Impact of past, present and future land use and land cover changes on water yield and evapotranspiration in a small urban watershed in Texas, USA

Change in Land use and land cover (LULC) is a primary driver of watershed hydrological processes, significantly influencing hydrological variability. Rapid LULC changes in the southwestern United States have intensified these effects. The study examined how LULC changes impact water yield and evapotranspiration (ET) in the Cypress Creek watershed, Texas, USA. The Soil and Water Assessment Tool (SWAT+) model simulated watershed hydrology, while TerrSet Land Change Modeler (LCM) predicted future LULC patterns for 2030 and 2040. The analysis employed LULC maps from 2000 to 2040 and comprehensive datasets to simulate hydrology under each LULC scenario. SWAT+ was successfully calibrated and validated using streamflow data from three-gauge stations. SWAT+ calibration performance, measured by the Kling-Gupta Efficiency (KGE), ranged from 0.74 to 0.86 during calibration and from 0.62 to 0.80 during validation. TerrSet LCM also demonstrated high prediction accuracy.Results revealed declining pasture coverage from 49% to 34%, while urban development increased, with developed medium-intensity areas expanding from 6.1% to 20.8%. Water yield exhibited upward trends (70.7%) corresponding to LULC change, while ET (6.7%) and percolation (21%) showed reductions. Pasture coverage demonstrated strong positive correlations with ET and percolation but negative correlations with water yield. Urban areas showed strong positive correlations with water yield ( r > 0.9) and negative correlations with ET and percolation. The study's results identified an increased flood risk associated with LULC changes, as indicated by changes in the flood severity duration-frequency curves. The study concludes that continued urbanization triggers hydrological changes, particularly increasing water yield and reducing ET, thereby intensifying downstream flood risk in the Cypress Creek watershed. SWAT+/TerrSet LCM framework offers a transferable tool for anticipating hydrological change with the LULC change in similarly urbanizing watersheds.