Impact Assessment of Land-use change on water resources using the Soil and Water Assessment Tool (SWAT)

Land-use change significantly impacts water balance components by altering the distribution and movement of water within a basin. The Upper Kharun Catchment (UKC) in India represents an area with significant recent land-use changes, namely by substantial population growth, urban expansion, industrialization, and changes in irrigation practices such as extension and intensification. This study investigates the impact of such modifications in land-use on water balance components using the Soil and Water Assessment Tool (SWAT) exemplified in the UKC. Therefore, we produced and analyzed land use maps for the time periods of 1991, 2001, 2011 and 2021. Our research findings indicate that the increasing amount of groundwater pumped for irrigation is the primary factor contributing to reduced groundwater flow into streams, which in turn leads to a decrease in discharge and overall water supply especially in drought periods. Conversely, annual surface runoff has significantly increased due to the expansion of built-up areas due to surface sealing over the decades in the relevant parts of the study area. Comparing the effects at catchment and sub-catchment levels highlights the importance of choosing the appropriate spatial scale for water management activities. At the catchment scale, the impact of land-use change on the water balance is small because different effects, such as urbanization and the intensification of agriculture, tend to offset each other. However, at the sub-catchment level, where local land-use dynamics are more pronounced, the effects of land-use change become evident. The combination of remote sensing techniques and hydrological modeling has allowed for identifying hotspot areas with changes in land use, which significantly affect on the components of the water balance. These areas should be prioritized for enhanced modeling and monitoring as basis for the development of water management strategies that can mitigate negative impacts on the water balance and in turn on improving the livelihood of the population as well as towards conserving ecosystems’ functioning. However, it's important to view these sites not in isolation but as part of an integrated approach for coordinated water management throughout the entire basin.