Hydrus-3D Simulations: Irrigation Management Strategies for the Texas High Plains.

Half of the cultivated area and more than 80% of crop production in the Texas High Plains (THP) comes from irrigated agriculture, which depends on water from the Ogallala Aquifer. The water table of this aquifer is declining because groundwater withdrawals exceed recharge. This fact compromises its long-term sustainability and tools to manage diminishing water are needed to reduce withdrawals without reductions in irrigated land area and/or crop yields. Increasing weather-based irrigation scheduling using weather networks has been proposed and has the potential to increase water use efficiency. However, evapotranspiration information alone does not solve the challenge of extending the aquifer's sustainability. The water balance of an irrigated agricultural field is complex and involves many variables, including, crop-type, soil physical properties, and well capacity. Therefore, irrigation-optimization of an agricultural field that considers all variables is difficult and a strategy is to use models in combination with field experiments. For example, Hydrus-3D, a numerical simulation model that calculates soil-water movement and root-water uptake could be used to explore different irrigation scenarios applicable to the THP. Our objective is to use the Hydrus-3D model with sub-surface drip irrigation to explore cotton irrigation strategies under declining water supplies for the THP