Analysis of groundwater level trend and groundwater drought using Standard Groundwater Level Index: a case study of an eastern river basin of West Bengal, India

Global water demand has far exceeded the total available water resources which in turn have put a serious concern on food security. Changes in the land use and land cover scenario and rapid population growth are putting unavoidable stress over the water resources of the nation. The Indian aquifer system is facing an acute crisis due to the unscientific abstraction of groundwater for agricultural, industrial and domestic sector by the 1.3 billion growing population. To investigate the groundwater degradation, 20 wells from a river basin of West Bengal have been selected to study their seasonal groundwater level trend using Mann-Kendall test statistics from 1996 to 2018 where 60% of the wells are showing a decline in water level particularly in post-monsoon season. These wells are mainly located near the agricultural land where extraction of groundwater from submersible pumping wells is extensive as observed from socio-economic survey. Agglomerated hierarchical cluster analysis has been executed to classify the wells based on their magnitude of fluctuation. The wells have been classified in four clusters where cluster I consists most of the wells about 15 numbers whose fluctuation ranged between 1.8 and 4.33 m below groundwater level (mbgl). Finally, Standard Groundwater Level Index has been applied to understand the groundwater drought years. Well locations like Simla pal, Bheduasol and Neradeul have a higher frequency of drought years. The recharge potential of the wells is now decreasing day by day. Such kind of studies is required and will help the stakeholders to focus on sustainable management of this valuable water resource.