Texas Water Development Board

groundwater management plan, a groundwater conservation district shall use groundwater availability modeling information provided by the executive administrator in conjunction with any available site-specific information provided by the district and acceptable to the executive administrator. Information derived from groundwater availability models that shall be included in groundwater management plans include: (1) the annual amount of recharge from precipitation, if any, to the groundwater resources within the district; (2) for each aquifer within the district the annual volume of water that discharges from the aquifer to springs and any surface water bodies, including lakes, streams, and rivers; and (3) the annual volume of flow into and out of the district within each aquifer and between aquifers in the district. The purpose of this model run is to provide information to the Sterling County Underground Water Conservation District needed for its groundwater management plan. The groundwater management plan for the Sterling County Underground Water Conservation District is due for approval by the executive administrator of the Texas Water Development Board before January 25, 2011. This report discusses the methods, assumptions, and results from a model run using the groundwater availability model for the Edwards-Trinity (Plateau) Aquifer. Table 2 summarizes the groundwater availability model data required by statute for the Sterling County Underground Water Conservation Districts groundwater management plan. METHODS: We ran the groundwater availability model for the Edwards-Trinity (Plateau) Aquifer, and (1) extracted water budgets for each year of the 1980 through 1999 period and (2) averaged the water budget values for recharge, surface water inflow, surface water outflow, inflow to the district, outflow from the district, net inter-aquifer flow (upper) and net inter-aquifer flow (lower) for the portions of the Edwards and the Trinity aquifers located within the district