The Texas Water Development Board on October 26 announced the completion of its project, mandated by the 77th Legislature (2001), to develop or obtain groundwater availability models (GAM's) for all of the major aquifers of Texas. All of the models, reports, and support data are available at the TWDB website - www.twdb.state.tx.us/gam - or by request from the Board.

The Legislature funded the GAM program to develop numerical groundwater flow models to help groundwater conservation districts, regional water planning groups, and others assess current groundwater availability and the effect of pumping and drought on the state's groundwater resources. New models developed via the GAM process also had substantial stakeholder involvement. Some of the GAM's represent the first water modeling of any kind in the area.

TWDB staff developed five of the models - the Hill Country segment of the Trinity Aquifer; the northern and San Antonio segments of the Edwards Aquifer; the southern part of the Gulf Coast Aquifer; and the Edwards-Trinity (Plateau) and Cenozoic Pecos Alluvium Aquifers.

TWDB contractors developed eight of the models - the northern and southern parts of the Ogallala Aquifer; the northern, central, and southern parts of the Carrizo-Wilcox Aquifer; the Seymour Aquifer; the northern segment of the Trinity Aquifer; and the Barton Springs segment of the Edwards Aquifer. TWDB staff and a contractor jointly developed a model of the central Gulf Coast Aquifer.

The Board and Harris-Galveston Coastal Subsidence District funded a project for the U.S. Geological Survey to develop a model of the northern part of the Gulf Coast Aquifer. El Paso Water Utilities and the U.S. Geological Survey supported development of models for the Mesilla and Hueco Bolson Aquifers. The Edwards Aquifer Authority is developing a new model for the San Angonio segment of the Edwards Aquifer that will be available by the end of 2004.