WMS:Gages

The Gages command can be used to establish the position and rainfall accumulation for rainfall gages. Gages may be entered with or without a terrain model present, but if a terrain model is present then gage weights (using the Thiessen polygon method) for each basin are automatically computed when the Compute Basin Data command is chosen. When a terrain model is not present the gage weights for each basin must be entered manually from within the Precipitation dialog.

In order for gage information to be used during the simulation, the basin precipitation type must be set to gage in the Precipitation dialog.

Defining/Editing Gages

The Gage dialog consists of a list of defined gages as well as the fields necessary to define a new gage. When a gage is selected from the list, its values are copied into the appropriate fields for editing. When the New button is chosen, a new gage is created with default values. If the Copy button is chosen a new gage is created with the values of the currently selected gage. The Delete button can be used to remove the currently selected gage.

The Gage Position

If a terrain model is being used then the X and Y position in a consistent coordinate frame need to be entered in the appropriate edit fields. Once there are three or more defined gages, the Thiessen polygon network can be displayed. If a terrain model is not being used then the weights must be assigned manually and the position information is not important. In this case the Define rain gage location toggle should be turned off.

The rain gage coverage may also be used to define the position of the gages. Each feature point in the rain gage coverage is converted to a gage location and will automatically appear in the HEC-1 Gages dialog. Click here for more information on the rain gage coverage.

The Gage Type

A gage may be a storm total and/or temporal distribution (recording) station type. Recording stations allow for a continuous (incremental or cumulative) rainfall accumulation to be entered. The storm total station only allows for a single rainfall value for the event. A station may be both types if the distribution corresponds to the storm total value entered. However, a more typical situation is to have several stations for which only a storm total is known and to which some type of standard distribution will be applied. To accomplish this, the storm total stations may be entered along with one "imaginary" gage that is used to define the distribution. When automatically computing weights, only storm total stations are used in the Thiessen network, and the distribution for each storm total station is found by locating the nearest distribution gage.

Related Topics

• Editing HEC-1 Parameters
• Defining Precipitation
• Precipitation from gages