29 



Flows, which are completely regulated by Clark Canyon Reservoir, are 

 summarized for the Hildreth Section in Table 2. Average daily flows were 

 derived from U.S.G.S. records for the gage near Grant, located 0.4 mile 

 below the dam. From October through March and April through September, 

 35 and 45 cfs, respectively, were added to the average daily flows near 

 Grant to account for accretion. Due to accretion and leakage at the dam, 

 the lowest instantaneous flow that can occur in the Hildreth Section is 

 approximately 50 cfs. During the study, average daily flows ranged from 

 57 to 1365 cfs. Mean irrigation flows ranged from 320 to 870 cfs and 

 mean nonirrigation flows ranged from 97 to 467 cfs. 



Trout populations in the Hildreth Section early in this study may 

 reflect water quality problems in addition to flows. In January of 1965, 

 a fish kill attributed to toxic concentrations of hydrogen sulfide in 

 reservoir releases occurred in the river immediately below the dam 

 (Wipperman, 1965). Results of field bioassays with caged fish and 

 censusing with electrofishing gear indicated that the kill was restricted 

 to approximately the upper 1.5 miles of river. This did not include 

 the Hildreth Section. Elevated concentrations of hydrogen sulfide were 

 measured in the summer of 1965 and were believed to have eliminated fish 

 in the upper 1.5 miles of river, although a fish kill was not documented 

 (Needam and Wipperman, 1967). A kill also attributed to hydrogen sulfide 

 occurred in September of 1967 in approximately the upper 3 miles of 

 river (Wipperman and Elser, 1968). This partially included the Hildreth 

 Section. 

 Numbers of trout (Hildreth Section) 



Brown Trout 



The estimated numbers of brown trout by age groups are given in 



