Modelling the Impact of Land Use Change on Hydrological Processes in the Katsina-Ala Basin Using SWAT

The hydrology of the Katsina-Ala Basin is increasingly influenced by climate change and land-use/land-cover (LULC) changes, raising concerns about the sustainability of water resources. This study utilized the Soil and Water Assessment Tool (SWAT) to simulate hydrological processes and assess the impacts of LULC changes over a 20-year period (2000-2020). Sensitivity analysis identified CN2.mgt, SURAG.hru, and ESCO.hru as the most influential parameters. The model calibration (2012-2015) and validation (2016-2019) demonstrated high performance, with Nash-Sutcliffe Efficiency (NSE) of 0.987 and 0.986, Coefficient of Determination (R2) of 0.990 and 0.995, and Percent Bias (PBIAS) of 0.014 and 0.013, respectively. The P-factor values were 0.81 (calibration) and 0.94 (validation), while the R-factor values were 2.82 and 2.0, respectively, indicating the model’s reliability in capturing observed hydrological processes. The calibrated model revealed significant LULC changes indicating an 11% increase in cultivated land, an 8.19% decline in forest cover due to logging and agricultural expansion, a 3.22% net gain in grassland, and a slight increase in artificial surfaces (0.34%). These changes resulted in increased surface runoff (7.79%) due to reduced infiltration, decreased evapotranspiration (1.58%), lateral flow (1.49%), and groundwater recharge (0.66%)—largely attributed to deforestation and land management practices. A slight increase in water yield (1.05%) was observed as a cumulative effect of these changes. The findings underscore the importance of adopting sustainable land-use practices to mitigate hydrological imbalances and ensure the long-term sustainability of water resources in the Katsina-Ala Basin.