8251

• UCREFRP Catalog Number: 8251
• Author: Rakowski, C. L. and J. C. Schmidt.
• Title: The Geomorphic Basis of Colorado Squawfish Nursery Habitat in the Green River Near Ouray, Utah.
• USFW Year: 1996.
• USFW - Doc Type: #93-1070,
• Copyright Material: NO

Draft Fmal Completion Report to UDWR for Contract #93-1070. Amendment 3

15

amount of fish habitat during base flows (for example, Tennant, 1975). More recent work suggests that a suite of flows

are necessary to maintain ecological integrity of fish habitat rather than just protecting the habitat at base flows (Hill and

others, 1991). This approach is based on the assumption that habitat and nutrient availability for the fishes requires

mllintemlllr.e of the linkages of the stream with riparian, floodplain and upland areas.

Two philosophies have shaped the design of instream flow for Colorado River native fishes (Tyus, 1992). The

first philosophy is to prov ide minimum flows needed for species survival during periods of low river discharge. These

minimum flows do not ensure availability of optimal habitat, but seek to maintain and maximize the availability of

existing habitat. The second philosophy is to assist species recovery by increasing the availability of optimal habitats,

The latter philosophy requires that existing habitat be improved and that "lost" habitats (i.e., habitats that are no longer

formed and/or available as a consequence of flow regulation) be restored. "Optimal" habitat for fishes considers the

river under regulated conditions, inclucJing changes in river hydrology and the presence of exotic species, rather than

pristine river conditions prior to regulation. For example, a habitat that was optimal prior to river regulation may no

longer be optimal due to its use by a predatory species. For species recovery to occur in a system as altered, both

physically and biologically, as the Green River, the second philosophy is the only viable option for species recovery.

Other Flow Recommendation Research

ligon and others (1995) noted the need for multi-scale, interdisciplinary studies to quantify and mitigate the

downstream effects of dams. Hill and others (1991) integrated several standard assessment methods into a methodology

for determining the suite of flows necessary to mllintaip ecological integrity and applied their methodology to the Salmon

River at Whitebird, Idaho. They noted the need for four flow components: base flows for fish, and channel-, riparian-

and valley-process maintenance flows. Each of these flows inundated different ecosystems (for example, stream channel

vs. riparian), and combinations of methodologies were necessary to evaluate the appropriate flow regime for each

component.

The Physical Habitat Simulation system (pHABSIM), a part of the Instream Row Incremental Methodology

(IF1M) (Bovee, 1982), was used by Hill and others (1991) to quantify the low flow habitat needs of the targeted fish

species. IFIM was used to develop a relationship between stream discharge and the area of available habitat for a given

stream, particularly during summer low flows (Hill and others, 1991). Physical parameters for utilized microhabitat,

such as depth, velocity, cover, substrate and distance to cover, were measured by marking targeted fish species locations