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• Near stream areas, and areas with shallow soils over a slowly permeable glacial till or bedrock produce the majority of runoff
• Hydrology is, to a great extent, driven by topography
VSA CHARACTERISTICS
Total runoff and the saturated portion of the watershed is a function of amount of precipitation
If rainfall > ET, soil wets up
MODELING VSA HYDROLOGY
If rainfallexcess
> soil storage, overland flow
SPPQ
e
e
+=
2
Modeling approaches:
⎟⎟⎠
⎞⎜⎜⎝
⎛⋅⋅
=DK
A
sβλ
tanln
Soil topographic wetness indexSteenhuis et al. 1995, Walter et al. 2000
Knowledge of location of VSA is crucial for control of non-point source pollution
VSA HYDROLOGY AND BMP PLACEMENTVSA HYDROLOGY AND BMP PLACEMENT
Existing models often require extensive expertise and effort to be used on a routine basis for BMP planning
Need of maps of distributed runoff over the landscape for each storm
Spatial predictions that can be used to direct manure spreading schedules
• Develop a tool that readily indicates the likelyhood of runoff generation (and saturation)
• Spatially based and easy to use
• easily accessible, but scientifically sound
INTERACTIVE WEB TOOL ‐ CONCEPT
BACKGROUNDPROCESSING
GIS
• Topographic index• Administrative and infrastructural data
• Air photographs
INPUTTmax, Tmin, Pobs
Bedrock reservoir
Evaporation
Hydrologically sensitive area
root zone
runoff
deep percolation
snowmelt module(Pcalc)
Streamflow
OUTPUTHSA extent and
dynamic
DEM
Soil Topographic Index
HYDROLOGICAL MODEL