Groundwater trend analysis and regional groundwater drought assessment of a semi-arid region of Rajasthan, India

Groundwater, being an important natural resource, has a dynamic character owing to climate change. The precarious nature of groundwater, especially in the arid and semi-arid regions, demands sustainable management of the same. The present work aims to study the groundwater trend and change point detection with a focus on groundwater drought severity in a semi-arid region of NW India (Rajasthan). Pre-monsoon and post-monsoonal groundwater levels of 65 wells for the period of 2006 to 2018 have been utilised for the various statistical analysis of Mann-Kendall (MK) test, Sen's slope estimator, Buishand U test, depth variation and recharge probability, SGLI and Cluster analysis. Primarily, both the pre- and post-monsoonal groundwater level trend and magnitude have been analysed using the Mann-Kendall test and the magnitude of slope seconded by Sen's slope estimator. A Buishand U test has been performed to detect groundwater level change point detection. A cluster analysis was done to categorise the wells based on their pre-monsoon and post-monsoon groundwater level magnitude trends. According to cluster analysis, the maximum number of stations had a negative trend during the pre-monsoon. Standard The groundwater depth level index has been undertaken for pre- and post-monsoonal drought analysis, and the growth rate formula was used to analyse the depth fluctuation and recharge probability. The result of MK indicated an overall negative trend which is extreme in Sardarshahar tehsil (pre-monsoon) and Rajgarh tehsil (post-monsoon). The results yielded a declining trend in groundwater over the study area. The Buishand U test revealed that about 66.15% and 50.76% of the stations had changed ground water depth during the pre- and post-monsoon period, respectively. Groundwater drought severity has been increasing in both seasons, which is especially extreme during the pre-monsoonal period. The study of depth fluctuation and recharge probability indicated that 46.13% of the stations have excessive use of groundwater while having less groundwater recharge probability.