ORDER NO. 30098
HEADWATERS GROUNDWATER CONSERVATION DISTRICT
AQUIFER MODELING
Came to be heard this the 8th day of January, 2007, with a motion made by
Commissioner Williams, seconded by Commissioners Letz. The Court
unanimously approved by vote of 4-0-0 to:
Approve scheduling and receiving a detailed presentation from Headwaters
Groundwater Conservation District (HGCD) consulting Geologist Feather
Wilson on aquifer modeling in Kerr County and present status of
Groundwater Availability Modeling efforts and the use of same to determine
water availability in specific areas of Kerr County, by posting on
Commissioners' Court Agenda for January 22, 2007 at 1:00 p.m.
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COMMISSIONERS' COURT AGENDA REQUEST
PLEASE FURNISH ONE ORIGINAL AND NINE COPIES OF THIS REQUEST
AND DOCUMENTS TO BE REVIEWED BY THE COURT.
MADE BY: Commissioner Williams OFFICE: Precinct 2
MEETING DATE: January 8, 2007 TIME PREFERRED:
SUBJECT: (Please be specific).Consider, discuss and take appropriate action to schedule
and receive a detailed presentation from Headwaters Groundwater Conservation District
(HGCD) consulting Geologist Feather Wilson on aquifer modeling in Ken County.
Presentation to include water availability of the Middle Trinity, Lower Trinity, Edwards-
Trinity, Glen Rose and other aquifers based on scientific data and consulting work done
for HGCD; and present status of Groundwater Availability Modeling efforts and the use
of same to determine water availability in specific areas of Kerr county. Presentation to
be scheduled for Commissioners' Court meeting of January 22, 2007, at i l a.m.
EXECUTIVE SESSION REQUESTED:
NAME OF PERSON(S) ADDRESSING THE COURT: Commissioners Williams and Letz.
ESTIMATED LENGTH OF PRESENTATION:
IF PERSONNEL MATTER-NAME OF EMPLOYEE:
Time for submitting this request for Court to assure that the matter is posted in
accordance with Title 5, Chapter 551 and 552, Government Code, is as follows:
Meeting scheduled for Mondays: 5:00 P.M. previous Tuesday
THIS REQUEST RECEIVED BY:
THIS REQUEST RECEIVED ON: @
All Agenda Requests will be screened by the County Judge's Office to determine if adequate
information has been prepazed for the Court's formal consideration and action at time of Court
"' meetings. Your cooperation is appreciated and contributes towazd your request being addressed
at the earliest opportunity. See Agenda Request Rule adopted by Commissioners Court.
GROUNDWATER AYA/LABIL/TY
..,:. -
MODEL/NG
~` Groundwater, along with surface water, is impottant for maintaining the viability
of the state's narural resources, health, and economic development. A projected
doubling of the state's population by the year 2050, coupled with the constant
threat of drought, makes it imperative that Texas develops effective plans ro meet
~~:' future warer needs. Efkctive planning, however, requires aceumte assessments of
the availability of water, and assessing the availability of groundwater is often much
more difficult than assessing that of surface water. Surface water is easily observed
at the land surface, and the response of rivers and lakes to rainfall can be repeatedly
t measured over time. Groundwater is mote difficult to observe and measure because
it resides below the land surface and responds ro rainfall much more slowly than
- ~^ rivers and lakes do. Aquifer systems aze complex due to flows into and out of the
aquifer, the imeraction between surface water and groundwater, and the uncertainty
of aquifer properties. Because of this complexity, computer models are excellem
- tools for assessing the efkcc of pumping and droughts on groundwater availability.
Groundwater availability modeling is the process of developing and using computer
programs to estimate furure trends in the amount of water available in an aquifer
and is based. on hydrogeologic principles, actual aquifr measurements, and
stakeholder guidance.
The 76th Texas Legislature, recognizing the importance of accurate groundwater
availability estimates, approved initial funding for the Groundwater Availability
Modeling (GAM) program. The GAM program's goal is ro provide useful and
timely information kr determining groundwater availability kr the utizens of
- `, Texas. The GAM program will result in standardized, thoroughly documented,
"" "' and publicly available groundwater models. These models will be important tools
~~ for Groundwarer Conservation Districts and Regional Water Planning Groups to
evaluate water-management strategies and to assess present and future groundwater
availability trends under normal and drought conditions.
Stakeholder involvement is critical ro the success of the GAM program.
Stakeholders, pazticipating in Stakeholder Advisory Forums (SAFs), aze relied upon
ro voice wncerns and provide information. Stakeholder input ensures the models
address the importantwater-resource issues concerning them for each major aquifer.
SAFs typically consist of representatives from Groundwater Conservation Districts,
Regional Warer Planning Groups, the Texas Commission on Environmental
Quality, the Texas Department of Agriculture, the Texas Pazks and Wildlife
Department, industry, water utilities, higher education, agriculture, and private
landowners.
Groundwater Availability Models include comprehensive information on each
aquifr, including: recharge (amount of water emering the aquifer); geology and
-- strutture; rivers, lakes, and springs; water levels; aquifer properties; and, pumping.
Each model is calibrated to ensure that the models can reasonably reproduce past
water levels and groundwater flows.
The nine major aquifers in Texas required seventeen different models to provide full coverage. TWDB staff developed four
,gf the models: (1) the Hill Country segment of the Trinity aquifer, (2) the northern segment of the Edwards aquifer, (3)
e southern part of the Gulf Coast aquifer, and (4) the Edwards Trinity (Plateau) and Cenozoic Pecos Alluvium aquifers.
r'WDB contractors developed eight of the models: (5) the northern and (6) southern part of the Ogallala aquifer; the (7)
notthern, (8) central, and (9) southern parts of the Carrizo-Wilcox aquifer, (10) the Seymour aquifer; (11) the northern
segment of the Trinity aquifer, and (12) the Barton Springs segment of the Edwards aquifer. TWDB staff and a contmcror
developed a model of (13) the central Gulf Coast aquifer. The TWDB and Harris-Galveston Coastal Subsidence District
funded a project for the U.S. Geological Survey ro develop a model of (14) the notthern part of the Gulf Coast aquifer The
U.S. Geological Survey in cooperation with the U.S. Department of Defense and the Edwards Aquifer Authority developed
a model for (15) the San Antonio segment of the Edwards aquifer. EI Paso Water Utilities and the U.S. Geological Survey
supported the development of models for the (16) Mesilla and (17) Hueco Bolson aquifer.
Completed models have already proven valuable to water planning. The model of the Hill Country Trinity aquifer has been
used ro evaluate the possible effects of increased pumping and drought on water levels. The model of the notthern part of the
Ogallala aquifer has been used to assess water-level declines and Future groundwater availability trends due to continued and
increased pumping. Models for the Barton Springs segment of the Edwards and the Hueco Bolson aquifers have also been
successfully used as predictive tools.
The success of the GAM program depends on the continued interest and support of stakeholders and the Texas Legislature.
Ongoing interest is vital ro ensure that the most up-to-date model information will be available to address groundwater
resource issues for each aquifer. Continued funding is required to update models and develop models for the minor aquifers.
The GAM models for the major aquifers, representing 95 percent of groundwater used in Texas, were completed by October
1, 2004. Information and reports on the models are available to the public on TWDB's web site and the models are available
on CD upon request.
Please comact Dr Robett E. Mace az (512) 936-0861, or Ms. Cindy Ridgeway at (512) 936-2386 or visit
~s•~~~~.rv~ d'u.s race. tt t is / L r,w :v1 for more information about the GAM program.
Location of GAMs for the major aquifers of Texas

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~~ email: fealhergl?~ece.nrl
~~ William Feathergail Wilson, PG
Consulting Geologist
1305 F'M 462
Bandera YCarpley b'CX 781813A22n
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