla port municipality is collecting river’s water from September to
Mid of January every year.
Figure 07: River’s Water Quality

The river basin was analysed for why Mongla River’s water is acceptable salinity fordrinking purposes from September to December than Pousu River.
Figure 08: Mongla River Flow Analysis
Water flow comesfrom Padma River
Water flow to Arial khan riverfrom jointly two mighty rivers
Padma and Jamuna
Pousu river
Water body, Kendua beel
Mongla river
Mongla port municipality

Mongla River’s water comes from multiple water bodies, one of them being Kendual
beel. Basically, the Arial khan river originated from two mighty rivers- Padma and Jamuna havebeen contributing their flow to the branch’s river from which the Mongla River originated. Theriver morphology of Mongla River makes it for comparatively less senility than Pousu
67

Calculation of Pond’s Water Capacity
The rainfed pond’s catchment area was analyzed physically, and interaction with themunicipality and Google map has been shown in the below map and pictures. The total
catchment area of the ponds is 224,040 square meters. And the average depth is 1.5 meters.
The total volume of the pond is 336060 m3.
Figure 09: Water Bodies

Water Demand Vs Supply
Pond’s volume is 336060 m3. Currently, 2980 Households and 220 establishments relate tothe pipeline water supply system. So, the current monthly water demand is 61500 m3
considering 2980 HHs and 220 establishments.
Table 10: Water Demand Vs Supply
MonthJanuary
February
MarchApril
May
June
July
AugustSeptember
OctoberNovember
DecemberCurrent Water
Demand (m3)
61500
61500
61500
61500
61500
61500
61500
61500
61500
61500
61500
61500

Harvested
Rainwater (m3)00
015,68033,60067,20071,68060,48035,84026,88000

River’s Water(m3)00000000
150,000
364,620
61,50061,500

Cumulative water (m3) afterMonthly Consumption
268,500
207,000
145,500
99,68071,78077,48087,66086,640124,340
330,000
330000330000

Water Quality
For getting an understanding of water quality, the study team analyzed the water quality datatested by Mongla Port municipality and discussed with users at different levels such as Riksha
Van pullers, labours, teachers, shopkeepers, and house owners, especially females. During
68the interaction, the study team asked them if its sweet water. how much salinity do they feel
during drinking and when it increases? Did you get a smell? Are they satisfied with this water?
Most answered where salinity is acceptable, but 15 percent said during the dry season salinity
is high but drinkable. No smell they found but sometimes get more turbidity said 25 percent
responded. The municipality’s water data showed that the salinity range is 600 mg/l to 850
mg/l. The study team observed and analyzed the treatment facility, baffle filter with alum dosing
aiming to get turbidity below 5 NTU, sand filtration and chlorination system, and testing dataof residual chlorination at the endpoint of service which are almost okay. But sometimes get
more turbidity, users responded, because of poor operation like alum and chlorination dosing
does not give properly.

Conclusion
The study team found from the analytical results that Mongla River’s water salinity is
acceptable for four months from September to December which is not sufficient to meet thewater demand all-round the year. In this case, rainwater harvesting in the pond when riverwater is not available gives support to addressing the water demand all-round the year. Inaddition, from April to August, water is sweeter than in other months as rainwater reduces theconcentration of salinity of pond water. So, from the facts and statistics of the result, this study
is telling what technology is taken at Mongla Port municipality for the town’s water supply
system is sustainable due to adapting the nature-based solution. Therefore, this study has
been evidenced to promote this nature-based technology in climate-vulnerable coastal areas
where it is feasible.
References
1. Threats to the Sundarbans Mangrove Wetlands Ecosystems from Transboundary Water Allocationin the Ganges Basin: A Preliminary Problem Analysis; M. Shafi N., Albrecht Gnauck
2. Monitoring bacterial Contamination of piped water supply in rural coastal Bangladesh; Md. Sabbir,Ali, Islam, Kabir and Hoque
3. River salinity and climate change evidence from coastal Bangladesh; Susmita, Kamal, Khan andAinun Nishat, World Bank 2014
4. Rainfall data from Bangladesh Agricultural Research Council
5. Groundwater Zoning map-2004 and (2010) developed by Agricultural Development Corporation
6. Quadir D. A. (2006) Climate variability of Bangladesh. Contribution to monsoon Asia IntegratedRegional Study (MAIRS). SMRC, Dhaka7. Ahmed, A.U. and Haque, N., (2002) Climate Change and Sustainable Development. Paper
presented at the Dhaka Meet on Sustainable Development, March 14-18, 2002.Incorporated in Q.K.
Ahmad and A.U. Ahmed (eds.), Citizens’ Perspectives on Sustainable Development
8. Md. Zahid Hossain, Imrul Kayes Muniruzzaman, Hasin Jahan-Prospect of Rainwater Harvesting in
RMG and Textile Industry: Lessons Learned From 4 Factories in Bangladesh, published atInternational Journal of Scientific & Engineering Research Volume 12, Issue 2, February-2021.
9. Ali M. M., Ahmed M., Talukder M.S.U. and Hye M. A. (1994) Rainfall distribution and agricultural
droughts influencing cropping pattern at Mymensingh region. Progressive Agriculture, 5: 197 204
10. Hussain M.A. and Sultana N. (1996) Rainfall distribution over Bangladesh stations during themonsoon months in the absence of depression and cyclonic Stoilils. Mausam.
11. Feasibility of Rainwater Harvesting at Dhaka Export Processing Zone Area: A Potential Approach
to Reducing Dependency on Groundwater published at GSJ: Volume 9, Issue 11, Nov. 2021.
12. Bangladesh 8th FYP, National water policy (1999) National water supply and sanitation policy(1998) Coastal zone policy (2005) Climate change strategy and action plan (2009) National adaption
plan (2023), Water act (2013) and Water rules (2018)69