Altered Hydrology: Going Beyond Best Management Practices (BMPs) to Clean Water
Jim Solstad, Retired
Division of Ecological and Water Resources
Cedar River Watershed District – October 16, 2017 1
GSSHA – Gridded Surface Subsurface Hydrologic Analysis
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Collaborative for Sediment Source ReductionGreater Blue Earth River Basin
Summary of Findings (March 2017):
• “Achieving water quality standards will require priority investment in more temporary water storage to reduce high river flows and bluff erosion. This is a critical component of a strategy to reduce sediment in the Minnesota River.”
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Dr. Shawn Schottler Clean Water Council presentation(March 20, 2017):
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Perennial Cover …. Cover Crops …. “Soil Health”
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Miller, T. P. , J. R. Peterson, C. F. Lenhart,and Y. Nomura. 2012. The AgriculturalBMP Handbook for Minnesota. MinnesotaDepartment of Agriculture.
BWSR Targeted Watershed Program: Dobbins CreekCedar River Watershed District
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Prime Farmland …. if drained
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High Water Table Extensive subsurface drainage
Optional Tagline Goes Here | mn.gov/websiteurl 8
Existing riparian corridor ….. few depressions
3/5/2019 9
570 ft
140 ft
Few depressions
Well-defined floodplain
BMPs of choice:
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Water and Sediment Control Basins (WASCOBs) Grassed Waterways Buffers
Photo courtesy USDA NRCS Photo courtesy MN NRCS
Model Scenarios
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Riparian Corridor (No BMPs) with BMPs
CornSoybeansDevelopedForestGrassland
Example Land Use Maps
• Riparian Corridor(No BMPs)
• Conservation Tillage
• With BMPs
• BMPs w/ 30% Perennial Cover
• 100% Perennial Cover
• Prairie
Computed Flows(2.6” rainfall – June 2015)
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Computed Flows(4.6” rainfall – September 2010)
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Average Peak Flow Reduction8 summer rainfall events (2009-2015)
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0%
10%
20%
30%
40%
50%
60%
70%
80%
No PerennialCover
Exist RiparianCorridor
ConservationTillage
with BMPs BMPs with30% "SoilHealth"
100% "SoilHealth"
Prairie
Sediment Entering Channels
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0
50
100
150
200
250
300
350
No PerennialCover
Exist RiparianCorridor
ConservationTillage
With BMPs BMPs & 30%"Soil Health"
100% "SoilHealth"
Prairie
Lbs
/ A
cre
/ Y
ear
WEPP: Water Erosion Prediction Project
3/5/2019
Chapter 7: Soil Component
X 2.4
A very small percent of the landscape controlledby the proposed WASCOBs
Optional Tagline Goes Here | mn.gov/websiteurl 17
Average Annual Flow
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0
2
4
6
8
10
12
Prairie Existing w/o Tile Existing w-Tile
Inch
es
Total Water Yield Total Tile Flow
Cover Crops/Soil Health ….. Subsurface Drainage
3/5/2019 19
Increased infiltration
• Higher water table
• Increased tile flow
Partially Offset by
• Greater spring and fall plant transpiration
• Higher soil water holding capacity
Take Home Message re: Altered Hydrology
• Traditional BMPs: “individually effective, collectively not enough”
• Widespread adoption of perennial cover (cover crops, 2nd crop; “soil health”) will move a long ways to achieving whatever “altered hydrology” goal is established.
• Significant reduction in surface runoff and associated erosion
• Potential increase in subsurface flow where tile are present
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Questions / Comments?
Jim Solstad, Retired
Division of Ecological and Water Resources
Cedar River Watershed District – October 16, 2017 21