Modelling the Relationship Between Land Use Change and Stream Flow Regimes in the Sokoto River Watershed, North West Nigeria

Changes in land use and land cover across the Sokoto River watershed have altered hydrological processes, affecting seasonal stream flow patterns critical for downstream water supply and irrigation. This study modelled the relationship between observed land use change and stream flow regime shifts using the Soil and Water Assessment Tool applied to a 12,000 square kilometre sub-watershed in North West Nigeria. Multi-temporal land cover datasets for 2003, 2012, and 2021 were derived from Landsat imagery and used as model inputs. The model was calibrated and validated against daily stream flow records from two gauging stations with at least fifteen years of continuous data. Scenario analysis compared simulated flow regimes under historical land cover trajectories with business-as-usual and reforestation scenarios. Results showed statistically significant increases in peak flow and reductions in baseflow index over the study period, correlated with progressive forest to cropland conversion. The reforestation scenario projected 22 percent improvement in dry-season baseflow relative to the business-as-usual projection. Sensitivity analysis identified soil erodibility and initial abstraction parameters as key model uncertainties. The study fills a critical research gap by quantifying land use hydrology linkages in a semi-arid West African watershed and provides model outputs directly applicable to integrated catchment management planning. Recommendations include embedding hydrological modelling capacity within Sokoto State water resources management institutions. Keywords: land use change, stream flow modelling, Sokoto River, Soil and Water Assessment Tool, watershed management.