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

15

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