Effects of climate change on surface water flows and crop water requirements in North-Central Texas

Abstract:

Intensive anthropogenic activities have increased the concentrations of greenhouse gases in the atmosphere, and altered the climate patterns globally. Future climatic changes are likely to further affect the global hydrologic cycle. Anticipated changes in rainfall-runoff and streamflow are likely to vary spatially depending on the future changes in direction, magnitude, and frequency of climatic variables and events (e.g., heavy rainfall). Therefore, regional analyses of climate change effects are necessary to develop climate-resilient adaptation and mitigation strategies. In this study, we used future (2020-2099) temperature and precipitation projections for the Bosque river basin (4,300 km²) located in North-Central Texas to evaluate the effects of climate change on streamflow and crop water requirements. Selection of Global Climate Models (GCMs), CO­­₂ emission scenarios, downscaling methods, and input climate data, introduces a large uncertainty in future predictions. We used an ensemble of future climate projections generated from three GCMs (MIROC5, MPI-ESM-LR, CCSM4), three Representative Concentration Pathways (RCPs; 2.6, 4.5 and 8.5), three downscaling methods (delta-change method, Equidistant Quantile Mapping and Piecewise Asynchronous Regression Model) and three input climate datasets (Daymet, PRISM, and Livneh) to account for the uncertainty in future climate predictions. ArcGIS Soil and Water Assessment Tool (ArcSWAT) was used to simulate the effects of climate change on water balance components in the basin. In-situ streamflow data (2000-2019) obtained from three USGS gauges were used in SWAT-CUP (Calibration and Uncertainty Program) to calibrate and validate ArcSWAT. Model performance was evaluated using NSE, KGE, RSR, and PBIAS. The Sequential Uncertainty Fitting (SUFI-2) method was used in SWAT-CUP to quantify the uncertainty in future streamflow predictions. Preliminary results indicated slight declines in precipitation (0-15%) and streamflow (0-25%) in the basin along with increased irrigation demands due to increased temperatures and reduced precipitation in the future. This study should help decision-makers and other stakeholders to understand the potential impact of climate change on streamflow and crop water requirements.