title: Improving risk estimates of runoff producing areas: formulating variable source areas as a bivariate process.
abstract: Predicting runoff producing areas and their corresponding risks of generating storm runoff is important for developing watershed management strategies to mitigate non-point source pollution. However, few methods for making these predictions have been proposed, especially operational approaches that would be useful in areas where variable source area (VSA) hydrology dominates storm runoff. The objective of this study is to develop a simple approach to estimate spatially-distributed risks of runoff production. By considering the development of overland flow as a bivariate process, we incorporated both rainfall and antecedent soil moisture conditions into a method for predicting VSAs based on the Natural Resource Conservation Service-Curve Number equation. We used base-flow immediately preceding storm events as an index of antecedent soil wetness status. Using nine sub-basins of the Upper Susquehanna River Basin, we demonstrated that our estimated runoff volumes and extent of VSAs agreed with observations. We further demonstrated a method for mapping these areas in a Geographic Information System using a Soil Topographic Index. The proposed methodology provides a new tool for watershed planners for quantifying runoff risks across watersheds, which can be used to target water quality protection strategies.
authors.affiliation: Department of Biological and Environmental Engineering, Cornell University, Ithaca, NY 14853-5701, USA.
authors.forename: Xiaoya
authors.initials: X
authors.lastname: Cheng
authors.affiliation: Department of Environmental Resources Engineering, State University of New York College of Environmental Science and Forestry, Syracuse, NY 13210, USA.
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Shaw
authors.affiliation: Department of Biological and Environmental Engineering, Cornell University, Ithaca, NY 14853-5701, USA.
authors.forename: Rebecca D
authors.initials: RD
authors.lastname: Marjerison
authors.affiliation: Upper Susquehanna Coalition, 4729 State Route 414, Burdett, NY 14818, USA.
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Yearick
authors.affiliation: Department of Crop and Soil Sciences, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Stephen D
authors.initials: SD
authors.lastname: DeGloria
authors.affiliation: Department of Biological and Environmental Engineering, Cornell University, Ithaca, NY 14853-5701, USA. Electronic address: mtw5@cornell.edu.
authors.forename: M Todd
authors.initials: MT
authors.lastname: Walter
mesh_terms: D003247:Conservation of Natural Resources; D040362:Geographic Information Systems; D008962:Models, Theoretical; D011891:Rain; D018570:Risk Assessment; D045483:Rivers; D012987:Soil; D014876:Water Pollution / Q000517:prevention & control*
chemical_list: D012987:Soil
keywords: Bivariate; Curve number (CN); Nonpoint source (NPS) pollution; Soil topographic index; Storm runoff; Variable source area (VSA); Water quality