Water infiltration rate in the Kathmandu Valley of Nepal amidst present urbanization and land-use change

The rapid urbanization and land-use change prominently decreased groundwater recharge areas. Infiltration occurring through permeable areas is responsible for groundwater recharge. However, detailed studies of infiltration in low-income countries especially in human-encroached recharge areas are limited. Thus, this study mainly aims to measure the infiltration rate in major recharge areas of the Kathmandu Valley (KV) using a double-ring infiltrometer (concentric ring size 30 and 15 cm). It also aims to estimate the volume of groundwater recharge with respect to the decrease in permeable areas in the northern part of the KV. The results revealed the infiltration rate ranging from 0.01 to 37.2 cm/h with an average of 7.3 ± 8.4 cm/h. The infiltration is found to be dependent upon land-use among different categories and organic matter among different soil properties. Additionally, the volume of water recharge in 2010, 2020, and 2030 was estimated as 67.73, 59.05, and 51.5 million cubic meter per year (MCM/year), respectively, which clearly showed a decrease in recharge water with respect to a decrease in the permeable areas. Hence, the findings would be useful for policymakers, stakeholders, and urban planners regarding the preservation and conservation of permeable areas for sustainable water resource management and urban flood management.