Rainfall Zones
Rainfall is handled by two different feature classes. The first (and traditional one) is named "Rainfall Stations" and contains point features that represent rain gage locations in or near the model domain (gages do not need to be within the Basin feature class). The second, newer way, is to use a feature class named "Rainfall Zones" that contains polygons representing areas with the same rainfall. In the extreme these polygons may represent individual NEXRAD cells, but they are most commonly used to represent aggregated NEXRAD values, for example, integrated over HUC 12 polygons.
If the Rainfall Zones feature class is not present, or if the user decides not to use it, a Theissen polygonalization is used to interpolate rainfall data from the Rainfall Station gage data to each unique cell in the model domain. This options is presented during creation of the unique grids.
If the Rainfall Zones feature class is present and the user has collected the necessary NEXRAD data, the Rainfall Stations feature class still needs to be present and have a point feature that overlies each polygon in the Rainfall Zones feature class.
Generally, the Rainfall Stations point feature class will not need to have any data imported since the create rain stations tool on the WAM Toolbar is used to add points to the feature class. Data is then imported using the Feature Properties Editor with the Rain Station layer highlighted and the rain station selected.
The Rainfall Zones feature class is not imported using the Import GIS Data command. To add this feature class, first develop a feature class with polygon features that delineate the appropriate zones, e.g., HUC 12 polygons as mentioned above. Add a field named "RainZoneID" with type long integer, clip the feature class to the basin boundary using the Basin feature class, and copy it into the WAM GIS Database. Each polygon in the feature class needs to have the RainZoneID set to the same RainStationID of the point feature that overlies the polygon.
The required fields in the RainStaions feature class:
| Attribute | Alias | Data Type | Scenario_WAM Join Table |
|---|---|---|---|
| RainStationID | Rain Station ID | Long Integer | Weather_Rain_Type.ID |
| RainStationName | Rain Station Name | String (100) | N/A |
Rainfall Station Data Quality Assumptions
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The location of each point feature is accurate.
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The StationID attribute of each feature polygon corresponds to a station in the Weather_Rain_Type table in the Scenario_WAM database.
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A complete join can be created between the Station ID and the rainfall time series tabular records.
The required fields in the RainfallZones feature class:
| Attribute | Alias | Data Type | Scenario_WAM Join Table |
|---|---|---|---|
| RainZoneID | RainZoneID | Long Integer | N/A |
Rainfall Zones Data Quality Assumptions
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The spatial extent of each feature polygon is accurate and there are no gaps or overlaps between polygons.
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The RainZoneID attribute of each feature polygon corresponds to a station in the Weather_Rain_Type table in the Scenario_WAM database.