In addition to computing basin averages for each polygon in a shapefile, the program also has support for basin zones. A zone is a collection of one or more subbasins. Zones are useful for aggregating results. For example, a shapefile may contain polygons that define areas both above and below a dam. By defining each as a zone, the averages for each zone will be computed in addition to the individual subbasins and tabulated in the 'basin averages' pane. The zone is defined using the ZONE column in a shapefile DBF. To include a subbasin in a particular zone(s), add the zone name to the column. For example, the figure below shows the contents of a DBF file with zones a, b, c, and d defined. Both subbasins COUNW and COUNL are in zone 'a'. A subbasin can be a member of multiple zones simply by separating the zone names with a comma. COUNL and DUNLL are members of more than one zone.
