Predicting Potential Impact of Climate Change on Irrigation Water Requirements at the Brazos Headwaters Basin of Texas.

This study analyzed the potential impact of climate change on irrigation water requirements for four major crops (Cotton, corn, sorghum and wheat) at the Brazos Headwaters Basin, Texas. We used the statistical downscaling model (LARS-WG) to generate projected daily climate data at each grids (size = 0.3 x 0.3 degree) of the basin. The climate data for three future periods, i.e. 2020s, 2055s and 2090s, were generated using outputs from 15 General Circulation Models (GCMs) under three emission scenarios (B1, A1B and A2). We estimated irrigation water requirements at all grids of the basin using the Irrigation Management System (IManSys) model. In addition to irrigation water requirements, IManSys also calculates runoff, drainage, canopy interception, and effective rainfall based on plant growth parameters, soil properties, irrigation system, and long-term daily climate data (precipitation and evapotranspiration). Planting date, harvesting date and growing season of each crop were selected based on the geographic location of the area. Based on the preliminary result, monthly temperature and potential evapotranspiration will increase and annual precipitation will decrease in the future projection periods. Thus, irrigation water requirements for all crops will increase. In our Future work, we will use a crop model to estimate projected crop yield during future projection periods.