Surface-Groundwater interactions on the Eastern Snake River, ID

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Surface-Groundwater interactions on the Eastern
Snake River, ID
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Outline

• Objective Estimate of seepage loss along a
  segment of the Eastern Snake river

• River Channel Generation (RCMM)
• Unsteady flow simulation(10 non-raining days)
• Compare the outflow hydrograph with the actual
  hydrograph
• Calculate volume of water lost to the aquifer

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Misc. Facts about Idaho

• 3,100 miles of river, more than any other state
• 85 of all commercial trouts
• Number one producer of potatoes
• Paris and Montpellier 30 miles apart

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Study area
Unconfined aquifer Highly fractured basalt Water
Supply from snowmelt Precipitation 8 in/yr
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Human impact on the Eastern Snake system
(source IDWR)
Less surface water irrigation More efficient
irrigation Increased pumping
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Water Budget
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Increased stress on the aquifer
(source IDWR)
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Eastern Snake aquifer Model
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Eastern Snake aquifer
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River Channel generation
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3D Representation of river reaches

• Bathymetric data
• (Expensive, unavailable)
• 2D 3D representation
• 2D plan view (DOP)
• Calculate location of the thalweg
• Approximate cross-sections with analytical
  functions

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2D representation of the river segment

• Calculate Depth/Width for a 2 yr flow
• Offset the NHD flow line by W/2 to obtain the
  channel boundary

Depth
Width
2D Plan view
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River Channel generation (RCMM)

• REQUIRES 2D representation of the river segment
• GENERATES 3D representation
• Thalweg Calculates the radius of curvature
• Locates the thalweg using the
  radius of curvature/thalweg
• relationship
• Cross-sections Analytical (Beta functions) from
  the thalweg location

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Generated cross-sections
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Exporting river channel into HEC-RAS
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Unsteady simulation

• 10 day simulation
• Upstream boundary condition USGS flow hydrograph
  (_at_Minidoka)
• Downstream boundary condition stage hydrograph
  (_at_Kimberley)
• Compare the calculated/observed
• hydrograph

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Acknowledgments

• Dr Merwade (CRWR)
• Allan Willie (Hydrologist, IDWR)

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• Any questions?