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
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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)
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Edwards-Trinity Aquifer
Edwards-Trinity Aquifer GAM (Anaya and Jones, 2009)
Page 4 Edwards-Trinity Aquifer GAM (Jones et al., 2009)
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
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Groundwater Model Refinement
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Groundwater Model Mesh Refinement
Mesh refinement at areas where the surface-water flow
accumulation has selected stream channels
Sycamore Creek
Watershed
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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
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Flo
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rs/d
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Date
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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?
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Groundwater Pumping Scenario 8,000 gpm at Juno
200,000
300,000
400,000
500,000
600,000
700,000
800,000
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With pumping
Without pumping
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Self Selecting Spring Locations
Page 31
Self Selecting Spring Locations
Pre-Development Current Conditions With Juno Wellfield
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• 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)