Groundwater Supplies and Availability in Texas: Results from the 2002 State Water Plan

By

MACE, ROBERT E., and MULLICAN, WILLIAM F., III

Texas Water Development Board, Austin, TX

Because of the increasing demand for water and the frequency of drought, the State of Texas has conducted statewide water planning since 1957 resulting in seven adopted water plans (in 1961, 1968, 1984, 1990, 1992, 1997, and 2002). The most recent plan is the culmination of new water planning resulting from the passage of Senate Bill 1 by the Texas Legislature in 1997 which uses regional water planning groups to assess regional supplies, demands, needs, and solutions. The most recent planning shows that groundwater is an important source of water to the State of Texas, supplying about 60 percent of the 16.6 million acre-feet of water used by Texans in 1999. About 81 percent of the 10.0 million acre-feet of water produced from aquifers was used for irrigation. Most of the western half and a significant part of the eastern half of the State rely primarily on groundwater. Water supplies from existing groundwater sources are expected to decrease 19 percent, from 8.8 million acre-ft/yr (AFY) to 7.2 million AFY during drought conditions. Total current groundwater availability as assessed by the planning groups for drought conditions is about 14.9 million AFY. This availability decreases to 13.1 million AFY by 2050 because of projected declines in availability in the Ogallala, Gulf Coast, Hueco-Mesilla Bolson, and Carrizo-Wilcox aquifers. Estimates of groundwater supply and availability will be revised during future regional water planning due to additional studies and the release of Groundwater Availability Models.