A Dynamic River Temperature Model for the Colorado River within Grand Canyon
Location
Logan Golf & Country Club, Logan, UT
Start Date
3-26-2019 5:00 PM
End Date
3-26-2019 7:00 PM
Description
Completion of Glen Canyon Dam in 1963, subsequent filling of Lake Powell, and downstream release of reservoir water profoundly changed the temperature regime of the Colorado River from a seasonally warm river to a consistently cold river due to deep hypolimnetic releases. Because temperature is a key driver of ecosystem processes and of the ecology of valued native and non-native fish in the Grand Canyon, temperature models have been developed to predict the downstream evolution of river temperature. However, these temperature models use empirical or semi-empirical formulations based on equilibrium temperature algorithms that do not fully account for the detailed heat transfer mechanisms that drive river warming or cooling, including solar radiation which is a dominant heat flux of many rivers. On-going climate change, causing long-term decreases in runoff in the Colorado River watershed, is anticipated to lower Lake Powell water levels for prolonged periods, elevating water temperatures released from the reservoir. These future increases in air and reservoir release temperatures may exceed observed conditions and are beyond the predictive capacity of empirical models. Here, we present results from a process based one-dimensional dynamic river temperature model that accounts for the air-water interface heat exchanges while simultaneously accounting for the influences of the geographically complex terrain. Our model predicts river temperatures well, with a RMSE of 1.18 C, over the study reach of 225 miles. Future simulations will be conducted to assess the potential influences of climate change and identify management strategies that can meet both demand and environmental goals.
A Dynamic River Temperature Model for the Colorado River within Grand Canyon
Logan Golf & Country Club, Logan, UT
Completion of Glen Canyon Dam in 1963, subsequent filling of Lake Powell, and downstream release of reservoir water profoundly changed the temperature regime of the Colorado River from a seasonally warm river to a consistently cold river due to deep hypolimnetic releases. Because temperature is a key driver of ecosystem processes and of the ecology of valued native and non-native fish in the Grand Canyon, temperature models have been developed to predict the downstream evolution of river temperature. However, these temperature models use empirical or semi-empirical formulations based on equilibrium temperature algorithms that do not fully account for the detailed heat transfer mechanisms that drive river warming or cooling, including solar radiation which is a dominant heat flux of many rivers. On-going climate change, causing long-term decreases in runoff in the Colorado River watershed, is anticipated to lower Lake Powell water levels for prolonged periods, elevating water temperatures released from the reservoir. These future increases in air and reservoir release temperatures may exceed observed conditions and are beyond the predictive capacity of empirical models. Here, we present results from a process based one-dimensional dynamic river temperature model that accounts for the air-water interface heat exchanges while simultaneously accounting for the influences of the geographically complex terrain. Our model predicts river temperatures well, with a RMSE of 1.18 C, over the study reach of 225 miles. Future simulations will be conducted to assess the potential influences of climate change and identify management strategies that can meet both demand and environmental goals.