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Core Science Individual Discipline Summaries <br />Geomorphology <br />The main conclusion of the Geomorphology report is that flows are the limiting factor to <br />physical and ecological processes, and flow management is the key issue in terms of maintaining <br />or restoring these processes. Flow is not only the single most important driving factor; it is also <br />the driving factor that management has the greatest ability to influence. The analysis suggests <br />that reductions in high flows below McPhee Dam are a primary cause of geomorphic changes in <br />the Dolores River downstream of the dam. The primary changes that have occurred due to flow <br />modification have likely included changes in channel dimensions, including narrowing and <br />reduced depth, growth of lateral and mid-channel bars associated with reduced sediment mobility <br />and encroachment of riparian vegetation. Other changes may be changes in the size, <br />embeddedness, and mobility of bed sediments, simplification of bed morphology and reduced <br />channel-floodplain connectivity. <br />Warm Water Fishery: <br />There are currently few rivers in the Colorado that have high biomass populations of the native <br />fish species: roundtail chub, flaiulehnouth sucker and bluehead sucker. Declining populations <br />of roundtail chub and flaiulelmouth sucker have been documented at both state-wide and basin- <br />wide scales in recent years. The CDOW currently has fish monitoring sites established on the <br />Dolores River which indicate roundtail chub and flannelmouth sucker had a secure population in <br />the Dolores River until recently. Habitat protection for roundtail chub in the Dolores River has <br />become a priority issue for state fisheries managers and needs to be implemented quicldy in <br />order to avoid further population declines. Presumably the Dolores River genetic strain of <br />roundtail chub, flannelmouth sucker, and bluehead sucker is better fit to persist in the Dolores <br />River, since they were able to persist given historic (gage records) flow conditions. Maintenance <br />of a viable native fish community in the Dolores River potentially helps avoid additional native <br />species being listed for federal protection. <br />Cold Water Fishery: <br />Reach 1, at least from McPhee Dam to Bradfield Bridge, was intensively evaluated in the late <br />1980's and early 1990's pertaining to cold water fishery (trout) issues. Water temperature may <br />be an issue from Lone Dome to Bradfield Bridge. Habitat improvements would be beneficial and <br />should be focused on enhancing physical habitats for juvenile and adult trout, not for spawning <br />or rearing habitats. Early survey work conducted this year (1995) indicated a poor production of <br />Rainbow Trout in Reach 1 and good production of Brown Trout in portions of Reach 2. <br />Riparian Ecology: <br />Most changes in community structure do not result from a single event or single stressor but <br />from multiple interacting causes within a particular riparian corridor. Riparian vegetation plays a <br />key role in the human-valued services provided by rivers and also provides the fundamental <br />stn~cture for diversity of flora and fauna found along the river. <br />A variety of factors influence the stn~cture and composition of riparian vegetation growing along <br />a particular reach of river, such as flows, salinity and soil type. Along the lower Dolores River <br />study area a variety of habitats exist. These habitats range form a dominant Narrow leaf <br />Cottonwood communty in reach 1, Ponderosa Pine donunant in reach 2, Juniper and Pinion in <br />2 <br />