Event Title
Presentation Abstract
The Stillaguamish River watershed is a snow-and-rain mixed basin in northwestern Washington, with snowmelt being important for sustaining spring and summer streamflow and buffering stream-temperatures. Elevations in the 1700 sq-km Stillaguamish basin reach roughly 2000 m that sustain a historical snowpack above about 1000 m. Previous basin-specific modeling projected that snowpack will retreat to higher elevations and summer stream temperatures will increase, reaching both embryo lethality (16 °C) and adult lethality (22 °C) by 2075 in the North and South Forks in the Stillaguamish River. Stream temperature increases are of significant concern because of the threatened Chinook salmon population, which spawn in the spring and summer months. We reexamine projected stream temperatures using new dynamically downscaled meteorological forcings at a higher temporal resolution and simulate the entire Stillaguamish River basin. To estimate stream temperature changes through the 21st century, we use the Distributed Hydrology Soil and Vegetation Model, the River Basin Model, and dynamically derived meteorological forcing data from the Weather Research and Forecasting (WRF) model. We use digital spatial characteristics for the watershed at a 150 m cell resolution and WRF data at a 6 km resolution and a 1-hour interval. We calibrate modeled streamflow and temperature to several historical gauges and use field measurements from key tributaries within the watershed. Using the calibrated models, we project changes through 2099 from 12 dynamically downscaled global climate models developed with the WRF model. Our projections indicate a transition of the Stillaguamish to a rain-dominated basin and a decline and spring and summer streamflow. Lower streamflows and warmer air temperatures results in an increase in stream temperatures in all streams in the Stillaguamish and the number of days exceeding the seven-day average of the daily maximum temperature of 16 °C, further threatening salmon recovery.
Session Title
Integrating Climate Science into Flood Plain Management
Conference Track
SSE8: Climate Change
Conference Name
Salish Sea Ecosystem Conference (2022 : Online)
Document Type
Event
SSEC Identifier
SSE-traditionals-295
Start Date
27-4-2022 1:30 PM
End Date
27-4-2022 3:00 PM
Rights
Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.
Type
Text
Language
English
Modeling the effects of projected climate warming on stream temperatures in the Stillaguamish River basin
The Stillaguamish River watershed is a snow-and-rain mixed basin in northwestern Washington, with snowmelt being important for sustaining spring and summer streamflow and buffering stream-temperatures. Elevations in the 1700 sq-km Stillaguamish basin reach roughly 2000 m that sustain a historical snowpack above about 1000 m. Previous basin-specific modeling projected that snowpack will retreat to higher elevations and summer stream temperatures will increase, reaching both embryo lethality (16 °C) and adult lethality (22 °C) by 2075 in the North and South Forks in the Stillaguamish River. Stream temperature increases are of significant concern because of the threatened Chinook salmon population, which spawn in the spring and summer months. We reexamine projected stream temperatures using new dynamically downscaled meteorological forcings at a higher temporal resolution and simulate the entire Stillaguamish River basin. To estimate stream temperature changes through the 21st century, we use the Distributed Hydrology Soil and Vegetation Model, the River Basin Model, and dynamically derived meteorological forcing data from the Weather Research and Forecasting (WRF) model. We use digital spatial characteristics for the watershed at a 150 m cell resolution and WRF data at a 6 km resolution and a 1-hour interval. We calibrate modeled streamflow and temperature to several historical gauges and use field measurements from key tributaries within the watershed. Using the calibrated models, we project changes through 2099 from 12 dynamically downscaled global climate models developed with the WRF model. Our projections indicate a transition of the Stillaguamish to a rain-dominated basin and a decline and spring and summer streamflow. Lower streamflows and warmer air temperatures results in an increase in stream temperatures in all streams in the Stillaguamish and the number of days exceeding the seven-day average of the daily maximum temperature of 16 °C, further threatening salmon recovery.
