Study of groundwater conditions in the western part of grenter Rajshahi distric

Abstract

With the phenomenal increase in the use of groundwater in recent years, nee9 for helter understanding of the functioning of groundwater reservoirs in response to natural and man-made conditions in the system has come to the fore. The objective of groundwater exploration is to locate aquifers capable of yielding water of suitable quality and eco11om1c quantities for different purposes. Groundwater resource, although replenishable, is not inexhaustible. But the un·controlled exploration of this limited · resource has caused many environmental degradation which calls for the need to adopt scientific use of this natural resource. The wide and uneven distribution of underground water thus necessitates detailed study in specific areas for the conservation of this vital resource. The present study area- a part of Barind Tract- which is one of the ma.1or physiographic unit of Bangladesh- lies in the Western part of greater Rajshahi district. In recent years, the groundwater crisis of this area is highlighted. The present work attempts to study the feasibility of groundwater development in this region. Lithological data are an important source of hydrogeological investigation. The borehole data of Bholahat, Shibganj, Gomastapur, Nachole, Nawabganj, Godagari, Tanore and Niamatpur o.f greater Rajshahi district are processed, analyzed and .interpreted for the evaluation of groundwater condition. A Fence diagram has been prepared which clearly shows that the area mainly consists of three sub-surface geological formations: a top clayey layer, sandy layer of different grain size and at the bottom an impermeable clay zone. Computer aided groundwater maps have been prepared for qualitative and quantitative assessment of the aquifer system. The transmissivity and specific draw down maps prepared with their estimated values support the Eastern and Western sides favorable for well development. Maps of composite sand thickness and yield index have been presented for qmilitative study of groundwater potentiality in different regions of the area investigated. Interfacing planes between different geologic formations have been prepared m1cl presented for the necessaty assessment of the variation of individual subsurface stratum in different parts of the study area. Some representative cross-sectional views have fl lso been illustrated. The natural groundwater flow directions have been determined and the flow rate in different parts of the area has also been estimated. It is observed that the groundwater course is influenced by the topography and the upper surface of the impenneable zone. The fluctuation of groundwater level from 1986 to l 995 has been studied. The hydrographs show a gradual fall of water level since 1992. During this period the total amount of water discharged from and recharged to the aquifer system has been estimated and a negative balance is observed. finally, relc1ting to the investigated area, a few potential zones have been identified for groundwi1ter development.