APPENDIX C 



Hell's Canyon Creek Water Lease, Fish Screen, and Gravity Pipeline Project: 



Comparison of stream flow and fish loss to the irrigation system 



in 1992 (pre-project) and 1997 (post-project). 



Monitoring of stream flow of Hell's Canyon Creek and rainbow trout fry production was 

 conducted in 1992 to document the importance of the stream for providing recruitment of juvenile 

 trout to the JeflFerson River and to evaluate the need for improving stream flow and rearing 

 conditions in the creek. The Hell's Canyon Creek Project was implemented prior to the 1996 

 irrigation season, and post-project monitoring of stream flow and trout fiy production was 

 repeated in 1997 to evaluate effectiveness of the project. 



PRE-PROJECT SAMPLING (1992) 



Drought conditions in 1992 resulted in very low flow conditions throughout the Jefferson basin. 

 Discharge of Hell's Canyon Creek was measured near the mouth of the creek, and stream flow 

 ranged from 4.6 cfs on 15 July to 0.8 cfs on 19 August 1992. During much of August and early 

 September, discharge was less that 1.6 cfs at the mouth of Hell's Canyon Creek. Two 

 measurements were made at the Carroll Ditch during 1992. The canal contained 2.4 cfs on 15 

 July, and only 1.5 cfs on 19 August when stream flow above the canal was 2.3 cfs.. 



Traps were placed near the mouth of Hell's Canyon Creek to monitor trout fry migration to the 

 Jeflferson River and in the Carroll Ditch to monitor fry loss to the irrigation system. From 12 June 

 through 19 August, an estimated 16,913 rainbow trout fiy migrated to the JeflFerson River. 

 During the same period, 9,579 rainbow trout were lost to the Carroll Ditch. This loss to the 

 irrigation system was estimated to be 36% of the total fry production at Hell's Canyon Creek. 



POST-PROJECT SAMPLING (1997) 



In contrast to 1992, the irrigation season of 1997 was wet and stream flow was above average 

 throughout the upper Jeflferson basin. Consequently, improved flow conditions were expected at 

 Hell's Canyon Creek. Daily visits at a staff gage installed and monitored by U.S.G.S. document 

 significantly higher stream flow downstream of the pipeline withdrawal. Discharge ranged from 

 3.8 cfs to 16.4 cfs between 15 July and 30 September. The average discharge for the month of 

 August was 8.3 cfs. Daily flow records were also obtained from the gravity pipeline. 

 Withdrawal typically averaged 350 gpm throughout the irrigation season. Flow ranged from 

 gpm to a maximum of 650 gpm. 



A.21 



