Assessment of Groundwater Level Trends Using Mann--Kendall Test, Sen's Slope Estimator, and GIS Mapping in the Bandikhan District, Surkhandarya, Uzbekistan

Water security is a critical concern in the Bandikhan district of Surkhandarya, Uzbekistan, where agriculture predominantly relies on groundwater resources. This study assesses the spatial and temporal trends of groundwater levels during both vegetation (April–September) and non-vegetation (October–March) periods from 2018 to 2023. Data from 63 observation wells were analyzed using the Mann–Kendall trend test, Sen’s slope estimator, and linear regression methods. Geographic Information System (GIS) tools were employed to map the spatial distribution of groundwater level changes. The results indicated that the average depth to groundwater during the vegetation period ranged from 1.06 m to 5.84 m, with a mean fluctuation of 2.45 m. During the non-vegetation period, depths ranged from 1.04 m to 5.68 m, with a mean fluctuation of 1.04 m. Significant trends were observed in the groundwater levels. Sen’s slope estimates varied from –0.26 to +0.34 m/year, indicating both rising and declining groundwater levels across the district. The average rate of decline was found to be 0.22 m/year, with a standard deviation of 0.07 m/year. These findings highlight the overexploitation of groundwater resources in certain areas due to intensive agricultural practices, leading to declining water tables. Conversely, some areas exhibited rising groundwater levels, possibly due to irrigation return flows or inadequate drainage systems. The study underscores the need for sustainable groundwater management, including the implementation of advanced irrigation techniques and the promotion of crops requiring less water. The results provide valuable insights for planners and decision-makers to develop effective land use and water resource management strategies, ensuring the long-term sustainability of groundwater resources in the Bandikhan district.

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