7378 - Laserfiche WebLink

Home Browse Search

Recommendations for Streamflows Most methodologies for determining streamflow requirements of fish are intended for the preservation or maintenance of sport fisheries (Stalnaker and Arnette, 1976). However, the streamflow requirements or 55 . preferences of other key fish species such as game fish and the threat- . 5 1967). Streamflow requirements are least known for endemic fish inhabit- 45 I&J ..I i40 II..I&J II..D: ~:5!5 ;:)0 D:CIl ..I :5!Q ct~ ~I- ~t:j2 II.. I&J 520 ct Y. 0.681 X - 8037 r . 0.86.. ,2e 0.74 . ened and endangered endemic fish are not fully known (Orsborn and Allman, ing the main stem of the Upper Colorado River, In areas where there are great expanses of bare soil, as in the Intermountain West, the runoff would be expected to be high and to result in high peak flows (Branson and Owen, 1970; figure 7). Land use practices such as grazing can greatly change the natural runoff and accompanying sedtment load, For example, . o 'eired _e..lled' . Wot.rohed, 9 thru 17 a ten-year study near Grand Junction, Colorado, demonstrated that ungrazed 15 watersheds had 30 percent less runoff and 45 percent less sedtment yield o o 30 35 40 45 50 55 60 65 70 75 80 85 PERCENT 8ARE SOIL ~ .., .., 0<0 .. < than grazed watersheds (Lusby, 1970), The extent to which peak flows are ~ <. .. .. .. necessary for flushing action in the main stem streams to produce or main- tain backwater areas for the young of endemic species is not known, Peak ~ " .. .. ': flows in the higher mountain streams during floods could cause high mor- tality to young trout such as reported by Seegrist and Gard (1972) and Figure 7, Relation Between the Percentage of Bare Soil and Average Annual Runoff for Seventeen Watersheds , , .. ... Hoopes (1975). In high mountain streams, reduced streamflows could re- --- suIt in the formation of more anchor and frazil ice that could be detri- mental to the bottom organisms and force young fish from their micro- Source: F, A. Branson and J, E, Owen, "Plant Cover, Runoff and Sediment Yield Relationships on Mancos Shale in Western Colorado," Water Resources Research vol, 6, no. 3, 1970, habitats, thereby increasing mortality. The microhabitat available in the stream depends to a large extent on the flow. For example, reduc- tion in streamflow could increase the area of the slow-shallow or deep- slow portions of the stream (Hill, 1965; figure 8). Also, a reduction .