Evaluation of watershed conservation

Evaluation of Watershed Conservation Management Practices to Reduce

Pollutant Loads in Grand Lake St. MarysUsing AnnAGNPS

• Ronald L. Bingner, USDA-ARS, Oxford, MS• Yongping Yuan, USEPA, Las Vegas, NV• Henrique Momm, Middle TN State Univ.,

Murfreesboro, TN• Milo Anderson, USEPA, Chicago, IL• Martin Locke, USDA-ARS, Oxford, MS

Grand Lake St. Marys in northwestern Ohio is experiencing toxic levels of algal blooms resulting from nutrient input from agricultural runoff.

Problem

Grand Lake St Marys, Ohio

Grand Lake St Marys, Ohio

GLSM - Tributaries

Objective

To determine where and if conservation practices can be placed and/or adopted to reduce phosphorus loadings to Grand Lake St Marys, Ohio.

AnnAGNPS

Agricultural Research ServiceA partnering effort between the USDA:

andNatural Resource Conservation Service

National Sedimentation Laboratory

AnnAGNPS: USDA pollutant loading (PL) model

Erosion, yield, & loadings by type of PL:• Waterrainfall, snowmelt, irrigation, & point sources.

• Sediment by particle size-class and source: clay; silt; sand; small aggregate; and large aggregate.

• Chemicals (attached & dissolved): nutrientsnitrogen, phosphorous, & organic carbon; and pesticidesany number, any kind.

Necessary Datasets

►Terrain

►Soils

►Climate 1893 - 2010

►Landuse

Climate Stations

GLSM 3 Meter DEM

GLSM - Soils

GLSM – Landuse

GLSM – Landuse

SoybeansCornUrbanWheatPasture

Woods

2006

Alfalfa

25.8%35.0%9.0%3.4%5.2%

1.9%2.7%

Water 17.0%

GLSM Feedlots

3214 AnnAGNPS Cell Subdivision for GLSM

Average Annual Monthly Precipitation & RunoffConventional Tillage

30 Year Average Annual Loads to Grand Lake St. Marys Tillage Effects

Practice Runoff (in)

SedimentLoad (t/ac)

Total N (lb/ac)

Attached P

(lb/ac)

Dissolved P

(lb/ac)

Total P

(lb/ac)

Existing Tillage

12.4 0.98 18.45 5.70 0.53 6.23

Minimum Tillage

9.8 0.69 13.73 4.46 0.46 4.92

No-Tillage

8.7 0.61 12.43 4.11 0.43 4.54

30 Year Average Annual Loads to Grand Lake St. Marys Riparian Buffer Effects

Practice Runoff (in)

SedimentLoad (t/ac)

Total N (lb/ac)

Attached P

(lb/ac)

Dissolved P

(lb/ac)

Total P

(lb/ac)

50 meter Grass Buffer

12.4 0.317 9.28 3.48 0.44 3.92

No Buffer

12.4 0.975 18.45 5.70 0.53 6.23

Average Annual Monthly Phosphorus LoadingVarious Scenarios

Phosphorus Load Reduction From Conservation Practices

A. Conventional Tillage

B. Minimum Tillage

C. No-Tillage

D. Buffers w/ Conv. Till.

E. Rye Cover w/ Conv. Till.

F. Clover Cover w/ Conv. Till.

G. Wheat Cover w/ Conv. Till.

H. Vetch Cover w/ Conv. Till.

I. Radish Cover w/ Conv. Till.

J. No-Till w/ Radish Cover

w/ Buffers

Phosphorus Loads to GLSMExisting Conditions – 30 Year Simulation

lb/ac

Contributed Phosphorus Load vs. Contributing Drainage Area

26% of the GLSM Watershed Contributes 50% of the Phosphorus Load

Areas Contributing 50% of the Phosphorus Load to GLSMExisting Conditions – 30 Year Simulation

lb/ac

Phosphorus Loads to GLSMWinter Wheat Cover – 30 Year Simulation

lb/ac

53% Phosphorus

Load Reduction to GLSM withWinter Wheat

Cover

Summary 26% of the watershed contributes 50% of the P

loads to GLSM.Many P loads entering GLSM originate near the

lake boundary. Reducing these loads alone would have a significant impact on reducing the total P loads into the lake.

Cover crops can reduce P loads by over 50% and up to 70%.

Riparian buffers can reduce P loads to the lake by up to 37%.

SummaryMinimum tillage and no-tillage conservation

practices can reduce P loads by up to 27%. Integrated conservation practices as part of an

overall watershed management plan could be implemented on high potential P loading source areas to minimize the economic impact and maximize the impact on reducing P loads.

Additional investigations can help understand how the changing lake boundary since 1938, with changing urbanization, has effected P loads into the lake.

Thank you

Observed versus SimulatedRunoff, sediment, total P, and SRP

Base conditions scenarioPBIAS, RSRS, NSE and r2

Load PBIAS RSR NSE r2

Runoff -10.8 0.87 .24 0.53

Sediment 637 7.8 -60 0.37

Total P 416 5.1 -25 0.50

SRP -20 0.77 0.4 0.66

30 Year Average Annual Loads to Grand Lake St. Marys Cover Condition Effects

Practice Runoff (in)

SedimentLoad (t/ac)

Total N (lb/ac)

Attached P

(lb/ac)

Dissolved P

(lb/ac)

Total P

(lb/ac)

Clover 6.7 0.58 14.18 3.25 0.18 3.43

Radish 7.5 0.28 6.77 1.67 0.12 1.79

Rye 7.4 0.59 13.93 3.26 0.17 3.43

Vetch 7.7 0.46 11.17 2.66 0.15 2.81

Wheat 12.6 0.52 10.77 2.80 0.15 2.95

Coldwater Creek554 μg/L Total Phosphorus

430 μg/L DRP (77.6%)

Beaver Creek1140 μg/L TP

846 DRP (74%)@2.9 cfs

Prairie Creek458 μg/L TP

433 μg/L DRP (94.5%)

Chickasaw Creek769 μg/L TP

611 μg/L DRP (79%)

@~4 cfs

Barnes Creek645 μg/L TP

532 μg/L DRP (82%)

GLSM Spillway Discharge 265 μg/L TP

12 μg/L DRP (4.5%)

GLSM Tributary Phosphorus Concentrations

September 27, 2011

Little Chickasaw Creek448 μg/L TP

370 μg/L DRP (83%)

A typical Ohio stream with a mixture of land uses has a phosphorus concentration of 50 μg/L

Burntwood Creek249 μg/L TP

183 μg/L DRP (83%)@1.8 cfs

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