Evaluation of The Nature of Groundwater Depletion: In The Context of Mohadebpur Upazila

Abstract

Groundwater (GW) is the main source of irrigation for increasing crop production as well as for climate change adaptation owing to sustainable agricultural intensification in the northwest region of Bangladesh. In this study, successive depletion of groundwater level (GWL) with expansion of GW irrigation in Barind Tract has been discussed in the background of Mohadebpur Upazila of Naogaon District and is conducted to assess the nature of hydrograph which reflects the history of the behaviors of the parameters of the shallow aquifers on the basis of lithology and other parameters concerning GWL depletion. It has been observed that GW development, sources of recharge and properties of upper finer materials influence the GWL depletion phenomenon. Hydrograph analysis, GWL mapping, GW depletion rate calculation are done from GWL observation well data of Bangladesh Water Development Board (BWDB). For scaling adjustment both groundwater table (GWT) and lithology are plotted from the ground surface throughout the study and analysed for the understanding of the geology surrounding the observation wells. From our analysis it has been found that out of seven observation wells in the study area some of them show the declining trend of GWL and excessive withdrawal of GW exceeds the potential recharge for most of the observation wells. Crop diversification, artificial recharging, increasing dependency on surface water, increasing irrigation efficiency, rainwater harvesting etc. can be option for the area. Based on the simulation and GWL fluctuation analysis, availability of GW resource has been assessed for the design year. In selecting design year, most weight has been considered for 80% dependable of annual rainfall, because this is considered most generally significant for domestic requirement considerations. The design year (2008 in this study) is selected based on the return period analysis of rainfall from the precipitation records for a period of 30 years spanning over 1980 to 2009 obtained from 18 rain gauge stations located in and around the model area. However, development of numerical GW modelling as well as simulation of GW flow has been performed in an integrated MIKE-11 and MIKE-SHE platform. From this assessment it is found that potential recharge for the study area is 444 mm.