TITLE:
Comparison of Three Delineation Methods Using the Curve Number Method to Model Runoff
AUTHORS:
William D. Troolin, Katherine Clancy
KEYWORDS:
Geographic Information Systems, Runoff, Watershed Management, Curve Number
JOURNAL NAME:
Journal of Water Resource and Protection,
Vol.8 No.11,
October
10,
2016
ABSTRACT: Digital Elevation
Models (DEMs) are spatial grids which are used to automate watershed boundary
determination. Sinks are present within most DEMs. In order to easily process
the watershed boundary, the sinks are reassigned to elevation equivalent to an
adjacent cell. The derived DEM is called a “filled” DEM. Due to its relative
simplicity, the use of the “filled” DEM is one of the most widely used methods
to delineate watershed boundaries and works well in about 70 percent of the
watersheds in the US. In landscapes with internal drainage, sinks may
accurately represent these depressions. In this study, we compare two
delineation methods that do not fill in sinks to another method that does fill
in sinks. We examined ten gaged watersheds in Wisconsin and Minnesota. We found
the spatial extent of the watersheds from the three methods were significantly
different. To evaluate the delineation methods, we modeled ten runoff events
using the Curve Number (CN) method and compared them to USGS gage discharge for
each watershed. For small storms we found that there were no significant
differences in the modeled runoff for three delineation methods. For large
storms, we found the no-fill methods had a smaller error, but overall the
difference was insignificant. This research suggests that capturing internal
drainage by the delineation does not have much of an impact on the widely used
CN model.