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ARS Home » Northeast Area » University Park, Pennsylvania » Pasture Systems & Watershed Management Research » Research » Publications at this Location » Publication #151319
Title: PROCESS REPRESENTATION IN WATERSHED-SCALE HYDROLOGIC MODELS: AN EVALUATION IN AN EXPERIMENTAL WATERSHED

Author
item Veith, Tameria - Tamie
item SRINIVASAN, M - PENN STATE UNIV.
item Gburek, William

Submitted to: First Interagency Conference on Research in the Watersheds
Publication Type: Proceedings
Publication Acceptance Date: 10/27/2003
Publication Date: 10/30/2003
Citation: Veith, T.L., Srinivasan, M.S., Gburek, W.J. 2003. Process representation in watershed-scale hydrologic models: An evaluation in an experimental watershed. First Interagency Conference on Research in the Watersheds. p. 241-247.

Interpretive Summary: Spatial and temporal variations in the hydrologic behavior of a watershed directly impact nutrient transport from land to water. Thus, accurate modeling of hydrologic responses within a watershed contributes to a better understanding of pollutant losses within that watershed. Three computer simulation models - Areal Nonpoint Source Watershed Environmental Response Simulation (ANSWERS-2000), Soil and Water Assessment Tool (AVSWAT2000), and Soil Moisture Distribution and Routing (SMDR) - were used to simulate the surface hydrologic processes in a study watershed. The three models vary in their temporal and spatial process representations. Overall, AVSWAT2000 was determined the most favorable for depicting hydrological processes in the study watershed, although spatial representation of runoff processes in this model may need further refinement. By accurately modeling hydrologic response in this type of watershed, future efforts in modeling pollutant source and transport can build on a solid foundation.

Technical Abstract: Hydrologic response varies within a watershed as a function of topography, soil, and land cover. Spatial and temporal data from experimental watersheds may provide information on where, when, how, and why the response varies. This study examined the hydrologic response of an agricultural watershed, FD-36, in the Appalachian Valley and Ridge physiographic region. FD-36 is characterized by shallow, fragipan soils in near-stream areas and deep, well-drained soils in upland areas. Three computer simulation models - Areal Nonpoint Source Watershed Environmental Response Simulation (ANSWERS-2000), Soil and Water Assessment Tool (AVSWAT2000), and Soil Moisture Distribution and Routing (SMDR) - were used to simulate the surface hydrologic processes in FD-36. The three models vary in their temporal and spatial process representations. AVSWAT2000 and SMDR are daily time-step models while ANSWERS-2000 runs at a one-minute time step. Spatially, ANSWERS-2000 and SMDR divide the watershed into grid cells; AVSWAT2000 uses hydrologic response units (HRUs). Of the three models, temporal output from AVSWAT2000 matched measured stream flow most closely (r2 = 0.67). ANSWERS-2000 and AVSWAT2000 both reacted to variations in land cover and soils, whereas SMDR did not. ANSWERS-2000 and AVSWAT2000 indicated the majority of high runoff depths from croplands on near-stream, fragipan soils. Overall, AVSWAT2000 was determined the most favorable for depicting hydrological processes in FD-36, although spatial representation of runoff processes in this model may need further refinement.