Developing a GIS for the lower Colorado River Delta

   Ground-work to collect biological data on the Colorado River delta is certainly time-consuming and difficult; it is also difficult in terms of matching differently scaled, transborder map data. If successful, monitoring the Colorado River delta using remote sensing tools (and constructing a hydrological and habitat model in the delta) can provide broader coverage in a more timely, accurate manner. A series of remote sensing imagery over time could help in the management of these sensitive areas and emphasize the impact of U.S. water releases. Monitoring the delta will further the understanding of the consequences of land-cover and land-use change on habitat value; knowing the amount and type of changes will allow decisions to be made about the future sustainability and resilience of the natural resources (i.e., water). Monitoring this ecosystem will also provide information to be used to assess vegetation spatial variability, economic models, and societal responses to land cover change.

   A GIS of the delta can be used to predict consequences of flow releases to the delta in terms of flooding and vegetation response. Inputs into the ecosystem model will include regression equations relating vegetation, evapotranspiration and flooded area to flow volumes and frequencies.

   “Hydrologic analysis tools may be implemented in a raster-based GIS, such as ArcInfo's Grid module or ArcView's Spatial Analyst, to yield flow direction, flow accumulation and watershed layers within the floodplain. From the elevation data it may be possible to construct a three-dimensional surface model of the delta region and perform a volumetric analysis of past floods. These data can then be used to model other flooding scenarios using different configurations of elevation within the floodplain (elevations change temporally due to siltation and channel-clearing activities). These results can then be overlaid on the habitat and vegetation maps to predict consequences of flooding or channel alteration on areas of environmental concern.”

   “A custom-built, simplified interface may be developed in ArcView to allow managers and researchers to use the GIS to predict the extent and duration of flooding as a function of flow releases, and predicted effects on vegetation and habitat. Predictions of the GIS may be tested against future flow releases, allowing this product to be verified and refined, similar to LCRAS (Glenn et al., 2001c).”