GROUNDWATER MODELS OF WEST TEXAS

Concerns about water resources in West Texas have increased interest in using numerical groundwater flow models to predict how aquifers might respond to pumping. This is particularly true in the Texas portion of the Hueco-Mesilla Bolson aquifer where recent modeling by the USGS suggested that the fresh groundwater supply in the Hueco Bolson could be depleted in 2025 if current trends of use continue. Because of this potential depletion, El Paso is exploring desalination of local brackish water and other aquifers in the area as possible supplementary water sources including the Bone Spring-Victorio Peak, the Capitan Reef, and the bolson fills of Wild Horse, Lobo, and Ryan Flats. While the Hueco-Mesilla Bolson aquifer has a long history of being modeled, other aquifers in West Texas have not been modeled until recently or not at all. There are several scientific models of groundwater flow in the area. While these models are useful for better understanding how groundwater flows through the aquifers, they are generally not useful for assessing groundwater availability or management practices. The aquifers of West Texas offer considerable challenges to modelers because of their geologic and hydrologic complexity, uncertain connectivity, and scarcity of information. Water-quality deterioration in some aquifers further complicates assessment of groundwater availability. A few models have been recently developed to assess groundwater availability in some of the area's aquifers. However, the calibration and implementation of these models vary considerably. Policymakers and groundwater managers need to carefully assess the quality of these models before using results to make policy and management decisions. The Texas Water Development Board (TWDB) has initiated the Groundwater Availability Modeling (GAM) program to develop models for the major and minor aquifers of the State. As part of this program, the TWDB convened a technical advisory group of experts and policymakers to develop a set of requirements to ensure that all models developed for GAM meet minimum requirements for model development, calibration, and documentation. Models developed for the West Texas area should strive to meet these minimum requirements to ensure that useful tools are developed to help answer the pressing groundwater resource questions in the area.