Impact of urbanization on groundwater recharge: altered recharge rates and water cycle dynamics for Arusha, Tanzania

The profound effects of urbanization on groundwater recharge rates are investigated by conducting a comprehensive land use and land cover analysis in Arusha, Tanzania, using the WetSpass model. Between 1995 and 2016, the urban area has expanded from 14 to 45% within the study area. This rapid urbanization has resulted in the conversion of forested areas, agricultural land, shrublands, and bare soil into urban zones. Results indicated that under preurban conditions, groundwater recharge from precipitation was ~116 mm/year, which increased to an average of 148 mm/year by 2016. When accounting for anthropogenic factors such as drinking water leakage and on-site sanitation, recharge further increased to 195 mm/year. These supplementary recharge sources, along with reduced evapotranspiration due to land-use changes, contributed to the increase, despite higher surface runoff. These findings underscore the significance of land use and leakage management in urban areas, as well as the spatial variability in groundwater recharge rates across different urban zones, emphasizing the importance of local factors. This study advances the understanding of the intricate relationship between urbanization and groundwater dynamics, and provides insights for future water resource management in rapidly growing urban regions.