Tuesday, April 30, 2013: 2:55 p.m.
Regency East 3 (Hyatt Regency San Antonio)
A multi-crop acreage and evapotranspiration (ET) based irrigation demand model has been developed for use in regional water planning and conservation efforts in the northern Texas High Plains. Accuracy is essential as irrigation accounts for nearly 90% of the entire regional water resource use (Marek et al., 2010). The Texas A&M-Amarillo (TAMA) irrigation demand model computes a regional based 26 county estimate using a per crop per county process. Model input includes long-term county based crop ET, effective growing season precipitation, seasonal soil profile water utilization per crop and producer-based pumping percentage of the respective fully watered crop ET requirement. The producer applied value is generally less than 100% of the crop ET requirements as producers can no longer meet fully irrigated crop water requirements in most operations. The producer based pumping percentage per crop includes average irrigation systems application efficiencies. Crop acreage is based primarily on Farm Service Agency (FSA) data and is augmented within the counties from local knowledge of acreage outside of the FSA reporting process, which can be substantial. Hail-out and graze-out acreage and water use percentage is also estimated per crop within the model. The model utilizes 12 major crop categories. Average total irrigated acreage in the region is currently estimated at 1.351 million acres. The total estimated irrigation demand for the decade of 2010 for the 26 county region is 1.513 million ac-ft annually. The weighted mean application is 1.12 ac-ft/ac or 13.4 in/ac. Over 60% of the entire regional water resource is attributed to the production of corn followed by 16% for wheat. Model performance has agreed extremely well (>95%) with groundwater district well level data and most recently with metered well values. Model estimates do not include the near record drought conditions of 2011 and 2012.
