ABSTRACT: The Soil and Water Assessment Tool (SWAT) model, designed for use on rural ungaged basins and incorporating a GRASS GIS interface, was used to model the hydrologic response of the Ariel Creek watershed of northeastern Pennsylvania. Model evaluation of daily flow prior to calibration revealed a deviation of runoff volumes (Dv) of 68.3 percent and a Nash‐Sutcliffe coefficient of‐0.03. Model performance was affected by unusually large observed snowmelt events and the inability of the model to accurately simulate baseflow, which was influenced by the presence of fragipans. Seventy‐five percent of the soils in the watershed contain fragipans. Model calibration yielded a Dv of 39.9 percent and a Nash‐Sutcliffe coefficient of 0.04, when compared on a daily basis. Monthly comparisons yielded a Nash‐Sutcliffe coefficient of 0.14. Snowmelt events in the springs of 1993 and 1994, which were unusually severe, were not adequately simulated. Neglecting these severe events, which produced the largest and third largest measured flows for the period of record, a Dv of 4.1 percent and Nash‐Sutcliffe coefficient of 0.20 were calculated on a daily comparison, while on a monthly basis the Nash‐Sutciffe coefficient was 0.55. These results suggest that the SWAT model is better suited to longer period simulations of hydrologic yields. Baseflow volumes were accurately simulated after calibration (Dv= ‐0.2 percent). Refinements made to the algorithms controlling subsurface hydrology and snowmelt, to better represent the presence of fragipans and snowmelt events, would likely improve model performance.
[1]
Jeffrey G. Arnold,et al.
Estimating hydrologic budgets for three Illinois watersheds
,
1996
.
[2]
Ronald L. Bingner,et al.
Runoff simulated from goodwin creek watershed using SWAT
,
1996
.
[3]
W. Waltman,et al.
Fragipans in Pennsylvania Soils1
,
1995
.
[4]
Raghavan Srinivasan,et al.
Alternative River Management Using a Linked GIS-Hydrology Model
,
1995
.
[5]
Raghavan Srinivasan,et al.
INTEGRATION OF A BASIN‐SCALE WATER QUALITY MODEL WITH GIS
,
1994
.
[6]
Drainage Division,et al.
Criteria for Evaluation of Watershed Models
,
1993
.
[7]
K. Loague,et al.
Statistical and graphical methods for evaluating solute transport models: Overview and application
,
1991
.
[8]
Marc B. Parlange,et al.
SUBSURFACE FLOW ABOVE A FRAGIPAN HORIZON
,
1989
.
[9]
A. Rango,et al.
MERITS OF STATISTICAL CRITERIA FOR THE PERFORMANCE OF HYDROLOGICAL MODELS1
,
1989
.
[10]
C. W. Richardson.
Stochastic simulation of daily precipitation, temperature, and solar radiation
,
1981
.
[11]
Contribution of Lateral Soil Water Movement above a Fragipan to Streamflow1
,
1977
.
[12]
J. Monteith.
Radiation and Crops
,
1965,
Experimental Agriculture.