PLUM CREEK CONSERVATION
DISTRICT
Groundwater Management Plan
Adopted As Amended
January 17, 2023

PLUM CREEK CONSERVATION DISTRICTP.O. Box 328
Lockhart, Texas 78644
Phone: (512) 398-2383
Fax: (512) 398-7776
Email: info@pccd.org
Website: www.pccd.org
President: James A. Holt, Jr.; Vice-President: Peter Reinecke
Directors: Lucy Knight, Fred Rothert, Tom Owen

Groundwater Management Plan
TABLE OF CONTENTS
1.

DISTRICT MISSION

2.

TIME PERIOD OF THIS PLAN

3.

BACKGROUND
1.

Introduction

2.

Policy3.

Governing Board

4.

Daily Operations

5.

Topography

6.

Location and Extent

7.

Water Resources

4.

GROUNDWATER RESOURCES

5.

MANAGEMENT ZONES

6.

PRODUCTION AND SPACING OF WELLS7.

MANAGEMENT OF GROUNDWATER SUPPLIES8.

ACTIONS, PROCEDURES, PERFORMANCE AND PLAN IMPLEMENTATION

9.

METHODOLOGY FOR TRACKING DISTRICT PROGRESS IN ACHIEVING MANAGEMENT
GOALS

10.

MANAGEMENT GOALS, OBJECTIVES, & PERFORMANCE STANDARDS

10.1

Providing the Most Efficient Use of Groundwater

10.2

Controlling and Preventing Waste of Groundwater

10.3

Controlling and Preventing Subsidence

10.4

Addressing Conjunctive Surface Water Management Issues

10.5

Addressing Drought Conditions

10.6

Addressing Natural Resource Issues That Impact the Use and Availability of Groundwater and Whichare Impacted By the Use of Groundwater

10.7

Addressing Conservation Recharge Enhancement, Rainwater Harvesting, Precipitation Enhancement,
and/or Brush Control

10.8

Mitigation & Desired Future Conditions of Groundwater Resources

10.9

Addressing Desired Future Conditions of Groundwater Resources

10.10

Alternative Supply

11.

PROJECTED TOTAL DEMAND FOR WATER WITHIN THE DISTRICT12.

PROJECTED SURFACE WATER SUPPLIES WITHIN THE DISTRICT13.

WATER NEEDS WITHIN THE DISTRICT14.

WATER MANAGEMENT STRATEGIES WITHIN THE DISTRICT15.

AMOUNT OF GROUNDWATER BEING USED IN THE DISTRICT ON AN ANNUAL BASIS

16.

MODELED AVAILABLE GROUNDWATER REPORTS

17.

ANNUAL AMOUNT OF RECHARGE FROMRESOURCES WITHIN THE DISTRICT.

18.

ANNUAL VOLUME OF WATER THAT DISCHARGES FROM THE AQUIFER TO SPRINGS AND
SURFACE WATER BODIES.

19.

ESTIMATE OF THE ANNUAL VOLUME OF FLOW INTO THE DISTRICT, OUT OF THE DISTRICT,AND BETWEEN AQUIFERS IN THE DISTRICT.

20.

ESTIMATE OF MODELED AVAILABLE GROUNDWATER IN DISTRICT BASED ON DESIRED
FUTURE CONDITIONS.

21.

GEOLOGY MAP OF PCCDPRECIPITATION TO

THE GROUNDWATERAPPENDICES TABLE OF CONTENTSAPPENDIX AESTIMATED HISTORICAL GROUNDWATER USE AND 2022 STATE WATER PLANDATASETSGAM RUN 21-018 MAG AQUIFERS IN GROUNDWATER MANAGEMENT AREA 10

APPENDIX B

SUMMARY OF MODELED AVAILABLE GROUNDWATER FOR THE PLUM CREEKCONSERVATION DISTRICTGAM RUN 16-033 MAG AQUIFERS IN GROUNDWATER MANAGEMENT AREA 13

APPENDIX CGAM RUN 12-001 PCCD MANAGEMENT PLAN

APPENDIX DGEOLOGY MAP OF PCCDPLUM CREEK CONSERVATION DISTRICTGROUNDWATER MANAGEMENT PLAN
1. DISTRICT MISSION
The Plum Creek Conservation District (PCCD) mission for groundwater management is to conserve and preserve
groundwater availability and protect permitted and exempt groundwater users, by gathering information about
groundwater conditions and uses within the District; obtaining information from surrounding Groundwater Districts toassist in understanding groundwater availability within Plum Creek’s area; by using that information to adopt Rules
consistent with state law in order to maximize the beneficial development and use of the groundwater resources on asustainable basis in keeping with the desired future conditions of aquifers within Plum Creek Conservation District’s
jurisdictional area; and by then enforcing these adopted Rules. The District will accomplish this mission by identifying
aquifers within the District; and then by (1) determining zones of the various aquifers within the District, (2) imposing
spacing requirements, (3) limiting production, (4) requiring permits for non-exempt wells and groundwater production, (5)noting information on exempt wells, (6) establishing water drawdown levels, (7) monitoring aquifer levels andproduction, (8) making appropriate adjustments to allowable and permitted production as more data become available, and(9) encouraging conservation to limit pumping. These actions are designed to extend the quantity and preserve the qualityof the water available in the aquifers in Caldwell and Hays counties regulated by the District. PCCD is committed toprotecting, conserving, and preventing waste of the groundwater resources in its District for the benefit of the citizens,
economy, and environment.
2. TIME PERIOD OF THIS PLAN
This plan will become effective upon adoption by the PCCD Board of Directors and approval as administratively
complete by the Texas Water Development Board. The plan will remain in effect for five years after the date of approvalor until a revised plan is adopted and approved, or as otherwise directed by the Texas Legislature.

13. BACKGROUND
The PCCD is situated in parts of Caldwell and Hays Counties. The District was created as a Water Control and
Improvement District in the 55th Texas Regular Legislative Session in 1957 with the passage of Senate Bill 289 under theprovisions of Section 59, Article XVI of the Texas Constitution. The enabling statute provided the District with thepower to control, conserve, protect, distribute and utilize the storm and floodwaters and unappropriated flow ofPlum Creek and its tributaries as a Water Control and Improvement District. In 1989 the original 1957 legislation wasamended to additionally authorize the District, upon approval of the qualified voters of the District, to exercise thepowers and duties imposed under what is now Chapter 36 of the Texas Water Code, for the preservation, conservation,
protection, recharge, and prevention of waste and pollution of the underground water of the District except in those areasof the District that were part of the Barton Springs-Edwards Aquifer Conservation District or the Edwards Underground
Water District on January 1, 1989. The voters in the District approved the implementation of the powers granted by theLegislature after the 1989 amendment was passed in the Legislature.
1.

Introduction: The District recognizes that the groundwater resources of the region are of vital importancenot only within the District but to areas outside the District. The District was created, in part, to conserve, preserve,
protect, and prevent waste of all the water resources within its jurisdiction. The District believes that the groundwater
resources in the District can be managed in a prudent and cost-effective manner through education and conservation,
coupled with reasonable regulation, including permitting of new and existing non-exempt wells and registering of exempt
wells. Although the District has undertaken studies and has developed information about the occurrence and quality ofgroundwater in various geologic formations in and near the District, the District continues to conclude that one of thegreatest threats to prevent the District from achieving the stated mission are inadequate information about groundwater
occurrence, quality, groundwater production volumes, groundwater production rates, groundwater movement andgroundwater uses within and from aquifers regulated by the District based in part on a lack of knowledge about
groundwater production from exempt wells both within the District and groundwater occurrence and production from all
aquifers in areas without groundwater districts adjacent to or in close proximity with the area of Plum Creek Conservation
District. The District has concerns about the potential for groundwater quality degradation in some areas of the District
related to existing groundwater pumping and to old oil and gas activities. The District continually needs to develop more
information to understand how groundwater production, recharge, and flow into and out of the District are interrelated2with production, recharge and flow in areas surrounding the District. Basic knowledge of the aquifers and theirhydrogeological properties, a quantification of resources, and development of data on groundwater quality are thefoundation from which to build prudent planning measures. This Management Plan is intended as a tool to focus thethoughts and actions of those given the responsibility for the execution of the District’s activities in developing
information and in driving activities implementing the District’s goals.
2.

Policy: It shall be the policy of the Board of Directors that the most beneficial use of groundwater in theDistrict is to maintain present non-wasteful groundwater uses of those in the District and then to provide for future
groundwater needs of citizens. Groundwater shall be beneficially used, conserved, preserved, protected, and waste
prevented within the District to maintain the viability of those resources for current users and for users in the future whoare in the District’s area. The Board of Directors, with the cooperation of the citizens of the District and of surrounding
political subdivisions, shall implement this management plan and any necessary modifications thereof to achieve this goal.
3. Governing Board: The District is governed by an appointed six-member Board of Directors.
4. Daily Operations: The day-to-day management of District activities is carried out currently by a fourmember staff led by Daniel Meyer, Executive Manager.
5. Topography: The land surface of Caldwell County ranges from nearly flat to hilly. The minimum elevation,
about 295 feet, is at the southern tip of the County where Plum Creek joins the San Marcos River. The maximum
elevation in Caldwell County, about 725 feet, is in the area of the so-called “Iron Mountains” peaks, approximately 2.5
miles southeast of McMahan, a small community approximately nine miles southeast of Lockhart. Regionally, thetopographic elevations increase from southeast to northwest.
The portion of District located in Hays County generally exhibits the same type of terrain, although the elevationdifferences are more pronounced. Some of the surface of the District’s area extends into Hays County, which overlies the
Balcones Escarpment, and provides drainage to a portion of Plum Creek.
Plum Creek drains about 310 square miles, or about 60% of Caldwell County. In addition, a portion of Hays County thatis drained by Plum Creek is also in the boundaries of the District. There is a small area of Travis County that drains into
Plum Creek, but that area is not within the District’s boundaries.

3

6.

Location and Extent: The District is situated within parts of Caldwell and Hays Counties, but theDistrict’s boundaries are not conterminous with those of either Caldwell or Hays Counties. The original boundaries of theDistrict are described in Section 3 of the enabling statute that first created the District. In 2008 there were additional
properties located in the southeastern portion of Caldwell County annexed into PCCD at the request of the landowners of
the properties, however; the area where those properties were located was also annexed into the Gonzales County
Underground Water Conservation District. S.B 1225 of the 82nd legislature enacted in 2011 was passed to and allowed theproperty owners annexed by Plum Creek to choose which district they wanted to belong to with the result that the original
boundaries of the District were expanded by approximately 4,672 acres. The most downstream point of the boundaries of
the District is in the most southernly corner of Caldwell County near the confluence of Plum Creek and the San Marcos
River. The calls in the original description of the boundaries of Plum Creek Conservation District are, generally, alongtract or survey lines.
7.

Water Resources: The District does not hold, own or otherwise control any groundwater or surface waterrights. The District is located within the territory of the Guadalupe-Blanco River Authority (“GBRA”), which controls
substantial surface water rights associated with GBRA owned or operated facilities and reservoirs, including Canyon
Lake. Some water supply corporations providing retail water service within the District have access to surface watersupplies either through direct ownership, through lease, or through long term supply contracts. Most of the permitted
surface water rights in the vicinity of Plum Creek Conservation District are from the San Marcos River, which is not in
the Boundaries of the District. There are few surface water rights permits for diversions from Plum Creek and none
known for diversion from Plum Creek for any purpose other than agricultural use.
As a part of this Plan, each year the District will strive to confer at least once with GBRA on cooperative opportunities forconjunctive resource management between ground and surface water suppliers to retail providers and other users.
4. GROUNDWATER RESOURCES
The PCCD has within its surface area boundaries the following geological formations: Quaternary Alluvium, Leona
Gravel, Austin-Pecan Gap, Navarro, Midway, Wilcox Group, Queen City, Reklaw, Saline Edwards, Trinity Group and the
Carrizo Sands. A geologic map of the area of the District is appended as Appendix D. The Texas Water Development

4

Board recently ran a groundwater availability model for the Southern portions of the Carrizo-Wilcox, Queen City, andSparta, aquifers within the District.

No information on discharges from, exchanges among aquifers, or flow into or outof the Leona Gravel, or from recent alluvium deposits in the District is currently available from the Texas Water
Development Board. The full modeling report, GAM Run 12-001-Plum Creek Conservation District Management Plan, isappended to this Plan as Appendix C.
5. MANAGEMENT ZONES
1. Alluvium – occurs along present-day streams and rivers. Consists of sand, silt and clay. Serves as alimited household and livestock aquifer within the predominant sand facies.
2. Leona – occurs along scattered outcrops perpendicular to the Balcones Fault System and the IH-35
corridor. Serves as a shallow limited aquifer utilized manly as a small lot irrigation aquifer. Much of theaquifer has varying levels of nitrates, which are not recommended for human or livestock consumption.
3. Weches – is primarily a glauconitic marine clay and is seldom utilized as stray sand or silt aquifer.
4. Queen City – occurs as a shallow limited sand and silt aquifer with lesser amounts of clay. The
completed wells are generally utilized for household and livestock.
5. Reklaw – primarily consists of clay with broken silt and sand intervals that can serve as shallow
household and livestock aquifers in limited areas.
6. Carrizo – occurs as a major irrigation and municipal aquifer. Consists of ancient barrier island loose finecoarse sand bodies separated by thin estuary silty clays. It is the major aquifer along the Upper Gulf
Coastal Plain across southern Texas capable of high production rates of fresh water.
7. Wilcox – often studied and associated with the overlying Carrizo aquifer. It is separated from the Carrizo
by a regional disconformity and exhibits some very different deltaic facies as compared to the Carrizo. It
is utilized as a household, livestock, irrigation, and municipal source of fresh water over a wide area.
8. Midway – occurs primarily as a thick clay with minor amounts of silt near the top of the unit. It does not
generally serve as a reliable aquifer, even in limited silty zones.
9. Navarro – consists mainly as a thick sequence of expansive clay. It does not serve as an aquifer within
the boundaries of the Plum Creek Conservation District.
10. Pecan Gap – this limestone and chalk unit does serve as a very limited household and livestock fractured
low yield aquifer along and parallel to the southeast side of the IH-35 corridor. Many of the wells
eventually go dry.
11. Austin Chalk – this very limited limestone and chalk aquifer immediately underlies the Pecan Gap andexhibits similar characteristics.

512. Eagle Ford – this unit is a petroliferous thin clay and does not serve as an aquifer.
13. Buda – occurs as a dense limestone unit in the PCCD area and does not serve as any known aquifer. It
does serve as an aquifer in the Uvalde County area.
14. Del Rio – does not serve as an aquifer in Texas. It occurs as a weathered volcanic ash expansive clay.
15. Georgetown – occurs as a dense limestone and is not expected to serve as a brackish or saline aquifer in
the PCCD area.
16. Edwards – this limestone and dolomite karst aquifer is the major fresh water source for the cities, towns
and industries along the IH-35 corridor which partially fall within the PCCD area. The unit is also a verystrong future candidate of brackish and saline water southeast of the IH-35 corridor that may eventually
rival the Carrizo aquifer.
17. Glen Rose – certain areas within the Glen Rose along the axis of the San Marcos Arch do harbor large
carbonate patch reefs that do contain substantial amounts of brackish and saline water. These Glen Rosepatch reefs will undoubtedly be utilized as desalination targets.
18. Bexar – occurs as a thin clay and does not serve as an aquifer.
19. James (Cow Creek) – does serve as a highly-used household and livestock aquifer along the northwestside of the IH-35 corridor in the Hill Country Balcones Fault System. Recently discovered higher yield
Cow Creek wells have been tested in a limited area of the Balcones Fault System.
20. Pine Island – occurs as natural gas charged expansive clay that does not serve as an aquifer.
21. Sligo – occurs as sandy glauconitic limestone that may serve as a future limited brackish and saline
aquifer.
22. Hosston – occurs as a sand and basal gravel aquifer, it serves most of the small-town fresh watermunicipal needs across the Texas Hill Country. The future desalination era will undoubtedly target thebrackish and saline portions of the Hosston clastics with the PCCD boundaries.
Management Zone Descriptive Table:

PeriodQuaternary

Epoch
Holocene
Pleistocene

Tertiary

Eocene/Paleocene

Group/Formation/Member
Alluvium
Leona
WechesQueen City
Reklaw

6

Description
Sand, silt, clay
Gravel, sand, silt, clay
Clay, silt, sandSand, clay
Clay, sand, silt

UpperCretaceous
Lower

Carrizo
Wilcox
MidwayNavarroPecan Gap
Austin Chalk
Eagle Ford
Buda
Del RioGeorgetown
Edwards
Glen Rose
Bexar
James (Cow Creek)
Pine Island (Hammett)
Sligo
Hosston

Sand, clay
Sand, clay. silt
Clay, silt, sandClay, silt, sand
Limestone, clay
Limestone, clay
Clay
Limestone
Clay
Limestone
Limestone, dolomite
Limestone, dolomite, clay
Clay
Limestone
Clay
Limestone, silt
Sand, clay

6. PRODUCTION AND SPACING OF WELLS
Production and spacing of all wells within the District is regulated by the District according to the Rules of the District.
As noted, the Rules may be changed from time to time. The District has recently revised its Rules, with the latest revision
becoming effective as of December 16, 2018, to take into account knowledge gained through its geologic studies that havebeen ongoing and to address anticipated increases in demands on the aquifers in and regulated by the District.
7.

MANAGEMENT OF GROUNDWATER SUPPLIESThe District evaluates and monitors groundwater availability, and regulates production consistent with the District Rules,
the GMAs (10 & 13) adopted Desired Future Conditions, (“DFC”) and the Modeled Available Groundwater determinationof the Texas Water Development Board. In consideration of the importance of groundwater availability to the economy
and welfare of those in the District, the District anticipates that in the future, groundwater production will be regulated asneeded to conserve groundwater, preserve groundwater availability, and protect permitted and exempt groundwater users,
in a manner not to unnecessarily and adversely limit production or impact the economic viability of public and private
groundwater users. The District will identify and engage in such activities and practices that will permit groundwaterproduction and, as appropriate, will protect the aquifer and groundwater availability by restricting future requested
pumping quantities, if necessary, according to the best information then available to the District.
Currently there are a number of monitoring wells that are in PCCD’s Aquifer Water Level Observation Program that are
being used in order to monitor aquifer conditions within the district and to track compliance with the DFCs. On an annual
7
basis, in accord with advice from its technical consultant, PCCD
will, if necessary, modify the program. The District will

make a regular assessment of water supply and groundwater storage conditions as observed in data from its network andwill report those conditions to the Board and to the public. The District will undertake investigations, and co-operate withthird-party investigations including neighboring districts, of the groundwater resources within the District, and the resultsof the investigations will be made available to the public upon being presented at a meeting of the Board. The District
will manage the available groundwater based on the “Desired Future Conditions” and Modeled Available Groundwater
determination of the aquifers.
The District has adopted Rules to regulate groundwater withdrawals by means of well spacing and production limits or,alternatively, in accord with a study of the effects of the proposed well on the targeted aquifer. The District may deny awater well production permit or limit groundwater withdrawals in accordance with the Rules of the District. In making adetermination to deny a permit or limit groundwater withdrawals, the District will consider the available data andevidence and then weigh the public benefit against the individual needs and hardship in accord with State law.
The relevant factors to be considered in a determination to grant or deny a well or a production permit or limit
groundwater withdrawals are stated in the District's Rules and information furnished can include:(a) Whether the application contains all the information required to be submitted to the District pursuant to theseRules;(b) Whether the application is in conformance with any applicable requirements under Rule 19 – Classification,
Spacing and Production Provisions established by the District;(c) Whether the proposed use of groundwater unreasonably affects existing groundwater or surface water resources;(d) Whether the proposed use of groundwater is a beneficial use consistent with District’s Certified Groundwater
Management Plan;(e) Whether the applicant has agreed to avoid waste and achieve water conservation;(f) Whether the proposed use of the groundwater will result in subsidence;(g) Whether the applicant has agreed that reasonable diligence will be used to protect groundwater quality, and that theapplicant will follow well plugging guidelines at the time of well closure;8

(h) The equitable distribution of the resource; and(i) The potential effect the permit may have on the aquifer, sustainability of the recharge on the aquifer as a whole, andpotential impacts to prior existing permitted groundwater users and exempt groundwater users;(j) The modeled available groundwater determined by the executive administrator;(k) The executive administrator's estimate of the current and projected amount of groundwater produced under
exemptions granted by district rules and Section 36.117;(l) The amount of groundwater authorized under permits previously issued by the district;(m) A reasonable estimate of the amount of groundwater that is actually produced under permits issued by the district;(n) Yearly precipitation and production patterns;(o) Estimated Average Annual Recharge.
The transport of groundwater out of the District is regulated by the District according to the Rules of the District.
In pursuit of the District's mission of protecting the resource to facilitate its maximum beneficial use, the District may
require reduction of permitted groundwater withdrawals to amounts that, based on then available current information, will
not knowingly cause permanent harm to an aquifer. To achieve this purpose, the District may, at the Board's discretion
and after notice and hearing, amend or revoke any permit for non-compliance, or reduce the production authorized bypermit based upon reliable scientific data for the purpose of protecting the aquifer and groundwater availability. The
determination to seek the amendment of a permit will be based on aquifer conditions observed by the District confirmedby reliable scientific analysis. The determination to seek revocation of a permit will be based on compliance and noncompliance with the District's Rules and regulations, and reliable scientific evidence. The District will enforce the terms
and conditions of permits and the Rules of the District, as necessary, by fine and/or enjoining the permit holder, or nonpermit holder, in a court of competent jurisdiction as provided for in Chapter 36, Texas Water Code.
A drought management plan has been adopted by the Board to cope with the effects of water supply deficits due toclimatic or other conditions. In its annual review of the drought management plan, the District, in establishing drought
triggers and stages, anticipates consideration of the economic effect of conservation measures upon all water resource
user groups, the local implications of the degree and effect of changes in water storage conditions, the unique9hydrogeological conditions of the aquifers within the District and the appropriate conditions under which to implement
the drought management plan.
The District will employ reasonable and necessary technical resources at its disposal to evaluate the groundwater
resources available within the District and to determine the effectiveness of regulatory or conservation measures. The
District anticipates that its drought management plan will provide that a public or private user may appeal to the Board
for discretion in enforcement of the provisions of the water supply deficit drought management plan on grounds ofadverse economic hardship or unique local conditions. The exercise of discretion by the Board, shall not be construed aslimiting the power of the Board.
8. ACTIONS, PROCEDURES, PERFORMANCE AND PLAN IMPLEMENTATIONThe District will implement the provisions of this Plan and will utilize the provisions of this Plan as a guidepost for ongoing evaluation determining the direction or priority for all District activities. All operations of the District, allagreements entered into by the District and any additional planning efforts in which the District may participate will beconsistent with the provisions of this Plan.
The District has adopted Rules relating to the permitting of wells, production and transport of groundwater. The Rules
adopted by the District will be modified to take into account this Plan once it has been approved and shall be amended asnecessary, pursuant to Chapter 36 of the TEXAS WATER CODE consistent with the provisions of this Plan based uponreliable scientific evidence. All Rules will be enforced. The promulgation and enforcement of the Rules will be based on
the best technical data reasonably available. A link to the District rules is provides as follows:

http://www.pccd.org/PCCD%20GW%20Management%20&%20Protection%20Rules.pdf
The District shall treat all citizens equally. Citizens may apply to the District for a variance in enforcement of the Rules ongrounds of adverse economic effect or unique local conditions. In granting a variance to any rule, the Board shall consider
the potential for adverse effect on adjacent landowners and the rights of other groundwater owners and users within theDistrict. The exercise of said discretion by the Board shall not be construed as limiting the power of the Board.
The District will seek cooperation with other agencies in the implementation of this Plan and the management ofgroundwater supplies within the District.

10

The District believes that there is a significant issue that affects groundwater within its boundaries and affects theDistrict’s ability to effectively manage the groundwater resources within the District and that issue is that there are very
productive regions of aquifers that are near but not within Plum Creek Conservation District’s regulatory authority.
Should there be large volume water production from aquifers in these areas, there is significant potential that suchproduction will impact water quantity and/or water quality of users in the District.
The fact that Plum Creek Conservation District's surface boundaries also includes areas that are within the Barton Springs
Edwards Aquifer Conservation District and the Edwards Aquifer Authority [the District does have authority over any
aquifers in Hays and Caldwell County within its boundary that are not regulated by either the Edwards Aquifer Authority
or the Barton Springs-Edwards Aquifer Conservation District -] indicates that Plum Creek should cooperate with [andprovide some assistance to] the EAA and the Barton Springs-Edwards District while developing plans for understanding
and use of water resources to the fast growing area along Interstate 35 between San Antonio and Austin. PCCD's territory
extends from Northwest of IH-35 to IH-10 and encompasses much of an area that is projected to have continued rapid
growth. The completion of SH-130, along with other regional projects is considered by many to be a necessary
infrastructure component to allow for population and economic growth. Developers and retail water suppliers are alreadysearching for additional water supplies to meet growing demand.
Finally, there are significant long-existing oil and gas operations in the southern part of the District along with thepossible future exploration and development of gas-liquids shale plays. Should those activities continue to increase as theprice for oil and gas resources stays high, there may be significant consumption of water, or other groundwater impacts
such as the potential for pollution, related to such activities that is outside the scope of regulatory power of any
groundwater district.
For these reasons, all activities of the District will be undertaken in co-operation and coordinated with the appropriate
state, regional or local water management entities where they are present. However, simply stated, in Hays County there
are many such agencies looking at management of groundwater; in Caldwell County the absence of a groundwater agency
in the eastern and western part of the county makes management of the groundwater resources in the District morechallenging.

119. METHODOLOGY FOR TRACKING DISTRICT PROGRESS IN ACHIEVING MANAGEMENT GOALSThe Groundwater Manager of the District will prepare and present an annual report to the Board of Directors on theperformance of the District with respect to achieving its management goals and objectives. The presentation of the reportwill occur during the last monthly Board meeting each fiscal year, beginning after the adoption and approval of this Plan.
The report will include an enumeration and listing of activities furthering the District’s management objectives during the
fiscal year. Each activity will be referenced to the estimated expenditure of staff time and District resources used inaccomplishment of the activity. The notations of activity frequency, staff time and resources used will be referenced to theappropriate performance standard for each management objective describing the activity, so that the effectiveness andefficiency of the District’s operations may be evaluated. The Board will maintain the adopted report on file for public
inspection at the District's office. This methodology will apply to all management goals contained within this plan.
10.

MANAGEMENT GOALS, OBJECTIVES, & PERFORMANCE STANDARDS

10.1 Providing the Most Efficient Use of Groundwater
Management Objectives:
1. The PCCD Aquifer Water Level Observation Well Program will have at least 6 observation wells locatedaccording to management zones within the District and measure those wells at least one time a year.
2. As part of the Aquifer Water Level Observation Program, the District will geographically divide the surface area
overlying the aquifers of Plum Creek Conservation District into a grid-type network of units and will have a goal ofestablishing at least one monitoring water well in each of these units.
3. The District will provide educational leadership to citizens within the District concerning this subject. The activity
will be accomplished annually through at least one printed publication, such as a brochure, and public speaking at service
organizations and/or public schools as provided for in the District's Public Education Program.
4. The District will use its best efforts to obtain information on water being produced from areas in Caldwell County
that are outside the boundaries of the District.

12

5. The District will use its best efforts to obtain information on groundwater being produced from groundwateraquifers in counties surrounding the District as well as in areas close to the District that are not in a groundwater
conservation district in order to develop information about impacts of such production on groundwater in the District.
Performance Standards:
1. The PCCD Aquifer Water Level Observation Well Program will have at least 6 observation wells located according
to management zones within the District.
2. Water levels at these observation wells will be measured a minimum of one time during the year.
3. As part of the Aquifer Water Level Observation Program the District will geographically divide the surface area
overlying the aquifers of Plum Creek Conservation District into a grid type network of units within one year of the adoption ofthis plan and on an annual basis, the district will assess the District’s progress of establishing at least one monitoring well ineach of these units.
4. PCCD representatives will circulate at least one publication and participate in one speaking engagement each year.
5. PCCD representatives will attend and participate in GMA meetings appropriate to the District’s regulatory authority.
6. PCCD will periodically gather information from nearby groundwater districts not in the same GMA but drawing
from the same aquifers regulated by the District.
10.2 Controlling and Preventing Waste of Groundwater
Management Objective:
The District will provide educational leadership to citizens within the District concerning this subject. The activity
will be accomplished annually through at least one printed publication, such as a brochure.
Performance Standards:
1. Each calendar year Representatives of Plum Creek will prepare at least one informational article listing current
data related to groundwater production and well levels. The goal of the article is to make those who use and depend on
the groundwater aware of their use, aware of the impacts of their use, and the need to be responsible in that use.
2. At its offices, Plum Creek will maintain an inventory of publications of others, such as those prepared by the
Guadalupe Blanco River Authority about the necessity for conservation and serve as a local source for distribution of
those publications.

13

10.3 Controlling and Preventing SubsidenceManagement Objectives:
1. PCCD has reviewed the Texas Water Development Board’s (TWDB) Subsidence Report (Final Report:
Identification of the Vulnerability of the Major and Minor Aquifers of Texas to Subsidence with Regard to Groundwater
Pumping TWDB Contract Number 1648302062 by LRE). This report can be found at this link below.
http://www.twdb.texas.gov/groundwater/models/research/subsidence/subsidence.asp. The report indicated that thesubsidence risk vulnerability levels in Plum Creek Conservation District range from medium to high for the CarrizoWilcox Aquifer( figure 4.7 on page 4-13) The District will monitor those areas that have been categorized as a highsubsidence risk for signs of subsidence.
Performance Standard:
1. Once every 3 years the District will monitor those areas that have been categorized as a high subsidence risk forsigns of subsidence.
10.4 Addressing Conjunctive Surface Water Management Issues
Management Objective:
1. Each year, the District will send invitations to meet with the Guadalupe-Blanco River Authority (GBRA) and/or
other local political subdivisions and water and wastewater utilities on cooperative opportunities for conjunctive resource
management.
2. Each year, the District will participate in the regional planning process by attending the Region L Water PlanningGroup meetings to encourage the development of surface water supplies to meet the needs of water user groups in theDistrict. A representative of the District will attend a minimum of 25 percent of the Region L Water Planning Group
meetings.
Performance Standard:
1. Each year the District will send invitations to meet with the GBRA, other political subdivisions or water andwastewater utilities providing retail water service within Plum Creek’s boundaries, to gain information about conjunctive
resource management.
2. The District will continue to participate in the quarterly meetings of the Plum Creek Watershed Project through thetime of completion of the water quality management plan being developed in that effort. The Plum Creek Watershed Project
was initiated to address water quality issues in Plum Creek. As part of the project a watershed protection plan was implemented
14

with the goal of identifying strategies, management measures, outreach and education within the watershed to reduce pollutants
and improve water quality in the Plum Creek Watershed. More information can be found here: https://plumcreekwatershed.org
3. The District will, in each annual report, document the participation of District representatives in Region L meetings
and the number of meetings attended in the preceding calendar year. Documentation will consist of a table listing all Region L
meetings scheduled during the preceding 12 months, and the name(s) of District staff attending.
10.5 Addressing Drought Conditions
Management Objective:
1. Review the Drought Management Strategy Plan annually and revise if necessary, based upon the availability ofadditional scientific data collected by or presented to the Board. The Drought Management Strategy Plan will be implemented
when specified conditions require. Please see the drought management plan here : https://pccd.org/wpcontent/uploads/2014/11/Drought-Management-Plan-FINAL-2012.pdf
Performance Standards:
1. Review on an annual basis all the conditions and requirements specified in the Drought Management Strategy
Plan that would trigger its implementation.
2. Use data that are available from District monitoring wells and local weather stations monitoring rainfall, looking at
rainfall, water levels, and availability.
3. Within one year after the management plan has been approved a link will be provided on the District’s website for
TWDB’s drought web page. https://waterdatafortexas.org/drought
10.6. Addressing Natural Resource Issues That Impact the Use and Availability of Groundwater and Which are
Impacted By the Use of Groundwater
Management Objectives:
1. Each year the District will send invitations to meet with a representative of the Texas Railroad Commission (RRC)
on the impact of oil and gas production or waste and disposal operations associated with oil and gas production on groundwater
availability and quality, as well as the impact of groundwater production on the production of oil and gas in the District.
2. During each year the District will evaluate all permit applications for new production injection or disposal wells
permitted by the Railroad Commission, if any are filed, and the information submitted by the applicants on those wells prior to
drilling to assess the impact of these wells on the groundwater resources in the District.
15

The PCCD may inspect abandoned wells to ensure proper closing of wells in accordance to rules set forth by PCCD. Notices
will be sent to well owners whose wells do not adhere to District Rules.
Performance Standards:
1. Will send invitations to meet annually with a representative of the Texas RRC;
2. The addition of available RRC well data to the District’s database;
3. Report to the PCCD Board of Directors when new groundwater well permit applications are filed, and the possible
impacts of those new wells on the groundwater resources in the District; and4. Annual reports to the Board about consumption and use of groundwater for commercial purposes, including
irrigation uses and enhanced oil and gas production when information is available.
5. The following will be the expected key metrics used to measure progress of Management Objectives 3:
the number of notices sent out and possible fines assessed to well owners or operators concerning violations of District rules;
the number of wells plugged each year.
10.7. Addressing Conservation, Recharge Enhancement, Rainwater Harvesting, Precipitation Enhancement,
and/or Brush Control
Management Objectives:
1. The District will provide educational leadership and encouragement to citizens within the District on the need forwater conservation and publicize the benefits of rainwater harvesting and brush control. The educational efforts and publicity
will be through distribution of brochures produced either by the District or by others and made available by the District andthrough the presentation annually of informational articles that tabulate data developed by the District on the groundwater
resources being monitored. Each of the following topics will be addressed in the publications:(a) Conservation(b) Rainwater Harvesting(C) Brush Control
2. With respect to recharge enhancement, the District will continue to develop geologic data to map and gain
understanding of the relationship between recharge to and discharge from various formations to each other and to Plum Creek
as it flows through the District. At this time, the relationships among the aquifers and the Creek are not well documented orunderstood. It is known that recharge of much of the groundwater that can be found in the District and in areas next to the16District that are not in any groundwater district, originate outside the boundaries of the District. There is some natural recharge
to aquifers in the District from both streams and from areas where those aquifers are at the surface. However, the formations
found in the District are not readily susceptible to recharge enhancement.
3. The District has an active brush control program for the flood water retention structures that it maintains. The
District also cooperates with the US Department of Agriculture in agricultural conservation efforts and actively supports the
local Soil and Water Conservation District.
4. The District has participated in the funding of a rainwater harvesting demonstration project at the Luling Foundation
and will continue to monitor the results of that project and report those results in its articles.
5. The District does not believe that precipitation enhancement is appropriate and cost effective in its area. At the sametime, PCCD is aware of efforts being implemented by other districts and will continue to monitor the information gathered fromthose and determine whether such efforts might be attempted by the District. The District will continue to assess the need andopportunity for precipitation enhancement in the District at least once every five years.
Performance Standards
1. Preparation and distribution of at least one publication each year containing information about conservation,
rainwater harvesting and brush control efforts.
2. The District staff will continue to cooperate with the Natural Resource Conservation Service to control brush on the
28 flood water retention structures maintained by the District. In addition, the District will participate in at least one meeting
each year with the local soil and water conservation district to discuss brush control efforts and will continue to support the
local soil and water conservation districts efforts through an annual financial contribution.
3. The District will obtain, if available, at least one report each year about the relationship between recharge ofaquifers in the District and rainfall on the surface to determine whether it would be appropriate and cost effective to develop atrial plan for recharge enhancement.
4. At least once every 5 years the staff will report to the Board on the results of nearby precipitation enhancement
activities so the Board can consider the feasibility of participating in any efforts in the area of lands that are serving as sourcesof recharge for groundwater found in the District. If the Board determines that precipitation enhancement might be appropriate
and cost effective, within two years the Board will develop and adopt a program allowing participation in precipitation efforts
ongoing in the region.
1710.8. Mitigation & Desired Future Conditions of Groundwater Resources
1. The mitigation plan will be reviewed on an annual basis and revised, if necessary, in order to be compliant with the
adopted DFCs and any current or new state law in effect. Further, any projects that have been mitigated will also be reviewed
on an annual basis.
2. Review of groundwater resources in the District in comparison with the Desired Future Conditions of thoseresources and preparation of a recommendation for any mitigation actions within six months or later if warranted.
10.9 Addressing Desired Future Conditions
Management Objective:
1. At least once every three years, the District will monitor water levels and evaluate whether the change in water levels
is in conformance with the DFCs adopted by the District.
2. The District will estimate total annual groundwater production for each aquifer based on the water use reports,
estimated exempted use, and other relevant information, and compare these production estimates to the MAGs.
Performance Standards:
1. At least once every three years, the executive manager will report to the Board the measured water levels obtained
from the monitoring wells within each Management Zone, the average measured drawdown for each Management Zone
calculated from the measured water levels of the monitoring wells within the Management Zone, a comparison of the averagemeasured drawdowns for each Management Zone with the DFCs for each Management Zone, and the District’s progress inconforming with the DFCs.
2. At least once every three years, the executive manager will report to the Board the total permitted production and theestimated total annual production for each aquifer and compare these amounts to the MAGs for each aquifer.
3. In conjunction with information from PCCD’s drought management plan, Aquifer Water Level Observation Well
Program, water use production patterns, analysis from PCCD’s geological consultant and other pertinent technical data, theboard, at least once every three years will determine if conditions are present that would jeopardize DFC compliance and if so,schedule a hearing to address limiting water use for water well production permit holders.
10.10

Alternative Supply

Management Objective:
The District will assess the need and feasibility, including funding options, of developing a program to research,
participate in regional studies with other groundwater conservation districts and regional agencies in order to look at the18

potential benefits of alternative water supply sources such as underdeveloped aquifers, one being the Trinity Aquifer,desalinization, rainwater harvesting, and aquifer recovery and storage in and around our district.
Performance Standards:
1. Assess the groundwater resources of the Trinity Group and saline Edwards. The district will assess the need todevelop one or more monitoring wells to determine the aquifer characteristics and potential for public supply and to cooperatewith GCDs that have similar goals.
2. The district will evaluate and support studies on ASR and on desalination projects through cooperative
collaboration or financial assistance.
11.

PROJECTED TOTAL DEMAND FOR WATER WITHIN THE DISTRICT
Please refer to Appendix A-Estimated Historical Groundwater Use and 2022 State Water Plan Datasets.

12.

PROJECTED SURFACE WATER SUPPLIES WITHIN THE DISTRICT
Please refer to Appendix A-Estimated Historical Groundwater Use and 2022 State Water Plan Datasets.

13.

PROJECTED WATER SUPPLY NEEDS
Please refer to Appendix A-Estimated Historical Groundwater Use and 2022 State Water Plan Datasets.
TWC § 36.1071(e)(4) The District has reviewed and considered the 2022 State Water Plan data on water supply
needs within the District. The Plum Creek Conservation District is situated within parts of Caldwell and Hays
Counties. According to the State Water Plan “When existing water supplies—water that is already anticipated tobe legally and physically available during a drought of record—are less than the projected water demands
required to support regular economic and domestic activities, potential water shortages exist. These potential
water shortages are referred to as “identified water supply needs.” The total water supply needs as projected forwater user groups in Hays and Caldwell County according to the 2022 State Water plan projects a total watersupply need of 766 acre-feet by 2020, rising to 51,409 acre-feet by 2070. Because some of these water supply
needs are not exclusively within the District boundaries the detailed data from the 2022 State Water Plan on
projected water supply needs as attached in Appendix A were evaluated geographically.

14.

PROJECTED WATER MANAGEMENT STRATEGIES
Please refer to Appendix A-Estimated Historical Groundwater Use and 2022 State Water Plan Datasets.
TWC § 36.1071(e)(4) The District has reviewed and considered projected water management strategies andparticipates in TWDB Regional Water Planning of the South Central Texas Regional Water Planning Area
(Region L) Planning Group. The District works with other Groundwater Conservation Districts in Region L to19

assess potential water management strategies and provide local insight regarding technical groundwater data andinsights to support the Modeled Available Groundwater (MAG) estimates by TWDB. In managing its
groundwater supplies, the District considers the water management strategies contained in the 2022 State Water
Plan. These strategies include development of groundwater and surface water supplies, Aquifer Storage andRecovery, reuse, and demand reduction through water conservation. There are ten strategies listed in the 2022
State Water Plan for Caldwell County in the amount of 7,055 acre-feet per year by 2070. There are 12 strategies
listed in the 2022 State Water Plan for Hays County in the amount of 90,058 acre-feet per year by 2070.
15.

AMOUNT OF GROUNDWATER BEING USED IN THE DISTRICT ON AN ANNUAL BASIS
Please refer to Appendix A-Estimated Historical Groundwater Use and 2022 State Water Plan Datasets.

16.

MODELED AVAILABLE GROUNDWATER REPORTS
Please refer to Appendix B-Modeled Available Groundwater Reports
GAM Run 16-033 MAG (Groundwater Management Area 10)
GAM Run 21-018 MAG (Groundwater Management Area 13)

17.

ANNUAL AMOUNT OF RECHARGE FROM PRECIPITATION TO THE GROUNDWATER RESOURCESWITHIN THE DISTRICT
Please refer to Appendix C-GAM Run 12-001: Plum Creek Conservation District Management Plan.

18.

ANNUAL VOLUME OF WATER T HAT DISCHARGES FROM THE AQUIFER TO SPRINGS AND
SURFACE WATER BODIES
Please refer to Appendix C-GAM Run 12-001: Plum Creek Conservation District Management Plan.

19.

ESTIMATE OF THE ANNUAL VOLUME OF FLOW INTO THE DISTRICT, OUT OF THE
DISTRICT, AND BETWEEN AQUIFERS IN THE DISTRICT
Please refer to Appendix C-GAM Run 12-001: Plum Creek Conservation District Management Plan.

20.

ESTIMATE OF MODELED AVAILABLE GROUNDWATER IN DISTRICT BASED ON DESIRED
FUTURE CONDITIONS
Texas Water Code § 36.001 defines modeled available groundwater as “the amount of water that the executive
administrator determines may be produced on an average annual basis to achieve a desired future condition
established under Section 36.108”. The joint planning process set forth in Texas Water Code § 36.108 must becollectively conducted by all groundwater conservation districts within the same GMA. The District is a memberof GMA 10 & 13. GMA 10 and GMA 13 adopted DFCs, as summarized below, and then forwarded them to the
TWDB for MAG development which are also shown below

21.

GEOLOGY MAP OF PCCD
Please refer to Appendix D.
20

We, the undersigned members of the Board of Directors, do hereby certify and confirm the adoption of this revised
and amended Groundwater Management Plan of the Plum Creek Conservation District on this the, 2022 as evidenced by our signatures below:

Board of Directors

James A. Holt, Jr., PresidentPeter Reinecke, Vice President

Lucy Knight, Director

Fred Rothert, Director

Tom Owen, Director

Attested by:

Daniel Meyer, Executive Manager

21

day of

APPENDIX A

Estimated Historical Groundwater Use
And 2022 State Water Plan Datasets:

Plum Creek Conservation District

Texas Water Development Board
Groundwater Division
Groundwater Technical Assistance Section
stephen.allen@twdb.texas.gov(512) 463-7317
June 27, 2022

GROUNDWATER MANAGEMENT PLAN DATA:This package of water data reports (part 1 of a 2-part package of information) is being provided to
groundwater conservation districts to help them meet the requirements for approval of their fiveyear groundwater management plan. Each report in the package addresses a specific numberedrequirement in the Texas Water Development Board's groundwater management plan checklist. The
checklist can be viewed and downloaded from this web address:
http://www.twdb.texas.gov/groundwater/docs/GCD/GMPChecklist0113.pdf
The five reports included in this part are:
1. Estimated Historical Groundwater Use (checklist item 2)

from the TWDB Historical Water Use Survey (WUS)
2. Projected Surface Water Supplies (checklist item 6)
3. Projected Water Demands (checklist item 7)
4. Projected Water Supply Needs (checklist item 8)
5. Projected Water Management Strategies (checklist item 9)from the 2022 Texas State Water Plan (SWP)
Part 2 of the 2-part package is the groundwater availability model (GAM) report for the District(checklist items 3 through 5). The District should have received, or will receive, this report from the
Groundwater Availability Modeling Section. Questions about the GAM can be directed to Dr. Shirley
Wade, shirley.wade@twdb.texas.gov, (512) 936-0883.

22

DI SCLAI MER:

The data presented in this report represents the most up-to-date WUS and 2022 SWP data available
as of 6/27/2022. Although it does not happen frequently, either of these datasets are subject tochange pending the availability of more accurate WUS data or an amendment to the 2022 SWP.
District personnel must review these datasets and correct any discrepancies in order to ensure
approval of their groundwater management plan.
The WUS dataset can be verified at this web address:

http://www.twdb.texas.gov/waterplanning/waterusesurvey/estimates/

The 2022 SWP dataset can be verified by contacting Sabrina Anderson(sabrina.anderson@twdb.texas.gov or 512-936-0886).
The values presented in the data tables of this report are county-based. In cases where
groundwater conservation districts cover only a portion of one or more counties the data values are
modified with an apportioning multiplier to create new values that more accurately represent
conditions within district boundaries. The multiplier used in the following formula is a land area
ratio: (data value * (land area of district in county / land area of county)). For two of the four SWP
tables (Projected Surface Water Supplies and Projected Water Demands) only the county-wide wateruser group (WUG) data values (county other, manufacturing, steam electric power, irrigation, mining
and livestock) are modified using the multiplier. WUG values for municipalities, water supply
corporations, and utility districts are not apportioned; instead, their full values are retained when
they are located within the district, and eliminated when they are located outside (we ask each
district to identify these entity locations).
The remaining SWP tables (Projected Water Supply Needs and Projected Water Management
Strategies) are not modified because district-specific values are not statutorily required. Each districtneeds only “consider” the county values in these tables.
In the WUS table every category of water use (including municipal) is apportioned. Staff determinedthat breaking down the annual municipal values into individual WUGs was too complex.
TWDB recognizes that the apportioning formula used is not perfect but it is the best available
process with respect to time and staffing constraints. If a district believes it has data that is moreaccurate it can add those data to the plan with an explanation of how the data were derived.
Apportioning percentages that the TWDB used are listed above each applicable table.
For additional questions regarding this data, please contact Stephen Allen(stephen.allen@twdb.texas.gov or 512-463-7317).

23

Estimated Historical Water Use
TWDB Historical Water Use Survey (WUS) Data
Groundwater and surface water historical use estimates are currently unavailable
for calendar year 2020. TWDB staff anticipates the calculation and posting ofthese estimates at a later date.

CALDWELL COUNTY

All values are in acre-feet

51.56% (multiplier)Year

Source

2019

GW

927

0

0

0

SW

1,588

7

0

0

GW

887

0

0

0

SW

1,663

7

0

2018
2017
2016
2015
2014
2013
2012
2011
2010
2009
2008
2007
2006
2005
2004

Municipal

Manufacturing

MiningSteam Electric

Irrigation

Livestock

Total

245

120

1,292

112

478

2,185

236

118

1,241

0

74

472

2,216

GW

999

0

0

0

199

111

1,309

SW

1,610

0

0

0

88

445

2,143

GW

944

0

0

0

203

74

1,221

SW

1,577

7

0

0

43

292

1,919

GW

934

0

0

0

207

72

1,213

SW

1,513

4

0

0

27

286

1,830

GW

1,053

0

1

0

335

81

1,470

SW

1,521

3

0

0

30

322

1,876

GW

1,046

0

1

0

297

77

1,421

SW

1,509

2

0

0

20

306

1,837

GW

1,207

0

0

0

390

77

1,674

SW

1,614

0

0

0

42

305

1,961

GW

1,546

0

0

0

527

86

2,159

SW

1,624

0

0

0

41

344

2,009

GW

1,357

1

2

0

368

87

1,815

SW

1,580

0

3

0

19

349

1,951

GW

1,400

1

0

0

76

85

1,562

SW

1,486

0

0

0

9

338

1,833

GW

1,278

1

0

0

134

91

1,504

SW

1,617

0

0

0

589

360

2,566

GW

914

1

0

0

32

107

1,054

SW

1,593

0

0

0

606

427

2,626

GW

1,582

1

0

0

179

99

1,861

SW

1,393

0

0

0

0

396

1,789

GW

1,131

1

0

0

155

140

1,427

SW

1,257

0

0

0

13

558

1,828

GW

1,922

1

0

0

82

39

2,044

SW

704

0

0

0

12

503

1,219

24

HAYS COUNTY

All values are in acre-feet

9.11% (multiplier)Year

SourceMunicipal

Manufacturing

MiningSteam Electric

Irrigation

Livestock

Total

2019

GW

1,023

15

27

0

44

8

1,117

SW

1,571

0

0

94

1

214

1,880

GW

907

14

28

0

38

8

995

SW

1,527

0

0

92

0

224

1,843

GW

934

14

31

0

34

7

1,020

SW

1,469

0

0

92

17

226

1,804

GW

951

13

24

0

39

9

1,036

SW

1,234

0

0

127

2

283

1,646

GW

821

16

27

0

23

9

896

SW

1,262

0

0

145

17

272

1,696

GW

842

17

34

69

57

7

1,026

SW

1,208

0

0

0

0

293

1,501

GW

1,092

16

34

91

42

7

1,282

SW

1,193

0

0

0

0

254

1,447

GW

1,204

18

45

0

60

6

1,333

SW

1,214

0

0

0

8

223

1,445

GW

1,285

16

31

0

80

9

1,421

SW

1,221

0

0

0

1

213

1,435

GW

1,201

14

61

0

60

9

1,345

SW

797

0

32

0

1

249

1,079

GW

1,096

14

60

0

67

28

1,265

SW

797

0

31

0

0

260

1,088

GW

1,103

16

59

0

65

28

1,271

SW

724

0

30

0

2

581

1,337

GW

941

13

31

0

112

29

1,126

SW

635

1

1

0

18

353

1,008

GW

1,120

17

32

0

22

28

1,219

SW

581

0

0

0

0

313

894

GW

965

16

32

0

13

26

1,052

SW

481

0

0

0

3

309

793

GW

938

14

32

0

11

18

1,013

SW

437

1

0

0

29

384

851

2018
2017
2016
2015
2014
2013
2012
2011
2010
2009
2008
2007
2006
2005
2004

25

Projected Surface Water Supplies
TWDB 2022 State Water Plan Data
CALDWELL COUNTY

51.56% (multiplier)

All values are in acre-feet

RWPG

WUG

WUG Basin

Source Name

2020

2030

2040

2050

2060

2070

L

County Line SUD

Guadalupe

CanyonLake/Reservoir

403

403

371

340

306

270

L

County-Other, Caldwell

Guadalupe

Guadalupe Run-ofRiver

0

0

0

0

0

0

L

Gonzales County WSC

Guadalupe

CanyonLake/Reservoir

9

10

11

12

12

13

L

Livestock, Caldwell

Colorado

Colorado Livestock
Local Supply

15

15

15

15

15

15

L

Livestock, Caldwell

Guadalupe

Guadalupe Livestock
Local Supply

243

243

243

243

243

243

L

Martindale WSC

Guadalupe

CanyonLake/Reservoir

226

224

222

220

218

218

L

Martindale WSC

Guadalupe

Guadalupe Run-ofRiver

11

11

11

11

11

11

L

Maxwell WSC

Guadalupe

CanyonLake/Reservoir

694

710

720

724

727

727

L

Maxwell WSC

Guadalupe

Guadalupe Run-ofRiver

9

10

10

10

10

10

L

San Marcos

Guadalupe

CanyonLake/Reservoir

2

2

2

3

3

3

L

Tri Community WSC

Guadalupe

Guadalupe Run-ofRiver

492

490

490

491

490

490

2,104

2,118

2,095

2,069

2,035

2,000

Sum of Projected Surface Water Supplies (acre-feet)

HAYS COUNTY

9.11% (multiplier)

All values are in acre-feet

RWPG

WUG

WUG Basin

Source Name

2020

2030

2040

2050

2060

2070

K

AustinColorado

Colorado Run-ofRiver

188

827

1,304

2,063

3,025

4,357

K

Buda

Colorado

CanyonLake/Reservoir

1,381

1,292

1,181

1,041

882

701

K

Deer Creek Ranch
Water

Colorado

Highland Lakes
Lake/Reservoir
System

125

125

125

125

125

125

K

Dripping Springs WSC

Colorado

Highland Lakes
Lake/Reservoir
System

1,632

1,632

1,632

1,632

1,632

1,632

K

Hays County WCID 1

Colorado

Highland Lakes
Lake/Reservoir
System

821

808

801

798

717

717

K

Hays County WCID 2

Colorado

Highland Lakes
Lake/Reservoir
System

580

593

600

603

684

684

K

Livestock, Hays

Colorado

Colorado Livestock
Local Supply

20

20

20

20

20

20

K

Steam-Electric Power,
Hays

Colorado

CanyonLake/Reservoir

127

127

127

127

127

127

26

K

West Travis County
Public Utility Agency

Colorado

Highland Lakes
Lake/Reservoir
System

4,349

4,349

4,349

4,349

4,349

4,349

L

Buda

Guadalupe

CanyonLake/Reservoir

299

388

499

639

798

979

L

County Line SUD

Guadalupe

CanyonLake/Reservoir

905

905

937

968

1,002

1,038

L

County-Other, Hays

Guadalupe

CanyonLake/Reservoir

64

0

84

140

364

365

L

Crystal Clear WSC

Guadalupe

CanyonLake/Reservoir

323

317

319

329

340

354

L

Goforth SUD

Guadalupe

CanyonLake/Reservoir

4,186

4,186

4,186

4,186

4,186

4,186

L

Irrigation, Hays

Guadalupe

Guadalupe Run-ofRiver

2

2

2

2

2

2

L

Kyle

Guadalupe

CanyonLake/Reservoir

5,443

5,443

5,443

5,443

5,443

5,443

L

Livestock, Hays

Guadalupe

Guadalupe Livestock
Local Supply

69

69

69

69

69

69

L

Maxwell WSC

Guadalupe

CanyonLake/Reservoir

194

178

168

164

161

161

L

Maxwell WSC

Guadalupe

Guadalupe Run-ofRiver

3

2

2

2

2

2

L

San Marcos

Guadalupe

CanyonLake/Reservoir

9,998

9,998

9,998

9,997

9,997

9,997

30,70931,261

31,84632,69733,92535,308Sum of Projected Surface Water Supplies (acre-feet)27

Projected Water Demands
TWDB 2022 State Water Plan Data
Please note that the demand numbers presented here include the plumbing codesavings found in the Regional and State Water Plans.

CALDWELL COUNTY

All values are in acre-feet

51.56% (multiplier)

RWPG

WUG

WUG Basin

2020

2030

2040

2050

2060

2070

L

Aqua WSC

Colorado

43

51

59

68

77

86

L

Aqua WSC

Guadalupe

241

288

336

L

County Line SUD

Guadalupe

226

318

384

384

434

483

436

468

480

L

County-Other, Caldwell

Colorado

13

7

7

8

9

11

L

County-Other, Caldwell

Guadalupe

60

30

32

34

43

50

L

Creedmoor-Maha WSC

Colorado

167

L

Creedmoor-Maha WSC

Guadalupe

15

186

207

231

257

283

17

18

21

23

25

L

Goforth SUD

Guadalupe

45

43

43

43

42

42

L

Gonzales County WSC

Guadalupe

54

65

76

87

98

110

L

Irrigation, Caldwell

Colorado

12

12

12

12

12

12

L

Irrigation, Caldwell

Guadalupe

401

401

401

401

401

401

L

Livestock, Caldwell

Colorado

29

29

29

29

29

29

L

Livestock, Caldwell

Guadalupe

377

377

377

377

377

377

L

Lockhart

Guadalupe

2,258

2,683

3,114

3,557

4,021

4,477

L

LulingGuadalupe

956

1,131

1,309

1,493

1,688

1,879

L

Manufacturing, Caldwell

Guadalupe

3

3

3

3

3

3

L

Martindale WSC

Guadalupe

361

453

529

626

747

894

L

Maxwell WSC

Guadalupe

428

503

579

659

745

829

L

Mining, Caldwell

Colorado

6

5

3

2

1

1

L

Mining, Caldwell

Guadalupe

58

46

34

22

9

4

L

Polonia WSC

Colorado

285

338

391

447

505

562

L

Polonia WSC

Guadalupe

605

717

831

948

1,071

1,193

L

San Marcos

Guadalupe

1

2

3

4

5

6

L

Tri Community WSC

Guadalupe

174

206

239

272

308

343

Sum of Projected Water Demands (acre-feet)

6,818

7,911

9,016

10,164

11,373

12,580

2020

2030

2040

2050

2060

2070

HAYS COUNTY

All values are in acre-feet

9.11% (multiplier)

RWPG

WUG

WUG Basin

K

AustinColorado

188

827

1,304

2,063

3,025

4,357

K

Buda

Colorado

1,768

2,508

3,419

4,563

5,860

7,338

K

Cimarron Park Water

Colorado

244

236

230

226

225

225

K

County-Other, Hays

Colorado

123

95

141

176

205

284

K

Deer Creek Ranch Water

Colorado

26

29

33

35

38

41

28

K

Dripping Springs WSC

Colorado

1,930

3,190

4,103

5,278

6,716

7,476

K

Goforth SUD

Colorado

153

196

249

317

395

484

K

Hays

Colorado

183

235

294

348

435

533

K

Hays County WCID 1

Colorado

821

808

801

798

797

797

K

Hays County WCID 2

Colorado

285

369

464

551

688

844

K

Irrigation, Hays

Colorado

48

48

48

48

48

48

K

Livestock, Hays

Colorado

2

2

2

2

2

2

K

Manufacturing, Hays

Colorado

25

30

30

30

30

30

K

Mining, Hays

Colorado

77

98

124

132

151

172

K

Steam-Electric Power, Hays

Colorado

108

108

108

108

108

108

K

West Travis County Public
Utility Agency

Colorado

4,499

5,590

6,273

7,711

9,151

10,593L

Buda

Guadalupe

298

388

499

639

797

978

L

County Line SUD

Guadalupe

508

714

971

1,241

1,532

1,842

L

County-Other, Hays

Guadalupe

119

45

138

194

604

1,077

L

Creedmoor-Maha WSC

Guadalupe

7

8

9

10

11

12

L

Crystal Clear WSC

Guadalupe

632

716

827

973

1,143

1,338

L

Goforth SUD

Guadalupe

2,605

3,871

5,136

6,415

7,712

9,015

L

Irrigation, Hays

Guadalupe

14

14

14

14

14

14

L

Kyle

Guadalupe

4,898

7,680

9,133

9,118

9,108

9,104

L

Livestock, Hays

Guadalupe

254

254

254

254

254

254

L

Manufacturing, Hays

Guadalupe

4

5

5

5

5

5

L

Maxwell WSC

Guadalupe

120

126

135

149

165

184

L

San Marcos

Guadalupe

10,901

12,713

14,96817,746

21,13625,193

L

South Buda WCID 1

Guadalupe

214

275

345

409

510

626

L

Texas State University

Guadalupe

928

911

902

898

897

896

L

Wimberley WSC

Guadalupe

1,015

1,399

1,889

2,503

3,197

3,988

Sum of Projected Water Demands (acre-feet)

32,99743,48852,84862,95474,95987,85829

Projected Water Supply Needs
TWDB 2022 State Water Plan Data
Negative values (in red) reflect a projected water supply need, positive values a surplus.

All values are in acre-feet

CALDWELL COUNTY
RWPG

WUG

WUG Basin

2020

2030

2040

2050

2060

2070

L

Aqua WSC

Colorado

51

43

35

26

17

8

L

Aqua WSC

Guadalupe

L

County Line SUD

Guadalupe

290

243

195

147

97

48

227

135

33

-54

-124

-177

L

County-Other, Caldwell

Colorado

203

216

215

214

211

207

L

County-Other, Caldwell

Guadalupe

1,112

1,170

1,165

1,162

1,145

1,131

L

Creedmoor-Maha WSC

L

Creedmoor-Maha WSC

Colorado

0

0

0

0

0

0

Guadalupe

0

0

0

0

0

0

L

Goforth SUD

Guadalupe

-16

-23

-27

-25

-20

-18

L

Gonzales County WSC

Guadalupe

32

31

28

24

16

9

L

Irrigation, Caldwell

Colorado

0

0

0

0

0

0

L

Irrigation, Caldwell

Guadalupe

0

0

0

0

0

0

L

Livestock, Caldwell

Colorado

0

0

0

0

0

0

L

Livestock, Caldwell

Guadalupe

0

0

0

0

0

0

L

Lockhart

Guadalupe

817

392

-39

-482

-946

-1,402

L

LulingGuadalupe

127

-49

-226

-411

-606

-796

L

Manufacturing, Caldwell

Guadalupe

0

0

0

0

0

0

L

Martindale WSC

Guadalupe

-124

-218

-296

-395

-518

-665

L

Maxwell WSC

Guadalupe

445

391

328

253

170

86

L

Mining, Caldwell

Colorado

3

2

2

1

1

0

L

Mining, Caldwell

Guadalupe

0

0

0

0

0

0

L

Polonia WSC

Colorado

508

455

398

340

276

213

L

Polonia WSC

Guadalupe

1,078

963

846

720

587

451

L

San Marcos

Guadalupe

1

0

0

0

-1

-2

L

Tri Community WSC

Guadalupe

318

284

251

219

182

147

-140

-290

-588

-1,367-2,215-3,060

2020

2030

2040

2050

2060

2070

Sum of Projected Water Supply Needs (acre-feet)

All values are in acre-feet

HAYS COUNTY
RWPG

WUG

WUG Basin

K

AustinColorado

0

0

0

0

0

0

K

Buda

Colorado

1,411

582

-440

-1,724-3,180-4,839K

Cimarron Park Water

Colorado

47

55

61

65

66

66

K

County-Other, Hays

Colorado

966

1,279

764

388

72

-801

K

Deer Creek Ranch Water

Colorado

99

96

92

90

87

84

K

Dripping Springs WSC

Colorado

727

-533

-1,446-2,621-4,059-4,81930

K

Goforth SUD

Colorado

-60

-113

-168

-232

-308

-393

K

Hays

Colorado

0

-55

-114

-168

-255

-353

K

Hays County WCID 1

Colorado

0

0

0

0

-80

-80

K

Hays County WCID 2

Colorado

295

224

136

52

-4

-160

K

Irrigation, Hays

Colorado

257

257

257

257

257

257

K

Livestock, Hays

Colorado

903

903

903

903

903

903

K

Manufacturing, Hays

Colorado

191

144

144

144

144

144

K

Mining, Hays

Colorado

-531

-761

-1,047-1,131-1,340-1,579K

Steam-Electric Power, Hays

Colorado

511

511

511

511

511

511

K

West Travis County Public
Utility Agency

Colorado

128

-963

-1,646-3,084-4,524-5,966

L

Buda

Guadalupe

1

0

0

0

1

1

L

County Line SUD

Guadalupe

509

303

82

-153

-406

-675

L

County-Other, Hays

Guadalupe

0

106

0

0

-2,029-7,220L

Creedmoor-Maha WSC

Guadalupe

0

0

0

0

0

0

L

Crystal Clear WSC

Guadalupe

-35

61

-45

-168

-310

-472

L

Goforth SUD

Guadalupe

3,175

1,928

669

-608

-1,906-3,212L

Irrigation, Hays

Guadalupe

349

349

349

349

349

349

L

Kyle

Guadalupe

1,375-1,407-2,860-2,845-2,835-2,831

L

Livestock, Hays

Guadalupe

0

0

0

0

0

0

L

Manufacturing, Hays

Guadalupe

502

494

494

494

494

494

L

Maxwell WSC

Guadalupe

125

98

76

57

38

19

L

San Marcos

Guadalupe

2,181

369

-1,887-4,666-8,056-12,113

LSouth Buda WCID 1

Guadalupe

436

375

305

241

140

24

L

Texas State University

Guadalupe

202

219

228

232

233

234

L

Wimberley WSC

Guadalupe

137

-247

-737

-1,351-2,045-2,836-626-4,079-10,390-18,751-31,337-48,349

Sum of Projected Water Supply Needs (acre-feet)31

Projected Water Management Strategies
TWDB 2022 State Water Plan Data
CALDWELL COUNTY
All values are in acre-feet

WUG, Basin (RWPG)
Water Management Strategy

Source Name [Origin]

2020

2030

2040

2050

2060

2070

0

0

0

1

1

1

0

0

0

1

1

1

Aqua WSC, Guadalupe (L)Municipal Water Conservation

DEMAND REDUCTION[Caldwell]County Line SUD, Guadalupe (L)ARWA - Phase 2

Carrizo-Wilcox Aquifer[Caldwell]

0

0

190

174

157

138

ARWA - Phase 3

Direct Reuse [Hays]

0

0

0

0

42

37

ARWA Shared Project (Phase 1)

Carrizo-Wilcox Aquifer[Caldwell]

148

148

135

124

112

99

County Line SUD - Brackish Edwards
Wellfield

Edwards-BFZ Aquifer[Hays]

0

0

0

130

234

310

County Line SUD - Trinity Wellfield

Trinity Aquifer [Hays]

0

0

0

130

173

153

Reuse - County Line SUD

Direct Reuse [Hays]

172

345

476

582

655

695

320

493

801

1,140

1,373

1,432

Goforth SUD, Guadalupe (L)Drought Management – Goforth SUD

DEMAND REDUCTION[Caldwell]

2

0

0

0

0

0

GBRA Shared Project (Phase 1)

Carrizo-Wilcox Aquifer[Caldwell]

32

20

15

12

10

9

GBRA Shared Project (Phase 1)

Carrizo-Wilcox Aquifer[Gonzales]

32

21

16

13

10

9

66

41

31

25

20

18

3

9

16

24

34

45

3

9

16

24

34

45

Gonzales County WSC, Guadalupe (L)Municipal Water Conservation

DEMAND REDUCTION[Caldwell]

Lockhart, Guadalupe (L)GBRA Shared Project (Phase 1)

Carrizo-Wilcox Aquifer[Caldwell]

1,489

1,489

1,489

1,489

1,489

1,489

GBRA Shared Project (Phase 1)

Carrizo-Wilcox Aquifer[Gonzales]

1,511

1,511

1,511

1,511

1,511

1,511

Municipal Water Conservation

DEMAND REDUCTION[Caldwell]

0

0

0

0

0

71

3,000

3,000

3,000

3,000

3,000

3,071

Luling, Guadalupe (L)Local Carrizo Aquifer Development

Carrizo-Wilcox Aquifer[Caldwell]

0

349

350

702

702

1,056

Municipal Water Conservation

DEMAND REDUCTION[Caldwell]

0

0

0

0

0

2

32

0

349

350

702

702

1,058

Martindale WSC, Guadalupe (L)CRWA - Wells Ranch (Phase 3)

Carrizo-Wilcox Aquifer[Guadalupe]

0

61

131

231

484

779

Drought Management - Martindale

DEMAND REDUCTION[Caldwell]

20

0

0

0

0

0

FE - CRWA Hays Caldwell WTP
Expansion

Guadalupe Run-of-River[Hays]

242

241

238

235

233

233

Martindale WSC - Alluvial Well

San Marcos River Alluvium
Aquifer [Caldwell]

0

226

224

222

219

219

262

528

593

688

936

1,231

0

0

187

188

188

188

0

0

187

188

188

188

0

0

0

0

0

1

0

0

0

0

0

1

0

0

0

0

0

3

0

0

0

0

0

3

Maxwell WSC, Guadalupe (L)Maxwell WSC - Trinity Well Field

Trinity Aquifer [Hays]

Polonia WSC, Colorado (L)Municipal Water Conservation

DEMAND REDUCTION[Caldwell]

Polonia WSC, Guadalupe (L)Municipal Water Conservation

DEMAND REDUCTION[Caldwell]

San Marcos, Guadalupe (L)ARWA - Phase 2

Carrizo-Wilcox Aquifer[Caldwell]

0

0

2

2

2

2

ARWA - Phase 3

Direct Reuse [Hays]

0

0

0

0

1

1

ARWA Shared Project (Phase 1)

Carrizo-Wilcox Aquifer[Caldwell]

0

1

1

1

1

1

FE - CRWA Hays Caldwell WTP
Expansion

Direct Reuse [Hays]

0

0

0

0

0

0

Reuse - San Marcos (Non-Potable)

Direct Reuse [Hays]

0

0

0

0

0

0

Reuse - San Marcos (Potable)

Direct Reuse [Hays]

0

0

0

1

1

1

0

1

3

4

5

5

0

0

0

0

0

2

0

0

0

0

0

2

3,651

4,421

4,981

5,772

6,259

7,055

2020

2030

2040

2050

2060

2070

9

38

59

94

137

198

9

38

59

94

137

198

Tri Community WSC, Guadalupe (L)Municipal Water Conservation

DEMAND REDUCTION[Caldwell]

Sum of Projected Water Management Strategies (acre-feet)

HAYS COUNTY
All values are in acre-feet

WUG, Basin (RWPG)
Water Management Strategy

Source Name [Origin]

Austin, Colorado (K)Drought Management

DEMAND REDUCTION[Hays]

Buda, Colorado (K)33

ARWA - Phase 2

Carrizo-Wilcox Aquifer[Caldwell]

0

0

1,067

1,067

1,067

1,067

ARWA - Phase 3

Direct Reuse [Hays]

0

0

0

0

157

157

ARWA Shared Project (Phase 1)

Carrizo-Wilcox Aquifer[Caldwell]

762

762

762

762

762

762

Direct Potable Reuse - Buda

Direct Reuse [Hays]

0

2,240

2,240

2,240

2,240

2,240

Direct Reuse - Buda

Direct Reuse [Hays]

0

920

520

520

880

680

Drought Management

DEMAND REDUCTION[Hays]

322

443

607

813

1,045

1,309

Edwards/Middle Trinity ASR

Trinity Aquifer ASR [Hays]

150

600

600

600

600

600

Municipal Conservation - Buda

DEMAND REDUCTION[Hays]

159

292

382

499

636

793

Municipal Water Conservation

DEMAND REDUCTION[Hays]

11

42

61

90

126

172

Saline Edwards Desalination and ASR(Storage)

Edwards-BFZ Aquifer(Saline Portion) ASR[Travis]

0

0

800

800

800

800

1,404

5,299

7,039

7,391

8,313

8,580

18

12

12

11

11

11

18

12

12

11

11

11

Cimarron Park Water, Colorado (K)Drought Management

DEMAND REDUCTION[Hays]County-Other, Hays, Colorado (K)Brush Management

Trinity Aquifer [Hays]

0

83

83

83

83

83

Drought Management

DEMAND REDUCTION[Hays]

158

103

132

155

176

243

Edwards/Middle Trinity ASR

Trinity Aquifer ASR [Hays]

0

289

289

289

289

289

Expansion of Current Groundwater
Supplies - Trinity Aquifer

Trinity Aquifer [Hays]

0

0

0

0

0

200

GBRA - MBWSP - Surface Water w/ASR Carrizo-Wilcox Aquifer ASR[Gonzales]

0

1,000

1,000

1,000

1,000

1,000

Rainwater Harvesting - Hays CountyOther

Rainwater Harvesting[Hays]

0

16

24

31

36

50

Saline Edwards Desalination and ASR(Storage)

Edwards-BFZ Aquifer(Saline Portion) ASR[Travis]

0

0

500

500

500

500

158

1,491

2,028

2,058

2,084

2,365

1

1

2

2

2

2

1

1

2

2

2

2

Direct Potable Reuse - Dripping Springs Direct Reuse [Hays]
WSC

0

560

560

560

560

560

Direct Reuse - Dripping Springs WSC

Direct Reuse [Hays]

0

390

460

531

601

672

Drought Management

DEMAND REDUCTION[Hays]

351

580

753

972

1,239

1,380

Expansion of Current Groundwater
Supplies - Trinity Aquifer

Trinity Aquifer [Hays]

0

0

300

300

300

300

LCRA - Mid Basin Reservoir

LCRA New Off-Channel
Reservoir (2030 Decade)[Reservoir]

0

0

0

1,000

2,000

2,000

Deer Creek Ranch Water, Colorado (K)Drought Management

DEMAND REDUCTION[Hays]Dripping Springs WSC, Colorado (K)34Municipal Conservation - Dripping
Springs WSC

DEMAND REDUCTION[Hays]

174

289

339

417

522

576

Rainwater Harvesting - Dripping
Springs WSC

Rainwater Harvesting[Hays]

0

34

44

57

73

81

525

1,853

2,456

3,837

5,295

5,569

Goforth SUD, Colorado (K)Drought Management

DEMAND REDUCTION[Hays]

8

10

12

16

20

24

Drought Management – Goforth SUD

DEMAND REDUCTION[Hays]

6

0

0

0

0

0

GBRA Shared Project (Phase 1)

Carrizo-Wilcox Aquifer[Caldwell]

108

95

91

122

191

264

GBRA Shared Project (Phase 1)

Carrizo-Wilcox Aquifer[Gonzales]

110

96

92

94

97

102

Municipal Water Conservation

DEMAND REDUCTION[Hays]

0

0

0

0

0

3

232

201

195

232

308

393

Hays, Colorado (K)Development of New Groundwater
Supplies - Trinity Aquifer

Trinity Aquifer [Hays]

0

100

100

100

100

100

Drought Management

DEMAND REDUCTION[Hays]

37

47

59

70

87

107

Edwards/Middle Trinity ASR

Trinity Aquifer ASR [Hays]

0

146

146

146

146

146

New Water Purchase - Hays

Edwards-BFZ Aquifer[Hays]

0

0

0

0

70

140

Rainwater Harvesting - Hays

Rainwater Harvesting[Hays]

0

3

4

4

6

7

37

296

309

320

409

500

Hays County WCID 1, Colorado (K)Drought Management

DEMAND REDUCTION[Hays]

149

134

121

114

114

114

Municipal Conservation - Hays County
WCID 1DEMAND REDUCTION[Hays]

74

136

196

226

225

225

223

270

317

340

339

339

Hays County WCID 2, Colorado (K)Drought Management

DEMAND REDUCTION[Hays]

52

61

70

76

95

117

Municipal Conservation - Hays County
WCID 2

DEMAND REDUCTION[Hays]

26

62

114

169

211

259

78

123

184

245

306

376

Mining, Hays, Colorado (K)Direct Reuse - Buda

Direct Reuse [Hays]

0

200

600

600

800

1,000

Expansion of Current Groundwater
Supplies - Trinity Aquifer

Trinity Aquifer [Hays]

600

600

600

600

600

600

600

800

1,200

1,200

1,400

1,600

0

97

99

104

111

116

819

921

933

1,033

1,104

1,151

GBRA - MBWSP - Surface Water w/ASR Carrizo-Wilcox Aquifer ASR[Gonzales]

0

3,000

3,000

3,000

3,000

3,000

LCRA - Excess Flows Reservoir

0

1,400

1,400

2,500

2,500

3,300

West Travis County Public Utility Agency, Colorado (K)Direct Reuse - West Travis County PUA Direct Reuse [Travis]
Drought Management

DEMAND REDUCTION[Hays]LCRA New Off-Channel
35Reservoir (2030 Decade)[Reservoir]
Municipal Conservation - West Travis
County PUA

DEMAND REDUCTION[Hays]

405

984

1,610

2,546

3,631

4,840

1,224

6,402

7,042

9,183

10,346

12,407

Buda, Guadalupe (L)ARWA - Phase 3

Direct Reuse [Hays]

0

0

0

0

21

21

Municipal Water Conservation

DEMAND REDUCTION[Hays]

2

6

9

13

17

23

2

6

9

13

38

44

County Line SUD, Guadalupe (L)ARWA - Phase 2

Carrizo-Wilcox Aquifer[Caldwell]

0

0

479

495

512

531

ARWA - Phase 3

Direct Reuse [Hays]

0

0

0

0

136

141

ARWA Shared Project (Phase 1)

Carrizo-Wilcox Aquifer[Caldwell]

330

330

343

354

366

379

County Line SUD - Brackish Edwards
Wellfield

Edwards-BFZ Aquifer[Hays]

0

0

0

370

766

1,190

County Line SUD - Trinity Wellfield

Trinity Aquifer [Hays]

0

0

0

370

567

587

Reuse - County Line SUD

Direct Reuse [Hays]

388

775

1,204

1,658

2,145

2,665

718

1,105

2,026

3,247

4,492

5,493

GBRA - MBWSP - Surface Water w/ASR Carrizo-Wilcox Aquifer ASR[Gonzales]

0

0

0

0

2,029

7,220

Municipal Water Conservation

0

0

0

0

0

232

0

0

0

0

2,029

7,452

County-Other, Hays, Guadalupe (L)DEMAND REDUCTION[Hays]

Crystal Clear WSC, Guadalupe (L)ARWA - Phase 2

Carrizo-Wilcox Aquifer[Caldwell]

0

0

929

957

989

1,029

ARWA - Phase 3

Direct Reuse [Hays]

0

0

0

0

263

274

ARWA Shared Project (Phase 1)

Carrizo-Wilcox Aquifer[Caldwell]

671

659

663

683

707

735

Drought Management - Crystal Clear
WSC

DEMAND REDUCTION[Hays]

24

0

0

0

0

0

Municipal Water Conservation

DEMAND REDUCTION[Hays]

0

0

0

0

0

22

695

659

1,592

1,640

1,959

2,060

Goforth SUD, Guadalupe (L)Drought Management – Goforth SUD

DEMAND REDUCTION[Hays]

101

0

0

0

0

0

GBRA Shared Project (Phase 1)

Carrizo-Wilcox Aquifer[Caldwell]

1,837

1,863

1,872

1,842

1,770

1,694

GBRA Shared Project (Phase 1)

Carrizo-Wilcox Aquifer[Gonzales]

1,866

1,892

1,901

1,902

1,902

1,897

Municipal Water Conservation

DEMAND REDUCTION[Hays]

0

0

0

0

0

50

3,804

3,755

3,773

3,744

3,672

3,641

0

0

5,916

5,916

5,916

5,916

Kyle, Guadalupe (L)ARWA - Phase 2

Carrizo-Wilcox Aquifer[Caldwell]
36

ARWA - Phase 3

Direct Reuse [Hays]

0

0

0

0

1,573

1,573

ARWA Shared Project (Phase 1)

Carrizo-Wilcox Aquifer[Caldwell]

4,225

4,225

4,225

4,225

4,225

4,225

Municipal Water Conservation

DEMAND REDUCTION[Hays]

0

0

0

52

266

480

4,225

4,225

10,141

10,193

11,98012,194

0

0

43

42

42

42

0

0

43

42

42

42

Maxwell WSC, Guadalupe (L)Maxwell WSC - Trinity Well Field

Trinity Aquifer [Hays]

San Marcos, Guadalupe (L)ARWA - Phase 2

Carrizo-Wilcox Aquifer[Caldwell]

0

0

7,528

7,528

7,528

7,528

ARWA - Phase 3

Direct Reuse [Hays]

0

0

0

0

2,001

2,001

ARWA Shared Project (Phase 1)

Carrizo-Wilcox Aquifer[Caldwell]

2,594

5,379

5,379

5,379

5,379

5,379

FE - CRWA Hays Caldwell WTP
Expansion

Direct Reuse [Hays]

1,288

1,288

1,288

1,288

1,288

1,288

Municipal Water Conservation

DEMAND REDUCTION[Hays]

0

0

54

395

949

1,706

Reuse - San Marcos (Non-Potable)

Direct Reuse [Hays]

1,826

1,971

1,971

1,971

1,971

1,971

Reuse - San Marcos (Potable)

Direct Reuse [Hays]

0

0

0

3,807

3,807

3,807

5,708

8,638

16,22020,36822,923

23,680

4

6

12

21

38

60

4

6

12

21

38

60

33

101

153

167

185

201

33

101

153

167

185

201

0

262

752

1,366

2,060

2,851

0

262

752

1,366

2,060

2,851

19,69835,54355,56465,71478,36890,058South Buda WCID 1, Guadalupe (L)Municipal Water Conservation

DEMAND REDUCTION[Hays]

Texas State University, Guadalupe (L)Municipal Water Conservation

DEMAND REDUCTION[Hays]

Wimberley WSC, Guadalupe (L)GBRA - MBWSP - Surface Water w/ASR Carrizo-Wilcox Aquifer ASR[Gonzales]
Sum of Projected Water Management Strategies (acre-feet)

37

APPENDIX A

GAM RUN 21-018 MAG:
MODELED AVAILABLE GROUNDWATER FOR THE
CARRIZO-WILCOX, QUEEN CITY, SPARTA, ANDYEGUA-JACKSON AQUIFERS INGROUNDWATER MANAGEMENT AREA 13
Shirley C. Wade, Ph.D., P.G.
Texas Water Development Board
Groundwater Division
Groundwater Availability Modeling Department(512) 936-0883
July 25, 2022

38

39

This page is intentionally left blank.

40

GAM RUN 21-018 MAG:
MODELED AVAILABLE GROUNDWATER FOR THE
CARRIZO-WILCOX, QUEEN CITY, SPARTA, ANDYEGUA-JACKSON AQUIFERS INGROUNDWATER MANAGEMENT AREA 13
Shirley C. Wade, Ph.D., P.G.
Texas Water Development Board
Groundwater Division
Groundwater Availability Modeling Department(512) 936-0883
July 25, 2022

EXECUTIVE SUMMARY:
The modeled available groundwater for Groundwater Management Area 13 for the CarrizoWilcox, Queen City, Sparta, and Yegua-Jackson aquifers is summarized by decade for the
groundwater conservation districts (Tables 1 through 4 respectively) and for use in theregional water planning process (Tables 5 through 8 respectively). The modeled available
groundwater estimates for the Carrizo-Wilcox Aquifer range from approximately 470,000
acre-feet per year in 2020 to approximately 575,000 acre-feet per year in 2080 (Table 1).
The modeled available groundwater estimates for the Queen City Aquifer range fromapproximately 23,000 acre-feet per year in 2020 to approximately 18,000 acre-feet per
year in 2080 (Table 2). The modeled available groundwater estimates for the Sparta
Aquifer range from approximately 6,000 acre-feet per year in 2020 to approximately 4,000
acre-feet per year in 2080 (Table 3). The estimates for the Carrizo-Wilcox, Queen City, andSparta Aquifers were extracted from the results of a model run using the groundwater
availability model for the southern part of the Carrizo-Wilcox, Queen City, and Sparta
aquifers (version 2.01). The modeled available groundwater estimates for the YeguaJackson Aquifer are approximately 6,700 acre-feet per year from 2020 to 2080 (Table 4).
The estimates for the Yegua-Jackson Aquifer were extracted from the results of a model run
using the groundwater availability model for the Yegua-Jackson Aquifer (version 1.01). The
explanatory report and other materials submitted to the TWDB were determined to beadministratively complete on April 15, 2022.

41

REQUESTOR:
Ms. Kelley Cochran, coordinator of Groundwater Management Area 13.

DESCRIPTION OF REQUEST:The desired future conditions for the Carrizo-Wilcox, Queen City, and Sparta aquifers
described in Resolution 21-02 from Groundwater Management Area 13, adopted
November 19, 2021, are:•

“The first desired future condition for the Carrizo-Wilcox, Queen City and Sparta
aquifers in Groundwater Management Area 13 is that 75 percent of the saturated
thickness in the outcrop at the end of 2012 remains in 2080. Due to the limitations of
the current Groundwater Availability Model, this desired future condition cannot be
simulated as documented during 2016 Joint Planning in GMA 13 Technical
Memorandum 16-08 (Hutchison, 2017a).”•“In addition, a secondary proposed desired future condition for the Carrizo-Wilcox,
Queen City, and Sparta aquifers in Groundwater Management Area 13 is an averagedrawdown of 49 feet (+/- 5 feet) for all of GMA 13. The drawdown is calculated fromthe end of 2012 conditions to the year 2080. This desired future condition is consistent
with simulation “GMA13_2019_001” summarized during a meeting of Groundwater
Management Area 13 members on March 19, 2021.”

The desired future conditions for the Yegua-Jackson Aquifer described in Resolution 21-03
from Groundwater Management Area 13, adopted November 19, 2021 are:•“For Gonzales County, the average drawdown from 2010 to 2080 is 3 feet (+/- 1 foot).”•“For Karnes County, the average drawdown from 2010 to 2080 is 1 foot (+/- 1 foot).”•“For all other counties in GMA 13, the Yegua-Jackson is classified as not relevant for
purposes of joint planning.”

The Edwards (Balcones Fault Zone), Gulf Coast, and Trinity aquifers were declared not
relevant for purposes of joint planning by Groundwater Management Area 13 in Resolution
21-01 (Groundwater Management Area 13 Joint Planning Committee and others, 2022;
Appendix B).

On January 14, 2022, Dr. Jordan Furnans, on behalf of Groundwater Management Area 13,
submitted the Desired Future Conditions Packet to the TWDB. TWDB staff reviewed themodel files associated with the desired future conditions and received clarifications on
procedures and assumptions from the Groundwater Management Area 13 Technical
Coordinator on March 3, 2022, and on March 7, 2022. Groundwater Management Area 13
adopted two desired future conditions for the Carrizo-Wilcox, Queen City, and Sparta
Aquifers and they were not mutually compatible in the groundwater availability model. The
42

technical coordinator for the groundwater management area confirmed that their intention
was for the modeled available groundwater values to be based on the secondary desired
future condition and MODFLOW pumping simulation GMA13_2019_001 (Groundwater
Management Area 13 Joint Planning Committee and others, 2022; Appendix 2). The first
proposed desired future condition was not intended for the calculation of modeled
available groundwater.
The model run pumping file, which meets the secondary desired future condition adopted
by district representatives of Groundwater Management Area 13 for the Carrizo-Wilcox,
Queen City, and Sparta Aquifers, was submitted to the TWDB as supplemental information
for the original submittal on February 9, 2022. The model run files, which meet the desired
future conditions adopted by district representatives of Groundwater Management Area 13
for the Yegua-Jackson Aquifer, were submitted to the TWDB on January 14, 2022, as part of
the Desired Future Conditions Explanatory Report for Groundwater Management Area 13.
In an email dated March 3, 2022, the Technical Coordinator and consultant for
Groundwater Management Area 13 confirmed that they intended to use the end of 2011 as
the reference year for the drawdown calculations for the Carrizo-Wilcox, Queen City, andSparta aquifers and they intended to use the end of 2009 as the reference year for the
Yegua-Jackson Aquifer. In an email dated March 7, 2022, they also confirmed that theconfining unit model layers representing the Reklaw and Weches formations should be
included in the desired future condition calculation of average drawdown for the combined
Carrizo-Wilcox, Queen City, and Sparta aquifers.
All clarifications are included in the Parameters and Assumptions Section of this report.

METHODS:

The groundwater availability model for the southern part of the Carrizo-Wilcox, Queen
City, and Sparta aquifers (Figures 1 through 3) was run using the model files submittedwith the explanatory reports (Groundwater Management Area 13 Joint Planning
Committee and others, 2022) on January 14 and February 9, 2022. Model-calculated waterlevels were extracted for the years 2011 (stress period 12) and 2080 (stress period 81). An
overall drawdown average was calculated for the entire Groundwater Management Area
13 using all model layers in the average. As described in the Technical Memorandum
submitted with the Explanatory Report on January 14, 2022 (Furnans, 2022) drawdowns
for cells that became dry during the simulation (water level dropped below the base of thecell) were calculated as the reference year water level elevation minus the elevation of themodel cell bottom. The calculated drawdown average was compared with the desired
future condition of 49 feet to verify that the pumping scenario achieved the desired future
conditions within the stated tolerance of five feet.
43

The groundwater availability model for the Yegua-Jackson Aquifer (Figure 4) was run using
the model files submitted on January 14, 2022. Model-calculated water levels wereextracted for the years 2009 (stress period 39) and 2080 (stress period 110). County-wide
average drawdowns were calculated for Gonzales and Karnes counties within Groundwater
Management Area 13 by averaging the drawdown values for all model layers. There were
no dry cells in Karnes County or Gonzales County, so no additional dry cell calculations
were needed. The calculated drawdown averages were compared with the desired future
conditions for Gonzales and Karnes counties to verify that the pumping scenario achieved
the desired future conditions within the stated tolerance of one foot.
The modeled available groundwater values were determined by extracting pumping rates
by decade from the model results using ZONEBUDGET Version 3.01 (Harbaugh, 2009).
Annual pumping rates by aquifer are presented by county and groundwater conservation
district, subtotaled by groundwater conservation district, and then summed for
Groundwater Management Area 13 (Tables 1 through 4). Annual pumping rates by aquifer
are also presented by county, river basin, and regional water planning area within
Groundwater Management Area 13 (Tables 5 through 8) in order to be consistent with theformat used in the regional water planning process.
Modeled Available Groundwater and Permitting

As defined in Chapter 36 of the Texas Water Code (2011), “modeled available
groundwater” is the estimated average amount of water that may be produced annually toachieve a desired future condition. Groundwater conservation districts are required toconsider modeled available groundwater, along with several other factors, when issuing
permits in order to manage groundwater production to achieve the desired future
condition(s). The other factors districts must consider include annual precipitation andproduction patterns, the estimated amount of pumping exempt from permitting, existing
permits, and a reasonable estimate of actual groundwater production under existing
permits.

PARAMETERS AND ASSUMPTIONS:The parameters and assumptions for the modeled available groundwater estimates aredescribed below:

44Carrizo-Wilcox, Queen City, and Sparta aquifers
•

•

•
•

•
•

•

•
•

We used Version 2.01 of the groundwater availability model for the southern part of
the Carrizo-Wilcox, Queen City, and Sparta aquifers. See Deeds and others (2003)
and Kelley and others (2004) for assumptions and limitations of the groundwater
availability model for the southern part of the Carrizo-Wilcox, Queen City, andSparta aquifers.

This groundwater availability model includes eight layers, which generally
represent the Sparta Aquifer (Layer 1), the Weches Confining Unit (Layer 2), theQueen City Aquifer (Layer 3), the Reklaw Confining Unit (Layer 4), the Carrizo(Layer 5), the Upper Wilcox (Layer 6), the Middle Wilcox (Layer 7), and the Lower
Wilcox (Layer 8). Since the model extends beyond the official TWDB aquifer extents,
please note that model layers 1 and 3 instead represent geologic units equivalent to
the Sparta and Queen City aquifers, respectively, in those areas falling outside of theofficial aquifer extents.
The model was run with MODFLOW-96 (Harbaugh and McDonald, 1996).

Although the original groundwater availability model was only calibrated to 1999,
an analysis during the second round of joint planning (Hutchison, 2017b) verified
that the model satisfactorily matched measured water levels for the period from1999 to 2011. For this reason, TWDB considers it acceptable to use the end of 2011
as the reference year for drawdown calculations.

Drawdown averages and modeled available groundwater values were based on the
TWDB defined aquifer boundaries rather than the model extent.

Drawdowns for cells that became dry during the simulation (water level dropped
below the base of the cell) were calculated as the reference year water levelelevation minus the elevation of the model cell bottom. Pumping in dry cells was
excluded from the modeled available groundwater calculations for the decades after
the cell went dry.
A tolerance of five feet was assumed when comparing desired future conditions tomodeled drawdown results. This tolerance was specified by the GMA in theirdefinition of the desired future conditions.
Estimates of modeled available groundwater from the model simulation wererounded to the nearest whole number.

The verification calculation for the desired future conditions is based on an averageof all model layers (Layers 1 through 8). The modeled available groundwater45

calculations are based on Layer 1 for the Sparta Aquifer, Layer 3 for the Queen City
Aquifer, and the sum of Layers 5 through 8 for the Carrizo-Wilcox Aquifer.

Yegua-Jackson Aquifer
•

•

•
•

•
•

•

•
•

We used version 1.01 of the groundwater availability model for the Yegua-Jackson
Aquifer. See Deeds and others (2010) for assumptions and limitations of thegroundwater availability model.

This groundwater availability model includes five layers which represent theoutcrop of the Yegua-Jackson Aquifer and younger overlying units—the Catahoula
Formation (Layer 1), the upper portion of the Jackson Group (Layer 2), the lower
portion of the Jackson Group (Layer 3), the upper portion of the Yegua Group (Layer4), and the lower portion of the Yegua Group (Layer 5).
The model was run with MODFLOW-2000 (Harbaugh and others, 2000).

Although the original groundwater availability model was only calibrated to 1997, a
TWDB analysis (Oliver, 2010) verified that the model satisfactorily matchedmeasured water levels for the period from 1997 to 2009. For this reason, TWDB
considers it acceptable to use the end of 2009 as the reference year for drawdown
calculations.
Drawdown averages and modeled available groundwater values were based on the
TWDB-defined aquifer boundaries rather than the model extent.

No dry cells occurred in the simulation in Gonzales County or Karnes County. As
these were the only counties with defined desired future conditions, no dry cellconsiderations were required during the verification calculation for the desired
future conditions. Pumping in dry cells was excluded from the modeled available
groundwater calculations for the decades after the cell went dry.

A tolerance of one foot was assumed when comparing desired future conditions tomodeled drawdown results. This tolerance was specified by the GMA in theirdefinition of the desired future conditions.
Estimates of modeled available groundwater from the model simulation wererounded to the nearest whole number.

The verification calculation for the desired future conditions is based on an averageof all model layers representing the Yegua or Jackson formations (Layers 1 through5). The modeled available groundwater calculations are the sum of all model layers
representing the Yegua or Jackson formations (Layers 1 through 5).

46

RESULTS:
The modeled available groundwater estimates for the Carrizo-Wilcox Aquifer range fromapproximately 470,000 acre-feet per year in 2020 to approximately 575,000 acre-feet per
year in 2080 (Table 1). The modeled available groundwater estimates for the Queen City
Aquifer range from approximately 23,000 acre-feet per year in 2020 to approximately
18,000 acre-feet per year in 2080 (Table 2). The modeled available groundwater estimate
for the Sparta Aquifer ranges from approximately 6,000 acre-feet per year in 2020 toapproximately 4,000 acre-feet per year in 2080 (Table 3). The modeled available
groundwater is summarized by groundwater conservation district and county for the
Carrizo-Wilcox, Queen City, and Sparta aquifers (Tables 1, 2, and 3 respectively). The
modeled available groundwater has also been summarized by county, river basin, andregional water planning area for use in the regional water planning process for the CarrizoWilcox, Queen City, and Sparta aquifers (Tables 5, 6, and 7 respectively). Small differencesin values between table summaries are due to rounding.

The modeled available groundwater estimate for the Yegua-Jackson Aquifer isapproximately 7,000 acre-feet per year from 2020 to 2080 (Table 4). The modeled
available groundwater for the Yegua-Jackson Aquifer is summarized by groundwater
conservation district and county (Table 4) and by county, river basin, and regional waterplanning area for use in the regional water planning process (Table 8). Small differences ofvalues between table summaries are due to rounding.

47

FIGURE 1.

GROUNDWATER MANAGEMENT AREA (GMA) 13 BOUNDARY, REGIONAL WATERPLANNING AREAS (RWPAS), RIVER BASINS, GROUNDWATER CONSERVATION
DISTRICTS (GCDS), AND COUNTIES OVERLAIN ON THE EXTENT OF THE CARRIZOWILCOX AQUIFER.

48

FIGURE 2.

GROUNDWATER MANAGEMENT AREA (GMA) 13 BOUNDARY, REGIONAL WATERPLANNING AREAS (RWPAS), RIVER BASINS, GROUNDWATER CONSERVATION
DISTRICTS (GCDS), AND COUNTIES OVERLAIN ON THE EXTENT OF THE QUEEN CITY
AQUIFER.

49

FIGURE 3.

GROUNDWATER MANAGEMENT AREA (GMA) 13 BOUNDARY, REGIONAL WATERPLANNING AREAS (RWPAS), RIVER BASINS, GROUNDWATER CONSERVATION
DISTRICTS (GCDS), AND COUNTIES OVERLAIN ON THE EXTENT OF THE SPARTAAQUIFER.

50

FIGURE 4.

GROUNDWATER MANAGEMENT AREA (GMA) 13 BOUNDARY, REGIONAL WATERPLANNING AREAS (RWPAS), RIVER BASINS, GROUNDWATER CONSERVATION
DISTRICTS (GCDS), AND COUNTIES OVERLAIN ON THE EXTENT OF THE YEGUAJACKSON AQUIFER.

51

TABLE 1.

MODELED AVAILABLE GROUNDWATER FOR THE CARRIZO-WILCOX AQUIFER IN GROUNDWATER MANAGEMENT AREA 13
SUMMARIZED BY GROUNDWATER CONSERVATION DISTRICT (GCD) AND COUNTY FOR EACH DECADE BETWEEN 2020 AND
2080. VALUES ARE IN ACRE-FEET PER YEAR.

Groundwater
Conservation
District
Evergreen UWCD
Evergreen UWCD
Evergreen UWCD

Evergreen UWCD
Evergreen UWCD
Total
Gonzales County
UWCD
Gonzales County
UWCD
Gonzales County
UWCD Total
Guadalupe County
GCD
McMullen GCD
Medina County
GCD
Plum Creek CD
Uvalde County
UWCD

CountyAtascosa
Frio
KarnesWilsonCaldwell

GonzalesAquifer

2020

2030

2040

2050

2060

2070

2080

Carrizo-Wilcox
Carrizo-Wilcox
Carrizo-Wilcox
Carrizo-Wilcox

51,924
114,827693

246,372

125,670

59,982
79,131
1,043

209,318

105,947

59,982
79,131
1,043

184,919

68,60958,40681,0181,001

180,434

43,60456,82882,950931

205,673

38,28455,32985,143
843

Carrizo-Wilcox

38,22954,39786,995758

265,826

265,826

Carrizo-Wilcox

468

9,472

16,401

25,51030,08730,08730,087

125,670

Carrizo-Wilcox

Carrizo-Wilcox

60,43160,89976,26585,73790,788107,189

102,373

127,883

102,747

132,834

103,707

133,794

126,248

Guadalupe
McMullen

Carrizo-Wilcox
Carrizo-Wilcox

55,637
7,789

39,563
7,768

41,6684,867

43,315
4,854

42,1184,854

42,1994,854

41,6594,854

MedinaCaldwell

Carrizo-Wilcox
Carrizo-Wilcox

2,635
17,673

2,628
15,366

2,635
16,335

2,628
16,965

2,628
15,562

2,628
19,5092,628
19,468

UvaldeCarrizo-Wilcox

01

0

0

0

0

0

0

1 A zero value indicates the groundwater availability model pumping scenario did not include any pumping in the aquifer.

52

96,161TABLE 1 (CONTINUED)

Groundwater
Conservation
District
Wintergarden GCD
Wintergarden GCD
Wintergarden GCD
Wintergarden
GCD Total
No District-County
No District-County
No District-County
No District-County
No District-County
No DistrictCounty Total
Total for GMA 13

CountyDimmit
La Salle
ZavalaBexar
Caldwell
GonzalesMaverick
Webb

Aquifer

2020

2030

2040

2050

2060

2070

2080

Carrizo-Wilcox
Carrizo-Wilcox
Carrizo-Wilcox

3,895
6,554
38,303

3,885
6,536
36,6753,895
6,554
35,3993,885
6,536
35,2043,885
6,536
35,0063,885
6,536
34,831

3,885
6,536
34,540Carrizo-Wilcox
Carrizo-Wilcox

48,752
69,727
39
02
547
912

71,225470,283

47,09668,451
39
0
545
910

45,84868,928
39
0
547
912

45,62568,739
39
0
545
910

45,42767,653
39
0
545
910

45,252
67,849
39
0
276
910

44,961
67,849
39
0
276
910

Carrizo-Wilcox
Carrizo-Wilcox
Carrizo-Wilcox
Carrizo-Wilcox
Carrizo-Wilcox
Carrizo-Wilcox

69,945448,537

70,426473,887

70,233
520,821

69,147558,9422 A zero value indicates the groundwater availability model pumping scenario did not include any pumping in the aquifer.

53

69,074583,136

69,074
574,718

TABLE 2.

MODELED AVAILABLE GROUNDWATER FOR THE QUEEN CITY AQUIFER IN GROUNDWATER MANAGEMENT AREA 13
SUMMARIZED BY GROUNDWATER CONSERVATION DISTRICT (GCD) AND COUNTY FOR EACH DECADE BETWEEN 2020 AND
2080. VALUES ARE IN ACRE-FEET PER YEAR.

Groundwater
Conservation
District
Evergreen UWCD
Evergreen UWCD
Evergreen UWCD
Evergreen UWCD
Total
Gonzales County
UWCD
Gonzales County
UWCD
Gonzales County
UWCD Total
Guadalupe County
GCD
McMullen GCD
Plum Creek CD
Wintergarden
GCD
Total for GMA 13

CountyAquifer

2020

2030

2040

2050

2060

2070

2080

Atascosa
Frio
WilsonQueen City
Queen City
Queen City

Queen City

4,070
6,702
2,631

13,403

4,525
4,533
1,423

10,481

4,537
4,380
1,267

10,184

4,495
4,231
1,123

9,849

4,390
4,066
1,000

9,456

4,285
3,927
892

9,104

9,104

CaldwellQueen City
Queen City

4,842

9,505

4,500

3,977

9,505

4,960

3,977

9,530

4,960

4,545

9,789

4,973

4,545

9,815

4,960

4,557

Queen City

4,973

4,829

8,477

8,477

Guadalupe
McMullen
CaldwellQueen City
Queen City
Queen City

03
3
0

0
3
0

0
3
0

0
3
0

0
3
0

0
3
0

0
3
0

La Salle

Queen City
Queen City

1
23,222

1
20,274

1
19,7181
19,3581
18,965

1
17,585

1
17,585

Gonzales3 A zero value indicates the groundwater availability model pumping scenario did not include any pumping in the aquifer.

54

4,285
3,927
892

4,500

TABLE 3.

MODELED AVAILABLE GROUNDWATER FOR THE SPARTA AQUIFER IN GROUNDWATER MANAGEMENT AREA 13 SUMMARIZEDBY GROUNDWATER CONSERVATION DISTRICT (GCD) AND COUNTY FOR EACH DECADE BETWEEN 2020 AND 2080. VALUESARE IN ACRE-FEET PER YEAR.

Groundwater
Conservation District

Evergreen UWCD

Evergreen UWCD
Evergreen UWCD
Evergreen UWCD Total
Gonzales County UWCD
McMullen GCD
Wintergarden GCD
Total for GMA 13
TABLE 4.

CountyAtascosa
Frio
WilsonGonzalesMcMullen
La Salle

Aquifer
SpartaSpartaSpartaSpartaSpartaSpartaSpartaSparta

2020

2030

2040

1,218

1,187

1,043

897
335
2,450
3,524
04
0
5,974

623
182
1,992
2,451
0
0
4,443

603
163
1,809
2,457
0
0
4,266

2050
998

576
144
1,718
2,451
0
0
4,169

2060

2070

961

932

557
128
1,646
2,451
0
0
4,097

534
114
1,580
2,451
0
0
4,031

2080
932

534
114
1,580
2,451
0
0
4,031

MODELED AVAILABLE GROUNDWATER FOR THE YEGUA-JACKSON AQUIFER IN GROUNDWATER MANAGEMENT AREA 13
SUMMARIZED BY GROUNDWATER CONSERVATION DISTRICT (GCD) AND COUNTY FOR EACH DECADE BETWEEN 2020 AND
2080. VALUES ARE IN ACRE-FEET PER YEAR.

Groundwater
Conservation District
Evergreen UWCD
Gonzales County UWCDNo District-County
Total for GMA 13

CountyKarnesGonzalesGonzalesAquifer
Yegua-Jackson

Yegua-Jackson
Yegua-Jackson
Yegua-Jackson

2020

2030

2040

2,013

2,013

2,013

4,155
573
6,741

4,155
573
6,741

4,155
573
6,741

2050
2,013

4,155
573
6,741

4 A zero value indicates the groundwater availability model pumping scenario did not include any pumping in the aquifer.

55

2060

2070

2,013

2,013

4,155
573
6,741

4,155
573
6,741

2080
2,013

4,155
573
6,741

TABLE 5.

CountyAtascosa
Atascosa
Bexar

Bexar
CaldwellCaldwellDimmitDimmitFrio
GonzalesGonzalesGuadalupe
Guadalupe
KarnesKarnesKarnes
La Salle
MedinaMODELED AVAILABLE GROUNDWATER BY DECADE FOR THE CARRIZO-WILCOX AQUIFER IN GROUNDWATER MANAGEMENTAREA 13. RESULTS ARE IN ACRE-FEET PER YEAR AND ARE SUMMARIZED BY COUNTY, REGIONAL WATER PLANNING AREA
(RWPA), RIVER BASIN, AND AQUIFER.

RWPA
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L

River
Basin
NuecesSan
Antonio
NuecesSan
Antonio
Colorado
Guadalupe
NuecesRio Grande
NuecesGuadalupe
LavacaGuadalupeSan
Antonio
Guadalupe
NuecesSan
Antonio
NuecesNuecesAquifer

2030

2040

2050

2060

2070

2080

Carrizo-Wilcox

54,31055,241

56,73958,31659,89059,89029,68905
24,8773,765
120
86,99576,265032,40029,935032,7753,775
120
85,14390,788034,20029,605042,514
3,765
120
82,950102,373
035,631

28,519045,6883,765
120
81,018102,747
034,65528,562049,635
3,765
120
79,131
103,7070
34,73628,562049,594
3,765
120
79,131
96,161034,345

843
6,554
2,630

931
6,536
2,623

1,001
6,536
2,623

1,043
6,536
2,623

Carrizo-Wilcox

87
38,762Carrizo-Wilcox
Carrizo-Wilcox

Carrizo-Wilcox
Carrizo-Wilcox
Carrizo-Wilcox
Carrizo-Wilcox
Carrizo-Wilcox
Carrizo-Wilcox
Carrizo-Wilcox
Carrizo-Wilcox
Carrizo-Wilcox

7,163
0
0

Carrizo-Wilcox
Carrizo-Wilcox
Carrizo-Wilcox

758
6,536
2,623

Carrizo-Wilcox
Carrizo-Wilcox

88
38,993

7,468
0
0

89
39,134

7,684
0
0

90
39,1347,463
00

5 A zero value indicates the groundwater availability model pumping scenario did not include any pumping in the aquifer.

56

92
39,287

7,463
0
0

92
39,287

7,314
0
0
1,043
6,536
2,623

TABLE 5 (CONTINUED)CountyMedinaUvaldeWilsonWilsonWilsonZavalaMaverick
Maverick
Webb
Webb
McMullen
GMA 13 Total

RWPA
L
L
L
L

L
L
M
M
M
M
N

River
Basin
San
Antonio
NuecesGuadalupe
NuecesSan
Antonio
NuecesNuecesRio Grande
NuecesRio Grande
NuecesAquifer
Carrizo-Wilcox

Carrizo-Wilcox
Carrizo-Wilcox
Carrizo-Wilcox
Carrizo-Wilcox

Carrizo-Wilcox
Carrizo-Wilcox
Carrizo-Wilcox
Carrizo-Wilcox
Carrizo-Wilcox
Carrizo-Wilcox
Carrizo-Wilcox

2030

2040

2050

2060

2070

2080

5
06
443
10,7745
0653
11,1715
0
762
11,5785
03,870
12,0275
0
3,982
12,546

5
0
3,982
12,546

27,067
31,78056,26990,050 109,142
36,67535,39935,20435,006
34,831
542
544
542
542
273
3
3
3
3
3
890
892
890
890
890
20
20
20
20
20
7,768
4,867
4,854
4,854
4,854
448,537 473,887 520,821 558,942 583,136

6 A zero value indicates the groundwater availability model pumping scenario did not include any pumping in the aquifer.

57

109,142
34,540
273
3
890
20
4,854
574,718

TABLE 6.

CountyAtascosa
CaldwellFrio
GonzalesGuadalupe
La Salle
WilsonWilsonWilsonMcMullen
GMA 13
Total

MODELED AVAILABLE GROUNDWATER BY DECADE FOR THE QUEEN CITY AQUIFER IN GROUNDWATER MANAGEMENT AREA
13. RESULTS ARE IN ACRE-FEET PER YEAR AND ARE SUMMARIZED BY COUNTY, REGIONAL WATER PLANNING AREA (RWPA),
RIVER BASIN, AND AQUIFER.

RWPA
L
L
L
L
L
L
L
L
L
N

River
Basin
NuecesGuadalupe
NuecesGuadalupe
Guadalupe
NuecesGuadalupe
NuecesSan Antonio
NuecesAquifer
Queen City
Queen City
Queen City
Queen City
Queen City
Queen City
Queen City
Queen City
Queen City
Queen City

Queen City

2030
4,525
4,829
4,533
4,960
07
1
106
181
1,136
3

20,274

2040
4,537
4,557
4,380
4,973
0
1
95
161
1,011
3

19,718

2050
4,495
4,545
4,231
4,960
0
1
84
143
896
3

19,358

2060
4,390
4,545
4,066
4,960
0
1
75
127
798
3

18,9657 A zero value indicates the groundwater availability model pumping scenario did not include any pumping in the aquifer.

58

2070
4,285
3,977
3,927
4,500
0
1
67
114
711
3

17,585

2080
4,285
3,977
3,927
4,500
0
1
67
114
711
3

17,585TABLE 7.

MODELED AVAILABLE GROUNDWATER BY DECADE FOR THE SPARTA AQUIFER IN GROUNDWATER MANAGEMENT AREA 13.
RESULTS ARE IN ACRE-FEET PER YEAR AND ARE SUMMARIZED BY COUNTY, REGIONAL WATER PLANNING AREA (RWPA),
RIVER BASIN, AND AQUIFER.

CountyAtascosa
Frio
Gonzales
La Salle
WilsonWilson

RWPA
L
L
L
L
L
L

WilsonL
McMullenN
GMA 13 Total

River
Basin
NuecesNuecesGuadalupe
NuecesGuadalupe
NuecesSan
Antonio
NuecesAquifer
SpartaSpartaSpartaSpartaSpartaSpartaSpartaSpartaSparta

2030

2040

2050

2060

2070

2080

1,187
623
2,451
08
12
19

1,043
603
2,457
0
11
17

998
576
2,451
0
10
15

961
557
2,451
0
9
13

932
534
2,451
0
8
12

932
534
2,451
0
8
12

151
0
4,443

135
0
4,266

119
0
4,169

106
0
4,097

8 A zero value indicates the groundwater availability model pumping scenario did not include any pumping in the aquifer.

59

94
0
4,031

94
0
4,031

TABLE 8.

MODELED AVAILABLE GROUNDWATER BY DECADE FOR THE YEGUA-JACKSON AQUIFER IN GROUNDWATER MANAGEMENTAREA 13. RESULTS ARE IN ACRE-FEET PER YEAR AND ARE SUMMARIZED BY COUNTY, REGIONAL WATER PLANNING AREA
(RWPA), RIVER BASIN, AND AQUIFER.

CountyRWPAAtascosa
Frio
GonzalesGonzalesKarnesKarnes

L
L
L
L
L
L

Karnes
La Salle
WilsonWilsonWilsonWebb
Webb
ZapataMcMullen
GMA 13 Total

L
L
L
L

L
M
M
M
N

River
Basin
NuecesNuecesGuadalupe
LavacaGuadalupe
NuecesSan
Antonio
NuecesGuadalupe
NuecesSan
Antonio
NuecesRio Grande
Rio Grande
NuecesAquifer

2030

2040

2050

2060

2070

2080

Yegua-Jackson
Yegua-Jackson
Yegua-Jackson
Yegua-Jackson
Yegua-Jackson
Yegua-Jackson
Yegua-Jackson

NR
NR
4,709
19
292
91

NR
NR
4,709
19
292
91

NR
NR
4,709
19
292
91

NR
NR
4,709
19
292
91

NR
NR
4,709
19
292
91

NR
NR
4,709
19
292
91

Yegua-Jackson
Yegua-Jackson
Yegua-Jackson
Yegua-Jackson

NR
NR
NR
NR

NR
NR
NR
NR

NR
NR
NR
NR

NR
NR
NR
NR

NR
NR
NR
NR

NR
NR
NR
NR

Yegua-Jackson
Yegua-Jackson
Yegua-Jackson
Yegua-Jackson

1,630
NR
NR
NR
NR

Yegua-Jackson

6,741

1,630
NR
NR
NR
NR

6,741

1,630
NR
NR
NR
NR

6,741

1,630
NR
NR
NR
NR

6,741

1,630
NR
NR
NR
NR

6,741

NR: Groundwater Management Area 13 declared the Yegua-Jackson Aquifer not relevant in these areas.

60

1,630
NR
NR
NR
NR

6,741

LIMITATIONS:
The groundwater model used in completing this analysis is the best available scientific toolthat can be used to meet the stated objectives. To the extent that this analysis will be used
for planning purposes and/or regulatory purposes related to pumping in the past and into
the future, it is important to recognize the assumptions and limitations associated with theuse of the results. In reviewing the use of models in environmental regulatory decision
making, the National Research Council (2007) noted:“Models will always be constrained by computational limitations, assumptions, andknowledge gaps. They can best be viewed as tools to help inform decisions rather
than as machines to generate truth or make decisions. Scientific advances will nevermake it possible to build a perfect model that accounts for every aspect of reality or
to prove that a given model is correct in all respects for a particular regulatory
application. These characteristics make evaluation of a regulatory model more
complex than solely a comparison of measurement data with model results.”

A key aspect of using the groundwater model to evaluate historic groundwater flow
conditions includes the assumptions about the location in the aquifer where historic
pumping was placed. Understanding the amount and location of historic pumping is as
important as evaluating the volume of groundwater flow into and out of the district,between aquifers within the district (as applicable), interactions with surface water (asapplicable), recharge to the aquifer system (as applicable), and other metrics that describe
the impacts of that pumping. In addition, assumptions regarding precipitation, recharge,
and streamflow are specific to a particular historic time period.
Because the application of the groundwater model was designed to address regional scalequestions, the results are most effective on a regional scale. The TWDB makes nowarranties or representations relating to the actual conditions of any aquifer at a particularlocation or at a particular time.
It is important for groundwater conservation districts to monitor groundwater pumping
and groundwater levels in the aquifer. Because of the limitations of the groundwater modeland the assumptions in this analysis, it is important that the groundwater conservation
districts work with the TWDB to refine this analysis in the future given the reality of how
the aquifer responds to the actual amount and location of pumping now and in the future.
Historic precipitation patterns also need to be placed in context as future climaticconditions, such as dry and wet year precipitation patterns, may differ and affectgroundwater flow conditions.

61

REFERENCES:
Deeds, N., Kelley, V., Fryar, D., Jones, T., Whallon, A.J., and Dean, K.E., 2003, Groundwater
Availability Model for the Southern Carrizo-Wilcox Aquifer: Contract report to the
Texas Water Development Board, 452 p.,
http://www.twdb.texas.gov/groundwater/models/gam/czwx_s/CZWX_S_Full_Repo
rt.pdf.

Deeds, N. E., Yan, T., Singh, A., Jones, T. L., Kelley, V. A., Knox, P. R., and Young, S. C., 2010,
Groundwater availability model for the Yegua-Jackson Aquifer: Final report
prepared for the Texas Water Development Board by INTERA, Inc., 582 p.,
http://www.twdb.texas.gov/groundwater/models/gam/ygjk/YGJK_Model_Report.p
df.
Furnans, J., 2022, Technical Memorandum: Groundwater Availability Modeling Technical
Elements, Memo to Groundwater Management Area 13, 5p.

Groundwater Management Area 13 Joint Planning Committee, Furnans, J., and Keester, M.,
2022, 2021 Joint Planning Desired Future Conditions Explanatory Report, 510 p.
Harbaugh, A. W., 2009, Zonebudget Version 3.01, A computer program for computing
subregional water budgets for MODFLOW ground-water flow models, U.S.
Geological Survey Groundwater Software.

Harbaugh, A.W. and McDonald, M.G., 1996, User’s documentation for MODFLOW-96, an
update to the U.S. Geological Survey Modular Finite-Difference Ground-Water Flow
Model: U.S. Geological Survey, Open-File Report 96-485.

Harbaugh, A. W., Banta, E. R., Hill, M. C., and McDonald, M. G., 2000, MODFLOW-2000, theU.S. Geological Survey modular ground-water model -- User guide to modularization
concepts and the Ground-Water Flow Process: U.S. Geological Survey Open-File
Report 00-92, 121 p.
Hutchison, W.R., 2017a, GMA 13 Technical Memorandum 16-08 Final, Sparta, Queen City,
and Carrizo-Wilcox Aquifers: Summary of Scenario 9 Drawdown and Outcrop
Results, 13 p.

Hutchison, W.R., 2017b, GMA 13 Technical Memorandum 17-01 Final, Extension of GAM
Calibration Period for Carrizo-Wilcox, Queen City, and Sparta Aquifers, 81p.

Kelley, V.A., Deeds, N.E., Fryar, D.G., and Nicot, J.P., 2004, Groundwater availability models
for the Queen City and Sparta aquifers: Contract report to the Texas Water
Development Board, 867 p.

62

National Research Council, 2007, Models in Environmental Regulatory Decision Making
Committee on Models in the Regulatory Decision Process, National Academies Press,
Washington D.C., 287 p., http://www.nap.edu/catalog.php?record_id=11972.
Oliver, W., 2010, GAM Task 10-012 Model Run Report: Texas Water Development Board,
GAM Task 10-012 Report, 48 p.,
http://www.twdb.texas.gov/groundwater/docs/GAMruns/Task10-012.pdf

Texas Water Code, 2011, http://www.statutes.legis.state.tx.us/docs/WA/pdf/WA.36.pdf.

63

APPENDIX A
Total Pumping Associated with Modeled Available Groundwater Run for
the Carrizo-Wilcox Aquifer Split by Model Layers for Groundwater
Management Area 13

64

TABLE A.1.

TOTAL PUMPING SPLIT BY MODEL LAYERS FROM THE MODELED AVAILABLE GROUNDWATER RUN FOR THE CARRIZOWILCOX AQUIFER IN GROUNDWATER MANAGEMENT AREA 13. THE VALUES ARE SUMMARIZED BY GROUNDWATERCONSERVATION DISTRICT (GCD) AND COUNTY FOR EACH DECADE BETWEEN 2020 AND 2080. VALUES ARE IN ACRE-FEET PER
YEAR.

GCD
Evergreen UWCD
Evergreen UWCD
Evergreen UWCD
Evergreen UWCD
Evergreen UWCD
Evergreen UWCD
Evergreen UWCD
Evergreen UWCD
Evergreen UWCD
Evergreen UWCD
Evergreen UWCD
Evergreen UWCD
Evergreen UWCD
Evergreen UWCD
Evergreen UWCD
Evergreen UWCD
Evergreen UWCD
Total

CountyAtascosa
Atascosa
Atascosa
Atascosa
Frio
Frio
Frio
Frio
KarnesKarnesKarnesKarnesWilsonWilsonWilsonWilsonBlank cell

Aquifer
Carrizo
Upper Wilcox
Middle Wilcox
Lower Wilcox
Carrizo
Upper Wilcox
Middle Wilcox
Lower Wilcox
Carrizo
Upper Wilcox
Middle Wilcox
Lower Wilcox
Carrizo
Upper Wilcox
Middle Wilcox
Lower Wilcox
CarrizoWilcox

2020

2030

2040

2050

2060

2070

2080

50,266
250
224
1,184
114,827
09
0
0
693
0
0
0
36,086
125
125
1,893

52,745
249
223
1,180
86,995
0
0
0
758
0
0
0
32,648
125
125
5,386

53,671
250
224
1,184
85,143
0
0
0
843
0
0
0
34,096
125
125
9,258

55,176
249
223
1,180
82,950
0
0
0
931
0
0
0
35,482125
125
32,87756,754
249
223
1,180
81,018
0
0
0
1,001
0
0
0
36,994125
125
68,70358,330
249
223
1,180
79,131
0
0
0
1,043
0
0
0
38,730125
125
86,69058,330
249
223
1,180
79,131
0
0
0
1,043
0
0
0
38,730125
125
86,690205,673

180,434

184,919

209,318

246,372

9 A zero value indicates the groundwater availability model pumping scenario did not include any pumping in the aquifer.

65

265,826

265,826

TABLE A.1. (CONTINUED)

GCD
Gonzales County
UWCD
Gonzales County
UWCD
Gonzales County
UWCD
Gonzales County
UWCD
Gonzales County
UWCD
Gonzales County
UWCD
Gonzales County
UWCD
Gonzales County
UWCD
Gonzales County
UWCD Total
Guadalupe County
GCD
Guadalupe County
GCD

CountyAquifer

2020

2030

2040

2050

2060

2070

2080

Caldwell

Carrizo

453

9,457

16,38625,49530,07230,07230,072

Caldwell

Middle Wilcox

0 10

0

0

0

0

0

0

CaldwellCaldwell

GonzalesGonzalesGonzalesGonzalesGuadalupe
Guadalupe

Upper Wilcox

Lower Wilcox

15

15

0

0

15
0

15
0

15
0

15
0

15
0

Carrizo

47,131

51,90855,242

55,83256,20657,166

49,620

Middle Wilcox
Lower Wilcox
CarrizoWilcox

11,096

15,563

20,11424,55624,55624,55624,55660,89985,737

107,189

127,883

132,834

133,794

126,248

Carrizo

28,943

14,834

14,627

14,532

14,224

14,624

14,624Upper Wilcox

Upper Wilcox

0

0

2,204

8,794

0

0

0

15,4320

021,9850021,985

10 A zero value indicates the groundwater availability model pumping scenario did not include any pumping in the aquifer.

66

0

0

21,9850021,9850TABLE A.1 (CONTINUED)

GCD
Guadalupe County
GCD
Guadalupe County
GCD
Guadalupe County
GCD Total
McMullen County GCD
McMullen County GCD
McMullen County GCD
McMullen County GCD
McMullen County
GCD Total
Medina County GCD
Medina County GCD
Medina County GCD
Medina County GCD
Medina County GCD
Total
Plum Creek CD
Plum Creek CD
Plum Creek CD
Plum Creek CD
Plum Creek CD Total

CountyAquifer

Guadalupe

Middle Wilcox

Guadalupe
McMullen
McMullen
McMullen
McMullenMedinaMedinaMedinaMedinaCaldwellCaldwellCaldwellCaldwellLower Wilcox
CarrizoWilcox
Carrizo
Upper Wilcox
Middle Wilcox
Lower Wilcox
CarrizoWilcox
Carrizo
Upper Wilcox
Middle Wilcox
Lower Wilcox
CarrizoWilcox
Carrizo
Upper Wilcox
Middle Wilcox
Lower Wilcox
CarrizoWilcox

2020

2030

2040

2050

2060

2070

2080

6,609

6,373

7,926

9,428

9,207

9,075

8,986

20,085

18,356

19,115

19,355

18,68718,50018,04955,637
7,789
0 11
0
0

39,5637,768
0
0
0

41,6684,867
00043,3154,854
0
0042,1184,854
00042,1994,854
00041,659
4,854
0
0
0

2,635
0
0
5,733
11,940

2,628
1,990
0
5,717
7,659

2,635
5,048
0
5,733
5,554

2,628
5,709
0
5,717
5,539

2,628
6,046
0
3,977
5,539

2,628
9,993
0
3,977
5,539

2,628
9,993
0
3,936
5,539

7,789
517
0
1,252
866

17,673

7,768
515
0
1,249
864

15,366

4,867
517
0
1,252
866

16,335

4,854
515
0
1,249
864

16,965

4,854
515
0
1,249
864

15,562

11 A zero value indicates the groundwater availability model pumping scenario did not include any pumping in the aquifer.

67

4,854
515
0
1,249
864

19,509

4,854
515
0
1,249
864

19,468TABLE A.1 (CONTINUED)

GCD
Uvalde County GCD
Uvalde County GCD
Uvalde County GCD
Uvalde County GCD
Uvalde County
GCD Total
Wintergarden GCD
Wintergarden GCD
Wintergarden GCD
Wintergarden GCD
Wintergarden GCD
Wintergarden GCD
Wintergarden GCD
Wintergarden GCD
Wintergarden GCD
Wintergarden GCD
Wintergarden GCD
Wintergarden GCD
Wintergarden
GCD Total
No District-County
No District-County
No District-County
No District-County

CountyUvaldeUvaldeUvaldeUvaldeDimmitDimmitDimmitDimmit
La Salle
La Salle
La Salle
La Salle
ZavalaZavalaZavalaZavalaBlank cell
Bexar
Bexar
Bexar
Bexar

Aquifer
Carrizo
Upper Wilcox
Middle Wilcox
Lower Wilcox
CarrizoWilcox
Carrizo
Upper Wilcox
Middle Wilcox
Lower Wilcox
Carrizo
Upper Wilcox
Middle Wilcox
Lower Wilcox
Carrizo
Upper Wilcox
Middle Wilcox
Lower Wilcox
CarrizoWilcox
Carrizo
Upper Wilcox
Middle Wilcox
Lower Wilcox

2020

2030

0 12

2040
0
0
0
0

0
0
0

0
2,722
993
142
38
4,597
1,957
0
0
27,969
6,329
3,683
322

0
2,715
990
142
38
4,584
1,952
0
0
26,368
6,312
3,673
322

48,752
43,05710
58
26,60247,09642,9391058
25,444

2050
0
0
0
0

0
2,722
993
142
38
4,597
1,957
0
0
25,065
6,329
3,683
322

45,84843,3461058
25,514

2060
0
0
0
0

0
2,715
990
142
38
4,584
1,952
0
0
24,897
6,312
3,673
322

45,62543,2271058
25,444

0
0
0
0

0
2,715
990
142
38
4,584
1,952
0
0
24,699
6,312
3,673
322

45,42743,22710
58
24,35812 A zero value indicates the groundwater availability model pumping scenario did not include any pumping in the aquifer.

68

2070

2080
0
0
0
0

0
2,715
990
142
38
4,584
1,952
0
0
24,524
6,312
3,673
322

45,252
43,42310
58
24,358

0
0
0
0

0
2,715
990
142
38
4,584
1,952
0
0
24,233
6,312
3,673
322

44,961
43,42310
58
24,358TABLE A.1 (CONTINUED)

GCD
No District-County
No District-County
No District-County
No District-County
No District-County
No District-County
No District-County
No District-County
No District-County
No District-County
No District-County
No District-County
No District-County
No District-County
No District-County
No District-County
No District-County
Total
Total for GMA 13

CountyCaldwellCaldwellCaldwellCaldwell
GonzalesGonzalesGonzalesGonzalesMaverick
Maverick
Maverick
Maverick
Web
Web
Web
Web

Blank cell

Aquifer
Carrizo
Upper Wilcox
Middle Wilcox
Lower Wilcox
Carrizo
Upper Wilcox
Middle Wilcox
Lower Wilcox
Carrizo
Upper Wilcox
Middle Wilcox
Lower Wilcox
Carrizo
Upper Wilcox
Middle Wilcox
Lower Wilcox
CarrizoWilcox
CarrizoWilcox

2020

2030

NP 13

NP
NP
39
0
0
0
0
0
541
0
2
2
896
13
1
0

NP
39
0 14
0
0
0
0
543
0
2
2
898
13
1
0

2040

2050

2060

2070

2080

NP
NP
39
0
0
0
0
0
543
0
2
2
898
13
1
0

NP
NP
39
0
0
0
0
0
541
0
2
2
896
13
1
0

NP
NP
39
0
0
0
0
0
541
0
2
2
896
13
1
0

NP
NP
39
0
0
0
0
0
272
0
2
2
896
13
1
0

NP
NP
39
0
0
0
0
0
272
0
2
2
896
13
1
0

71,22569,94570,426

70,233

69,147

69,074

69,074

470,283

448,537

473,887

520,821558,942

583,136

574,718

13 NP: The aquifer is not present in this part of the county.

14 A zero value indicates the groundwater availability model pumping scenario did not include any pumping in the aquifer.

69

APPENDIX B
Summary of Modeled Available Groundwater for the Plum Creek Conservation District (complete set ofvalues is available in the appendix)

GMA

Aquifers

MAG (acre-ft/ per year)

TWDB MAG Report

10

Trinity Group276

GAM Run 16-033 MAG

10Saline Edwards

812

GAM Run 16-033 MAG

13

Carrizo-Wilcox

13

Carrizo

13

Wilcox Group(Upper, Middle &Lower)

13

Queen City

Year 2020 = 17,673
Year 2080 = 19,468

GAM Run 21-018 MAG(Date issued: 7/25/2022)

Year 2030 = 1,990
Year 2080 = 9,993

GAM Run 21-018 MAG
Appendix A(Date issued: 7/25/2022)

Year 2020 =17,673
Year 2080 = 9,475
070

GAM Run 21-018 MAG
Appendix A(Date issued: 7/25/2022)

GAM Run 21-018 MAG(Date issued: 7/25/2022)

APPENDIX B

GAM RUN 16-033 MAG: MODELED
AVAILABLE GROUNDWATER FOR THE
AQUIFERS IN GROUNDWATER MANAGEMENTAREA 10

Robert G. Bradley, P.G. and Radu Boghici, P.G.
Texas Water Development Board
Groundwater Division(512) 463-5808
July 20, 201871

This page is intentionally left blank.

72

GAM RUN 16-033 MAG:
MODELED AVAILABLE GROUNDWATER
AQUIFERS IN GROUNDWATER MANAGEMENT AREA
10
Robert G. Bradley, P.G. and Radu Boghici, P.G.
Texas Water Development Board
Groundwater Division(512) 463-5808
July 20, 2018EXECUTIVE SUMMARY:

The modeled available groundwater for the relevant aquifers of Groundwater Management
Area 10—the Austin Chalk-Buda Limestone (relevant in Uvalde County), Barton Springs
segment of the Edwards (Balcones Fault Zone), saline portion of the Barton Springs
segment of the Edwards (Balcones Fault Zone), western portion of the San Antonio
segment of the Edwards (Balcones Fault Zone) in Kinney County, Leona Gravel (relevant in
Uvalde County), and Trinity—are summarized for the groundwater conservation districts(Tables 1, 3, 5, and 8) and by decade for use in the regional water planning process (Tables
2, 4, 6, and 9) . The modeled available groundwater estimates are 2,935 acre-feet per year
in the Austin Chalk Aquifer (Uvalde County); 758 acre-feet per year in the Buda Limestone
Aquifer (Uvalde County); 11,557 acre-feet per year in the Barton Springs segment of the
Edwards (Balcones Fault Zone) Aquifer during average recharge conditions (3,765 acrefeet per year during drought conditions); 8,564 acre-feet per year in the saline portion of
the Barton Springs segment of the Edwards (Balcones Fault Zone) Aquifer; 6,321 acre-feetper year in the freshwater portion of the western part of the San Antonio segment of the
Edwards (Balcones Fault Zone) Aquifer; 9,385 acre-feet per year in the Leona Gravel
Aquifer (Uvalde County); and 46,481 acre-feet per year in the Trinity Aquifer. Appropriate
groundwater availability models were used to determine the modeled available
groundwater for the Kinney County area of the Edwards (Balcones Fault Zone) Aquifer andto determine average recharge conditions for the Barton Springs segment of the Edwards(Balcones Fault Zone) Aquifer. Water budget methods were used to calculate the modeled
available groundwater for the rest of the relevant aquifers in Groundwater Management
Area 10. The Texas Water Development Board (TWDB) determined that the explanatory
report and other materials were administratively complete on February 12, 2018.

REQUESTOR:

Mr. John Dupnik, Chair of Groundwater Management Area 10.
73

DESCRIPTION OF REQUEST:In a letter dated November 3, 2017, Mr. John Dupnik provided the TWDB with the desired
future conditions of the relevant aquifers in Groundwater Management Area 10. The
desired future conditions, adopted June 26, 2017, by the groundwater conservation
districts within Groundwater Management Area 10, are reproduced below:
Austin [Chalk-]Buda Limestone Aquifer(s), relevant in Uvalde County only:••

Buda Limestone: no drawdown (including exempt and non-exempt use); andAustin Chalk: no drawdown (including exempt and non-exempt use).

Freshwater Edwards Aquifer in the Northern [Groundwater Management Area 10]
Subdivision••

Springflow at Barton Springs during average recharge conditions shall be no lessthan 49.7 [cubic feet per second] averaged over an 84-month (7-year) period;and,Springflow of Barton Springs during extreme drought conditions, including thoseas severe as a recurrence of the 1950s drought of record, shall be no less than
6.5 [cubic feet per second] average on a monthly basis.

Saline Edwards Aquifer in the Northern [Groundwater Management Area 10]
Subdivision•

No more than 75 feet of regional average potentiometric surface drawdown due
to pumping when compared to pre-development.

Freshwater Edwards Aquifer in the Western [Groundwater Management Area 10]
Subdivision•

The water level in well 70-38-902 shall not fall below 1,184 [feet above] meansea level.

Leona Gravel Aquifer, relevant in Uvalde County only:•

No drawdown (including exempt and non-exempt use).

74

Trinity Aquifer, in hydrologically confined zone downdip of the Trinity outcrop:•••

Outside of Uvalde and Bexar counties: average regional well drawdown notexceeding 25 feet during average recharge conditions (including exempt andnon-exempt use);

In Uvalde County: no (zero) regional well drawdown (including exempt and nonexempt use); [and]In Bexar County: non-relevant for joint planning purpose.

In response to a request for clarifications from the TWDB on December 14, 2017, andJanuary 29, 2018 Mr. John Dupnik indicated the following preferences for calculating
modeled available groundwater volumes in Groundwater Management Area 10:
Austin Chalk-Buda Limestone aquifers (only in Uvalde County)

The TWDB will use the methods and assumptions from AA 10-26 MAG and AA 1027 MAG, with a planning period from 2010 to 2060.

Freshwater Edwards, Northern Subdivision

The TWDB will use the methods and assumptions from GAM Run 10-059 MAG
Version 2, with a planning period from 2010 to 2060. Groundwater Management
Area 10 specified two desired future conditions for this aquifer. We will provide
only the drought conditions modeled available groundwater for regional waterplanning purposes because this corresponds to the methods used in regional waterplanning (planning for water in times of drought). We will provide both the average
recharge conditions and the drought conditions modeled available groundwater inthe final report. The modeled available groundwater values will be unchanged fromthe previous planning cycle.

Saline Edwards, Northern Subdivision

The TWDB will use aquifer parameters from AA 10-35 MAG, with a planning period
from 2010 to 2060, but we will recalculate with a simple water budget as outlined inTable 1 of the Saline Edwards explanatory report, instead of the method used in AA
10-35 MAG. On January 29, 2018, we received Technical Memo 2017-1221 from theBarton Springs/ Edwards Aquifer Conservation District, which outlines the technicalclarification on the method to use for this aquifer.

75

Freshwater Edwards, Western Subdivision (only in Kinney County)
The TWDB will use the methods and assumptions from GAM Run 12-002 MAG, witha planning period from 2010 to 2060. The modeled available groundwater values
will be unchanged from the previous planning cycle.

Leona Gravel (only in Uvalde County)

The TWDB will use the methods and assumptions from AA 10-28 MAG, with aplanning period from 2010 to 2060.

Trinity (downdip of recharge zone)

The TWDB will use the methods and assumptions from AA 10-06 with a planning
period from 2010 to 2060. The changes in groundwater district boundaries since AA
10-06 will require reapportionment of the modeled available groundwater.

METHODS:The desired future conditions for the Austin Chalk-Buda Limestone aquifers (relevant in
Uvalde County), Leona Gravel Aquifer (relevant in Uvalde County), Barton Springs segmentof the Edwards (Balcones Fault Zone) Aquifer, saline portion of the Barton Springs segmentof the Edwards (Balcones Fault Zone) Aquifer, Trinity Aquifer, and western portion of the
San Antonio segment of the Edwards (Balcones Fault Zone) Aquifer in Kinney County are
identical to the ones adopted in 2010. The applicable water budget methodologies tocalculate modeled available groundwater are unchanged except for the saline Edwards(Balcones Fault Zone) and Trinity aquifers.
Therefore, the modeled available groundwater volumes presented for most of the aquifers
are the same as those shown in the previous water budget assessments and model runs.
These reports are AA 10-26 MAG (Thorkildsen and Backhouse, 2011a), AA 10-27 MAG(Thorkildsen and Backhouse, 2011b), GAM Run 10-059 MAG Version 2 (Hutchison andOliver, 2011), GAM Run 12-002 MAG (Shi, 2012), and AA 10-28 MAG (Bradley, 2013).
The modeled available groundwater numbers were recalculated for the Trinity Aquifer toincorporate changes in the Groundwater Management Area 10 and groundwater
conservation district boundaries. Additionally, a change in methodology required therecalculation of the Saline Edwards (Balcones Fault Zone) Aquifer modeled available
groundwater, however, aquifer parameters from AA 10-35 MAG (Bradley, 2011) wereincorporated into this assessment.

For the water budget approaches, modeled available groundwater volumes were
determined by summing estimates of effective recharge and the change in aquifer storage.
The water budget for these analyses were a simplified version of one found in Freeze andCherry (1979, p.365).
76

This was the best method to calculate a modeled available groundwater estimate at thistime; however, this method has limitations and should be replaced with better tools,
including groundwater models and additional data as they become available. These
analyses assume homogeneous and isotropic aquifers; however, real aquifer conditions do
not satisfy these assumptions. These analyses further assume that precipitation is the only
source of aquifer recharge, that lateral inflow to the aquifer is equal to lateral outflow fromthe aquifer, and that future pumping will not alter this balance. In addition, certain
assumptions have been made regarding future precipitation, recharge, and streamflow indeveloping these estimates. Those assumptions also need to be considered and comparedto actual future data when evaluating achievement of the desired future condition.
Estimates of modeled available groundwater volumes from the numerical flow models
were determined by extracting pumping rates by decade from the model results using
ZONEBUDGET Version 3.01 (Harbaugh, 2009). Annual pumping rates were divided bycounty, river basin, regional water planning area, and groundwater conservation district
within Groundwater Management Area 10 (Figures 1 through 7 and Tables 1 through 9).

Modeled Available Groundwater and Permitting

Chapter 36 of the Texas Water Code defines “modeled available groundwater” to be theestimated average amount of water that may be produced annually to achieve a desired
future condition. Groundwater conservation districts are required to consider modeled
available groundwater, along with several other factors, when issuing permits to manage
groundwater production to achieve the desired future condition(s). Districts must also
consider include annual precipitation and production patterns, the estimated amount ofpumping exempt from permitting, existing permits, and a reasonable estimate of actual
groundwater production under existing permits.

PARAMETERS AND ASSUMPTIONS:
Austin Chalk-Buda Limestone Aquifers••

All parameters and assumptions for the Austin Chalk Aquifer are described in AA
10-26 MAG (Thorkildsen and Backhouse, 2011a) and for the Buda Limestone in
AA 10-27 MAG (Thorkildsen and Backhouse, 2011b). Both reports assumed aplanning period from 2010 to 2060.
The Austin Chalk Aquifer in Uvalde County is in a state of dynamic equilibrium
and the 2008 estimated pumpage of 2,935 acre-feet (Green and others, 2009)
achieves the adopted desired future condition.

77

•

•

The Buda Limestone Aquifer in Uvalde County is in a state of dynamic
equilibrium and the 2008 estimated pumpage of 758 acre-feet (Green andothers, 2009) achieves the adopted desired future condition.

Conditions are physically possible across the management area and a waterlevel decline of 0 feet is uniform across the aquifer(s).

Freshwater Edwards (Balcones Fault Zone) Aquifer

NORTHERN SUBDIVISION OF GROUNDWATER MANAGEMENT AREA 10
•

•

•

•

•

All parameters and assumptions for the freshwater portion of the Edwards(Balcones Fault Zone) Aquifer in the northern subdivision of Groundwater
Management Area 10 are described in GAM Run 10-059 MAG Version 2(Hutchison and Oliver, 2011). Both approaches discussed below assumed a 50year planning period. From clarifications we received from Mr. John Dupnik, we
assume a 50-year planning period from 2010 to 2060.

A water balance approach was used to estimate modeled available groundwater
during extreme drought conditions1 based on information provided by Barton
Springs/Edwards Aquifer Conservation District. See Hunt and others (2011) for
additional details on the methods and assumptions for this approach.

The total amount of water available for discharge by both springs and pumping
during extreme drought conditions (11.7 cubic feet per second or 8,470 acre-feetper year) was estimated using information from the 1950’s drought of record as
described in Hunt and (2011).

The water balance approach does not contain information about the spatial
distribution of pumping. For the purposes of regional water planning, theestimated total pumping available during extreme drought conditions was
divided by county, regional water planning area, river basin, and groundwater
conservation district based on the distribution of pumping in the modeled
approach under average recharge conditions (Hutchison and Oliver, 2011).

For average recharge conditions, we used the numerical groundwater flow
model that was recalibrated to include the 1950s drought for the Barton Springs
segment of the Edwards (Balcones Fault Zone) Aquifer. See Hutchison and Hill
(2011a) for assumptions and limitations of the numerical flow model.

1 The desired future conditions statement adopted by the district representatives in GMA 10 uses the term

“extreme drought conditions” to include the drought of record.
78

•

•

•

The model does not cover the Edwards Aquifer (Balcones Fault Zone) in thesouthernmost Barton Springs/Edwards Aquifer Conservation Districtjurisdiction (see Figure 4). However, given that, during average recharge
conditions, the contributing zone for the flow at Barton Springs does not extend
this far south, we deemed the use of the model appropriate for this purpose.

Similar to GAM Run 09-019 (Hutchison and Hill, 2011b), the simulations
consisted of 342 7-year simulations extending from 1648 through 1995 basedon a tree-ring dataset from Cleaveland (2006). Each 7-year simulation consistedof 84 monthly stress periods.

Model simulations indicated that, during average recharge conditions, anaverage springflow of 49.7 cubic feet per second could be maintained byallowing 11,557 acre-feet per year pumping.

KINNEY COUNTY•••

All parameters and assumptions for the freshwater portion of the Edwards(Balcones Fault Zone) Aquifer in the western subdivision of Groundwater
Management Area 10 (Kinney County) are described in GAM Run 12-002 MAG(Shi, 2012). We used a 50-year planning period from 2010 to 2060.

We used version 1.01 of the numerical groundwater flow model of the Kinney
County Area. See Hutchison and others (2011) for assumptions and limitationsof the numerical groundwater flow model. The model was run with MODFLOW2000 (Harbaugh and others, 2000).

The model has four layers: layer 1 represents the Carrizo-Wilcox and associatedaquifers, layer 2 represents the upper Cretaceous formations that yield
groundwater, layer 3 represents the Edwards (Balcones Fault Zone) Aquifer andthe Edwards Group of the Edward-Trinity (Plateau) Aquifer, and layer 4
represents the Trinity Aquifer.

Saline Edwards (Balcones Fault Zone) Aquifer•

A detailed description of all parameters is available for the saline portion of the
Edwards (Balcones Fault Zone) Aquifer in the northern subdivision of
Groundwater Management Area 10 in AA 10-35 MAG (Bradley, 2011). Table 1
from Barton Springs/Edwards Aquifer Conservation District Technical Memo2017-1221 (Hunt, 2017) outlines the approach used to estimate modeled
available groundwater. We used a 50-year planning period from 2010 to 2060.

79

•

•
•

Map areas (Figure 5) from AA 10-35 MAG (Bradley, 2011) were used to calculate
volumes based on a storage coefficient of 7.0 X 10-4 (Hunt and others, 2010) anda desired future condition of 75 feet of drawdown. Map areas are designated asPlum Creek Conservation District only where their jurisdiction does not overlap
with the Barton Springs/Edwards Aquifer Conservation District.
A water-level decline of 75 feet is uniform across the aquifer for the 50-yearplanning period.

The aquifer is homogeneous and isotropic, lateral inflow to the aquifer is equal
to lateral outflow from the aquifer, and future pumping will not alter thisbalance.

Leona Gravel Aquifer••

A detailed description of all parameters and assumptions is available for the
Leona Gravel Aquifer in Uvalde County in AA 10-28 MAG (Bradley, 2013). We
used a 50-year planning period from 2010 to 2060.

See George (2010) for assumptions and parameters used to estimate effective
recharge. Recharge is received mainly from inflow from the Edwards Aquifer(Green and others, 2008) with additional recharge from direct precipitation. The
period 1996 to 2011 was selected for analysis of J-27 water levels due to thestart of mandated management of the Edwards Aquifer in 1996.

Trinity Aquifer••

A detailed description of all parameters and assumptions is available in AA 1006 (Thorkildsen and Backhouse, 2010b). We used a 50-year planning period
from 2010 to 2060.

The methods and assumptions used to estimate modeled available groundwater
for the Trinity Aquifer remain unchanged from AA 10-06 (Thorkildsen andBackhouse, 2010b). Because the Groundwater Management Area 10 boundary
was adjusted since the last round of joint planning, this required areapportionment of the modeled available groundwater as estimated in theoriginal aquifer assessment. First, changes were made to the Groundwater
Management Area 10 boundary to exclude the Guadalupe County, Hays Trinity,and Trinity Glen Rose groundwater conservation districts. There were alsochanges in to the Barton Springs/Edwards Aquifer Conservation District
boundary to include a portion of the Trinity Aquifer in Hays County.

80

•

•

•

•

•

•
•

Bexar County is excluded from the modeled available groundwater calculations
because the groundwater management area designated the Trinity Aquifer in
Bexar County not relevant for joint planning.

Outcrop areas are calculated as unconfined areas of the aquifer and subcrop
areas are calculated as confined areas of the aquifer. Map areas 1-10 represent
outcrop areas, and map areas 11-31 are subcrop areas (see Figure 8 and Table
7).

Recharge is assigned only to the outcrop areas. The average annual precipitationfor outcrop map areas was determined from the Texas Climatic Atlas(Narasimhan and others, 2008), which is the average for years 1971 to 2000; thevalues range from 29 to 36 inches per year. The effective recharge rate isestimated to be 4 percent. The effective recharge calculation is the map area, inacres, multiplied by the estimated average annual precipitation, in feet, and theeffective recharge rate, in percent.
Lateral inflow to the Trinity Aquifer in Groundwater Management Area 10 isestimated to be 46,018 acre-feet per year based on the average outflow acrossthe Balcones Fault Zone results (Scenario 6) from GAM Task 10-005 (Hutchison,2010). This volume was apportioned across each county by aquifer map areas.
GAM Task 10-005 does not include inflows to Uvalde County, so a proportionalamount based on inflow to Medina County was used to estimate the inflow to
Uvalde County.

The storage coefficient for the Trinity Aquifer subcrop is assumed to be 1 X 10-5
derived from aquifer tests of the Trinity Aquifer subcrop in Travis and Hays
counties (Hunt and others, 2010). The storage coefficient for the Trinity Aquifer
subcrop in the remaining counties is assumed to be 5 X 10-5 as derived from thecalibrated groundwater availability model for the Hill Country portion of the
Trinity Aquifer system in Texas (Jones and others, 2009). The average specificyield of the Trinity Aquifer outcrop is estimated to be 5 X 10-2 (Ashworth, 1983).
Water-level drawdowns are uniform across the aquifer. Annual volumes fromdrawdowns are calculated by dividing the total volume by 50 years.

Modeled available groundwater estimates are the sum of the effective recharge,
lateral inflow, and volume from water-level decline.

81

RESULTS:
Tables 1 through 6 and 8 through 9 show the combination of modeled available
groundwater summarized (1) by groundwater conservation district and county; and (2) bycounty, river basin, and regional water planning area for use in the regional water planning
process. The modeled available groundwater results for the groundwater conservation
districts (Tables 1, 3, 5, and 8), reflect the ending year discussed in the Parameters andAssumption Section of this report. For purposes of planning (Tables 2, 4, 6, and 9), thevalues may have been populated past the dates noted in Parameters and Assumption
Section using the trend of results.

The modeled available groundwater estimates are 2,935 acre-feet per year in the Austin
Chalk Aquifer (Uvalde County); 758 acre-feet per year in the Buda Limestone Aquifer(Uvalde County); 11,557 acre-feet per year in the Barton Springs segment of the Edwards(Balcones Fault Zone) Aquifer during average recharge conditions (3,765 acre-feet per year
during drought conditions); 8,564 acre-feet per year in the saline portion of the Barton
Springs segment of the Edwards (Balcones Fault Zone) Aquifer; 6,321 acre-feet per year in
the freshwater portion of the western part of the San Antonio segment of the Edwards(Balcones Fault Zone) Aquifer; 9,385 acre-feet per year in the Leona Gravel Aquifer (Uvalde
County); and 46,481 acre-feet per year in the Trinity Aquifer.

82

FIGURE 1.

MAP SHOWING REGIONAL WATER PLANNING AREAS (RWPAS), GROUNDWATERCONSERVATION DISTRICTS (GCDS), AND COUNTIES IN THE VICINITY OF THE AUSTINCHALK AQUIFER IN UVALDE COUNTY.

83

FIGURE 2.

MAP SHOWING REGIONAL WATER PLANNING AREAS (RWPAS), GROUNDWATERCONSERVATION DISTRICTS (GCDS), AND COUNTIES IN THE VICINITY OF THE BUDA
LIMESTONE AQUIFER IN UVALDE COUNTY.

84

FIGURE 3.

MAP SHOWING REGIONAL WATER PLANNING AREAS (RWPAS), GROUNDWATERCONSERVATION DISTRICTS (GCDS), AND COUNTIES IN THE VICINITY OF THE
FRESHWATER AND SALINE EDWARDS (BALCONES FAULT ZONE) AQUIFER IN THE
NORTHERN SUBDIVISION OF GROUNDWATER MANAGEMENT AREA 10.

85

FIGURE 4.

MAP SHOWING GROUNDWATER AVAILABILITY MODEL EXTENT, EDWARDS(BALCONES FAULT ZONE) AQUIFER, AND ADMINISTRATIVE BOUNDARIES IN THE
NORTHERN PART OF THE BARTON SPRINGS/EDWARDS AQUIFER CONSERVATION
DISTRICT IN THE NORTHERN SUBDIVISION OF GROUNDWATER MANAGEMENT AREA
10.

86

FIGURE 5.

MAP SHOWING AREAS USED FOR ESTIMATING THE SALINE, EDWARDS (BALCONESFAULT ZONE) AQUIFER, MODELED AVAILABLE GROUNDWATER IN THE NORTHERNSUBDIVISION OF GROUNDWATER MANAGEMENT AREA 10, (MODIFIED FROMBRADLEY,2011) .

87

FIGURE 6.

MAP SHOWING REGIONAL WATER PLANNING AREAS (RWPAS), GROUNDWATERCONSERVATION DISTRICTS (GCDS), AND COUNTIES IN THE VICINITY OF THE
FRESHWATER EDWARDS (BALCONES FAULT ZONE) AQUIFER IN THE WESTERNSUBDIVISION OF GROUNDWATER MANAGEMENT AREA 10 (KINNEY COUNTY).

88

FIGURE 7.

MAP SHOWING REGIONAL WATER PLANNING AREAS (RWPAS), GROUNDWATERCONSERVATION DISTRICTS (GCDS, UWCDS), AND COUNTIES IN THE VICINITY OF THE
LEONA GRAVEL AQUIFER IN GROUNDWATER MANAGEMENT AREA 10 (UVALDECOUNTY).

89

FIGURE 8

MAP SHOWING REGIONAL WATER PLANNING AREAS (RWPAS), GROUNDWATER CONSERVATION DISTRICTS (GCDS), AND
COUNTIES IN THE VICINITY OF THE TRINITY AQUIFER IN GROUNDWATER MANAGEMENT AREA 10.

90

TABLE 1.

MODELED AVAILABLE GROUNDWATER FOR THE AUSTIN CHALK, BUDA LIMESTONE, AND LEONA GRAVEL AQUIFERS INUVALDE COUNTY IN GROUNDWATER MANAGEMENT AREA 10 FOR EACH DECADE BETWEEN 2010 AND 2060. VALUES ARE IN
ACRE-FEET PER YEAR.
Groundwater Conservation District

Uvalde County Underground Water Conservation District

CountyUvaldeTotal

TABLE 2.

CountyUvaldeAquifer

2010

2020

2030

2040

2050

2060

Austin Chalk

2,935

2,935

2,935

2,935

2,935

2,935

Leona Gravel

9,385

9,385

9,385

9,385

9,385

9,385

Buda Limestone758

16,013758

16,013758

16,013758

16,013758

758

16,01316,013

MODELED AVAILABLE GROUNDWATER FOR THE AUSTIN CHALK, BUDA LIMESTONE, AND LEONA GRAVEL AQUIFERS INUVALDE COUNTY IN GROUNDWATER MANAGEMENT AREA 10 SUMMARIZED BY COUNTY, REGIONAL WATER PLANNING AREA
(RWPA), AND RIVER BASIN FOR EACH DECADE BETWEEN 2020 AND 2070. VALUES ARE IN ACRE-FEET PER YEAR.
RWPA
L
Total

River Basin
NuecesAquifer

2020

2030

2040

2050

2060

2070

Austin Chalk

2,935

2,935

2,935

2,935

2,935

2,935

Leona Gravel

9,385

9,385

9,385

9,385

9,385

9,385

Buda Limestone

758

758

16,01316,01391758

16,013758

16,013758

16,013758

16,013

TABLE 3.

MODELED AVAILABLE GROUNDWATER FOR THE FRESHWATER PORTION OF THE EDWARDS (BALCONES FAULT ZONE)AQUIFER IN GROUNDWATER MANAGEMENT AREA 10 SUMMARIZED BY GROUNDWATER CONSERVATION DISTRICT (GCD)
AND COUNTY FOR EACH DECADE BETWEEN 2010 AND 2060. VALUES ARE IN ACRE-FEET PER YEAR.

Recharge
Condition

AverageGroundwater
Conservation District
Barton Springs/Edwards
Aquifer Conservation
District

County

2040

2050

2060

7,950

7,950

7,950

7,950

7,950

Travis

3,578

3,578

3,578

3,578

3,578

3,578

Hays

29

29

29

29

29

29

11,557

11,557

11,557

11,557

11,557

11,557

Hays

2,590

2,590

2,590

2,590

2,590

2,590

Travis

1,166

1,166

1,166

1,166

1,166

1,166

Hays

9

9

9

9

9

9

3,765

3,765

3,765

3,765

3,765

3,765

6,321

6,321

6,321

6,321

6,321

6,321

Non-District Areas
Total for drought recharge conditions
Kinney County Groundwater Conservation
District

2030

7,950

Total for average recharge conditions

Drought

2020

Hays

Non-District Areas

Barton Springs/Edwards
Aquifer Conservation
District2010

Kinney92

TABLE 4.

Recharge Condition

Average

MODELED AVAILABLE GROUNDWATER FOR THE FRESHWATER PORTION OF THE EDWARDS (BALCONES FAULT ZONE)AQUIFER IN GROUNDWATER MANAGEMENT AREA 10 SUMMARIZED BY COUNTY, REGIONAL WATER PLANNING AREA (RWPA),
AND RIVER BASIN FOR EACH DECADE BETWEEN 2020 AND 2070. VALUES ARE IN ACRE-FEET PER YEAR.
CountyRWPA

River Basin

Hays

K

Colorado

7,037

7,037

7,037

7,037

7,037

7,037

TravisK

Colorado

3,578

11,557

3,578

11,557

3,578

11,557

3,578

11,557

3,578

11,557

3,578

11,557

Hays

K

Colorado

2,292

2,292

2,292

2,292

2,292

2,292

TravisK

Colorado

Total for drought recharge conditions

1,166

3,765

1,166

3,765

1,166

3,765

1,166

3,765

1,166

3,765

1,166

3,765

KinneyJ

Nueces

6,319

6,319

6,319

6,319

6,319

6,319

Hays

L

Guadalupe

Total for average recharge conditions

Drought

Not applicable

Hays

L

2020

2030

942

Guadalupe307

Rio Grande

2

93

2040

942

307

2

2050

942

307

2

2060

942

307

2

2070

942

307

2

942

307

2

TABLE 5.

MODELED AVAILABLE GROUNDWATER FOR THE SALINE PORTION OF THE EDWARDS (BALCONES FAULT ZONE) AQUIFER INGROUNDWATER MANAGEMENT AREA 10 SUMMARIZED BY GROUNDWATER CONSERVATION DISTRICT (GCD) AND COUNTYFOR EACH DECADE BETWEEN 2010 AND 2060. VALUES ARE IN ACRE-FEET PER YEAR.
Groundwater
Conservation District
BartonSprings/Edwards
Aquifer Conservation
Non-District Areas

Plum Creek
Conservation District
TABLE 6.

Total

County

2010

2020

2030

2040

2050

2060

Caldwell
Hays
TravisCaldwellTravisCaldwell

858
1,171
1,770
369
3,583
210

858
1,171
1,770
369
3,583
210

858
1,171
1,770
369
3,583
210

858
1,171
1,770
369
3,583
210

858
1,171
1,770
369
3,583
210

858
1,171
1,770
369
3,583
210

Hays

602

8,563

602

8,563

602

8,563

602

8,563

602

8,563

602

8,563

MODELED AVAILABLE GROUNDWATER FOR THE SALINE PORTION OF THE EDWARDS (BALCONES FAULT ZONE) AQUIFER INGROUNDWATER MANAGEMENT AREA 10 SUMMARIZED BY COUNTY, REGIONAL WATER PLANNING AREA (RWPA), AND RIVER
BASIN FOR EACH DECADE BETWEEN 2020 AND 2070. VALUES ARE IN ACRE-FEET PER YEARCountyCaldwell
Hays
Travis

RWPA
L

K
L

K

Total

River Basin

2020

2030

2040

2050

2060

2070

Colorado

469

469

469

469

469

469

Guadalupe

1,707

1,707

1,707

1,707

1,707

1,707

Guadalupe

280

280

280

280

280

280

Guadalupe
Colorado
Colorado

968
66

5,073
8,563

94

968
66

5,073
8,563

968
66

5,073
8,563

968
66

5,073
8,563

968
66

5,073
8,563

968
66

5,073
8,563

TABLE 7.

INPUTS TO CALULATE MODELED AVAILABLE GROUNDWATER FOR THE TRINITY AQUIFER INGROUNDWATER MANAGEMENT AREA 10, SUMMARIZED BY MAP AREA REPRESENTING EACHGROUNDWATER CONSERVATION DISTRICT (GCD), COUNTY, RIVER BASIN, AND REGIONAL WATERPLANNING AREA (RWPA) COMBINATIONS. AREA VALUES ARE IN ACRES, AND OTHER VALUES ARE IN
ACRE-FEET PER YEAR.

ArealextentEstimatedannualeffective
recharge

Estimatedannuallateralinflow

Estimatedannualvolumefromwaterlevel
declineModeledavailable
groundwater

Map
area1,2,3

GCD

County

River
Basin

RWPG

1

UvaldeCountyUWCDUvaldeNueces

L

372

36

4

0

40

L

N/A

N/A

N/A

N/A

N/A

L

1,282

149

318

32

499

2
3
4
5
6

7

8
9
10
11
12

Medina GCD
No GCD

Comal Trinity
GCD
Comal Trinity
GCD
BartonSprings/
Edwards
Aquifer
Conservation
District
BartonSprings/
Edwards
Aquifer
Conservation
District
BartonSprings/
Edwards
Aquifer
Conservation
DistrictSouthwestern
TravisCounty GCD
UvaldeCountyUWCDMedina GCD
Medina GCD

Medina
Bexar

Comal

San
AntonioSan
AntonioSan
Antonio

L
L

1

594

0

67

0

147

0

15

0

229

Comal

Guadalupe

Hays

Guadalupe

L

505

61

13

13

87

Hays

Colorado

K

494

57

12

12

81

TravisColorado

K

3

0

0

0

0

TravisColorado

K

11

1

0

0

1

UvaldeNuecesL

63,464

N/A

755

0

755

MedinaMedinaNuecesSan
AntonioLL

459,975

98,983N/A

N/A

1. Map areas 1-10 represent outcrop areas and were assumed to be under unconfined aquifer conditions.

2. Map areas 11-31 represent subcrop areas and were assumed to be under confined aquifer conditions.

5,470

1,177

12
2

3. Map areas 24-26 cover the Barton Springs/Edwards Aquifer Conservation District and Plum Creek Conservation District where the two districts overlap.
These values are assigned to the Barton Springs/Edwards Aquifer Conservation District.
95

5,482

1,179

Map
area1,2,3

GCD

County13

No GCD

Bexar

14
15
16
17
18
19
20

21

22
23

Comal
Trinity GCD
No GCD

No GCD
Comal
Trinity GCD
BartonSprings/
Edwards
Aquifer
Conservation
District
No GCD
BartonSprings/
Edwards
Aquifer
Conservation
District
BartonSprings/
Edwards
Aquifer
Conservation
District
BartonSprings/
Edwards
Aquifer
Conservation
District
Plum Creek
CD

River
basin

RWPG

472

0

N/A

L

104,045

N/A

CaldwellGuadalupe

L

420

Hays

ColoradoK

Hays

Guadalupe

Hays
Hays

Guadalupe

N/A

1,907

Guadalupe

Comal

N/A

N/A

Hays

Guadalupe

N/A

N/A

Guadalupe

Comal

Modeledavailable
groundwater

Areal
extentEstimatedannuallateralinflow

San
AntonioSan
AntonioSan
Antonio
GuadalupeL

Estimatedannualvolumefromwaterlevel
declineEstimatedannualeffective
recharge

L

9,243

N/A

2,290

L
L

757

123,232

N/A

N/A

188

30,533

L

0

2,290

0

188

472

3

30,536

2,597

3

2,600

N/A

10

0

10

36,033

N/A

899

0

899

K

354

N/A

9

0

9

Colorado

L

1,286

N/A

32

0

32

Guadalupe

L

9,934

N/A

248

0

248

1. Map areas 1-10 represent outcrop areas and were assumed to be under unconfined aquifer conditions.

2. Map areas 11-31 represent subcrop areas and were assumed to be under confined aquifer conditions.

3. Map areas 24-26 cover the Barton Springs/Edwards Aquifer Conservation District and Plum Creek Conservation District where the two districts overlap.
These values are assigned to the Barton Springs/Edwards Aquifer Conservation District.

96

Map
area1,2,3

24

25

26
27
28
29

30
31

GCD

BartonSprings/
Edwards
Aquifer
Conservation
District3
BartonSprings/
Edwards
Aquifer
Conservation
District3
BartonSprings/
Edwards
Aquifer
Conservation
District3
Plum Creek
CD
Southwestern
Travis County
GCD
BartonSprings/
Edwards
Aquifer
Conservation
District
BartonSprings/
Edwards
Aquifer
Conservation
District
No GCD

Areal
extentEstimatedannualeffective
recharge

Estimatedannuallateralinflow

Estimatedannualvolumefromwaterlevel
declineModeledavailable
groundwaterCounty

River
basin

RWPG

Hays

Guadalupe

K

17

N/A

0

0

0

Hays

Colorado

K

1

N/A

0

0

0

Hays

Guadalupe

L

5,864

N/A

146

0

146

Hays

Guadalupe
Colorado

L

K

1,108

N/A

28

0

28

TravisColoradoK55,223

N/A

339

0

339

TravisGuadalupe

K

396

N/A

2

0

2

TravisColoradoK53,547

N/A

329

0

329

Travis18

N/A

1. Map areas 1-10 represent outcrop areas and were assumed to be under unconfined aquifer conditions.

2. Map areas 11-31 represent subcrop areas and were assumed to be under confined aquifer conditions.

0

0

0

3. Map areas 24-26 cover the Barton Springs/Edwards Aquifer Conservation District and Plum Creek Conservation District where the two districts overlap.
These values are assigned to the Barton Springs/Edwards Aquifer Conservation District.

97

TABLE 8.

MODELED AVAILABLE GROUNDWATER FOR THE TRINITY AQUIFER IN GROUNDWATER MANAGEMENTAREA 10 SUMMARIZED BY GROUNDWATER CONSERVATION DISTRICT (GCD) AND COUNTY FOR EACH
DECADE BETWEEN 2010 AND 2060. VALUES ARE IN ACRE-FEET PER YEAR.
Groundwater Conservation
District
Barton Springs/ Edwards
Aquifer Conservation District
Comal Trinity GCD
Medina County GCD
Non-District Areas

2010

2020

2030

2040

2050

2060

Hays
TravisComal
MedinaCaldwellGuadalupe

3,854
341
33,554
6,661
10

3,854
341
33,554
6,661
10

3,854
341
33,554
6,661
10

3,854
341
33,554
6,661
10

3,854
341
33,554
6,661
10

3,854
341
33,554
6,661
10

Hays

276

276

276

276

276

276

TravisPlum Creek
Conservation District
Southwestern Travis
County GCD
Uvalde County UWCD
Total
TABLE 9.

CountyTravisUvalde

660
329

1
795
46,481

660
329

1
795
46,481

660
329

1
795
46,481

660
329

1
795
46,481

660
329

1
795
46,481

660
329

1
795
46,481

MODELED AVAILABLE GROUNDWATER FOR THE TRINITY AQUIFER IN GROUNDWATER MANAGEMENTAREA 10 SUMMARIZED BY COUNTY, REGIONAL WATER PLANNING AREA (RWPA), AND RIVER BASIN
FOR EACH DECADE BETWEEN 2020 AND 2070. VALUES ARE IN ACRE-FEET PER YEAR.
CountyRWPA

River Basin

2020

2030

2040

2050

2060

2070

CaldwellL

GuadalupeL

Guadalupe
Guadalupe
San Antonio
Guadalupe
San Antonio
Colorado

10
31,035
2,519
188
472
980

10
31,035
2,519
188
472
980

10
31,035
2,519
188
472
980

10
31,035
2,519
188
472
980

10
31,035
2,519
188
472
980

10
31,035
2,519
188
472
980

Guadalupe
Nueces

2
795

2
795

2
795

2
795

2
795

2
795

Comal

Hays
MedinaTravisUvalde

L

K
L
L

K
L

Guadalupe
Colorado
Guadalupe
NuecesSan Antonio
Colorado

9
32
3,109
5,482
1,179
669

98

9
32
3,109
5,482
1,179
669

9
32
3,109
5,482
1,179
669

9
32
3,109
5,482
1,179
669

9
32
3,109
5,482
1,179
669

9
32
3,109
5,482
1,179
669

LIMITATIONS:
The groundwater model used in completing this analysis is the best available scientific toolthat can be used to meet the stated objectives. To the extent that this analysis will be used
for planning purposes and/or regulatory purposes related to pumping in the past and into
the future, it is important to recognize the assumptions and limitations associated with theuse of the results. In reviewing the use of models in environmental regulatory decision
making, the National Research Council (2007) noted:“Models will always be constrained by computational limitations, assumptions, andknowledge gaps. They can best be viewed as tools to help inform decisions rather
than as machines to generate truth or make decisions. Scientific advances will
never make it possible to build a perfect model that accounts for every aspect ofreality or to prove that a given model is correct in all respects for a particularregulatory application. These characteristics make evaluation of a regulatorymodel more complex than solely a comparison of measurement data with model
results.”

A key aspect of using the groundwater model to evaluate historical groundwater flow
conditions includes the assumptions about the location in the aquifer where historical
pumping was placed. Understanding the amount and location of historical pumping is as
important as evaluating the volume of groundwater flow into and out of the district,between aquifers within the district (as applicable), interactions with surface water (asapplicable), recharge to the aquifer system (as applicable), and other metrics that describe
the impacts of that pumping. In addition, assumptions regarding precipitation, recharge,
and streamflow are specific to a particular historical time period.

Because the application of the groundwater model was designed to address regional scalequestions, the results are most effective on a regional scale. The TWDB makes nowarranties or representations relating to the actual conditions of any aquifer at a particularlocation or at a particular time.
It is important for groundwater conservation districts to monitor groundwater pumping
and groundwater levels in the aquifer. Because of the limitations of the groundwater modeland the assumptions in this analysis, it is important that the groundwater conservation
districts work with the TWDB to refine this analysis in the future given the reality of how
the aquifer responds to the actual amount and location of pumping now and in the future.
Historical precipitation patterns also need to be placed in context as future climaticconditions, such as dry and wet year precipitation patterns, may differ and affectgroundwater flow conditions.

99

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Bradley, R. G., 2013, Aquifer Assessment 10-28 MAG: Aquifer Assessment for the Leona
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100

Hunt, B.B., Smith, B.A., Kromann, J.,Wierman, D.A., and Mikels, J.K., 2010, Compilation ofpumping tests in Travis and Hays counties, central Texas: Barton Springs/Edwards
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Estimate Monthly Average Discharge from Barton Springs under Alternative
Pumping Scenarios and Alternative Initial Conditions, June 1, 2011, 29 p.

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Management Area 10 Model Runs to Estimate Springflow Under Assumed Future
Pumping and Recharge Conditions for the Northern Subdivision of the Edwards(Balcones Fault Zone) Aquifer, Texas Water Development Board, 17.p.
http://www.twdb.texas.gov/groundwater/docs/GAMruns/GR10-059_MAG_v2.pdf

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Country portion of the Trinity Aquifer system, Texas, Texas Water Development
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Narasimhan, B., Srinvasan, R., Quiring, S., and Nielsen-Gammon, J.W., 2008, Digital Climatic
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101

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102

APPENDIX CGAM RUN 12-001: PLUM CREEK CONSERVATION
DISTRICT MANAGEMENT PLAN
by William Kohlrenken
Texas Water Development Board
Groundwater Resources Division
Groundwater Availability Modeling Section(512) 463-8279
July 2, 2012

Cynthia K. Ridgeway is the Manager of the Groundwater Availability Modeling Section and is
responsible for oversight of work performed by William Kohlrenken under her direct supervision. The
seal appearing on this document was authorized by Cynthia K. Ridgeway, P.G. 471 on July 2, 2012.

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GAM RUN 12-001: PLUM CREEK CONSERVATION
DISTRICT MANAGEMENT PLAN
by William Kohlrenken
Texas Water Development Board
Groundwater Resources Division
Groundwater Availability Modeling Section(512) 463-8279
July 2, 2012EXECUTIVE SUMMARY:
Texas State Water Code, Section 36.1071, Subsection (h), states that, in developing
its groundwater management plan, a groundwater conservation district shall use
groundwater availability modeling information provided by the executive
administrator of the Texas Water Development Board (TWDB) together with any
available site-specific information provided by the district for review and comment to
the executive administrator. Information derived from groundwater availability
models that shall be included in the groundwater management plan includes:•

the annual amount of recharge from precipitation to the groundwater
resources within the district, if any;•for each aquifer within the district, the annual volume of water thatdischarges from the aquifer to springs and any surface water bodies,including lakes, streams, and rivers; and•the annual volume of flow into and out of the district within each aquiferand between aquifers in the district.

The purpose of this report is to provide Part 2 of a two-part package of informationfrom the TWDB to Plum Creek Conservation District management plan to fulfill therequirements noted above. The groundwater management plan for Plum Creek
Conservation District is due for approval by the executive administrator of the TWDB
before January 29, 2013.

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This report discusses the method, assumptions, and results from model runs using the
groundwater availability model for the southern portions of the Carrizo-Wilcox, Queen
City, and Sparta aquifers. Tables 1 and 2 summarize the groundwater availability
model data required by the statute, and Figures 1 and 2 show the area of the modelfrom which the values in the tables were extracted. This model run replaces theresults of GAM Run 06-18. GAM Run 12-001 meets current standards set after the
release of GAM Run 06-18 and it is based on the most current groundwater district
boundaries. If after review of the figures, Plum Creek Conservation District
determines that the district boundaries used in the assessment do not reflect current
conditions, please notify the TWDB immediately.

METHODS:
The groundwater availability model for the southern portion of the Carrizo-Wilcox,
Queen City, and Sparta aquifers was run for this analysis. Water budgets for each yearof 1980 through 1999 were extracted and the average annual water budget values forrecharge, 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 theaquifers located within the district are summarized in this report.

PARAMETERS AND ASSUMPTIONS:Carrizo-Wilcox and Queen City Aquifers•

Version 2.01 of the groundwater availability model for the southern part of
the Carrizo-Wilcox, Queen City, and Sparta aquifers was used for thisanalysis. See Deeds and others (2003) and Kelley and others (2004) forassumptions and limitations of the groundwater availability model for thesouthern part of the Carrizo-Wilcox, Queen City, and Sparta aquifers.

•

This groundwater availability model includes eight layers, which generally
correspond to (from top to bottom):
1. the Sparta Aquifer,
2. the Weches Confining Unit,
3. the Queen City Aquifer,
4. the Reklaw Confining Unit,
5. the Carrizo Aquifer,106

6. the Upper Wilcox Aquifer,
7. the Middle Wilcox Aquifer, and8. the Lower Wilcox Aquifer.
•

Of the eight layers listed above, individual water budgets for the district
were determined for the Queen City Aquifer (Layer 3), and the combined
layers of the Carrizo-Wilcox Aquifer (Layers 5 through 8). Budget terms
were not determined for the Sparta Aquifer because it is not present in the
Plum Creek Conservation District.

•

The root mean square error (a measure of the difference between simulated
and actual water levels during model calibration) in the groundwater
availability model is 23 feet for the Sparta Aquifer, 18 feet for the Queen
City Aquifer, and 33 feet for the Carrizo Aquifer for the calibration period(1980 to 1990) and 19, 22, and 48 feet for the same aquifers, respectively,in the verification period (1991 to 1999) (Kelley and others, 2004). Theseroot mean square errors are between seven and ten percent of the range ofmeasured water levels (Kelley and others, 2004).

•

Groundwater in the Carrizo-Wilcox, Queen City, and Sparta aquifers ranges
from fresh to brackish in composition (Kelley and others, 2004).
Groundwater with total dissolved solids concentrations of less than 1,000
milligrams per liter (mg/l) are considered fresh and total dissolved solids
concentrations of 1,000 to 10,000 mg/l are considered brackish.

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RESULTS:
A groundwater budget summarizes the amount of water entering and leaving theaquifer according to the groundwater availability model. Selected groundwater
budget components listed below were extracted from the model results for theaquifers located within the district and averaged over the duration of the calibrationand verification portion of the model runs in the district, as shown in Tables 1 and 2.
The components of the modified budget shown in Tables 1 and 2 include:•

Precipitation recharge—The areally distributed recharge sourced fromprecipitation falling on the outcrop areas of the aquifers (where the aquifer
is exposed at land surface) within the district.

•Surface water outflow—The total water discharging from the aquifer(outflow) to surface water features such as streams, reservoirs, and drains(springs).

•

Flow into and out of district—The lateral flow within the aquifer between
the district and adjacent counties.

•

Flow between aquifers—The net vertical flow between aquifers or confining
units. This flow is controlled by the relative water levels in each aquifer or
confining unit and aquifer properties of each aquifer or confining unit thatdefine the amount of leakage that occurs. “Inflow” to an aquifer from an
overlying or underlying aquifer will always equal the “Outflow” from theother aquifer.

The information needed for the District’s management plan is summarized in Tables 1
and 2. It is important to note that sub-regional water budgets are not exact. This isdue to the size of the model cells and the approach used to extract data from themodel. To avoid double accounting, a model cell that straddles a political boundary,such as a district or county boundary, is assigned to one side of the boundary based on
the location of the centroid of the model cell. For example, if a cell contains twocounties, the cell is assigned to the county where the centroid of the cell is located(Figures 1 and 2).

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TABLE 1: SUMMARIZED INFORMATION FOR THE QUEEN CITY AQUIFER THAT IS NEEDED FOR PLUMCREEK CONSERVATION DISTRICT’S GROUNDWATER MANAGEMENT PLAN. ALL VALUES AREREPORTED IN ACRE-FEET PER YEAR AND ROUNDED TO THE NEAREST 1 ACRE-FOOT. THESE
FLOWS INCLUDE BRACKISH WATERS.

Management Plan requirement

Aquifer or confining unit

Results

Estimated annual amount of recharge fromprecipitation to the district

Queen City Aquifer

119

Estimated annual volume of water that discharges
from the aquifer to springs and any surface water
body including lakes, streams, and rivers

Queen City Aquifer

41

Estimated annual volume of flow into the district
within each aquifer in the district

Queen City Aquifer

66

Estimated annual volume of flow out of the district
within each aquifer in the district

Queen City Aquifer

159

Estimated net annual volume of flow between
each aquifer in the district

From Queen City Aquifer into
the underlying Reklaw
Formation confining unit

10

109

FIGURE 1: AREA OF THE GROUNDWATER AVAILABILITY MODEL FOR THE SOUTHERN PORTION OF THE
CARRIZO -WILCOX, QUEEN CITY, AND SPARTA AQUIFERS FROM WHICH THE INFORMATIONIN TABLE 1 WAS EXTRACTED (THE AQUIFER EXTENT OF THE QUEEN CITY AQUIFER WITHINTHE DISTRICT BOUNDARY).

110

TABLE 2: SUMMARIZED INFORMATION FOR THE CARRIZO-WILCOX AQUIFER THAT IS NEEDED FOR
PLUM CREEK CONSERVATION DISTRICT’S GROUNDWATER MANAGEMENT PLAN. ALL
VALUES ARE REPORTED IN ACRE-FEET PER YEAR AND ROUNDED TO THE NEAREST 1 ACREFOOT. THESE FLOWS MAY INCLUDE FRESH AND BRACKISH WATERS.

Management Plan requirement

Aquifer or confining unit

Results

Estimated annual amount of recharge fromprecipitation to the district

Carrizo-Wilcox Aquifer

5,743

Estimated annual volume of water that discharges
from the aquifer to springs and any surface water
body including lakes, streams, and rivers

Carrizo-Wilcox Aquifer

6,847

Estimated annual volume of flow into the district
within each aquifer in the district

Carrizo-Wilcox Aquifer

4,043

Estimated annual volume of flow out of the district
within each aquifer in the district

Carrizo-Wilcox Aquifer

3,616

Estimated net annual volume of flow between
each aquifer in the district

From the Reklaw Formation
confining unit into the CarrizoWilcox Aquifer

58

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FIGURE 2: AREA OF THE GROUNDWATER AVAILABILITY MODEL FOR THE SOUTHERN PORTION OF THE
CARRIZO-WILCOX, QUEEN CITY, AND SPARTA AQUIFERS FROM WHICH THE INFORMATIONIN TABLE 2 WAS EXTRACTED (THE AQUIFER EXTENT OF THE CARRIZO-WILCOX AQUIFER
WITHIN THE DISTRICT BOUNDARY).

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LIMITATIONS
The groundwater model(s) used in completing this analysis is the best available
scientific tool that can be used to meet the stated objective(s). To the extent that
this analysis will be used for planning purposes and/or regulatory purposes related topumping in the past and into the future, it is important to recognize the assumptions
and limitations associated with the use of the results. In reviewing the use of models
in environmental regulatory decision making, the National Research Council (2007)
noted:“Models will always be constrained by computational limitations, assumptions,and knowledge gaps. They can best be viewed as tools to help inform decisions
rather than as machines to generate truth or make decisions. Scientificadvances will never make it possible to build a perfect model that accounts
for every aspect of reality or to prove that a given model is correct in all
respects for a particular regulatory application. These characteristics makeevaluation of a regulatory model more complex than solely a comparison of
measurement data with model results.”
A key aspect of using the groundwater model to evaluate historic groundwater flow
conditions includes the assumptions about the location in the aquifer where historic
pumping was placed. Understanding the amount and location of historic pumping is as
important as evaluating the volume of groundwater flow into and out of the district,between aquifers within the district (as applicable), interactions with surface water(as applicable), recharge to the aquifer system (as applicable), and other metrics that
describe the impacts of that pumping. In addition, assumptions regarding
precipitation, recharge, and interaction with streams are specific to particular
historic time periods.
Because the application of the groundwater model was designed to address regional
scale questions, the results are most effective on a regional scale. The TWDB makes
no warranties or representations related to the actual conditions of any aquifer at aparticular location or at a particular time.
It is important for groundwater conservation districts to monitor groundwater
pumping and overall conditions of the aquifer. Because of the limitations of thegroundwater model and the assumptions in this analysis, it is important that the
groundwater conservation districts work with the TWDB to refine this analysis in the
future given the reality of how the aquifer responds to the actual amount andlocation of pumping now and in the future. Historic precipitation patterns also need
to be placed in context as future climatic conditions, such as dry and wet year
precipitation patterns, may differ and affect groundwater flow conditions.

113

REFERENCES:
Deeds, N., Kelley, V., Fryar, D., Jones, T., Whallon, A.J., and Dean, K.E., 2003,
Groundwater Availability Model for the Southern Carrizo-Wilcox Aquifer:
Contract report to the Texas Water Development Board, 452 p.,
http://www.twdb.texas.gov/groundwater/models/gam/czwx_s/CZWX_S_Full_
Report.pdf.
Kelley, V.A., Deeds, N.E., Fryar, D.G., and Nicot, J.P., 2004, Groundwater availability
models for the Queen City and Sparta aquifers: Contract report to the Texas
Water Development Board, 867 p.,
http://www.twdb.texas.gov/groundwater/models/gam/qcsp/QCSP_Model_Rep
ort.pdf.
National Research Council, 2007, Models in Environmental Regulatory Decision Making
Committee on Models in the Regulatory Decision Process, National Academies
Press, Washington D.C., 287 p.
Smith, R., 2006, GAM Run 06-18: Texas Water Development Board, GAM Run 06-18
Report, 5 p., http://www.twdb.texas.gov/groundwater/docs/GAMruns/GR0618.pdf.

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