Impact of water diversion on hydrological regime of the Atreyee river of Indo-Bangladesh

Abstract

ABSTRACTHydrological alteration plays a crucial role in regulating a hydro-ecological and socio-economic framework. Apart from climate change issue and its impact on flow alteration, human interventions have brought a new paradigm on hydrological regime. The Atreyee river (390 km long) of Indo-Bangladesh is highly affected by the construction of reservoir at Mohanpur of Bangladesh. The present paper concentrates on regulating flow through the reservoir construction and its possible impacts on downstream courses at different hierarchical scales such as alteration of the dynamics of peak flow, monthly flow, average flow, minimum flow, seasonal flow, instability of flow and diurnal flow. Result shows that (1) the discharge ratio of maximum discharge from the reservoir after construction has reduced 4.15–5.66 times in the Atreyee river. (2) After the construction of the reservoir, on an average 53% discharge has curtailed down. On a seasonal scale, total run-off reduction rates are 30.97%, 66.86% and 64.01% during pre-monsoon, monsoon and post-monsoon periods. (3) Post-reservoir condition peakiness of average and maximum monthly water flow has reduced and flow variation (calculated CV) has also reduced by 4.5 and 10 times, respectively. (4) Volume of base flow has attenuated by 18.26% (26.34–21.53 cumec). (5) Percentages of discharge reduction in reservoir after condition are 30.97%, 66.86% and 64.01%, respectively, during pre-monsoon, monsoon and post-monsoon seasons. (6) Modal discharge during pre-monsoon, monsoon and post-monsoon has reduced by 13.38%, 80.31% and 72.20%, respectively. (7) Diurnal range of flow, flow volume, instantaneous flow pulses and mean up and down-ramp rates have reduced in the post-reservoir period. (8) In the post-reservoir period, flow magnitude is so lowered that it cannot maintain the natural threshold limits of flow for sustaining normal environmental performances.