This study evaluates the implications of variations in rainfall and land use on groundwater level fluctuations in the Kathmandu Valley, Nepal. The authors selected and analysed data from 35 monitoring wells observed by citizen scientists. Over 2 years, groundwater levels varied spatially from -0.11 m (negative sign denotes a groundwater level higher than the ground surface) to 11.5 m, with a mean of 4.24 m and a standard deviation of 2.29 m.The results indicated a strong positive correlation between rainfall and groundwater levels, as the fluctuation was influenced by the rainfall of that area. The seasonal fluctuations in groundwater level showed the direct influence of monsoonal rainfall. In areas with agricultural land use, 80% of the analysed wells showed a strong and statistically significant correlation between rainfall and groundwater levels. In contrast, higher groundwater extraction rates and surface sealing limited groundwater recharge in built land uses; therefore, wells across non-agricultural land uses showed a weak correlation in most of the cases. In the northern groundwater district, we found areas with highly permeable sand and gravel have nearly constant groundwater levels (shallow in agricultural land use and deep in built land use) year-round and act as potential recharge zones for the aquifer. The areas with less permeable but highly porous clay and silt in agricultural land use show greater seasonal groundwater fluctuations. This study highlights the ability of citizens to generate meaningful hydrogeologic data sets and the importance of rainfall and land use planning to groundwater recharge. Understanding these complex relationships must form the basis for the sustainable management of the rapidly declining groundwater resources of the Kathmandu Valley.
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