coupled surface-water/groundwater evaluation in the
TRANSCRIPT
Page 1
Coupled Surface-Water/Groundwater Evaluation in the Edwards Plateau
Groundwater Management Area 7 October 19, 2017
Ronald T. Green, Ph.D., P.G., Beth Fratesi, Ph.D.,
Nathaniel Toll, and Rebecca Nunu
Southwest Research Institute®
Photo: Texas Parks and Wildlife Department
Page 2
Edwards-Trinity Aquifer
Edwards-Trinity Aquifer GAM (Anaya and Jones, 2009)
Page 3
Edwards-Trinity Aquifer
Edwards-Trinity Aquifer GAM (Anaya and Jones, 2009)
Page 4 Edwards-Trinity Aquifer GAM (Jones et al., 2009)
Edwards-Trinity Aquifer Regional-Scale Groundwater
Availability Model
Page 5
The Problem
Regional-scale models not capable of replicating local-
scale hydraulic features
Page 6
Related Studies Provide Insight on Modeling Watersheds Independently
Edwards Aquifer
Refined Model Distinct Watersheds
Refined Grid
Edwards Aquifer FEM (Fratesi et al., 2014)
Page 7
Edwards-Trinity Aquifer Major Watersheds Act Separately
Page 8
Challenge: Adjoining Basins Merge at Downdip Boundaries
8
Edwards Plateau
Schleicher
County
Sutton
County
Val Verde
County
Unconfined Partially Confined Confined
No Communication Communication
Between Watersheds Between Watersheds
Page 9
What is the nature of river and groundwater flow in the headwater areas of the Edwards Plateau?
Page 10
Rain Water Is Focused into River Beds and Acts as a Mild Acid That Dissolves the Limestone
The preferential flow paths that are formed may be a “pipe”, but it is more likely the flow paths are simply
zones of enhanced permeability
Incised River Channels
Preferential Flow Paths
Woodruff and Abbott, 1970s, 1980s
Page 11
Groundwater Chemistry Indication of Conduit Location
Page 12
Pipes in a sponge
Page 13
Hydraulic couplings are more complex than just SW ↔GW
Page 14
Headwater Streams are Mostly Gaining
2006 – TCEQ 2013 – Jeff Bennett/NPS; Marcus
Gary/EAA; Ron Green/SwRI; Kevin Urbanczyk/Sul Ross;
students
Page 15
Watershed-Scale Studies
Lower Pecos River
Watershed
Devils River
Watershed
Page 16
Parsing Out the Lower Pecos River Watershed
Independence Creek
Live Oak Creek
Page 17
Devils River Watershed
Devils River watershed has
features that make it difficult
or impossible to model with
just any SW-GW software.
Drains southward off
Edwards Plateau
Page 18
The Problem
• Accurately predicting impact of groundwater
pumping on surface flow or depletion of surface
water on groundwater recharge requires modeling
interdependent surface and subsurface processes.
• Integrated models are available, but not well
developed, particularly for challenging environments
such as semi-arid karstic watersheds.
• TCEQ WAM is not coupled with TWDB GAM
Page 19
Surface Water
Owned by the State
Governed by TCEQ
Administered using WAMs
Groundwater
Owned by Land Owners
Governed by
TWDB/GMAs/GCDs
Administered using GAMs
(Winter et al., 1998)
Page 20
Surface-Water Model
Page 21
Long-Term Calibration 2000-2015
0
1
2
3
4
5
60
5000
10000
15000
20000
25000
30000
35000
40000
45000
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015
Pre
cip
itation (
in)
Direct
Dis
charg
e (
cfs
)
Year
2000-2015
Actual Discharge Model Discharge Precipitation
Storm absent in PRISM data
Page 22
Percolation is Calculated by Surface-Water Model and Imported into the Groundwater Model
(A)
Infiltration
2.4”
February 4, 2004 March 12, 2004
1
Saturated Fraction
Page 23
Groundwater Model Refinement
Page 24
Groundwater Model Mesh Refinement
Mesh refinement at areas where the surface-water flow
accumulation has selected stream channels
Sycamore Creek
Watershed
Page 25
Groundwater Model Mesh Refinement
Quad-Tree mesh
refined along stream
centerlines
Significantly reduces
mesh density while
preserving complexity
Page 26
Groundwater Model Performance
Page 27
Groundwater Model River Discharge: Pafford Crossing
100,000
300,000
500,000
700,000
900,000
1,100,000
1,300,000
1,500,000
1,700,000
1,900,000
2,100,000
9-F
eb
-99
9-F
eb
-00
8-F
eb
-01
8-F
eb
-02
9-F
eb
-03
9-F
eb
-04
8-F
eb
-05
8-F
eb
-06
9-F
eb
-07
9-F
eb
-08
8-F
eb
-09
8-F
eb
-10
9-F
eb
-11
9-F
eb
-12
8-F
eb
-13
8-F
eb
-14
9-F
eb
-15
9-F
eb
-16
8-F
eb
-17
Flo
w C
ub
ic M
ete
rs/d
ay
Date
Page 28
Groundwater Pumping Scenario
• Well field located near Juno
• Cumulative pumping of 8,000 gpm
(12,800 acre-ft/yr)
• What is the effect on baseflow to the
Devils River?
Page 29
Groundwater Pumping Scenario 8,000 gpm at Juno
200,000
300,000
400,000
500,000
600,000
700,000
800,000
9-F
eb
-99
9-F
eb
-00
8-F
eb
-01
8-F
eb
-02
9-F
eb
-03
9-F
eb
-04
8-F
eb
-05
8-F
eb
-06
9-F
eb
-07
9-F
eb
-08
8-F
eb
-09
8-F
eb
-10
9-F
eb
-11
9-F
eb
-12
8-F
eb
-13
8-F
eb
-14
9-F
eb
-15
9-F
eb
-16
Flo
w C
ub
ic M
ete
rs/d
ay
Date
With pumping
Without pumping
Page 30
Self Selecting Spring Locations
Page 31
Self Selecting Spring Locations
Pre-Development Current Conditions With Juno Wellfield
Page 32
• Improved insight on water resources provided when evaluating coupled surface water and groundwater.
• Individual watersheds in the Edwards Plateau can be evaluated and modeled separately.
• Groundwater flow controlled by the morphology of the area more than the hydraulic properties of the rocks. Model is relatively insensitive to assignment of hydraulic properties.
• Recharge in the Edwards Plateau is modest. • Pumping of groundwater in basin will result in proportional reduction
of flow in the Devils River. Impact is most pronounced during low flow conditions.
• Relatively modest pumping in upper Devils River watershed has shifted live water ~10 miles south.
Major Observations
Page 33
Acknowledgements
Regional reconnaissance water-resource evaluation – Six
Edwards Plateau counties & Del Rio: (2009-2010)
Devils River Watershed
Field studies – Coypu Foundation: (2012-2013)
Groundwater Model – Nueces River Authority: (2014-2015)
Surface-Water Model – Devils River Conservancy: (2016-2017)
Lower Pecos River/Devils River Watersheds
Field studies – Coypu Foundation: (2015-2016)
Page 34
Contact Information
Ronald T. Green, Ph.D., P.G.
Institute Scientist
Earth Science Section
Space Science and Engineering Division
Southwest Research Institute
6220 Culebra
San Antonio, Texas 78238
1.210.522.5305 (office)
1.210.316.9242 (cell)