June 14, 2016

DRAFT
Proposed Desired Future Conditions Explanatory Report
Austin Chalk and Buda Limestone Aquifers
Groundwater Management Area 10

Table of Contents
Section ...................................................................................................................................... Page
APPENDICES .............................................................................................................................. iv
FIGURES ........................................................................................................................................v
TABLES ........................................................................................................................................ vi
ABBREVIATIONS .................................................................................................................... viii
1.

Groundwater Management Area 10 ................................................................................1

2.

Aquifer Description ...........................................................................................................1

3.

Desired Future Conditions ...............................................................................................2

4.

Policy Justification ............................................................................................................4

5.

Technical Justification ......................................................................................................5

6.

Consideration of Designated Factors ...............................................................................8
6.1
Aquifer Uses or Conditions ..................................................................................9
6.1.1
Description of Factors in the Austin Chalk and Buda Limestone
Aquifers in Uvalde County..................................................................9
6.1.2
DFC Considerations.............................................................................9
6.2
Water-Supply Needs ...........................................................................................10
6.2.1
Description of Factors in the Austin Chalk and Buda Limestone
Aquifers in Uvalde County................................................................10
6.2.2
DFC Considerations...........................................................................11
6.3
Water-Management Strategies ..........................................................................11
6.3.1
Description of Factors in the Austin Chalk and Buda Limestone
Aquifers in Uvalde County................................................................11
6.3.2
DFC Considerations...........................................................................13
6.4
Hydrological Conditions ....................................................................................14
6.4.1
Description of Factors in the Austin Chalk and Buda Limestone
Aquifers in Uvalde County................................................................14
6.4.1.1
Total Estimated Recoverable Storage ..............................................14
6.4.1.2
Average Annual Recharge ................................................................14
6.4.1.3
Inflows .................................................................................................15
6.4.1.4
Discharge ............................................................................................15
6.4.1.5
Other Environmental Impacts Including Springflow and
Groundwater/Surface Water Interaction ........................................16
6.4.2
DFC Considerations...........................................................................16

7.

Subsidence Impacts .........................................................................................................16

8.

Socioeconomic Impacts Reasonably Expected to Occur .............................................16
ii

8.1
8.2

Description of Factors in the Austin Chalk and Buda Limestone
Aquifers in Uvalde County..................................................................................16
DFC Considerations.............................................................................................17

9.

Private Property Impacts ...............................................................................................17
9.1
Description of Factors in the Austin Chalk and Buda Limestone
Aquifers in Uvalde County..................................................................................17
9.2
DFC Considerations.............................................................................................17

10.

Feasibility of Achieving the DFCs .................................................................................17

11.

Discussion of Other DFCs Considered ..........................................................................18

12.

Discussion of Other Recommendations .........................................................................18
12.1 Advisory Committees ..........................................................................................18
12.2 Public Comments ............................................................................................18

13.

Any Other Information Relevant to the Specific DFCs ..............................................18

14.

Provide a Balance Between the Highest Practicable Level of Groundwater
Production and the Conservation, Preservation, Protection, Recharging, andPrevention of Waste of Groundwater and Control of Subsidence in theManagement Area ............................................................................................................18

15.

References .........................................................................................................................19iii

List of Appendices
Appendix A—Proposed Desired Future Condition Resolution
Appendix B—TWDB GAM Task xxxx (Revised): Total Estimated Recoverable Storage for
Aquifers in Groundwater Management Area 10
Appendix C—Socioeconomic Impacts Analyses for Region L

iv

FIGURES
Figure ....................................................................................................................................... Page
1

GCDs in GMA 10 (Texas Water Development Board website)..........................................22

Map showing the outcrop extent of the Austin Chalk in Uvalde County in GMA 10 (fromThorkildsen and Blackhouse, 2011a) ...................................................................................33

Map showing the outcrop extent of the Buda Limestone in Uvalde County in GMA 10
Aquifers (From Thorkildsen and Blackhouse, 2011b) ........................................................4

4

Water-level measurements for selected Austin Chalk wells in Uvalde County, Texas(Thorkildsen and Backhouse (2011a) ..................................................................................7

5

Water-level measurements for a selected Buda Limestone well in Uvalde County, Texas(Thorkildsen and Backhouse (2011b) ..................................................................................8v

TABLES
Table ....................................................................................................................................... Page
1

DFCs for the Austin Chalk and Buda Limestone aquifers within Uvalde County in
GMA 10 ...............................................................................................................................3

2

Estimates of exempt use for the Austin Chalk Aquifer in the Uvalde County Underground
Water Conservation District for each decade between 2010 and 2060. Results are in acreft /yr. Estimated exempt use calculated by TWDB and accepted by the district(Thorkildsen and Backhouse, 2011a) ..................................................................................63

Estimated total pumping for the Austin Chalk Aquifer in the Uvalde County
Underground Water Conservation District for each decade between 2010 and 2060.
Results are in acre-ft /yr (Thorkildsen and Backhouse, 2011a) ...........................................6

4

Estimates of MAG for the Austin Chalk Aquifer in the Uvalde County Underground
Water Conservation District for each decade between 2010 and 2060. Results are in acreft /yr (Thorkildsen and Backhouse, 2011a)..........................................................................8

5

Estimates of exempt use for the Buda Limestone Aquifer in the Uvalde County
Underground Water Conservation District for each decade between 2010 and 2060.
Results are in acre-ft /yr. Estimated exempt use calculated by TWDB and accepted by the
district (Thorkildsen and Backhouse, 2011b .......................................................................8

6

Estimated total pumping for the Buda Limestone Aquifer in the Uvalde County
Underground Water Conservation District for each decade between 2010 and 2060.
Results are in acre-ft /yr (Thorkildsen and Backhouse, 2011b)...........................................8

7

Estimates of MAG for the Buda Limestone Aquifer in the Uvalde County Underground
Water Conservation District for each decade between 2010 and 2060. Results are in acreft /yr (Thorkildsen and Backhouse, 2011b ...........................................................................88

Use of the minor and local aquifers in Uvalde County for the years 2007–2010 (Uvalde
County Underground Water Conservation District Groundwater Management Plan)(acre-ft) ..............................................................................................................................10

9

Uvalde County use divided between surface water (SW) and groundwater (GW) amongindustry sectors (Uvalde County Underground Water Conservation District Groundwater
Management Plan) (acre-ft) ...............................................................................................10

10

Projected water-supply and demand estimates for Uvalde County in the 2012 State Water
Plan ....................................................................................................................................12

11

Source water available after known demands are subtracted (South Central Texas InitiallyPrepared Plan, 2015) (acre-ft/yr) .......................................................................................12vi12Water-use categories where no water supply is available to meet its total need. These data
are not currently available in the South Central Region Water Planning Group Plan
(South Central Region Water Planning Group, 2015) (acre-ft/yr) ....................................13

13

Water-management strategies in Uvalde County in the 2012 State Water Plan
(acre-ft/yr) ..........................................................................................................................13

14

Total estimated recoverable storage for the Austin Chalk and Buda Limestone aquifers
within Uvalde County Underground Water Conservation District in GMA 10. Estimates
are rounded within two significant numbers (Jones et al., 2013) ......................................14vii

Abbreviations
DFC

Desired Future Conditions

GCD

Groundwater Conservation District

GMA

Groundwater Management AreaMAG

Modeled Available Groundwater

TWDB

Texas Water Development Board

viii

1.

Groundwater Management Area 10

Groundwater Management Areas (GMA) were created by the Texas Legislature to provide forthe conservation, preservation, protection, recharging, and prevention of waste of thegroundwater, and of groundwater reservoirs or their subdivisions, and to control subsidence
caused by withdrawal of water from those groundwater reservoirs or their subdivisions. Each
GMA is charged with facilitating joint planning efforts in the GMAs within its jurisdiction.
GMA 10 was created to oversee the Edwards (Balcones Fault Zone) and Trinity aquifers. Other
aquifers include the Leona Gravel, Buda Limestone, Austin Chalk, and the saline Edwards(Balcones Fault Zone) aquifers. The jurisdiction of GMA 10 includes all or parts of Bexar,
Caldwell, Comal, Guadalupe, Hays, Kinney, Medina, Travis, and Uvalde counties (Figure 1).
Groundwater Conservation Districts (GCD) in GMA 10 include Barton Springs/Edwards Aquifer
Conservation District, Comal Trinity GCD, Edwards Aquifer Authority, Kinney County GCD,
Medina County GCD, Plum Creek Conservation District, and Uvalde County Underground
Water Conservation District (UWCD).
As mandated in Texas Water Code § 36.108, districts are required to submit DFCs of thegroundwater resources in their GMA to the executive administrator of the Texas Water
Development Board (TWDB), unless that aquifer is deemed to be non-relevant. According toTexas Water Code § 36.108 (d-3), the district representatives shall produce a DFCs Explanatory
Report for the management area and submit to the TWDB a copy of the Explanatory Report.
The Austin Chalk and Buda Limestone aquifers are neither major nor minor aquifers, but havebeen determined to be locally relevant in Uvalde County for joint planning purposes. The Austin
Chalk and Buda Limestone aquifers have been determined to be non-relevant in Medina County
for joint planning purposes. This document is the Explanatory Report for the Austin Chalk andBuda Limestone aquifers where they is determined to be relevant within GMA 10.
2.

Aquifer Description

For jurisdicational purposes, the Austin Chalk and Buda Limestone aquifers are defined as theAustin Chalk and Buda Limestone aquifers within Uvalde County. The boundaries of the Austin
Chalk Aquifer and Buda Limestone Aquifer were determined using the Digital Geologic Atlas of
Texas (U.S. Geological Survey and Texas Water Development Board, 2006), the Uvalde County
boundary, and the GMA 10 boundary. The Buda Limestone Aquifer in Uvalde County is locatedentirely within the Regional Water Planning Area L, the Nueces River Basin, and the Uvalde
County Underground Water Conservation District. The geographic extents of the Austin Chalkand Buda Limestone aquifers are presented in Figures 2 (Thorkildsen and Backhouse, 2011a)
and 3 (Thorkildsen and Backhouse, 2011b), respectively. As illustrated, the jurisdiction is limited
to Uvalde County.

1Figure 1. GCDs in GMA 10 (TWDB website)
3.

Desired Future Conditions

The DFCs for the Austin Chalk and Buda Limestone aquifers in the Uvalde County part of GMA
10, as described in Resolution No. 2010-11 and adopted August 23, 2010 by the GCDs in GMA
10, are a regional average well drawdown of zero (0) feet (including exempt and non-exemptuse) (Table 1). The second round DFCs were adopted at the GMA 10 meeting on March 14,
2016. Resolution No. 2016-xx is attached in Appendix A.

2

Figure 2. Map showing the outcrop extent of the Austin Chalk in Uvalde County in GMA 10(from Thorkildsen and Blackhouse, 2011a)
Table 1. DFCs for the Austin Chalk and Buda Limestone aquifers within Uvalde County in
GMA 10Aquifer
DFC Summary
Date DFC Adopted
No drawdown (including exempt and nonAustin Chalk
8/23/2010
exempt use)
No drawdown (including exempt and nonAustin Chalk?/?/2015
exempt use)
No drawdown (including exempt and nonBuda Limestone
8/23/2010
exempt use)
No drawdown (including exempt and nonBuda Limestone?/?/2015
exempt use) ?/?/2015
3

Figure 3. Map showing the outcrop extent of the Buda Limestone in Uvalde County in GMA 10
Aquifers (From Thorkildsen and Blackhouse, 2011b)
4.

Policy Justification

The DFCs for the Austin Chalk and Buda Limestone aquifers in Uvalde County were adopted
after considering the following factors specified in Texas Water Code §36.108 (d):1.

Aquifer uses or conditions within the management area, including conditions that differ
substantially from one geographic area to another;a.
for each aquifer, subdivision of an aquifer, or geologic strata; andb.
for each geographic area overlying an aquifer4

2.

The water supply needs and water management strategies included in the state water
plan;

3.

Hydrological conditions, including for each aquifer in the management area the total
estimated recoverable storage as provided by the executive administrator, and the averageannual recharge, inflows, and discharge;

4.

Other environmental impacts, including impacts on spring flow and other interactions
between groundwater and surface water;

5.

The impact on subsidence;

6.

Socioeconomic impacts reasonably expected to occur;

7.

The impact on the interests and rights in private property, including ownership and therights of management area landowners and their lessees and assigns in groundwater asrecognized under Section 36.002;

8.

The feasibility of achieving the DFC; and9.

Any other information relevant to the specific DFCs.

These factors are discussed in detail in appropriate sections in this Explanatory Report.
5.

Technical Justification

There is no Groundwater Availability Model for either the Austin Chalk Aquifer or the Buda
Limestone Aquifer in Uvalde County. Technical justification for selection of the DFCs for theAustin Chalk and Buda Limestone aquifers in Uvalde County was provided using alternative
analyses.
Thorkildsen and Backhouse (2011a,b) noted that there are limited hydrogeologic data available
for either the Austin Chalk Aquifer or the Buda Limestone Aquifer in Uvalde County, but that
historical water-level data show significant variation in aquifer storage over time. Thorkildsen
and Backhouse (2011a,b) cite measurements (2005-2006) for several Austin Chalk Aquifer wells
and one Buda Limestone Aquifer well that show a degree of stabilization during that time period.
Hydrographs of the Austin Chalk Aquifer wells and the Buda Limestone well are shown in
Figures 4 and 5 (Thorkildsen and Backhouse (2011a,b).
Green et al, (2009b) estimated 2008 pumpage for the Austin Chalk Aquifer in Uvalde County
was 2,935 acre-feet. For the Managed {modeled} Available Groundwater analysis of the Austin
Chalk Aquifer in Uvalde County, Thorkildsen and Backhouse (2011a) assumed that the Austin
Chalk Aquifer was under a state of dynamic equilibrium and the estimated pumpage of 2,935
acre-feet/year would achieve the adopted DFC for the Austin Chalk Aquifer in Uvalde County.
Similarly, Thorkildsen and Backhouse (2011b) used the estimated 2008 pumpage for the Buda
Limestone Aquifer in Uvalde County of 758 acre-feet (Green et al. 2009b) and with the same5

assumption of dynamic equilibrium, estimated that a Managed {modeled} Available
Groundwater equivalent to the estimated 2008 pumpage of 758 acre-feet would achieve theadopted DFC for the Buda Limestone Aquifer in Uvalde County.
Since exempt uses are not available for permitting, it is necessary to account for them when
determining the Modeled Available Groundwater (MAG). To do this, the TWDB developed astandardized method for estimating exempt use for domestic and livestock purposes based on
projected changes in population and the ratio of domestic and livestock wells in an area to thetotal number of wells. Because other exempt uses can vary significantly from district to district
and there is much higher uncertainty associated with estimating use due to oil and gas
exploration, estimates of exempt pumping outside domestic and livestock uses have not been
included. If a district believes it has a more appropriate estimate of exempt pumping, they may
submit it, along with a description of how it was developed, to the TWDB for consideration.
Once established, the estimates of exempt pumping are subtracted from the total pumping
calculation to yield the estimated MAG for permitting purposes.
Exempt use in the Uvalde County Underground Water Conservation District was estimated forthe period 2010 to 2060 by TWDB and accepted by the district (Thorkildsen and Backhouse,
2011a). Table 2 contains the estimates of exempt pumping from the Austin Chalk Aquifer in the
Uvalde County Underground Water Conservation District for domestic and livestock uses
(Thorkildsen and Backhouse, 2011a). There is negligible exempt use due to oil and gas
exploration in Uvalde County.
Estimated total pumping from the Austin Chalk Aquifer within Uvalde County in GMA 10 that
achieves the adopted DFC is approximately 2,935 acre-feet per year (Thorkildsen andBackhouse, 2011a). Table 3 shows the total pumping estimates by the lone river basin (i.e.,
Nueces River) for each decade between 2010 and 2060 for use in the regional water planning
process. The MAG for the Uvalde County Underground Water Conservation District is thedifference between the total pumping (Table 3) and the estimated exempt use (Table 2) and isshown in Table 4 (Thorkildsen and Backhouse, 2011a). Tables 5-7 contain the same information
as Tables 2-4 for the Buda Limestone Aquifer in Uvalde County.
Table 2. Estimates of exempt use for the Austin Chalk Aquifer in the Uvalde County
Underground Water Conservation District for each decade between 2010 and 2060. Results arein acre-ft /yr. Estimated exempt use calculated by TWDB and accepted by the district(Thorkildsen and Backhouse, 2011a).
Year
2010
2020
2030
2040
2050
2060
223
272
313
345
366
382
Acre-ft
Table 3. Estimated total pumping for the Austin Chalk Aquifer in the Uvalde County
Underground Water Conservation District for each decade between 2010 and 2060. Results arein acre-ft /yr (Thorkildsen and Backhouse, 2011a).
Year
2010
2020
2030
2040
2050
2060
2,935
2,935
2,935
2,935
2,935
2,935
Acre-ft6

Figure 4. Water-level measurements for selected Austin Chalk wells in Uvalde County, Texas(Thorkildsen and Backhouse (2011a)

7

Figure 5. Water-level measurements for a selected Buda Limestone well in Uvalde County,
Texas (Thorkildsen and Backhouse (2011b)
Table 4. Estimates of MAG for the Austin Chalk Aquifer in the Uvalde County Underground
Water Conservation District for each decade between 2010 and 2060. Results are in acre-ft /yr(Thorkildsen and Backhouse, 2011a).
Year
2010
2020
2030
2040
2050
2060
2,712
2,663
2,622
2,590
2,569
2,553
Acre-ft
Table 5. Estimates of exempt use for the Buda Limestone Aquifer in the Uvalde County
Underground Water Conservation District for each decade between 2010 and 2060. Results arein acre-ft /yr. Estimated exempt use calculated by TWDB and accepted by the district(Thorkildsen and Backhouse, 2011b).
Year
2010
2020
2030
2040
2050
2060
23
29
33
36
39
40
Acre-ft
Table 6. Estimated total pumping for the Buda Limestone Aquifer in the Uvalde County
Underground Water Conservation District for each decade between 2010 and 2060. Results arein acre-ft /yr (Thorkildsen and Backhouse, 2011b).
Year
2010
2020
2030
2040
2050
2060
758
758
758
758
758
758
Acre-ft
Table 7. Estimates of MAG for the Buda Limestone Aquifer in the Uvalde County Underground
Water Conservation District for each decade between 2010 and 2060. Results are in acre-ft /yr(Thorkildsen and Backhouse, 2011b).
Year
2010
2020
2030
2040
2050
2060
735
729
725
722
719
718
Acre-ft
6.

Consideration of Designated Factors

In accordance with Texas Water Code § 36.108 (d-3), the district representatives shall produce a
Desired Future Condition Explanatory Report. The report must include documentation of how
factors identified in Texas Water Code §36.108 (d) were considered prior to proposing a DFC,
8

and how the proposed DFC impacts each factor. The following sections of the Explanatory
Report summarize the information that the GCDs used in its deliberations and discussions.
6.1

Aquifer Uses or Conditions

6.1.1 Description of Factors in the Austin Chalk and Buda Limestone Aquifers in Uvalde
County
GMA 10 incorporated information from the Uvalde County Underground Water Conservation
District Groundwater Management Plan and analyses from the TWDB during development of the
proposed DFCs.

Surface water in Uvalde County comes primarily from the Nueces River and its tributaries.
Groundwater is found in both major and local aquifers in Uvalde County. Although other rivers
traverse Uvalde County, only reaches in the Nueces River exhibit significant baseflow. Major
aquifers include the Edwards (Balcones Fault Zone), Edwards-Trinity (Plateau), Carrizo-Wilcox
and Trinity aquifers. Minor or local aquifers include the Leona Gravel, Buda Limestone,
Anacacho, Austin Chalk, and Glen Rose Formations. There is significant production from the
Buda Limestone, Austin Chalk and Leona Formation aquifers in areas of Uvalde County west of
the Knippa Gap (Green et al., 2006; 2009a.b). A report completed for the Uvalde County
Underground Water Conservation District in 2009 concludes that the Edwards (Balcones Fault
Zone) Aquifer is in hydraulic communication with these local aquifers, and that index well J-27,
although completed in the Edwards (Balcones Fault Zone) Aquifer, can indicate declines ingroundwater levels in the Buda Limestone, Austin Chalk and Leona Formation aquifers thatadversely impact the water resource (Green et al., 2009b). When the level in index well J-27
drops below 860 feet msl, recharge to the Leona Gravel Aquifer and discharge to Soldiers Camp
Springs and other related un-named springs in the Nueces River decline measurably (Green etal., 2009a.b).
Use of the minor and local aquifers in Uvalde County for the years 2007–2010, in terms ofpumping, is summarized in Table 8. The significant increase in pumping between what wasreported in 2007 and what was reported in 2008 is attributed to improved reporting of pumping,
not to a marked increase in aquifer use. Aquifer use in Uvalde County divided between surface
water and groundwater and among industry sector for the years 2000–2004 is summarized inTable 9 (Uvalde County Underground Water Conservation District Groundwater ManagementPlan).
6.1.2

DFC Considerations

The dominant use of the Austin Chalk and Buda Limestone aquifers in Uvalde County by pumping isdomestic use and irrigation, and the sustainability of that supply, especially for users who have noalternative supply physically or economically available and/or who are in vulnerable locations, must be
protected to the extent feasible (Texas Water Code §36). The primary concern with sustainability of thesekarst aquifer groundwater supplies is drought, notably extreme drought that stresses both aquifers. The
DFCs support and are, in fact, the primary concern with sustainability of these karst aquifer

9

Table 8. Use of the minor and local aquifers in Uvalde County for the years 2007–2010 (Uvalde
County Underground Water Conservation District Groundwater Management Plan) (acre-ft)
Aquifer
2007
2008
2009
2010
Alluvium
190
199
669
143
Austin Chalk
1,443
2,816
3,238
1,626
Buda Limestone
110
1,637
2,059
734
Glen Rose
26
50
26
48
Leona Gravel287
11,173
7,780
7,176
Serpentine
0010Trinity/Glen Rose
79
61
53
435
Trinity
228
267
1,667
908
Total
2,362
16,236
15,508
11,070Source: Uvalde County Underground Water Conservation District Annual Water Use Report
database
Table 9. Uvalde County use divided between surface water (SW) and groundwater (GW) amongindustry sectors (Uvalde County Underground Water Conservation District Groundwater
Management Plan) (acre-ft)
SteamElectric

Irrigation

MiningLivestock

Total

7,846
378
0
0
0
0
Total
7,846
378
0
GW
5,472
1,110
0
2001
SW
67
13
0
Total
5,539
1,123
0
GW
4,777
751
0
2002
SW
59
9
0
Total
4,836
760
0
GW
5,207
152
0
2003
SW
64
2
0
Total
5,271
154
0
GW
4,083
3
0
2004
SW
50
0
0
Total
4,133
3
0
GW = groundwater; SW = surface water
Source: TWDB Water Use Survey Database 1/5/2010

56,967
1,094
58,061
83,2761,700
84,97688,392
1,804
90,19667,820425
68,24566,399377
66,776

250
0
250
250
0
250
717
0
717
239
0
239
239
0
239

642
642
1,284
592
592
1,184
579
579
1,158
557
557
1,114
522
522
1,044

66,083
1,736
67,81990,7002,372
93,072
95,216
2,451
97,66773,975
1,048
75,02371,246949
72,195

Year

2000

SourceMunicipal

ManufacturingGW
SW

groundwater supplies is drought, notably extreme drought that stresses both aquifers. The DFCs
support and are, in fact, the linchpin of a drought management program to promote long-termsustainability of water supplies.
6.2

Water-Supply Needs

6.2.1 Description of Factors in the Austin Chalk and Buda Limestone Aquifers in Uvalde
County10

Water use in Uvalde County is divided between surface water and groundwater and amongindustry sector (Table 10) (Uvalde County Underground Water Conservation District
Groundwater Management Plan). Water use is not delineated by aquifer, thus water use of theAustin Chalk and Buda Limestone aquifers is not known.
6.2.2

DFC Considerations

The population growth of Uvalde County is projected by the Office of the State Demographer forState of Texas, Texas State Data Center Texas A&M University System to grow from 28,616 in2010 to 35,650 in 2040, an increase of 24.6 percent (http://txsdc.tamu.edu/tpepp/2001_txpopprj_
method.php). The DFCs maximize the amount of water that can be provided during non-drought
periods that is consistent with the implementation of a drought management program that
protects the supply for existing uses during drought, especially extreme drought. The drought
program response to the DFCs indexes the amount of aquifer water available to meet the needs
with the severity of drought.
6.3

Water-Management Strategies

6.3.1 Description of Factors in the Austin Chalk and Buda Limestone Aquifers in Uvalde
CountyThe following information is from the South Central Texas Region Initially Prepared Water Plan
(South Central Texas Region Water Planning Group, 2015). A major component of the South
Central Texas Region Initially Prepared Water Plan is to identify municipalities and water-use
categories that may, in times of severe drought, be unable to meet expected water-supply needs
based on today’s ability to access, treat, and distribute the supply. A goal of the South Central
Texas Region Initially Prepared Water Plan is to provide for the health, safety, and welfare of thehuman community, with as little detrimental effect to the environment as possible. Recreation
activities involve human interaction with the outdoor environment and are often directly
dependent on water resources. It is recognized that the maintenance of the regional
environmental community’s water supply needs serves to enhance the lives of citizens of theSouth Central Texas Region as well as the tens of thousands of annual visitors to this Region.
The implementation of water-management strategies recommended in the South Central Texas
Region Initially Prepared Water Plan is not expected to have any impact on native-water quality.
In particular, primary and secondary safe drinking water standards, which are the key parametersof water quality identified by the South Central Texas Region Water Planning Group as
important to the use of the water resource, are not compromised by the implementation of thestrategies. Also, no recommended strategies involve moving water from a rural location for use
in an urban area.
The data presented in this section are provided by the South Central Texas Region Water
Planning Group Plan (South Central Texas Region Water Planning Group, 2015). Recommended
alternatives, or water-management strategies, to meet anticipated drought-induced shortages arepresented in the South Central Texas Region Initially Prepared Water Plan for consideration. The
projected water supply and demand estimates for Uvalde County indicate that projected demands
exceed projected supplies (Table 10). Source water available after known demands are
11subtracted is presented in Table 11. Table 12 identifies water-use categories where no watersupply is available to meet its total need. As noted, these data are not currently available in theSouth Central Texas Region Water Planning Group Plan (South Central Region Water PlanningGroup, 2015).
To meet the needs of water-user groups in the Uvalde County Underground Water Conservation
District, Region L recommended water-management strategies to address the identified
shortages. Water-management strategies are projects or procedures that if implemented willproduce additional water to meet the identified needs of water-user groups. The total amount ofgroundwater and surface water resulting from implementation of the water-management
strategies recommended for Uvalde County in the 2007 State Water Plan is anticipated toprovide 4,487 acre-feet in 2010, increasing to 6,939 acre-feet in 2060. Transfers from the
Edwards (Balcones Fault Zone) Aquifer and municipal water conservation are the primarystrategies identified (Table 12).
Table 10. Projected water-supply and demand estimates for Uvalde County in the 2012 State
Water Plan
Supply/Shortage
Comment
Water User Group
2010
2060
(acft/yr) (acft/yr)
City of Sabinal
-127
-109
Projected shortage(2010 through 2060)
City of Uvalde-3,172-3,263
Projected shortage(2010 through 2060)
Rural Area Residential and Commercial
1,277
317
No projected shortage
Industrial
943
837
No projected shortage
Steam-Electric Power
00
No projected shortage
Mining105
0
No projected shortage
Irrigation
14,68024,768
No projected shortage
Livestock00
No projected shortage
Table 11. Source water available after known demands are subtracted (South Central Texas
Initially Prepared Plan, 2015) (acre-ft/yr)
Groundwater
Basin
Salinity 2020
2030
2040
2050
2060 2070
Buda Limestone
Nueces
Fresh
233
233
233
233
233
233
Aquifer
Carrizo-Wilcox
Nueces
Fresh
0
0
0
0
0
0
Aquifer
Edwards-Trinity
Nueces
Fresh
0
0
0
0
0
0
Aquifer
Leona Gravel
Nueces
Fresh
256
262
283
78
0
0
Aquifer
Trinity Aquifer
Nueces
Fresh
0
0
0
0
0
0

12

Table 12. Water-use categories where no water supply is available to meet its total need. These
data are not currently available in the South Central Region Water Planning Group Plan (South
Central Region Water Planning Group, 2015) (acre-ft/yr)
WUG/WWP Basin
2020
2030
2040
2050
2060
2070
Water-management strategies for Uvalde County that are identified in the 2012 State Water Planare summarized in Table 13. Water-management strategies that involve aquifer storage andrecovery (ASR) comprise approximately 9 percent of recommended new supplies and include an
Uvalde aquifer storage and recovery project (1,155 acre-ft/yr @ $2,803/acre-ft/yr) (South Central
Region Water Planning Group, 2015).
Table 13. Water-management strategies in Uvalde County in the 2012 State Water Plan (acreft/yr)
River
Basin

WUG

Water
Management
Strategy

Source
Name

2010

2020

2030

2040

2050

2060

139

135

130

125

121

121

Sabinal

NuecesEdwards
Transfers

Edwards(Balcones
Fault Zone)
Aquifer

Sabinal

NuecesMunicipal
Water
Conservation

Conservation

34

65

92

116

139

145

UvaldeNuecesEdwards
Transfers

Edwards(Balcones
Fault Zone)
Aquifer

3,793

3,830

3,850

3,854

3,856

3,884

CountyOther

NuecesConservation

0

0

0

33

73

137

UvaldeNuecesConservation

521

1,017

1,471

1,882

2,269

2,652

4,487

5,047

5,543

6,010

6,458

6,939

Municipal
Water
Conservation
Municipal
Water
Conservation

TOTAL

6.3.2

DFC Considerations

The DFCs under consideration here are specific to the Austin Chalk and Buda Limestone
Aquifers in Uvalde County. The Edwards Aquifer in Uvalde County has a different DFC and is
the subject of a separate groundwater management zone, designed to promote protection of thedowngradient springs in the Edwards Aquifer and the endangered species impacted by springdischarge. The DFCs for the Austin Chalk and Buda Limestone Aquifers, as described above,
underpin an aquifer-responsive drought management program that encourages both full-timewater conservation and further temporary curtailments in pumping during drought periods that
increase with drought severity.

13

6.4

Hydrological Conditions

6.4.1 Description of Factors in the Austin Chalk and Buda Limestone Aquifers in Uvalde
County6.4.1.1 Total Estimated Recoverable Storage
Texas statute requires that the total estimated recoverable storage of relevant aquifers be
determined. Total estimated recoverable storage is a calculation provided by the TWDB. Texas
Administrative Code Rule §356.10 (Texas Administrative Code, 2011) defines the total
estimated recoverable storage as the estimated amount of groundwater within an aquifer that
accounts for recovery scenarios that range between 25 percent and 75 percent of the porosityadjusted aquifer volume. As described in GAM Task 14-033 (Jones et al., 2013), The total
recoverable storage was estimated for the portion of the Austin Chalk Aquifer and the Buda
Limestone Aquifer within GMA 10 that lies within the official lateral aquifer boundaries asdelineated by Thorkildsen and Backhouse (2011a,b). Total estimated recoverable storage values
may include a mixture of water quality types, including fresh, brackish, and saline groundwater,
because the available data and the existing Groundwater Availability Models do not permit thedifferentiation between different water quality types. The total estimated recoverable storage
values do not take into account the effects of land surface subsidence, degradation of water
quality, or any changes to surface water-groundwater interaction that may occur due to pumping.
Per an email from Robert G. Bradley, TWDB, dated February 17, 2015 “We [TWDB] have notcompleted the [total estimated recoverable] report yet. We still have the Leona, Buda Limestone,
and Austin Chalk report to do, as well as the GMA 10 saline Edwards (Balcones Fault Zone)
Aquifer. Most of the Leona Gravel Aquifer is completed but we intend to write one report for
Uvalde County. However, we have been struggling with the numbers for the Austin Chalk andBuda Limestone. Anyway some other projects had priority and we are now able to complete thisreport with some information.” The TWDB Memorandum on Total Estimated Recoverable
Storage in GMA 10 is attached in Appendix B. These data will be entered into Table 14 whenavailable.
Table 14. Total estimated recoverable storage for the Austin Chalk and Buda Limestone aquifers
within Uvalde County Underground Water Conservation District in GMA 10. Estimates arerounded within two significant numbers (Jones et al., 2013).
Total Storage
25 percent of Total Storage 75 percent of Total Storage(acre-ft)(acre-ft)(acre-ft)
Under development by
Under development by
Under development by
TWDB
TWDB
TWDB
6.4.1.2 Average Annual Recharge
Using results from TWDB GAM Run 10-022 (Aschenbach, 2010), the estimated recharge fromthe Carrizo-Wilcox Aquifer in Uvalde County is 2,948 acre-ft/yr and the estimated recharge fromthe Edwards-Trinity Aquifer in Uvalde County is 28,213acre-ft/yr (Uvalde County Underground
Water Conservation District Groundwater Management Plan). The Uvalde County Underground
14

Water Conservation District Groundwater Management Plan does not include an estimate foraverage annual recharge from the Austin Chalk Aquifer and the Buda Limestone Aquifer.
6.4.1.3 Inflows
The Austin Chalk and Buda Limestone aquifers are recharged by distributed recharge where they
crop out. In addition, the intense faulting and significant offset inherent to the Balcones Fault
Zone within the confines of the Uvalde pool has sufficiently juxtaposed the Edwards, Austin
Chalk, and Buda Limestone aquifers that all three aquifers are in hydraulic communication.
Because of this hydraulic communication, the Austin Chalk and the Buda Limestone aquifers arereadily recharged by the Edwards (Balcones Fault Zone) Aquifer, however, the Austin Chalk andthe Buda Limestone can just as easily discharge to the Edwards (Balcones Fault Zone) Aquifer.
The direction of flow is a function of local hydraulic gradient. Whether recharge to the Austin
Chalk and Buda Limestone aquifers is from autogenic recharge or by discharge from the
Edwards (Balcones Fault Zone) Aquifer is complex due to the structure and not easily quantified.
6.4.1.4 Discharge
The Uvalde County Underground Water Conservation District has only partial estimation ofdischarge from the Austin Chalk Aquifer and the Buda Limestone Aquifer in Uvalde County.
The source for the Soldiers Camp Spring and related un-named springs on the Nueces Riverappears to be the Austin Chalk Aquifer where it crops out at the Nueces River. These springs areat the downdip boundary of where the Austin Chalk crops out in Uvalde County. The U.S.
Geological Survey gage on the Nueces River downstream from Soldier Camp Springs and theother unnamed springs provides a measure of the discharge from all the springs in addition tosurface runoff flow in the Nueces River. The baseflow component to flow measured at this gage
could be separated out from total flow to provide the quantity of discharge from the Austin Chalk
Aquifer. This separation has not yet been performed.
Similarly, the Buda Limestone Aquifer and possibly the Austin Chalk Aquifer crop out in the
bed of the Leona River north of Ft Inge and south of the City of Uvalde. The Buda Limestone
Aquifer and possibly the Austin Chalk Aquifer discharge to the Leona River and possibly to the
Leona Gravel Aquifer near this location.
Analysis by Green et al. (2008) indicates that as much as 74,000 acre-ft/yr is recharged to the
Leona Gravel Aquifer as inflow where the gravels abut with down gradient boundary of theAustin Chalk, Buda Limestone, and possibly the Edwards (Balcones Fault Zone) Aquifer in the
Leona River floodplain in the reach from Highway 90 in the north to Ft. Inge in the south. The
quantity of recharge to the Leona Gravel Aquifer is highly variable and is greatly affected byaquifer stage as measured at monitoring well J-27. This volume of water discharge by the Austin
Chalk and Buda Limestone aquifers to the Leona Gravel Aquifer has not been quantified.

15

6.4.1.5 Other Environmental Impacts Including Springflow and Groundwater/Surface Water
Interaction
Significant springs in Uvalde County include Soldiers Camp Spring and related un-named
springs on the Nueces River and Leona Springs on the Leona River. Soldiers Camp Spring andrelated un-named springs on the Nueces River contribute to surface flow in the Nueces River(Green et al., 2009a,b). The source for the Soldiers Camp Spring and related un-named springson the Nueces River appears to be the Austin Chalk Aquifer where it crops out at the Nueces
River. Baseflow in the Nueces River downstream from Soldiers Camp Spring and the related unnamed springs is wholly derived from the Austin Chalk Aquifer. Storm surge and surface runoff
are the only contribution to the Nueces River that flows from the north.
6.4.2

DFC Considerations

The DFCs are proposed on the basis that the Austin Chalk Aquifer and the Buda Limestone
Aquifer in Uvalde County are in direct hydrologic communication with each other and with the
Edwards Aquifer. The three aquifers are well-integrated hydrologically and have a common
potentiometric surface throughout the subdivision. This hydrologic condition denotes that all
three aquifers are jointly vulnerable to drought. The Austin Chalk Aquifer and the Buda
Limestone Aquifer in Uvalde County are more vulnerable to drought than the Edwards Aquifer
because they are above and have less saturated thickness that the Edwards Aquifer.
7.

Subsidence Impacts

Subsidence has historically not been an issue with the Austin Chalk and the Buda Limestone
aquifers in GMA10. The aquifer’s matrices in Uvalde County are well-indurated and the amountof pumping does not create compaction of the host rock and/or subsidence of the land surface.
Similarly, when the aquifer recharges the same volume of water is able to be stored as existed
before an equivalent volume was withdrawn. Hence, the proposed DFCs are not affected by anddo not affect land-surface subsidence or compaction of any aquifer.
8.

Socioeconomic Impacts Reasonably Expected to Occur

8.1
Description of Factors in the Austin Chalk and Buda Limestone Aquifers in Uvalde
CountyAdministrative rules require that regional water planning groups evaluate the impacts of not
meeting water needs as part of the regional water planning process, and rules direct TWDB staff
to provide technical assistance [§357.7 (4)(A)]. Staff of the TWDB’s Water Resources Planning
Division designed and conducted a report in support of the South Central Texas Regional Water
Planning Group (Region L). The report “Socioeconomic Impacts of Projected Water Shortages
for the South Central Texas Regional Water Planning Area (Region L)” was prepared by the
TWDB in support of the 2011 South Central Texas Regional Water Plan.
The report on socioeconomic impacts summarizes the results of the TWDB analysis anddiscusses the methodology used to generate the results for Region L. The report does not include
16

the socioeconomic impact associated with only the Austin Chalk and Buda Limestone aquifers.
The socioeconomic impact report for Water Planning Group L is included in Appendix C.
8.2

DFC Considerations

Because none of the water management strategies involve changes in the current use of theAustin Chalk and Buda Limestone aquifers in Uvalde County, as described in Section 6.3, theproposed DFCs do not have a differential socioeconomic impact. They are supportive of thestatus quo in this regard, which is considered positive.
9.

Private Property Impacts

9.1
Description of Factors in the Austin Chalk and Buda Limestone Aquifers in Uvalde
CountyThe impact on the interests and rights in private property, including ownership and the rights of
GMA landowners and their lessees and assigns in groundwater is recognized under Texas Water
Code Section 36.002. The legislature recognizes that a landowner owns the groundwater below

the surface of the landowner's land as real property. Nothing in this code shall be construed as
granting the authority to deprive or divest a landowner, including a landowner's lessees, heirs, orassigns, of the groundwater ownership and rights described by this section.
Texas Water Code Section 36.002 does not: (1) prohibit a district from limiting or prohibiting thedrilling of a well by a landowner for failure or inability to comply with minimum well spacing or
tract size requirements adopted by the district; (2) affect the ability of a district to regulate
groundwater production as authorized under Section 36.113, 36.116, or 36.122 or otherwise
under this chapter or a special law governing a district; or (3) require that a rule adopted by a
district allocate to each landowner a proportionate share of available groundwater for production
from the aquifer based on the number of acres owned by the landowner.
9.2

DFC Considerations

The DFCs are designed to protect the sustained use of the aquifer as a water supply for all users
in aggregate. The DFCs do not prevent use of the groundwater by landowners either now or in
the future, although ultimately total use of the groundwater in the aquifer is restricted by theaquifer condition, and that may affect the amount of water that any one landowner could use,
either at particular times or all of the time.
10.

Feasibility of Achieving the DFCs

The feasibility of achieving a DFC directly relates to the ability of the Uvalde County
Underground Water Conservation District to manage the Austin Chalk and Buda Limestone
aquifers toward that goal. The Uvalde County Underground Water Conservation District islimited by the hydrogeology of the resource (e.g. how it responds to drought) and the authority of
the Uvalde County Underground Water Conservation District to regulate pumping (e.g. uses
exempt from permitting and by virtue of the fact that the Edwards (Balcones Fault Zone)
17

Aquifer, the principal aquifer within its jurisdictional boundaries, is regulated by the Edwards
Aquifer Authority, not the Uvalde County Underground Water Conservation District. Because
the Edwards (Balcones Fault Zone) Aquifer is the principal source of recharge to Austin Chalkand Buda Limestone aquifers, the feasibility of achieving the DFC of the Austin Chalk and Buda
Limestone aquifers is dependent on the management and hydraulic condition of the Edwards(Balcones Fault Zone) Aquifer.
11.

Discussion of Other DFCs ConsideredNo other DFC of the Austin Chalk and Buda Limestone aquifers in Uvalde County wasconsidered.
12.

Discussion of Other Recommendations

12.1

Advisory Committees

An Advisory Committee for GMA 10 has not been established.
12.2

Public Comments

Each GCD must hold a public meeting within 90 days after the GMA approves its DFCs. During
this meeting, the GCD needs to document stakeholder input. This input is to be submitted by areport from the GCD to the GMA within 90 days after the GMA approves its DFC.
The GCDs have not yet approved their DFCs. The GCDs have not yet held public meetings togather public comment on the DFCs. No public comments have yet been offered regarding the
DFC for the Austin Chalk and Buda Limestone aquifers in Uvalde County.
13.

Any Other Information Relevant to the Specific DFCs

No additional information relevant to the specific DFCs has been identified.
14.
Provide a Balance Between the Highest Practicable Level of Groundwater
Production and the Conservation, Preservation, Protection, Recharging, and Prevention ofWaste of Groundwater and Control of Subsidence in the Management Area
TWDB has not developed guidance on how to approach this factor. It is up to the wishes of the
GCDs on how they wish to approach it, whether in a qualitative, quantitative, or combinationmanner. But, the GCDs need to include stakeholder input so that this factor can be satisfactory
addressed. Participation by the project team at town hall meetings or with individual GCDs is
not included in the scope of this work. GCD management plans will be used to complete thisrequirement.
Each GCD must hold a public meeting within 90 days after the GMA approves its DFCs. During
this meeting, the GCD needs to document stakeholder input regarding whether the DFCs provide
a balance between the highest practicable level of groundwater production and the conservation,
18

preservation, protection, recharging, and prevention of waste of groundwater and control ofsubsidence in the management area. This input is to be submitted by a report from the GCD to
the GMA within 90 days after the GMA approves its DFCs.
15.

References

Green, R.T., F. P. Bertetti, N.M. Franklin, A.P. Morris, D.A. Ferrill, and R.V. Klar. 2006.
Evaluation of the Edwards Aquifer in Kinney and Uvalde Counties, Texas. Southwest ResearchInstitute. Contract report for the Edwards Aquifer Authority.
Green, R.T., J.R. Winterle, and J.D. Prikryl. 2008. Discharge from the Edwards Aquifer throughthe Leona River Floodplain, Uvalde, Texas. J of American Water Resources Association.
44(4):887-901. DOI: 10.1111/j.1752-1688.2008.00187.x.
Green, R.T., F. P. Bertetti, and R.N. McGinnis. 2009a. Analysis of the Water Resources of the
Area Centered Within and Near Uvalde and Zavala Counties and Review of a Report on a
Potential Well Field and Pipeline in Uvalde County, Texas. Southwest Research Institute.
Contract project conducted for the Uvalde County Underground Water Conservation District andWintergarden Groundwater Conservation District. 53 p.
Green, R.T., F. P. Bertetti, and R.N. McGinnis. 2009b. Investigation of the Secondary Aquifers
in Uvalde County. Southwest Research Institute. Contract project conducted for the Uvalde
County Underground Water Conservation District. 74 p.
Jones, I.C., J Shi, and R Bradley. 2013. GAM Task 13-033: Total estimated recoverable storage
for aquifers in Groundwater Management Area 10.
Texas Administrative Code. 2011. http://info.sos.state.tx.us/pls/pub/readtac$ext.viewtac
Texas Water Development Board, 2011, Groundwater database: Texas Water Development
Board, Groundwater Resources Division.
Thorkildsen, D. and S. Backhouse. 2011a. GTA Aquifer Assessment 10-26 MAG, Groundwater
Management Area 10, Austin Chalk Aquifer, Managed Available Groundwater estimates. Texas
Water Development Board. 11 p.
Thorkildsen, D. and S. Backhouse. 2011b. GTA Aquifer Assessment 10-27 MAG, Groundwater
Management Area 10, Buda Limestone Aquifer, Managed Available Groundwater estimates.
Texas Water Development Board. 10 p.
U.S. Geological Survey and Texas Water Development Board, 2006, Digital Geologic Atlas of
Texas: U.S. Geological Survey and Texas Water Development Board, available through the
Texas Natural Resources Information System.

19