the annual volume of flow into and out of the district within each aquifer and

Staff Report & Agenda Item Details

3. the annual volume of flow into and out of the district within each aquifer and between aquifers in the district. The groundwater management plan for the Cow Creek Groundwater Conservation District should be adopted by the district on or before November 4,2019 and submitted to the Executive Administrator of the TWDB on or before December 4,20L9. The current management plan for the Cow Creek Groundwater Conservation District expires on GAM Run 79-}LL: Cow Creek Groundwater Conservation District Groundwater Management Plan March 5, 2019 Page 4 of 77 February 2,2020. We used two groundwater availability models to estimate the management plan information for the aquifers within the Cow Creek Groundwater Conservation District. Information for the Trinity and Edwards-Trinity (Plateau) aquifers is from version 2.0L of the groundwater availability model for the Hill Country portion of the Trinity Aquifer [Jones and others ,2017).lnformation for the Ellenburger-San Saba and Hickory aquifers is from version L.01 of the groundwater availability model for the minor aquifers of the Llano Uplift region (Shi and others, 2076). This report replaces the results of GAM Run 13-029 (Wade, 20L3). GAM Run 19-011 includes results from the newly released groundwater availability model for the minor aquifers of the Llano Uplift Area (Shi and others ,2016). Tables 1 through 4 summarize the groundwater availability model data required by statute and Figures 1 through 4 show the area of the models from which the values in the tables were extracted. If, after review of the figures, the Cow Creek Groundwater Conservation District determines that the district boundaries used in the assessment do not reflect current conditions, please notifii the TWDB at your earliest convenience. METHODS: In accordance with the provisions of the Texas State Water Code, Section 36.1077, Subsection (h), the two groundwater availability models mentioned above were used to estimate information for the Cow Creek Groundwater Conservation District management plan. Water budgets were extracted for the historical model periods for the Trinity and Edwards-Trinity (PlateauJ aquifers (1981 through L997), and the Ellenburger-San Saba and Hickory aquifers (1980 through 2010) using ZONEBUDGET Version 3.01 [Harbaugh, 2009) or ZONEBUDGET-USG (Panday and others,2013), as applicable. The average annual water budget values for recharge, surface-water outflow, inflow to the district, and outflow from the district for the aquifers within the district are summarized in this report. GAM Run 19-011: Cow Creek Groundwater Conservation District Groundwater Management Plan March 5, 2019 Page 5 of 17 PARAMETERS AN D ASSUMPTIONS : Edwards-Trini$ ehtuau) and Trinity Aquifers o We used version2.0I of the groundwater availability model for the Hill Country portion of the Trinity Aquifer System. See fones and others (2011) for assumptions and limitations of the groundwater availability model. r The groundwater availability m