Impact of land use and climate change on soil parameters in some selected LGA in South Eastern Nigeria using SWAT model

The increasing impacts of climate change and land-use alteration have emerged as major environmental challenges affecting soil water quality, agricultural productivity, and ecosystem resilience, particularly in tropical regions. In recent decades, rising global temperatures, irregular precipitation patterns, and unsustainable human activities such as deforestation and intensive cultivation have disrupted the natural hydrological balance, leading to soil degradation, reduced groundwater recharge, and declining water quality. This study focuses on assessing the effects of climate and land-use changes on soil water content and quality within selected local government areas in southeastern Nigeria using the Soil and Water Assessment Tool (SWAT). The model was employed to simulate the hydrological responses of different land-use and climatic scenarios on soil moisture, surface runoff, and river discharge within the study area. This study involved the acquisition and integration of spatial data such as Digital Elevation Model (DEM), soil classification maps, land-use data from Landsat imagery, and climatic data (rainfall, temperature, humidity, and wind speed). These datasets were processed and input into the SWAT model, which was calibrated and validated using observed hydrological data from 2013 to 2023. Calibration and sensitivity analysis identified key parameters influencing the hydrological response, including soil texture, infiltration rate, evapotranspiration, and precipitation intensity. Model validation produced acceptable statistical results, demonstrating a satisfactory correlation between simulated and observed values, thereby confirming the reliability of the simulation for predictive analysis. Scenario simulations were conducted to examine the impacts of varying rainfall and temperature levels, as well as different land-use patterns such as partial and complete deforestation, agricultural expansion, and reforestation. Results from the analysis revealed that increased temperature coupled with reduced rainfall significantly decreases soil moisture, groundwater recharge, and river discharge. Conversely, afforestation and proper land management practices enhance soil water retention, minimize erosion, and stabilize hydrological cycles. The findings indicated results for absolute values and percentage distributions between 2013 and 2023: Thick Forest 48128.76 (39.712%), Farmland 35001.54 (28.881%), Built-Up/Bare Surface 35237.07 (29.075%), and Water 2826.45 (2.332%). For 2023: Thick Forest 29273.57 (24.237%), Farmland 32031.00 (26.430%), Built-Up/Bare Surface 57268.08 (47.253%), and Water 2521.17 (2.080%). This research demonstrates the strong interdependence between climate dynamics, land-use patterns, and soil-water systems. The study emphasizes the necessity for integrated watershed management, climate-smart agriculture, and adaptive land-use planning as sustainable strategies for mitigating the adverse effects of climate change.