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 2
Collaborative for Sediment Source Reduction Greater 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 .” 3
Dr. Shawn Schottler Clean Water Council presentation (March 20, 2017): 4
Perennial Cover …. Cover Crops …. “Soil Health” Miller, T. P. , J. R. Peterson, C. F. Lenhart, and Y. Nomura. 2012. The Agricultural BMP Handbook for Minnesota. Minnesota Department of Agriculture. 5
BWSR Targeted Watershed Program: Dobbins Creek Cedar River Watershed District 6
Prime Farmland …. if drained 7
High Water Table Extensive subsurface drainage Optional Tagline Goes Here | mn.gov/websiteurl 8
Existing riparian corridor ….. few depressions 140 ft Few depressions 570 ft Well-defined floodplain 3/5/2019 9
BMPs of choice: Water and Sediment Grassed Waterways Buffers Control Basins (WASCOBs) Photo courtesy MN NRCS Photo courtesy USDA NRCS 10
Model Scenarios Example Land Use Maps • Riparian Corridor with BMPs Riparian Corridor (No BMPs) (No BMPs) Corn Soybeans • Conservation Tillage Developed Forest • With BMPs Grassland • BMPs w/ 30% Perennial Cover • 100% Perennial Cover • Prairie 11
Computed Flows (2.6” rainfall – June 2015) 12
Computed Flows (4.6” rainfall – September 2010) 13
Average Peak Flow Reduction 8 summer rainfall events (2009-2015) 80% 70% 60% 50% 40% 30% 20% 10% 0% No Perennial Exist Riparian Conservation with BMPs BMPs with 100% "Soil Prairie Cover Corridor Tillage 30% "Soil Health" Health" 14
Sediment Entering Channels 350 300 250 Lbs / Acre / Year 200 150 100 50 0 No Perennial Exist Riparian Conservation With BMPs BMPs & 30% 100% "Soil Prairie Cover Corridor Tillage "Soil Health" Health" 15
WEPP: Water Erosion Prediction Project X 2.4 Chapter 7: Soil Component 3/5/2019
A very small percent of the landscape controlled by the proposed WASCOBs Optional Tagline Goes Here | mn.gov/websiteurl 17
Average Annual Flow 12 10 8 Inches 6 4 2 0 Prairie Existing w/o Tile Existing w-Tile Total Water Yield Total Tile Flow 18
Cover Crops/Soil Health ….. Subsurface Drainage Increased infiltration • Higher water table • Increased tile flow Partially Offset by • Greater spring and fall plant transpiration • Higher soil water holding capacity 3/5/2019 19
Take Home Message re: Altered Hydrology • Traditional BMPs: “individually effective, collectively not enough” • Widespread adoption of perennial cover (cover crops, 2 nd 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 20
Questions / Comments? Jim Solstad, Retired Division of Ecological and Water Resources Cedar River Watershed District – October 16, 2017 21
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