DFC Updates and Explanatory Reports in GMA 13, Bill Hutchison

DFC Updates and Explanatory Reports

in GAM 13

Bill Hutchison, Ph.D., P.E., P.G.

TAGD Quarterly Meeting

February 25, 2014

Topics

• GMA 13 background– Geography– Groundwater Availability Model– Initial DFC

• Activities to date

• Overview of draft explanatory report

GMA 13

GMA 13:All or part of17 counties

GMA 13:All or part of8 GCDs

GMA 13:All or part of8 GCDs + EAA

Groundwater Availability Model:QCSP-South

• Aquifers– Sparta (Layer 1)– Queen City (Layer 3)– Carrizo-Wilcox Aquifer (Layers 5 to 8)

• Confining Layers– Weches (Layer 2)– Reklaw (Layer 4)

8

76

543 2

1

From pg 2-33 of GAM Report (Kelley and others, 2004)

Carrizo-Wilcox, Queen City and Sparta Aquifers

• GMA 13 Adopted DFC on April 9, 2010

• DFC establishment relied on results from several model simulations– DFC expressed as GMA-wide average (23 ft)– Scenario 4 of GAM Run 09-034

• 61 year simulation

• Assumed a starting point in 2000

Summary of Activities: Fall 2012 to Date

• Comparison of actual data with current DFC (Task 0)

• Extended GAM with updated pumping estimates from 2000 to 2011

• Updated future pumping

• Completed alternative simulations

• Completed draft of explanatory report







Comparison of Actual Data with Current DFC (Task 0)

• Initial task to assess current DFC

• Address issues regarding use of “average” drawdown as DFCs

• Key element of “Factor 1” (Aquifer Uses and Conditions)

DFC and GAM Run

• How to compare actual data to DFC?

• How to compare actual data to results from an “idealized” model run?

• How to compare “average” drawdown over entire GMA (23 ft) with individual well measurements?

Point-by-Point Comparison

• Comparisons at discrete locations

• Extract predicted groundwater levels/ drawdown from model files

• Compare to actual monitoring data

• Limited use of averaging

6,956 Wells in GMA 13 in the TWDB Database

• 1,844 wells with screen top and bottom

• 748 are completed in exactly one GAM layer

• 92 have 10 or more groundwater elevation measurements with at least one after 2000

Hydrographs for 92 Wells

• Presented in Task 0 report

• Pumping (in immediate area of the well)

• Land surface elevation

• Screen top and bottom elevation

• Actual groundwater elevation

• Calibrated model groundwater elevation

• Simulated groundwater elevation (DFC run)

Data Comparison Approach

• DFC Drawdown minus Actual Drawdown– Positive number means that actual groundwater

level is higher than DFC groundwater level• DFC drawdown = 10 ft

• Actual drawdown = 8 ft

• Difference = 2 ft

– Negative number means that actual groundwater level is lower than DFC groundwater level

Data Comparison

• Well-by-well drawdown comparison requires:– Groundwater elevation measurement in late

1999/early 2000– Groundwater elevation measurement in year of

interest

• Task 0 report contains maps, tables, and graphs for the GMA and for each County

• Only one GMA-level example shown here

90 101113

96

13274

86

14274 76

132

45

Precipitation as % Average

Observations

• Actual drawdown less than DFC drawdown– In most counties and in most years, MAG was

much higher than actual pumping

• Exception in 2010 and 2011– Increased use due to drought?– Increase use due to hydraulic fracturing water

use?– Decreased recharge due to drought?







Updated Pumping 2000 to 2011

• More accurate pumping estimates – Based on TWDB Water Use Survey and GCD

input

• Provides ability to use end of 2011 as starting point for any drawdown based DFC

Pumping Updates for 2000 to 2011

• WUS and GCD estimates were used as starting point– Included updated well locations in Gonzales and

Caldwell Counties

• “Calibrated” annual pumping on a county-aquifer basis based on groundwater elevation data from TWDB database

• Technical memorandum will be provided to TWDB







Future Pumping Estimates(2012 to 2070)

• “Factor 2” (Water Supply Needs and Water Management Strategies)– TWDB MAG report associated with 2010 DFCs– DB12 data from TWDB (Sources, Demands,

Water Management Strategies)– Oil and Gas Water Use Estimates (BEG study)– SAWS input (email of June 27, 2013)– GCD input







Alternative Simulations

• 59-year simulations (2012 to 2070)

• Use 2011 conditions as starting point– Based on model update that covered 2000 to

2011– Developed “Base Case” that included current

MAG and input from SAWS, GCDs

Alternative Scenarios

• Scenario 1 – 0.7*Base Case



• Scenario 4 – Base Case




Simulation Output

• Average Drawdown (Maps, Tables, Graphs)– GMA– County– GCD– Aquifer– County-Aquifer– GCD-Aquifer

300,000 400,000 500,000 600,000Pumping (AF/yr)

60

50

40

30

20

10

0

Dra

wd

ow

n (

ft)

Legend

Scenarios 1 to 7

Current DFC/MAG

GMA 13 Average Drawdown (ft)in 2070 (from 2011 Conditions)

Other Simulation Outputs

• Maps, Tables and Graphs– Storage change– Outcrop vs. confined drawdown or storage

• Individual well summaries– Groundwater elevation– Drawdown (from 2011)– Height of water above (or below) top of screen

Status of GAM Simulations

• Scenarios 1 to 7 presented to GMA 13 on October 9, 2013

• Requested input regarding changes by December 31, 2013– Two GCDs requested modifications to future

pumping• Gonzales UWCD

• Guadalupe County GCD

Status of GAM Simulations• Made changes and completed Scenario 8

– Presented preliminary results to Guadalupe on February 13, 2014

• Complete summary report before next GMA 13 meeting (March 13, 2014)

• Discuss results at GMA 13 meeting– Accept as basis for proposed DFC– Make additional revisions

• Discuss level of detail of DFC expression







Explanatory Report

• Statute requires that GMA 13 consider the nine factors (and the balancing) prior to adopting a “proposed” DFC

• An “explanatory” report is required when submitting “final” DFC to TWDB, and must include documentation of these factors– “Explanatory” report not required for

“proposed” DFC

GMA 13 Approach

• “Preliminary” explanatory report – Document factor review for “proposed” DFC– Useful documentation for GCDs during public

review period after “proposed” DFC is adopted

Initial Draft of Explanatory Report

• Covers elements required by statute and rule– Generally follows outline suggested by TWDB

• Main text

• Appendices

1.0 Groundwater Management Area 13

• Overview of GMA 13 Geography and GCDs

2.0 Proposed Desired Future Condition

• To be completed after “Proposed” DFC adoption

• Draft resolution is Appendix A (no signature block yet)

3.0 Policy Justification

• Lists nine factors

• Includes balancing language

• To be completed after “Proposed” DFC is adopted

4.0 Technical Justification

• Discusses GAM used and its limitations

5.0 Factor Consideration

• Discussion of nine factors required by statute

5.1 Aquifer Uses and Conditions

• Pumping estimates (Appendix B)– 1999 Pumping from GAM– 2000 to 2008 TWDB Water Use Survey

estimates– Gonzales UWCD estimates – Plum Creek CD estimates

• Also references and includes Task 0 report as Appendix C

5.2 Water Supply Needs and Water Management Strategies

• Included in Appendix D– DB12 data from TWDB (Sources, Demands,

Water Management Strategies)– Oil and Gas Water Use Estimates (BEG study)– SAWS input (email of June 27, 2013)– GCD input– TWDB MAG report associated with 2010

DFCs

5.3 Hydrologic Conditions• 5.3.1 – Storage (from TWDB)

– Included as Appendix E

• 5.3.2 – Recharge, Inflows and Discharge (Appendix F)– Table of Average Historic Water Budget (from

February 19, 2010 GMA 13 meeting) with a column for proposed DFC (pending GMA 13 action)

– More detailed water budget data from GAM Run 09-034

5.4 Other Environmental Impacts

• Spring flow and groundwater-surface water interactions

• Covered in water budget discussion in Section 5.3.2 and data in Appendix F

5.5 Subsidence

• Not applicable

5.6 Socioeconomic Impacts

• State Water Plan strategies are an important foundation for this DFC

• Included Region K, L, and M socioeconomic reports completed by TWDB in 2010 in Appendix G– Assesses impacts of not meeting water needs

5.7 Impact on Private Property Rights

• Balancing discussion– Existing well impacts vs. impacts to property

owners who “conserved” groundwater

• Will include maps of well specific impacts based on Task 0 wells– Feet of water above/below top of screen– Feet of water above/below bottom of screen

5.8 Feasibility of Achieving DFC

• Monitoring discussion

• Recommendation for analyses similar to Task 0 evaluation

• Discussion on updates every five years

5.9 Other Information

• Included James Bene paper and presentation to GMA 13 as Appendix H

• Include comparison of model output to simple Darcian approach forwarded by Bill Klempt

6.0 Discussion of Other DFCs Considered

• To be completed

• Drawn from alternative simulations

7.0 Discussion of Other Recommendations

• To be completed once public hearings are held (i.e. part of final explanatory report)

8.0 References

• References cited in report

Appendices

• A – DFC Resolution

• B – Historic use Estimates

• C – Task 0 report

• D – Various future pumping projections

• E – TWDB storage report

• F – Water budget estimates

• G – Socioeconomic reports

• H – Other information

TWDB Review

• TWDB staff developed a checklist of required elements

• Initiated a review of the draft

• All elements were found in draft (10/25/2013 email)

Summary• GMA 13 has reviewed and compared current DFC

and actual data (resulted in extended GAM – pumping through 2011)

• GMA 13 has considered the relevant factors to “propose” a new DFC

• GMA 13 has completed alternative GAM simulations (more to be completed?)

• GMA 13 is reviewing draft of explanatory report

• Next GMA 13 meeting is March 13, 2014

Questions?

Bill Hutchison512-745-0599

[email protected]

Education

DFC Updates and Explanatory Reports in GMA 13, Bill Hutchison