Surface-water quality and flow Modeling Interest Group
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Applications require an Arc/INFO grid of a digital elevation model (DEM) that contains the area of interest. A set of watershed boundaries are automatically delineated from the grid of the DEM. A watershed may be selected from this set or derived on the basis of a user-digitized point. After the watershed area is determined, the user is asked for the minimum drainage area assumed to support a channel. This value controls the density and configuration of the delineated drainage network. Summary statistics and iterative trials allow the user to experiment before choosing the final value. Once the basin and drainage network are established, HRU's can be delineated according to one of several different methodologies: 1) fixed interval grids; 2) irregular polygons; and 3) non-contiguous pixels. A menu for examining and modifying the HRU map and its attributes is provided. Data derived from the original elevation grid (e.g.; slope, aspect) or other grids of attribute data (e.g.; vegetation, soils) can be examined on the basis of HRU, grid cell, or attribute. The statistical distribution of an attribute within single HRU's or groups of HRU's can also be shown. HRU's can be grouped, divided, or eliminated. The GIS Weasel provides version control and documentation to track modifications of HRU maps. Once HRU's are defined, selected model parameters can be generated using HRU attributes and their statistical measures.
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