0016-7622/2018-91-5-613/$ 1.00 © GEOL. SOC. INDIA | DOI: 10.1007/s12594-018-0912-z JOURNAL GEOLOGICAL SOCIETY OF INDIA Vol.91, May 2018, pp.613-620 Morphometric Analysis and Hydrological Inference for Water Resource Management in Atrai-Sib River Basin, NW Bangladesh Using Remote Sensing and GIS Technique Chowdhury Sarwar Jahan 1* , Md. Ferozur Rahaman 2 , Riad Arefin 1 , Shamser Ali 2 and Quamrul Hasan Mazumder 1 1 Department of Geology and Mining, University of Rajshahi, Rajshahi 6205, Bangladesh 2 Institute of Environmental Science, University of Rajshahi, Rajshahi 6205, Bangladesh *E-mail: sarwar_geology@yahoo.com ABSTRACT Demand for irrigation water increases day by day along with meteorological vagaries and extension of irrigated area in the drought-prone Barind area of Bangladesh. This increasing stress on water resource is gradually making the area water scare. The study is aimed at studying the morphometric parameters of the Atrai-Sib river basin in the Barind area and on their relevance in water resource management based on satellite images and SRTM DEM. Computation and delineation of linear and areal aspects of the river basin and its morphometric components reveals that stream order ranges from first to eighth order showing dendritic drainage pattern. The basin represents homogeneity of soil texture; possibility of flash flood after heavy rainfall with low discharge of runoff; and is not largely affected by structural disturbance. Moderate drainage density of the river basin area indicates semi- permeable soil lithology with moderate vegetation. Mean bifurcation ratio of the basin is calculated as 3.92 and elongation ratio 0.75, which indicate elongated shape of the river basin with low to moderate relief bounded in the east and west by ‘moderate to steep’ sloping land area. It reveals a flatter peak of runoff flow for longer duration and gravity flow of water. The gentle but undulating slope of the basin represents ‘excellent’ category for groundwater management as the site is favorable for infiltration due to maximum time of runoff water percolation. The east facing slopes of the basin show higher moisture content and higher vegetation than the west-facing slope. The land use pattern of the area shows that major part (95.29%) comes under the cultivated land which will support future river basin development and management. Results obtained from the study would be useful in categorization of river basins for future water resource development and management, and selection of suitable sites for water conservation structures such as check dam, percolation tank, artificial recharge of groundwater through MAR technique etc. INTRODUCTION According to the Third Assessment Report of IPCC, South Asia is the most vulnerable region of the world to the impacts of climate change. The international community recognizes that Bangladesh - as a lower riparian country of the Ganges-Brahmaputra-Meghna (GBM) Deltaic region in South Asia ranks second in the list of most vulnerable countries in the world. Here efforts to reduce poverty are constrained due to reduction in availability of fresh water and food security as lives and livelihoods depend on water and agriculture. Presently groundwater based irrigation is adopted to cultivate high-yielding rice variety during dry season in South Asia as Bangladesh is the world’s fourth biggest rice-producing country (Scott and Sharma 2009; IRRI 2010). Here agriculture contributes nearly 20% of the GDP as rice crops cover 75% of the cropped areas and contribute over 95% to the total food grain production. Like the other natural calamities and disasters such as floods or cyclones (Brammer 1987; Alexander 1995), droughts affect especially northwestern parts of the country more severely when monsoon fails. This drought prone but agro-based area lies mostly in the north-western part of Bangladesh popularly known as Barind with an area of 7,500 km 2 - the granary where agricultural practices are dependent on groundwater irrigation (Fig. 1). Physiographically the Barind area is characterized by two distinct landforms: the Barind tract and the floodplains. According to Morgan and McIntire (1959) the Barind tract is one of the oldest Pleistocene terraces, north-south dome shaped area (20-25 km wide in east-west direction) and covered by older deposits - Pleistocene sediments, popularly known as ‘Barind Clay’ encountered within the Bengal Basin. The Tract, with comparatively high elevation of 47.0 m above MSL in its central part is bordered by parallel by river valleys of 11.0 m above MSL in the southeastern part of the floodplain area. According to Khandoker (1987) the Barind Tract was elevated horst block at the close of Pleistocene. It is south-westerly tilted block and its eastern margin is delineated by the Atrai-Sib river basins. The Atrai-Sib river basin has greater thickness of clay-silt layer with greater depth of the main aquifer than the Barind Tract. The river basin is characterized by step faulting having downthrown blocks towards south with numerous streams, depressions and channels along the flow direction of the rivers (Jahan and Ahmed 1997). The surface deposits of the floodplain area are Recent stream and inter-stream sediments deposited mainly by the major rivers along with their numerous tributaries and distributaries. The physiographic map of the Barind area is shown in Fig. 2. The Barind area enjoys mainly three seasons: winter (Nov-Feb) - cool and dry with almost no rainfall; pre-monsoon (Mar-May) - hot and dry; and monsoon (Jun-Oct) - rainy. Average rainfall in the area for the period 1980-2012 is 1525 mm (much less than the national average of 2550 mm) whereas the average value in the dry and monsoon seasons are 244 and 1266 mm respectively. Magnitude of change of the annual rainfall shows a significantly decreasing trend (20-23 mm/ year) along with negative periodic (dry and rainy) trends (Jahan et al. 2015). Monthly average temperature for the same period ranges from 10 o C (January) to 33 o C (May) with increasing rate of 0.0208°C/year. The moderate to high meteorological drought risk prevails here that creeps towards semi-aridity in recent years (Jahan et al. 2008). The area is characterized by low rainfall; low infiltration capacity of soil which is insufficient for groundwater recharge; limited scope to conserve rainwater in rivers, canals, swamps (bills) and existence of potential aquifer at greater depth for large scale groundwater