Layers in the CWMS CAVI are like transparencies laid one on top of the other. Each layer includes representations of physical images such as roads, county and state boundaries, rivers, and subbasins. These are layered in the map window as color pictures. Each of these images, along with the associated data, is a layer. This page describes how you create and manage layers so that required data and information are easily viewed.
There are two types of layers: primary layers and map layers. Primary layers are automatically generated when a new watershed is created, are present in all CWMS watersheds (although some primary layers may be empty in some watersheds), and are module specific. The software creates primary layers when a stream alignment, time series icons, map window elements, and gridded precipitation data are created. A primary layer is also created when a forecast alternative has been selected for computation. Primary layers can contain sub-layers, for example, the Time Series Icons Layer can have several user-defined sub-layers that represent various types of data and information, such as flow and precipitation.
Map layers are optional and are loaded into the watershed by the user. Map layers are physical images which help the user visualize a watershed. There are several formats for map layers in CWMS, including maps from the Internet (Google street map, for example).