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Aquifers underlying the arid lands of Rajasthan are under stress due to expansion in groundwater-irrigated areas. This study investigated trends in the long-term groundwater level and explored linkages of groundwater with rainfall and irrigated area in 12 districts of the arid region of Rajasthan, India using 64-year (1957-2020) rainfall data of 62 stations and 36-year (1984-2019) groundwater-level data of 4042 sites for pre-monsoon and post-monsoon seasons. Box-whisker plots of the district-wise average annual rainfalls were drawn. Trends in groundwater levels were identified by employing Mann-Kendall test and their magnitudes were quantified using Sen’s slope estimator test. Furthermore, linkages of groundwater levels with rainfall and groundwater-irrigated areas were evaluated through correlation and linear regression analysis. Results indicated that annual rainfall increased at a rate of 18 mm year-1 over the last 2 decades. Also, annual rainfall crossed an amount of 400 mm in 7 of recent 10 years. The declining trends (p0.60 m year-1) as compared to pre-monsoon (0.40-0.50 m year-1) season. Groundwater levels revealed poor response to rainfall as evidenced from weak linear relationship with low correlation coefficients (r) values. On the contrary, groundwater-level revealed moderate to strong linkages with irrigated areas based on r ranging from 0.58 to 0.94 and 0.68 to 0.96 during pre-monsoon and post-monsoon season, respectively. Findings of this study suggest need for adopting good strategies like harvesting surplus rain/runoff water and utilizing the harvested water judiciously for irrigation or groundwater recharge. However, this will require developing incentive-based policies to encourage farmers and other stakeholders to adopt water harvesting and help curtail excessive groundwater extraction for irrigation. In addition, reducing subsidies on electricity and promoting less water-requiring crops and adoption of water-saving technologies can be part of the policy framework.
Machiwal et al. (Thu,) studied this question.