The Influence of Lewiston Dam Releases on Water Temperatures of the Trinity River and Lower Klamath River, CA, April to October, 2014.

Water year 2014 was designated as “Critically Dry” in the Trinity River Basin, with 434,683 acre-feet of water released from Lewiston Dam to the Trinity River. This total water volume exceeded the Record of Decision prescribed volume of 369,000 acre-feet for a Critically DryWater Year due to additional releases made in the fall to reduce the risk of a fish kill occurring in the lower Klamath River. Water temperatures were monitored at several locations along the Trinity and lower Klamath rivers from April to mid-October 2014 to evaluate the influence of Lewistown Dam releases on downstream water temperatures. We compare observed values to water temperature objectives specified in the Trinity River Flow Evaluation Study and adopted by the Trinity River Record of Decision, including the spring-summer water temperature targets established for outmigrating salmonids and the objectives for the 64-kilometer reach located downstream of Lewiston Dam to protect holding and spawning adult salmonids. Additionally, we document the influence of Lewiston Dam releases on water temperatures in the lower Klamath River downstream of the confluence of the Trinity River and summarize data from 2002 to 2014 during the augmented fall flow period. This document is the thirteenth consecutive annual water temperature report generated for the Trinity River Restoration Program.