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Session 5b: BMP Representation in Models. Virginia Tech Biological Systems Engineering Department DEQ TMDL Modeling Workshop; Richmond November 19-20, 2013. To describe various ways that BMPs can be represented in models. Objective. Streamside Buffers. Representing BMPs in Models.
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Session 5b:BMP Representation in Models Virginia Tech Biological Systems Engineering Department DEQ TMDL Modeling Workshop; Richmond November 19-20, 2013
To describe various ways that BMPs can be represented in models Objective Streamside Buffers
Representing BMPs in Models • Land use changes • Riparian pasture to buffer • Hi-till to Lo-till cropland • Source reduction • Livestock exclusion • Reduced PS discharges • Streambank stabilization • Application of removal efficiencies • DCR Ag Cost-share tracking • Chesapeake Bay Model accounting • Reductions from upslope land uses • Grass and forest buffers
Land Use Change BMPs Each landuse in each sub-watershed has an area assigned Re-assign area between two land use categories, e.g. hi-till to lo-till • Add a new land use category
Modify time-series inputs from point sources Modify time series inputs of applied manure (bacteria and/or nutrients) Post-process loads, e.g. based on DMR data Source Reduction BMPs
If Existing BMPs are represented using efficiency factors, they can be calculated as an Aggregated Fraction (AF) of area treated in a given landuse to represent load reductions. Since models simulate loads, not reductions, the effect of BMPs on the loads is calculated as: Remaining load = simulated load x (1 – AF) Pass-thru Fractions Pass-thru fraction
Area Benefited (AB) by Riparian Buffers P and Sediment: AB = 2x buffer width N: AB = 4x buffer width