Flows and Recretion: A guide to studies for river professionals

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Flow Regimes, Long -Term Effects, and Recreation Most of the studies in this document focus on short -term or direct effects of flows on recreation, but long -term or indirect effects of flow regimes can also be substantial (Shelby et al., 1992; Whittaker et al., 1993). For example, flow regimes may affect riparian vegetation and the extent to which it encroaches on the river channel; the size, frequency, and distribution of beaches or other channel features; water quality; and aquatic and terrestrial species that use these ecosystems. These in turn affect "habitats" for boating, angling, camping, bird watching or other recreation activities. It is beyond the scope of this document to review research on this wide range of long -term effects; each area has a well - developed literature and research protocols. In addition, many of these biological and physical resources receive considerable attention in relicensing or other regulated river decision - making. But connections between their work and recreation impacts are seldom carefully developed or made explicit, even though effects can be profound. A few issues deserve consideration as river professionals look for ways to integrate findings from long -term biophysical studies with recreation information. 20 I Flows and Recreation: A Guide for River Professionals First, most long -term effects are not observable through reconnaissance -based or controlled flow studies, so assessing these effects may default to a comparison of current and pre- project conditions (to the extent these are even known). This may be helpful for describing how the current regime has altered the biophysical environment, but it is less useful for describing the effects of alternative future operation regimes and the "habitats" they may create. Second, recreation controlled flow studies focused largely on short term effects typically release flows well below bankfull levels, so they are probably not capable of triggering substantial geomorphic or riparian vegetation changes that researchers can study. Controlled flow studies can help model biological or physical responses to new flow regimes, but their findings depend upon the accuracy of model "assumptions.' For example, fish habitat modeling has become more sophisticated during the past twenty years, but it may take multiple years before some population -level effects can even be detected, and research that verifies model precision has been sparse. Similarly, while sediment transfer and beach - building studies in Grand Canyon have been intensive and illuminating, experimental "floods" or revised operating regimes have yet to dramatically restore Beaches provide "recreation habitat' for camping and swimming. High flows and sediment sources are needed to clean and replenish beaches, a biophysical process often affected by water development. Above: The number and size of beaches in Grand Can- yon have decreased since Glen Canyon Dam was built. Low flow regimes can produce warm temperatures with impacts such as stagnant pools and algae blooms. Left: California's Klamath River.