Future hydro-climate extremes in the cypress creek watershed in Texas under different CMIP6 scenarios

Quantifying the frequency and trends of climate extremes under the changing climate is crucial for sustainable water resource management. The current assessment utilized the restructured Soil and Water Assessment Tool (SWAT +) to investigate future hydro-climate extremes under changing climate and land cover conditions in the Cypress Creek watershed in Texas. Standardized Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI), Streamflow Drought Index (SDI), Interquartile Range (IQR) method-based flood peak assessment, and streamflow Severity-Duration-Frequency curves (SDF) were used to evaluate the future meteorological and hydrological status. This study used ensemble means from four CMIP6 GCMs from the NASA Earth Exchange (NEX) Global Daily Downscaled Projections (GDDP) dataset (NEX-GDDP-CMIP6) for the two shared socio-economic (SSP2-4.5 and SSP5-8.5) pathways during 2025–2065. Land use/land cover (LULC) inputs included a 2010 map representing the baseline period and a projected map for 2040. The result indicated that the (1) watershed is projected to experience increases in average temperature ranging from 2.32 °C to 2.68 °C. Precipitation is expected to decline by 6.12% under the SSP2-4.5 scenario and by 4.72% under the SSP5-8.5 scenario. (2) Both SPI and SPEI show declining trends across both scenarios, indicating an increased likelihood of drought. (3) Flood severity declines under future scenarios, with SSP5-8.5 producing the lowest flows. Findings reveal considerable hydroclimatic variability in the future of Cypress Creek watershed, which primarily triggers drought but also contributes to floods. These findings have important implications for water resource planning, targeted adaptation strategies, and infrastructure design.