COS 160-6 - Lessons Learned from Klamath Basin Water Temperature Studies: Key Drivers and Climate Change Implications

Wednesday, August 9, 2023

11:15 AM – 11:30 AM PDT

Location: B111

Presenting Author(s)

EA

Eli Asarian

Riverbend Sciences
Eureka, California, United States

Slides (PDF)

Coauthor(s)

JG

Jon Grunbaum

Klamath National Forest, Happy Camp Oak Knoll Ranger District
Happy Camp, California, United States
LC

LeRoy Cyr

Six Rivers National Forest, Orleans, Ukonom and Lower Trinity Ranger District
Orleans, California, United States
LC

Lyra Cressey

Salmon River Restoration Council
Sawyers Bar, California, United States
CR

Crystal Robinson

California Department of Fish and Wildlife
Yreka, California, United States
DG

David Gaeuman

Yurok Tribe Fisheries Program, Trinity River Division
Willow Creek, California, United States
SN

Seth Naman

NOAA Fisheries
Arcata, California, United States
JK

Jacob Kann

Aquatic Ecosystem Sciences, Oregon, United States
KD

Kyle De Juilio

Yurok Tribe, California, United States
AD

Aaron David

King County, Water and Land Resources Division
Seattle, Washington, United States
FL

Frank K. Lake, Ph.D.

Research Ecologist/PSW Tribal liaison
USDA Forest Service, Pacific Southwest Research Station
Arcata, California, United States
TS

Toz Soto

Karuk Tribe Department of Natural Resources
Orleans, California, United States
KP

Kate Perkins

Environmental Research
Seaview, Washington, United States

Abstract: Warm water temperatures threaten culturally and economically important salmon in Pacific Northwest rivers, causing chronic stress and direct mortality. Native American Tribes, federal and state agencies, and non-governmental organizations have monitored water temperatures in rivers and streams in the Klamath Basin (California and Oregon) for multiple decades. Beginning in 2015, we compiled and analyzed this massive dataset in seven projects, each with its own objectives. We used statistical methods (including generalized additive models, linear mixed models, and spatial stream network models) to assess relationships between water temperatures and hydroclimatic factors including river flow, snowpack, air temperature, and wildfire smoke; evaluate long-term trends; and make climate change projections. Sites span diverse ecosystems: coastal redwood rainforests, mountain streams, agricultural valleys, and semi-arid landscapes. This presentation summarizes these analyses’ key findings.

Summer water temperatures (especially in July) have warmed in recent decades, coincident with climate-driven increases in air temperatures and decreased snowpack and river flow. Water temperatures warmed most dramatically at sites that are cool during high-flow years but warm during droughts. Wildfire smoke helped limit increases in August water temperatures, but has not affected annual maximum water temperatures because in most years fires do not start until after the hottest temperatures have already occurred. At some sites, summer water temperatures have cooled as riparian vegetation and stream channels recovered from a major flood disturbance. High river flows have a greater cooling effect on water temperatures in the spring and early summer than in late summer and fall. Climate change analyses for the Salmon River indicate that August water temperatures will warm by 1.7–3.3 °C by 2070–2099 if global greenhouse gas emissions are not reduced substantially.

Insights from these analyses can inform climate-resilient restoration strategies. For example, creek mouth thermal refugia deserve priority for habitat restoration and watershed management because they will become increasingly important as peak summer river temperatures become increasingly inhospitable to coldwater species. Dam removal will allow anadromous fish to access Upper Basin cold volcanic springs that are more climate-resilient than Lower Basin rivers with dwindling snowpack. Restorationists and regulators need to reduce costs and accelerate implementation of floodplain restoration projects that increase thermal diversity by promoting groundwater-surface water interactions. Climate change will necessitate greater flood control capacity, increasing the risk of depleting reservoir cold-water pools and releasing warm water into rivers during fall salmon spawning. Retrofitting dams to allow multi-depth releases would help preserve cold water.