Performance of water temperature management on the Klamath and Trinity Rivers, 2017

Water temperature is an important factor in riverine environments, influencing the physiology and life history expression for salmonids and other aquatic organisms. Understanding the thermal regime of a river is a crucial component of successful environmental flow management, especially on rivers with dams and other anthropogenic influences. The U.S. Fish and Wildlife Service began monitoring water temperature in the Klamath basin in 2001 due to growing interest and concern over the effects of elevated water temperatures, particularly on Pacific salmon. This report summarizes the results of 2017 water temperature monitoring for a set of focal locations within the anadromous portion of the Klamath Basin from April 1 to October 31. Temperature criteria for the Trinity River have been recommended by the Trinity River Restoration Program (TRRP) and are based upon the Trinity River Flow Evaluation Study and the Trinity River Mainstem Fishery Restoration: Final Environmental Impact Statement/Environmental Impact Report. On the Klamath River the U.S. Environmental Protection Agency’s (EPA) Pacific Northwest salmonid life history stage temperature criteria are used, as they are the best science-based and peer-reviewed criteria available. In 2017, designated an ‘Extremely Wet’ water year, the Trinity River exceeded temperature criteria for 27 days at the monitoring location above the confluence with the Klamath. The Klamath River exceeded temperature criteria at all sites (range of 24 to 140 days), but only exceeded the long-term mean daily water temperatures at two sites, at Klamath River below Iron Gate Dam and at Klamath River above the mouth. Mean daily water temperatures were < 13.0°C before April 1 at all focal sites and were < 13.0°C after October 31 for 3 of 4 Trinity River focal sites and for 3 of 5 Klamath River focal sites. Most locations saw a decrease in days exceeding temperature criteria from 2016, as well as their respective long-term averages.