Assessment of Seasonal Groundwater Level Trends in Afzalpur Taluk, Karnataka Using Non-Parametric Statistical Techniques

Groundwater is the primary source of water supply in semi-arid regions of India, where its sustainability is increasingly threatened by overexploitation and climate variability. This study evaluates seasonal groundwater level variations in Afzalpur Taluk, Karnataka, using the Mann–Kendall (MK) trend test and Sen’s slope estimator. Groundwater depth data for pre-monsoon, monsoon, and post-monsoon seasons were analyzed to detect monotonic trends and quantify their magnitude. Results indicate pronounced seasonal variability, with deeper groundwater levels during pre-monsoon (7.9–24.6 m) and significant recovery in post-monsoon (4.2–12.9 m). The MK test results show no statistically significant trends (p > 0.05) across all seasons, with Kendall’s τ values ranging from −0.013 to 0.333. Sen’s slope estimates also indicate negligible to low trend magnitudes. These findings suggest that groundwater dynamics in the study area are predominantly controlled by seasonal recharge rather than long-term monotonic trends. The study highlights the need for localized groundwater management strategies, including recharge enhancement and controlled abstraction, to ensure sustainable utilization.