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 [0 UDWR for Contract #93-1070. Amendment 3

19

SPECIFlC STUDY DESIGN

To improve flow recommendations for Colorado squawfish nursery habitat, the controlling physical processes

and the spatial and temporal scales over which they occur were identified. While nO[ all aspects of the program of Hill

and others (1991) were appropriate for the Green River, their study served a model for the design of this study. This

study combined the approaches of Hill and others (1991), Pucherelli and others (1990), and Crowl (1994, pers. comm.).

Remotely-sensed data were used to assess and measure the area of nursery habitat available at base flows. These data

were combined with field-measured habitat-quality indicators. Physical channel behavior was measured and modeled to

determine how the channel and bars change with flood passage and subsequent low flows, and how those channel

changes related to changes in nursery habitat availability. Using this approach, it was possible to assess the year-to-year

change in availability of habitat, change in overall availability of high quality habitat, and the change in habitat as a

response to peak flows. In addition. field studies were utilized to discern how habitat availability varied with discharge

for a single year's topography, and how that relationship varied from year-to-year.

To significantly improve on existing flow recommendations of Pucherelli and others (1990), this study

addressed the following questions:

1) Was the geomorphic setting of available habitats similar from 'eason to season and year to year? ;

2) What was the relationship between channel form and geomorphically different types of nursery habitat? ;

3) What discharge maximized available nursery habitat during summer and fall? ;

4) Did this maximizing discharge vary from year to year? ;

5) Was there a relationship between the characteristics of each year's flood hydrograph and available habitat?;

6) To what extent was current channel topography a result of the previous year's topography? ;

7) Was it possible [0 model the impact of the flood hydrograph on the channel topography? ; and

8) What physical processes formed and maintained nursery habitat?

The above questions concern many spatial and temporal scales. The habitat of concern was on a scale of 10's of meters,

the geomorphic processes that formed habitats occurred on a channel width scale of l00's of meters, and the flows

responsible for the geomorphic processes affected the whole river reach at a scale of 10's of kilometers. Habitat

availability also displayed annual and seasonal variation. Consequently, this study addressed each spatial and temporal

scale and the linkages between them. A lO-km subset of a 15-km administrative smdy reach within the Ouray NWR