WWRC 83-06
Nonpoint-Pollution Model Sensitivity to Grid-Cell Size
Abstract
Nonpoint-pollution models estimate loadings of chemicals, sediment,
and nutrients that degrade water quality. Before controls can be implemented,
location and severity of pollution must be identified in the watershed basin.
Geographic information systems (GISs) are computer-automated, data management
systems simplifying the input, organization, analysis, and mapping of spatial
information. Because nonpoint-pollution models simulate distributed watershed basin
processes, a heterogeneous and complex land surface must be divided into
computational elements such as grid cells. Model parameters can be derived from each
grid cell directly from maps using GIS. Cell size selection, if arbitrarily determined
though, yields ambiguous if not erroneous results. This paper investigates the effects
of cell size selection through a sensitivity analysis of input parameters for the
nonpoint-pollution model, Agricultural Nonpoint Source Pollution Model (AGNPS),
using a GIS for a small research watershed. Model grid-cell sizes were found to be
the most important factor affecting sediment yield. As the grid-cell sizes increase,
stream meanders are short-circuited. The shortened stream lengths cause sediment
yield to increase by as much as 32%.
Water Resources Publications List
Water Resources Data System Library |
Water Resources Data System Homepage
