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Disturbance can be an important determinant of the foodweb that develops in the benthos. Wooton et al. (1996) found that predator-resistant ca.ddisflies (Dicosmoecusgilvipes) greatly increased in abundance in northern California rivers after flood frequencies were reduced from river regulation; this resulted in diminished energy in the food chain flowing to predatory fish by diverting most of the energy to predator-resistant grazers. The end result was lowered food availability for juvenile steelhead (Onchorynchus mykiss). Thus, reduction in invertebrate numbers or overall invertebrate productivity is only the most obvious means by which native fish faunas may be affected by changes in flow regime -- changes in invertebrate species composition may be equally important. While high spring flows are still the norm in the upper Colorado River, even with flow regulation, such regulation has resulted in a reduced frequency of years with flows of sufficient magnitude and duration to perform the dual role of cleaning the bed of fines and disturbing the benthic community. To what extent this reduction in frequency ultimately affects food availability for native fish is as yet unknown. We suspect that periods of back- to-back low-flow years would allow for the greatest changes to potentially occur. Studies are needed that will increase our understanding of the relationship between flows and the dynamics of invertebrate communities and foodweb linkages. Our study of embeddedness in relation to flows is only a first step in developing such an understanding. CONCLUSIONS 1) The sampling regime designed for and used in this study proved effective at identifying differences in embeddedness within different sites and habitat types and through time. 2) Though statistically significant, differences in depth-to-embeddedness detected between strata, bank position, and year were slight during the 1996 and 1997 study periods. 3) In general, depth-to-embeddedness was higher in riffles than in runs. 4) The years of our sampling represent a period of time when both reaches were freshly cleaned of fine sediments and should therefore provide a good baseline for future monitoring efforts. RECOMMENDATIONS We suspect that 5-6 years of consecutive monitoring will need to be done before trends in embeddedness can be adequately evaluated; the need is for a series of years containing a wide range of flow conditions. Depth-to-embeddedness was used in this study because many samples could be processed relatively quickly by a small field crew and no laboratory time was required. However, there 28