Protecting the Gulf Coast Aquifer of Colorado County

The Future of Groundwater AvailabilityJim Brasher General Manager, Colorado County Groundwater Conservation DistrictJanuary 25, 2011 LCRA Regional Council Meeting

OutlineDescription of AquiferGroundwater UsageFuture Groundwater Usage

Major Aquifers of Texas

Hydrostratigraphy

Gulf Coast Aquifer2 mill yrs ago.1 mill yrs ago7 mill yrs ago26 mill yrs ago Hydrologic Cross-Section

Groundwater Management Areas

GMA 15

Computer Simulations of the Gulf Coast Aquifer

3-D Conceptual Model

GAM Runs: Chicot Aquifer Pumpage Comparison

Simulation Results: Chicot AquiferEvangelineChicotJasper Pumpage versus Water Level Change12ChicotEvangeline Pumpage versus Water Level Change13EvangelineChicot Pumpage versus Water Level Change14

Summary of Gulf Coast AquiferComposed of Chicot, Evangeline and Jasper Aquifers (along with Burkeville Confining Unit)Chicot is best and Jasper is poorest qualityAquifers dip and thicken from NW to SE Computer simulations can project aquifer conditions based on pumpage assumptions at future points in time Types of Groundwater UsageMunicipal or Public Supply DomesticLivestockCommercialIrrigationMining

Irrigation

17

Mining

18 Colorado County Groundwater Usage

Colorado County Groundwater Usage

Ave water level of index wells (CBGCD)

200820072010200520062009 Future Water UsageUp until now:High availability of Colorado River water for irrigationAbundant groundwater in most of the countyNo accurate estimate of groundwater usage or availability plenty of waterNo regulation needed

Region K Water PlanCounty201020202030204020502060Bastrop1,6101,4071,2261,072934814Blanco696662585655Burnet10110098969593Colorado200,822192,465184,380176,555168,946161,663Fayette739692648606568533Gillespie2,0392,0131,9871,9601,9361,912Hays (p)111111111111Llano979963946930915900Matagorda193,048186,072179,353172,916166,722160,750Mills2,9362,8722,8102,7492,6892,631San Saba3,2403,1363,0352,9372,8412,749Travis1,2241,034951875805741Wharton (p)191,241176,441170,127164,044158,177135,911Williamson (p)000000TOTAL589,705567,272545,634524,809504,695468,763Lower Colorado Regional Water Planning Group (Region K) July 2010 (p) denotes that only the portion of the county in Region K was considered Projections of Irrigation Usage (Surface and Groundwater)County201020202030204020502060Bastrop5,0335,0355,036373839Blanco555555Burnet1,9562,0492,0982,1452,1902,235Colorado20,80421,19721,41621,62321,82121,996Fayette424242424242Gillespie888888Hays (p)1262000Llano149148148148148148Matagorda177172169167165163Mills000000San Saba163163163163163163Travis1,5311,6491,7271,8041,8801,935Wharton (p)731773798822844864Williamson (p)951000TOTAL30,62031,25231,61326,96427,30427,598Lower Colorado Regional Water Planning Group (Region K) July 2010 (p) denotes that only the portion of the county in Region K was considered Projections of Mining Usage (Surface and Groundwater)County201020202030204020502060Bastrop13,27518,62022,96430,04035,86043,208Blanco1,4671,7121,9472,1432,3602,626Burnet8,99011,43714,16616,86718,62620,550Colorado3,1553,2923,3283,2593,3203,409Fayette3,8904,4174,8795,2445,7516,495Gillespie4,7495,3985,6465,5765,5415,541Hays (p)7,20210,65613,44616,26619,74222,498Llano5,7226,2356,4466,6476,8757,139Matagorda5,5905,8305,9065,8835,8315,831Mills1,0101,0701,0931,0531,0861,104San Saba1,2991,3161,3281,3391,3311,336Travis199,677237,014274,610308,229342,865369,723Wharton (p)3,7763,8803,9103,8803,8423,806Williamson (p)8,84111,09513,76116,62519,74323,082TOTAL268,643321,972373,430423,051472,778516,348Lower Colorado Regional Water Planning Group (Region K) July 2010 (p) denotes that only the portion of the county in Region K was considered Projections of Municipal Usage (Surface and Groundwater)County201020202030204020502060Bastrop13,27518,62022,96430,04035,86043,208Blanco1,4671,7121,9472,1432,3602,626Burnet8,99011,43714,16616,86718,62620,550Colorado3,1553,2923,3283,2593,3203,409Fayette3,8904,4174,8795,2445,7516,495Gillespie4,7495,3985,6465,5765,5415,541Hays (p)7,20210,65613,44616,26619,74222,498Llano5,7226,2356,4466,6476,8757,139Matagorda5,5905,8305,9065,8835,8315,831Mills1,0101,0701,0931,0531,0861,104San Saba1,2991,3161,3281,3391,3311,336Travis199,677237,014274,610308,229342,865369,723Wharton (p)3,7763,8803,9103,8803,8423,806Williamson (p)8,84111,09513,76116,62519,74323,082TOTAL268,643321,972373,430423,051472,778516,348Lower Colorado Regional Water Planning Group (Region K) July 2010 (p) denotes that only the portion of the county in Region K was considered Projections of Municipal Usage (Surface and Groundwater) Future Water Use ProjectionsCurrently a shortage in some major urban areas such as San AntonioProjected Population of Texas expected to increase by 80% in the next 50 yearsState Water Management Plan prescribes how LCRA will allocate water during supply shortagesPlan directs curtailment of interruptible water supplies so that firm water users are protected In August of 2009, plans were developed to totally cut interruptible water supply to rice farmers Likelihood of interruptible supply of Colorado River water being maintained is low Future Water Use ProjectionsLocally, project only small population increases, butColorado, Wharton and Matagorda Counties will be viewed as prime areas to exploit for transport of water to urban areas!LCRA-SAWS Project was an exampleProject underway to transport water from Gonzales County to San Antonio

Future Groundwater UsageUp until now:High availability of Colorado River water for irrigationAbundant groundwater in most of the countyNo accurate estimate of groundwater usage or availability plenty of waterNo regulation neededWhats in store for the future:Dramatic population increases will dictate water needsSurface water availability from the Colorado River will likely be restrictedProjections of rice production and irrigation to decrease

Future Groundwater UsageWater will increasingly be treated as a commodityAnyone who can deliver water to urban areas could be well compensated (i.e. conducive to water marketers)Result:The days of no regulation of groundwater are gone!Local control or state control?

Questions? Geological Interpretations

WUGRiver BasinStrategySource NameIrrigationLavaca and Brazos-ColoradoCity of Austin Return FlowsIndirect ReuseDownstream Return FlowsIndirect ReuseConjunctive Use of GroundwaterGulf Coast AquiferDevelopment of New Rice VarietiesConservationIrrigation District Conveyance ImprovementsConservationOn-Farm ConservationConservationIrrigation Supply Reduction due to LSWPColorado River RORFirm Up ROR w/ Off-Channel ReservoirColorado River ROR Excess Flows PermitLCRA WMP Interruptible Water SupplyColorado River Combined ROR InterruptibleMiningColoradoDevelopment of Other AquiferOther AquiferBrazos-ColoradoExpansion of Gulf Coast AquiferGulf Coast AquiferLivestockColoradoExpansion of Gulf Coast AquiferGulf Coast AquiferLavacaExpansion of Gulf Coast AquiferGulf Coast AquiferCounty-OtherLavacaExpansion of Gulf Coast AquiferGulf Coast Aquifer Water Management StrategiesEvangelineChicotChicotEvangelineEvangelineChicotJasperEvangelineChicotPumpage versus Water Level Change35

Colorado County Rice36

3-Dimensional Computer Simulation Outcrop Map in Computer Simulation

Approximate Chicot Thickness