Invertebrate Communities Used as Indicators of River Restoration
River corridor restoration requires descriptions of degraded conditions and detection of deviations from desired conditions. Tools are needed to assess progress and to aid in adaptive management of restoration efforts. Riparian systems, however, may be difficult to characterize because communities are at the boundary between terrestrial and freshwater ecosystems. Theories regarding conditions at boundaries are understudied relative to river continuum and river mosaic concepts but it has been suggested that boundary concepts are important in understanding lotic systems. This Science and Technology (S&T) research project studies both butterfly communities (terrestrial component) and benthic invertebrates (aquatic component)as integrators for characterizing river restoration. Presence/absence of congruence between terrestrial and aquatic groups might suggest impact levels. Positive patterns in both groups might suggest completion of restoration, while a lag in either group might suggest specific adaptive alternatives.
Need and Benefit
Reclamation is involved in a large number of river restoration projects over a wide geographic range. Restoration projects are typically related to water delivery, water salvage, or avoiding impacts to endangered species. Reclamation is supporting restoration projects on the Elwha River, Rio Blanco, Trinity River, Umatilla River, and Yakima River to name but a few. A large amount of money has been directed towards these restorations and it is estimated that one billion dollars has been spent just in the Southwestern United States since the 1980s. Although it is recognized that successful restoration requires assessment, Bernhardt et al. (2005) found that only 10 percent of project records indicated that any form of characterization occurred. They also suggest that steps towards standardizing assessment methods would allow managers to understand whether goals are being accomplished. The present research would aid in standardizing these sorts of assessments and help Reclamation determine the success of projects.
It is suggested that initial studies would take place on rivers that Reclamation has a direct interest in, and with a variety of perceived problems. These include the San Diego River (water salvage), Las Vegas Wash (water suitability), and Yakima (endangered species). The use in these studies of both aquatic and terrestrial components will integrate assessment of the riverine ecosystem. One of the advantages in using invertebrates is that there is typically a quick response time to changing conditions and a gradient of responses within the communities. Information gained should be generalizable to other Reclamation projects with similar problems.
Project objectives for the San Diego River include increased water suitability and ground water recharge. Reclamation is helping construct flood control structures in Las Vegas Wash that are designed to decrease water suitability problems associated with nutrients, salinity, and sediment. Reclamation, as water master for Lake Mead and the Colorado River, is concerned with these constituents. In the Yakima, water reliability is a concern and methods are being developed to increase water reliability in conjunction with ecological concerns. Studying biotic responses to flow changes will aid in protection of the five hundred million dollar annual crop value in the Yakima area.
Bureau of Reclamation Review
The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.
San Diego River Invertebrate Monitoring Program- Final Report (final, PDF,
By Mr. S. Mark Nelson and Rick Wydoski
Report completed on May 11, 2008