Potential impact of climate change on irrigation water requirements for some major crops in the northern high plains of Texas

Future irrigation water requirements (IWRs) for different crops will be affected by the variation of rainfall and evapotranspiration that are projected to be impacted by future climate change. Thus, there is a need to investigate the potential impact of climate change and increasing climate extremes on the sustainability of agricultural production systems. The main goal of this study is to analyze the potential impact of climate change on IWRs for four major crops (corn, cotton, sorghum and winter wheat) in the Northern High Plains of Texas (NHPT). Specific objectives are to (i) generate and analyze projected daily climate data based on different Global Climate Models (GCMs) and (ii) assess the potential impact of climate change on IWRs and other water balance components of four major crops. Daily gridded climate data from the National Center for Environmental Prediction (NCEP) Climate Forecast System Reanalysis (CFSR) for the 1981 to 2010 period were used to represent observed historical daily climate data. We applied the statistical downscaling model Long Ashton Research Station Weather Generator (LARS-WG) to generate projected daily climate data at each grid cell (approximately 38 × 38 km) within the study region. The climate data for three future periods, that is, the 2020s, 2050s, and 2090s, were generated using outputs from 15 GCMs under three emission scenarios (B1, A1B, and A2). The hydrologic parameters of the major soil types in the study region were derived from the Soil Survey Geographic Database (SSURGO). Irrigation water requirements and major water budget components for all grid cells were calculated using the Irrigation Management System (IManSys) model based on crop specific growth parameters, site-specific soil hydrological properties, irrigation system efficiency, and long-term daily climate data (current and future climate scenarios). Monthly temperature and reference evapotranspiration were projected to increase; however, annual precipitation was expected to decrease in the future projection periods. Thus, gross irrigation requirements (GIRs) of all four crops, with an irrigation system efficiency of 75%, were assumed to increase (2.08-3.77% in the 2020s, 6.23-9.25% in 2055s and 6.81-19.52% in 2090s), threatening the possibility of serious groundwater depletion and long-term sustainable agriculture in this region. Further work is needed to predict crop yield responses to potential climate change scenarios for these different future periods