1.
Page 1
Texas Water Conservation Association
70th Annual Convention
The Importance of
Groundwater/Surface Water Interaction:
A Case Study on Rio Grande Water Supplies
March 6, 2014
by
Ronald T. Green, Ph.D., P.G., F. Paul Bertetti, P.G., and Marques Miller
Geosciences and Engineering Division
Southwest Research Institute®

2.
Page 2
Groundwater vs Surface Water in Texas
Surface water belongs to the state of Texas. It can be used
by a landowner only with the state's permission.
Generally, groundwater belongs to the landowner.
Groundwater is governed by the rule of capture.
There are exceptions…
"Underground water" means the water existing below the
earth's surface, …does not include defined subterranean
streams or the underflow of rivers (Texas Water Code)

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A Case Study on Rio Grande Water Supplies:
Devils River Basin, Texas

4.
Page 4
Groundwater Recharge of the Lower Rio Grande
What is groundwater’s importance to the Lower Rio Grande?
Conveyance of groundwater/surface water in Devils River
watershed
Importance of permeability architecture in Devils River to Rio
Grande

5.
Page 5
Amistad Reservoir Water Budget
Lake
Amistad
Devils
River
Pecos
River
Rio Grande at Langtry
San Felipe
Creek
Rio Grande below Amistad Dam
Cienegas
Creek
Gauging Station
Goodenough
Spring

6.
Page 6
Amistad Reservoir Water Budget (acre-ft/yr)
Lake
Amistad
Devils
River
263,000
Pecos
River
195,000
Rio Grande at Langtry
1,071,000
San Felipe
Creek
65,000
Rio Grande below Amistad Dam
1,659,000
Rio Grande at Del Rio
1,659,000
Cienegas
Creek
8,700
Gauging Station
Goodenough
Spring 103,000
Lower Rio Grande gets 1/3 of its
water from Val Verde County

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Page 7
How is Water Conveyed through the
Devil’s River Watershed?
Sutton County - Standen A. and P. Kirby, 2009
Crockett County - Inglehart, H.H. 1967
Val Verde County - Reeves, R.D. and T.A. Small. 1973.

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Where are the
High Capacity Wells in the
Devils River Watershed?
TWDB well driller reports: 752
wells with measured capacity
High capacity water wells are
only located near river channels

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0
500
1,000
1,500
2,000
2,500
3,000
0 2 4 6 8 10 12 14 16
WellPumpRate(gpm)
Distance from Closest River Channel (mi)
Distance from River Channel
versus Well Capacity
Virtually all wells with capacity of 500 gpm
are within 1.5 miles of a river

10.
Page 10
Development of Karst Conduits in
Edwards-Trinity Aquifer
Slightly acidic rain water funneled into existing river channels as the Edwards
Plateau was raised.
This mechanism resulted in development of preferential flow paths (i.e.,
conduits) in river channels.
In contrast, conduit development in the Edwards Aquifer was pervasive
because it was not exhumed (raised) similar to the Edwards Plateau.
Woodruff and Abbott, 1979, 1986
What this means is that you cannot assume you have
high capacity wells everywhere in the Edwards-Trinity
Aquifer just because you happen to have a high-capacity
well that’s near a river channel

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Refined Characterization of Devils River
Watershed Hydrogeology
Water is conveyed through Devils
River watershed as both
groundwater (particularly in the
upper reaches) and as surface
water (in the lower reaches).
Texas water law struggles with
groundwater/surface water
relationship, but reality insists it be
recognized.
Dye tracer tests in Sonora confirm
the presence of conduits in
Devils River channel

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How is Groundwater Flow Currently Characterized?

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Page 13
Permeability Structure of the
Edwards-Trinity Aquifer

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Refinement of Hydrogeology of
Devils River Watershed
Mapped geology of
Devils River watershed
TWDB GAM of
Devils River watershed
hydrogeology
Refined characterization of
Devils River watershed
hydrogeology
The 2010 TWDB Groundwater Availability Model (GAM)
does not characterize groundwater flow associated with the
river channels as subterranean streams or river underflow

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Page 15
Reclassification of Groundwater Conveyance in
the Devils River Watershed
If groundwater conveyance in the Devils River watershed is
classified as “subterranean streams or the underflow of
rivers”, then groundwater conveyance could be governed as
surface water and not by the rule of capture.

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Page 16
What Are the Consequences if Devils River Watershed
Groundwater is Governed by the Rule of Capture?

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Amistad Reservoir Water Budget
Lake
Amistad
Devils
River
Pecos
River
Rio Grande at Langtry
San Felipe
Creek
Rio Grande below Amistad Dam
Rio Grande at Del Rio
Cienegas
Creek
Gauging Station
Goodenough
Spring

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Page 18
Amistad Reservoir Water Budget (acre-ft/yr)
Lake
Amistad
Devils
River
263,000
Pecos
River
195,000
Rio Grande at Langtry
1,071,000
San Felipe
Creek
65,000
Rio Grande below Amistad Dam
1,659,000
Rio Grande at Del Rio
1,659,000
Cienegas
Creek
8,700
Gauging Station
Goodenough
Spring 103,000

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Page 19
Experience of Historical Groundwater Exploitation

20.
Page 20
Amistad Reservoir Water-Budget
Analysis (acre-ft/yr)
Groundwater Discharge
Amistad Reservoir
(1961-1967)
Pecos River 32,000
Goodenough Spring 89,000
Devils River 240,000
San Felipe Springs 58,000
Minor springs on the Rio Grande 2,000
Unmeasured springs on the Rio Grande 81,000
Total 502,000
Reeves, R.D. and T.A. Small. 1973.
Groundwater Resources of Val Verde County,
Texas. Report 172. Texas Water Development
Board.
Groundwater Discharge
Amistad Reservoir
(1961-2000)
Pecos River 194,000
Goodenough Spring 103,000
Devils River 264,000
San Felipe Springs 65,000
Cienegas Creek 8,700
Unmeasured springs Rio Grande -
Total 634,000
Data from IBWC website 1961-2000

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Amistad Reservoir Water Budget (acre-ft/yr)
(1961-2000)
Lake
Amistad
Devils
River
263,000
Pecos
River
195,000
Rio Grande at Langtry
1,071,000
San Felipe
Creek
65,000
Rio Grande below Amistad Dam
1,659,000
Rio Grande at Del Rio
1,659,000
Cienegas
Creek
8,700
Gauging Station
Goodenough
Spring 103,000

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Page 22
Lake
Amistad
Devils
River
263,000
Pecos
River
195,000
-?
32,000
Rio Grande at Langtry
1,071,000
San Felipe
Creek
65,000
Rio Grande below Amistad Dam
1,659,000 1,496,000
Rio Grande at Del Rio
1,659,000 1,496,000
Cienegas
Creek
8,700
Historical Impact of Pumping on
Amistad Reservoir Water Budget (acre-ft/yr)
Pecos River Discharge (1961-1967)
Gauging Station
Goodenough
Spring 103,000

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Potential Impact of Pumping on
Amistad Reservoir Water Budget (acre-ft/yr)
from Three Proposed Projects
150,000 acre-ft/yr
49,000 acre-ft/yr
93,826 acre-ft/yr

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Potential Impact of Pumping on
Amistad Reservoir Water Budget (acre-ft/yr)
from Three Proposed Projects
Lake
Amistad
Devils
River
263,000
-150,000
83,000
Pecos
River
195,000
-49,000
146,000
Rio Grande at Langtry
1,071,000
San Felipe
Creek
65,000
Rio Grande below Amistad Dam
1,659,000 1,460,000
Rio Grande at Del Rio
1,659,000 1,460,000
Cienegas
Creek
8,700
Gauging Station
Goodenough
Spring 103,000
Sycamore
Creek
-93,826
?
1,460,000 1,366,000

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Recharge/groundwater/surface water are intrinsically linked in a
watershed that recharges Amistad Reservoir
Conveyance of water through Devils River watershed is
facilitated by development of conduits coincident with river
channels
Other Edwards Plateau watersheds show similar characteristics
Can this conduit system be defined as subterranean streams or
the underflow of rivers?
This presentation provides a clear example of how a technical
study can be used to frame regulatory governance of a water
resource
Summary

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Acknowledgement
Funding for water resource assessment of
Devils River watershed provided by the
Coypu Foundation

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Contact Information
Ronald T. Green, Ph.D., P.G.
Institute Scientist
Geosciences and Engineering Division
Southwest Research Institute
6220 Culebra
San Antonio, Texas 78238
1.210.522.5305 (office)
1.210.522.5184 (fax)
1.210.316.9242 (cell)
rgreen@swri.edu