A CASE STUDY ON MANAGEMENT OF RAINWATER RESERVOIR IN HILLY AREAS OF BANGLADESH

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1 International Journal of Civil Engineering and Technology (IJCIET) Volume 7, Issue 6, November-December 2016, pp , Article ID: IJCIET_07_06_021 Available online at ISSN Print: and ISSN Online: IAEME Publication A CASE STUDY ON MANAGEMENT OF RAINWATER RESERVOIR IN HILLY AREAS OF BANGLADESH Maharam Dakua International Training Network Center, Bangladesh University of Engineering and Technology, Dhaka, Bangladesh Asef Mohammad Redwan Civil, Environmental and Construction Engineering Department, Texas Tech University, Lubbock, Texas, USA Begum Nazia Jahan Department of Civil Engineering, Military Institute of Science and Technology, Dhaka, Bangladesh Syed Mohammed Tareq Department of Civil Engineering, Military Institute of Science and Technology, Dhaka, Bangladesh Saifuddin Ahmed Department of Civil Engineering, Sonargaon University, Dhaka, Bangladesh Department of Civil Engineering, Bangladesh University of Engineering and Technology, Dhaka, Bangladesh ABSTRACT Due to complex geological profile, large depth of aquifer from the top of hilly surface and complex nature of hydro-geology, water supply system in hilly areas is largely dependent on surface water. During rainy season (June to September), surface water sources i.e. fresh water reservoirs, rivers, etc. provide water that people use, with or without any treatment. But during dry period, these sources become limited and scarce. Since the stored water in fresh water reservoirs is mainly rainwater, which reaches these ponds through surface runoff, availability of rainwater, rainfall pattern and storage capacity of reservoirs are critical to ensure water supply during the dry period in these areas. To address some of these issues, a study was undertaken on a rainwater based water supply system in Nayapara Refugee Camp in Teknafupa zila under Coxs-bazar district, where refugees of the camp are solely dependent on a reservoir which is fed by rainwater. During the study, analysis of surrounding catchments, potential of rainwater harvesting and capacity to store rainwater for the whole year were analyzed. The study thoroughly revealed the existing water crisis scenario of Nayapara refugee camp, based on which recommendations were editor@iaeme.com

2 A Case Study On Management of Rainwater Reservoir In Hilly Areas of Bangladesh made to increase the capacity of the reservoir to supply targeted amount of water to the refugees throughout the year. Key words: Hilly Areas, Fresh Water Reservoirs, Rainwater, Water Availability, Storage Capacity Cite this Article: Maharam Dakua, Asef Mohammad Redwan, Begum Nazia Jahan, Syed Mohammed Tareq, Saifuddin Ahmed and, A Case Study On Management of Rainwater Reservoir In Hilly Areas of Bangladesh. International Journal of Civil Engineering and Technology, 7(6), 2016, pp INTRODUCTION Despite increased water coverage in Bangladesh in the last few years, there exist pockets of areas in the country where water services are not satisfactory. Based on practical experience, many of these areas have been identified and termed as Hard-to-Reach Areas (HtRAs), which creates the notion that service providers fail to reach or find it difficult to provide services to these specific areas. For practical purposes, HtRAs are defined in Bangladesh in terms of both their remote geographical location as well as population residing out of the range of development activities [1]. According to National Strategy for Water and Sanitation (2011), with very little infrastructural development, road communication network in particular, water and sanitation coverage in these areas still remain much below the basic minimum level. Extreme poverty in these hard to reach (HtR) areas exacerbates the water and sanitation crisis. In order to achieve Bangladesh government's target of full coverage of water and sanitation, these areas need special attention in different aspects of development including technological options, social mobilization, financial resources, and service delivery mechanism because of special geographical, hydro-geological and social setting. Among the HtR areas identified by the government, the drinking water and sanitation challenges in the hilly areas results primarily from different geographic, socio-cultural and hydro-geologic conditions. Surface water sources in hilly areas, e.g., springs, charra and streams have seasonal fluctuations that exacerbate due to climate change as apparently observed during the past decades [2]. These surface water sources, despite subject to heavy pollution, are mostly used for drinking and other purposes by the people living in hilly areas. Groundwater extractions are not successful everywhere in the hilly areas due to varying altitude and rocky formation, and the water level also fluctuates seasonally. Therefore, developing water reservoirs at appropriate altitude for capturing and storage of spring and/or rainwater for distribution to downhill community through small pipe network could be adopted as a strategy. Individual or community rainwater harvesting systems with adequate storage for supplementing dry period requirements could also be built for solutions [2]. While surface water sources, i.e., sweet water ponds which are mainly stored rainwater, can provide sufficient water that people use in this area during rainy season (June to September), these sources become limited and scarce during dry period. Therefore, availability of rainwater, rainfall pattern and storage capacity of these reservoirs are critical in terms of water supply in dry period in these areas. To understand the dynamics of water supply in hard to reach hilly areas where groundwater is not available, a study was carried out in the Nayapara Refugee Camp, which is one of the two registered refugee camps in Teknaf sub-district under Cox's Bazar district of Bangladesh. Water scarcity during dry season is a huge problem for the camp, where United Nations High Commissioner for Refugees (UNHCR) have been working to provide support. The study was undertaken on a rainwater based water supply system in the camp, where refugees were solely dependent on a reservoir which stores rainwater. The main goal of this case study was to identify the main reasons of reservoir water getting dried out every year, which results into acute water scarcity during the period of April to May, and also to suggest the potential solutions. The main objectives of the study were: editor@iaeme.com

3 Maharam Dakua, Asef Mohammad Redwan, Begum Nazia Jahan, Syed Mohammed Tareq, Saifuddin Ahmed and Assessment of current deficit in water supply system of the camp from supply-demand analysis. Identification of major reasons of shortage of water in the reservoir during scarcity period each year. Identification of rainwater harvesting potential for the study area. Recommendation of measures/steps to minimize water scarcity during dry period. 2. BACKGROUD OF THE STUDY AREA Water supply system in hilly areas is different from other areas as the topography makes it difficult to transport water from one place to another. Hence, network based large water supply system is often not viable due to installation difficulties, and associated operation and maintenance cost. Though some of the hilly areas in Bangladesh have shallow/deep aquifers, people in many hilly areas are largely dependent on surface water. Water supply situation in Teknaf area is very critical as ground water is not easily available in most of these areas. According to Bangladesh Poush and Prattaya (2006), the crisis of fresh water can be categorized as one of the major problems in Teknaf. Some of the reasons identified behind scarcity of fresh water in Teknaf are high installation cost of deep tube wells, increasing population, reduced water flow in Chara (spring fountain), water pollution in Chara area, salinity in river water, salinity in groundwater etc [3]. Teknaf upazila is in the southeast corner of Bangladesh, where both hills and coastal ecosystem are prominent. The study area, Nayapara refugee camp, is surrounded by Bay of Bengal and Naf river, where dearth of water is acute due to absence of aquifer at shallow depth in and around the camp area, leaving no other option for people of this camp rather than depending solely on surface water sources like large reservoirs. An artificial water reservoir (Figure 1) is the prime source of water supply in the Nayapara refugee camp, which is mainly fed by rainwater runoff from the surrounding hilly areas. During dry season, this camp suffered from acute shortage of water which was mainly due to limited capacity of the reservoir to store sufficient water for dry period (November-May). As this reservoir's water storage totally depends on rainfall, it is critical that the amount of stored rainwater at the end of rainy season is equal or more than the demand of the whole dry period. If post monsoon (October-November) rainfall is not high in this area, there is a good chance of reservoir getting dried out in the last part of the dry season, during the months from March to May, which leaves the refugees with very limited fresh water. In the Nayapara refugee camp, initially the water supply system was fully dependent on a canal from where water was pumped into a 21 ft diameter reservoir and treated before distribution. In 2003, a reservoir was excavated in the camp on 2 acres land. In 2005, extension as well as re-excavation of the reservoir was done to increase its capacity. Further re-excavations were needed in 2008 and 2012, which have been the two largest maintenance works done by the camp authority till now to increase the capacity of the reservoir. Surface runoff from the catchment mainly feeds this reservoir. But this runoff carries huge amount of sediment, which reduces the capacity of the reservoir every year as it settles onto reservoir bed. During heavy rainfall events, the runoff brings a lot of sediment into the reservoir which results in significant reduction of volume of reservoir every year. Last time excavation was carried out in May 2012, but the reservoir was completely dried out in early part of April, After that, water was supplied in the camp by water trucking for the remaining period of dry season, which is also a troublesome job as the daily demand is huge [4] editor@iaeme.com

4 A Case Study On Management of Rainwater Reservoir In Hilly Areas of Bangladesh Figure 1 GOOGLE IMAGE of Nayapara refugee camp water reservoir Figure 2 Location of inlet and spillway of the reservoir Currently, surface runoff during rainy season enters into the reservoir through a box culvert which is the only inlet point for the whole reservoir (Figure 2). There are two 20 ft wide spillways constructed at the downstream of the reservoir to allow overflow of runoff during rainy season. There are three treatment plants to treat the reservoir water. Figure 3 shows the flow diagram for the treatment system. First, water is pumped into the sedimentation tank from the reservoir. There are two diesel powered intake pumps to lift water from the reservoir into the sedimentation tanks. The suspended particles of raw water settle down into the sedimentation tank and then water enters into filtration tank through gravity flow. After sedimentation and filtration, this water flows into chlorination tank for disinfection. After chlorination, water is distributed through the distribution tanks to the water points for the users. Figure 3 Flow diagram of water supply system at Nayapara Refugee Camp editor@iaeme.com

5 Maharam Dakua, Asef Mohammad Redwan, Begum Nazia Jahan, Syed Mohammed Tareq, Saifuddin Ahmed and Currently, the camp authority supplies 16 liter water for each of the refugees in the camp. Water is supplied two times every day, each time for 1.5 hours. Refugees collect water from 69 water points, each having 6 water taps, that are connected to distribution tanks [4]. 3. METHODOLOGY Field procedures followed for this study can be divided into four steps which have been discussed in this section: 3.1 FGD and KII The study team first conducted Focus Group Discussions (FGDs) as an extractive research methodology, with local peoples in different groups. FGD consists of systematic, semi-structured activities conducted onsite by a multi-disciplinary team with the aim of quickly and efficiently acquiring basic information about the livelihood of inhabitants, resources and associated issues of the study area. The basic idea was to quickly collect, analyze and evaluate information on site conditions, development issues and local knowledge to avoid unnecessary, costly and time consuming research procedures [5]. Therefore, the research methods were adjusted to suit local conditions. Key Informant Interviews (KIIs) were also conducted with a fairly open framework which allow for focused, conversational, two-way communication with the responsible engineers and local heads. KII was used both to give and receive information to obtain specific quantitative and qualitative information of past and existing systems, and gain a range of insights on specific issues associated with both [6]. 3.2 Historical Rainfall Data Analysis Rainfall data of past 30 years ( ) of Teknaf region was collected from Bangladesh Meteorological Department and was analyzed for average annual rainfall. Annual rainwater harvesting potential, which is the amount of rainfall that can be harvested for the total rainfall occurred in a year, was calculated from the equation (A * R * C), where A is the catchment area, R is the average annual rainfall, and C is the co-efficient of runoff (percentage of water than can flow over the surface as surface runoff without getting infiltrated or evaporated) [7]. For Nayapara camp area, the co-efficient of runoff was assumed 0.25 for flat lands as the land is sandy. For sandy soil with crops, the co-efficient would be [8]. As the area is sloppy towards the reservoir, highest range for sandy soil was assumed. For hilly areas and steep slopes, runoff coefficient was assumed as GIS Analysis GPS location data were collected of different points of the reservoir, catchment boundary, small channels that guide water from the catchment into the reservoir, important relevant points, e.g., inlet point, two spillways, surrounding water bodies and some structures surrounding infrastructures to draw their relative positions and also to calculate areas accurately. Arc GIS 10.0 software was used to produce GIS maps using GPS readings. All the readings were first entered as points in GOOGLE EARTH and saved as KML layer. Reservoir and catchment points were drawn as Polygon feature by connecting points through digitizing. Areas of these polygons were measured. Then KML layers were converted to Geo-referenced Data Based layers using Conversion tool from Arc tool box. Then by Projection and Transformation, all the Geo-referenced Data Based layers were projected as point, polyline (canals) and polygon (reservoir & catchment area) features. To measure the area of the reservoir accurately, GPS readings were taken of a number of points along the circumference of the reservoir. The actual catchment of the reservoir was difficult to demarcate as there are few hills that contribute to the open plain lands. Slope of the hills towards the reservoir contribute to the total runoff into the reservoir. Therefore, the calculated area from GPS readings as catchment would editor@iaeme.com

6 A Case Study On Management of Rainwater Reservoir In Hilly Areas of Bangladesh represent the flat part of the catchment, and part of the hills that contribute to the surface runoff into the reservoir. 3.4 Longitudinal and Cross-sectional Profile Analysis During the study, depths in both longitudinal and transvers (width) directions of the reservoir were measured. Longitudinal profiles were surveyed along three lines and x-sectional profiles (transverse section) were surveyed along 15 sections. Each profile was drawn with several data points and these data points were averaged to get the average depth (equivalent) of the reservoir. 71 data points were analyzed to prepare three longitudinal profiles. Volunteers were engaged to record the data along the length and width of the reservoir at pre-selected points. A marked stick was used to get the depth of the reservoir. During the survey, the reservoir was full up to its potential which helped to get the effective maximum depths. 15 transverse (X-section) sections have been surveyed where each section was chosen along the transverse direction of the reservoir (starting from the inlet). 4. RESULTS AND DISCUSSION The study undertaken on Nayapara camp reservoir helped to assess feasibility of rainwater harvesting system as a year-long solution for water supply system and how to better utilize rainwater to mitigate the crisis. During the two months long study, analysis of surrounding catchments, runoff pattern and quality of water were done. The study thoroughly revealed the existing water crisis scenario as well as potential of rainwater harvesting, and also helped identifying better engineering solutions for improvement of the existing crisis scenario. 4.1 Findings from FGD and KII From the FGD and KII conducted at the beginning of the study, following information regarding the camp population, areas and some other characteristics of the reservoir were found, which is presented in Table 1. Table 1: Data outputs from the FGD and KII Parameters Quantity Total camp population 18,496 [4] Total camp area 349,676 m 2 Reservoir capacity 60,000 m 3 Reservoir surface area 21,922 m 2 Frequency of reservoir excavation for extension every 3 or 4 years Siltation rate in the reservoir 6,400 m 3 /year It was reported by the informants that siltation in the reservoir, which is due to sediment transport from upstream runoff, is reducing the depth of the reservoir capacity approximately 6,400 m 3 every year and leads to water crisis in the later part of the dry season. According to camp authority, 4.5 ft siltation occurred in terms of depth during the period of ; indicating 1.5 ft siltation every year. After 2008, re-excavation was done in 2012 and excavation needed was 4.75 ft on average in This indicates that during the period from , 4.75 ft siltation occurred in 4 years. From this information, it can be said that approximately 1.2 ft siltation occurred per year for the period from So, averagely 1.33 ft/year was the rate of siltation depth increment in the reservoir during the span of , which is very significant amount to cause rapid reduction in the reservoir capacity editor@iaeme.com

7 Maharam Dakua, Asef Mohammad Redwan, Begum Nazia Jahan, Syed Mohammed Tareq, Saifuddin Ahmed and 4.2 Demand-Supply Analysis Demand and supply scenario: The target for water supply is 20 liter per capita per day (lpcd) for the refugees while current supply was found 16 lpcd due to lack of capacity. To fulfill the target of supplying 20 lpcd, total supply should be 20 x 18,496 liter/day (Per capita consumption per day x No. of people) = m 3 /day. But the supply when water is available in the reservoir is 325 m 3. With the current growth rate in the camp is 2.6% [4], projected population for the camp after 5 years will be 21,029. In that case, after 5 years, daily demand would be m 3. Deficit from scarcity period: To design the storage system, identification of scarcity period is very important. Scarcity period is the time assumed between two significant rainfall events [7]. Normally the time difference between the last rainfall of post-monsoon (October-November) and the first rainfall of premonsoon (March/April) is considered as the scarcity period. For areas where the reserve is dependent on rainwater, as is the case for Nayapara camp and some other rural areas in Bangladesh where rainwater is the only source of safe water, the reserve after the last rainfall event needs to be enough to supply water for the dry period till the next rainfall. Normally, in Bangladesh, this scarcity period is assumed to be 4-5 months which varies from year to year [7]. In this study, scarcity period was assumed to be 5 months. So, scarcity period demand = Daily demand x Scarcity period in days = (369.9 x 150) m 3 = 55,485 m 3. Therefore, total reserve of water after last rainfall should be 55,485 m 3 plus evaporation and seepage loss, to fulfill the demand during scarcity period i.e. five months of no rainfall period. Hence, the reservoir should have the capacity to store this amount of water plus the amount equal to seepage and evaporation loss for scarcity period i.e. five months to avoid any water scarcity in the dry period. For five months of storage, using the same formula and the population growth rate of the camp, requirement after 5 years would be 63,090 m 3, excluding evaporation and seepage loss. Catchment area from GIS: The calculated catchment area from GIS analysis represents both the flat lands and hills surrounding the reservoir and contributing as a catchment to the reservoir. Catchment of the reservoir was found 95, m 2 from flat lands and 80,000 m 2 from hilly areas through GIS mapping (Figure 4). So, total catchment area is approximately 175,614 m 2. Figure 1 GIS map of features related to water supply system of Nayapara camp editor@iaeme.com

8 A Case Study On Management of Rainwater Reservoir In Hilly Areas of Bangladesh Rainwater harvesting potential from runoff and reservoir: From rainfall data of 30 years ( ) of Teknaf, average annual rainfall was found 4,132 mm/year. The total rainwater harvesting potential in a year from (1) the agricultural (flat) lands was calculated as 98,770 m 3, (2) from slope of the hills as 115,696 m 3 and (3) from the reservoir area itself as 80,102 m 3. Therefore, Total rainwater harvesting potential (approximate) would be 294,568 m 3 per year. This amount of rainfall is sufficient to fulfill the annual demand which was 135,020 m 3 during the study period, excluding evaporation and seepage loss. It should be noted that all these runoffs cannot be harvested for use due to lack of reservoir capacity. Therefore, to ensure this required volume of stored rainwater for supplying water during scarcity period, reservoir volume should be increased and maintained properly. It should be also noted that there were a number of flows coming out of hills; the source of which could not be identified in the hills during the study. So the actual surface runoff could be higher than the estimated volume in this survey. 4.3 Reservoir Capacity Analysis: From measurement of depth along 3 longitudinal and 15 transverse sections of the reservoir, average depth of the reservoir was calculated as 9.89 ft. This average represents the depth averaged from 240 points at different locations along the sections of the reservoir. From GIS analysis, total reservoir area was found 19,387 m 2. With the measured average depth and calculated reservoir area, total volume of the reservoir was estimated as 58,453.5 m 3, which is less than the volume reported by UNHCR. To supply water at 16 lpcd to the refugees for five months of scarcity period, the total requirement would be 44,385 m 3. If the targeted amount (20 lpcd) of water is to be supplied for 5 months of scarcity period, the requirement for the same period would be 55,485 m 3. For 20 lpcd water consumption after five years with current population growth rate of the camp, total requirement would be 63,090 m 3. Therefore, for supplying 20 lpcd at present, for five months of scarcity period, the reservoir depth has to be increased by 12 inch. This can be done either by excavation of reservoir or increasing height of spillways by 12 inch. This will increase the reservoir volume by 5,922 m 3. For supplying 20 lpcd after five years (projected population 21,029), the reservoir capacity also needs to be increased. In that case, increasing the depth of reservoir by 3 ft will increase the volume by 17,772 m 3. In total, the reservoir capacity will have to be 76,225 m 3 after five years. 5. CONCLUSION AND RECOMMENDATION The water demand of the refugee camp (369.9 m 3 /day) was higher than the supply (325 m 3 /day); assuming 20 lpcd water to be supplied. Effective volume of the reservoir was found 58,453.5 m 3 based on the collected depths at 240 points within the reservoir. But this volume was not sufficient with the current supply rate of 325 m 3 /day. So, the reservoir must be large enough to accommodate water of this volume plus the amount that will be lost due to seepage loss. The availability of rainwater was found more than enough to fulfill the demand for the catchment size of the reservoir. But due to limited capacity of reservoir, this rainwater cannot be stored for the whole scarcity period. It was found from the study that for sufficient reserve to supply water at 20 lpcd rate for current population, reservoir depth has to be increased by 1 ft. For sufficient reserve to supply water at 20 lpcd rate after five years, the reservoir depth will have to be increased by 3 ft. During the study, analysis of collected data led to better understanding of source of water, water consumption, reservoir capacity, shortage of water and scarcity during dry season in Nayapara camp. The Nayapara camp reservoir is event-driven, surface runoff into the reservoir is highly responsive to rainfall events. Each year rainfall is needed to replenish the reservoir, but also the surface runoff carries lots of sediments which eventually reduce the capacity of the reservoir every year. From information gathered from local community and findings from field investigations, it has been found that sediment transport has been the major problem caused by phenomena like flash flood and heavy rainfall event, resulting into soil erosion and cutting of hills during rainy seasons. As a solution to this problem, sediment trap/basin could be designed to protect the reservoir from excess sediment transport into the reservoir in rainy season. But editor@iaeme.com

9 Maharam Dakua, Asef Mohammad Redwan, Begum Nazia Jahan, Syed Mohammed Tareq, Saifuddin Ahmed and at the same time, the sediment basin should allow water to flow through it at a good rate to replenish the reservoir during early rainy season. The sediment basin must consider the high velocity of flow during heavy rainfall events. Therefore, apart from constructing a sediment basin, diverting additional/unwanted amount of water (when the reservoir is full) through bypass line could be considered, which would reduce pressure on sediment basin. Apart from that, increasing capacity of reservoir is highly recommended to regain the required capacity of reservoir to supply water at desired rate to all the refugees, either by excavation or increasing height of spillways. 6. ACKNOWLEDGEMENTS Our deepest gratitude to all the staff, engineers & members of the United Nations High Commissioner for Refugees (UNHCR) for providing their continuous support in this project (November-December, 2013). Indispensable support and cooperation from the survey teams were truly excellent. REFERENCES [1] Bangladesh Climate Change Strategy and Action Plan (BCCSAP),Ministry of Environment and Forests,Government of the People's Republic of Bangladesh, Page-14, September [2] National Strategy for Water and Sanitation Hard to Reach Areas of Bangladesh, Government of Bangladesh, December [3] Bangladesh Poush and Prattaya, "Participatory Action Plan Development Cox s Bazar Teknaf Peninsular ECA Teknaf Union", Teknaf.BGD/99/G31- Coastal and Wetland Biodiversity Management Project: Community Mobilization at Cox s Bazar Component, Final Draft-3, [4] UNHCR; Report of United Nations High Commissioner for Refugees, Cox s Bazar, Bangladesh. [5] Krueger, R. A. (1994). Focus groups: A practical guide for applied research (2nd ed.). Thousand Oaks, CA: Sage Publications. [6] B.T. Hanyani-Mlambo, Discussion guide, Strengthening the pluralistic agricultural extension system: A Zimbabwean case study, Annex 1: Key informant interviews, Food and Agriculture Organization of the United Nations (FAO). [7] Neeraj D. Sharma, Dr. J. N. Patel,Department of Civil Engineering, S.V.N.I.T, Surat, Experimental Study of Groundwater Quality Improvement By Recharging with Rainwater. International Journal of Civil Engineering and Technology, 2(1), 2011, pp [8] Rahman, M. M.; Dakua, M.; "A case study on Rainwater Harvesting for Drinking Water with Solar Disinfection System", ITN publication, ISBN: , [9] Subramanya, K..; Engineering Hydrology, Second Edition, Tata McGraw-Hill Publishing Company Limited, New-Delhi, ISBN , editor@iaeme.com