Model Linkages

Linking of models in the DSS provides a way to examine water-resource problems at reach and cross-section scales using streamflow that reflect basin-wide water resources. Many water-management issues, such as fisheries and water-fowl habitat, water-quality concerns, and channel maintenance for river recreation, need reach-specific hydraulic and chemical information, conditioned on upstream streamflow. That is, the detailed hydrology of a given reach must include the constraints of the overall physical hydrology and water management within the basin.

One way to include these constraints is to use reach-specific models within the modeling sequence. Several reach-specific models are included in MMS and can be linked with both watershed-model or RiverWare output. For example, a one-dimensional hydraulic model using daily streamflow from RiverWare, along with detailed local topography and bed material information, can be used to predict a stage-discharge relation, reach-averaged vertical distributions of velocity, and stress at a cross-section (Nelson and others, 1991). These relations provide the necessary hydraulic input to compute bed sediment discharge (Parker and others, 1992). Identifying sediment discharge and associated hydraulic conditions, and predicting changes that occur with alterations in the hydrograph are critical to an understanding of channel and habitat maintenance.

A linkage being examined for the Yakima River Basin is the use of a river-reach habitat module in MMS and the linkage of this to RiverWare. For this work, relations between stream networks and the upstream area, slope, precipitation, runoff, forest density, and land use will be analyzed. Initially, a stream network was defined using the GIS Weasel. A stream channel was defined wherever the drainage area for a grid cell was greater than 0.47 square miles resulting in a detailed network (fig. 6). This network of more than 7,000 miles will then be compared to basin characteristics. Changes in stream-slope (gradient), width, depth, and flood-plain will then be related back to the relations found. If this linkage proves promising, the information may be used to develop habitat-type curves for a MMS module and linkage to RiverWare.

Future Efforts

Continued work in the WARSMP will be in the Yakima River Basin and the Rio Grande River Basin, New Mexico. The goal of each new project is to develop additional algorithms to the MMS and the RiverWare system in order to help solve additional water-resource problems, especially related to biologic problems and needs.

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