In Bangladesh, where numerous tributaries from the Himalayas meet the Bay of Bengal, flooding is not uncommon. However, despite the excess of water in some parts of the country, many people do not have regular access to clean drinking water.
Panchhari Upazila, a village in Khagrachari District, is one of the driest places in Bangladesh. Acute drinking water shortages are a major problem in the area, and are further exacerbated by a long dry winter that lasts from December to April. People walk for hours to collect scanty water from sources – primarily river runoff, ditches, ‘charas’ (creeks), and ‘patkua’ (a source of water created by waterfalls)– located 2–3 kilometres away from the village. Water collected from these sources are often mixed with mud and dirt, making it unsafe to drink.
Potential water storage reservoirs in the study area
Under ICIMOD’sSERVIR-Himalaya Small Grants Programme, the Centre for Environmental and Geographic Information Services (CEGIS) in Dhaka, Bangladesh, has developed a geospatial database and information system to identify potential water harvesting and storage options, with Panchhari Upazila as a project site. The geoinfomation system also examines the impacts of climate change on water availability.
A GIS-based watershed model – Soil and Water Assessment Tool (SWAT) – was applied to identify potential water storage areas and assess the daily water availability of each reservoir. The SWAT model used three basic datasets to delineate the river basin, sub-basins, and hydrological response units in the area – the ASTER Global Digital Elevation Model, a soil map obtained from the Soil Research Development Institute of the Governmnet of Bangladesh, and land use and land cover data, which was captured using Google Earth satellite images. Daily precipitation and daily maximum and minimum air temperature data for the years 1981 through 2014 were collected from gauge stations of the Bangladesh Meteorological Department (BMD) and Bangladesh Water Development Board (BWDB). Using this data, the model was simulated for both base conditions and potential conditions under the influence of climate change, and various trials were applied to identify the most suitable locations for water storage reservoirs. Seven potential storage reservoirs were identified considering flow availability, present and future water demand, population density, accessibility, and the impacts of climate change on rainfall and temperature.
People collect water from ‘patkua’, a source of water created by waterfalls in the foothills of Bangladesh
Data collected by the project can help government to construct similar reservoirs. Existing Rubber Dam on Chengi River.
The potential water storage reservoirs could serve local communities in many ways, including supporting agricultural practices and household activities like personal hygiene and livestock watering. They could also improve the scope of winter to summer irrigation both by extending irrigated area and by ensuring the supply of water.
“Five of the nine wards in Logang Union are facing a huge water crisis. During the rainy season, the flow of water in the Chengi and Logang rivers increases, but in the dry season from January to March, the rivers dry out, making it impossible for farmers to irrigate their land. If we build small dams on rivers, creeks, and land, then we can reserve water for irrigation, fisheries, and duck breeding”, said Samar Bikash Chakma Chairman, Logang Union, Panchhari.
A total of 613 hectares of agricultural land and around 10,000 local people could benefit directly from these reservoirs. The potential water storages will increase the cropping area for irrigated crops like Boro rice and Rabi by about 90 hectares and 110 hectares, respectively. About 1,110 tons of additional Boro rice and 315 tons of others crops (wheat, vegetables, chill, etc.) will be produced annually, which will help enhance household income, as well as the local and national economies.
Sattar Upazila, an engineer from the Local Government Engineering Department (LGED), said, “To conserve the dry season flow in this area, we need to build several water storages in the Chengi River and its tributaries. Due to inaccessibility and a lack of data, it was difficult for LGED to plan new water storages. With the data on potential water storage areas and other relevant information made available through this project, LGED will be able to take the steps necessary to implement solutions to make safe water available to local communities year-round”.
Data collected by the project have been organized in a geospatial information system that can be accessed through a GIS-based web application (http://188.8.131.52/icm/). Details of river and ‘chhara’ systems, watersheds, catchment-wise water demand and yield, and potential water storage reservoirs and their water availability can be used to support planning and decision making by the Chittagong Hill Tracts Development Board, LGED, and local administration under the Ministry of Chittagong Hill Tracts Affairs of the Government of the People’s Republic of Bangladesh.