On March 4, we posted two new reports under the “Reports” tab on our website.
This report is the analysis of the first known thermal imaging look at mid-summer temperature behavior in the lower river. There were many unanticipated surprises from the imaging, but two findings are of greatest importance.
- The thermal behavior of water discharged from the Pelton-Round Butte Complex during nighttime hours is unaffected by “canyon effect.” Canyon effect warms the water during the day as a product of solar radiation exposure. Nighttime discharge, however, avoids much of the daytime warming effect. Yet all temperature calculations used for temperature management by dam operations act as if water temperature and temperature behavior are the same day and night. It has also been stated by the dam operators that “cooler temperature discharge from the dams wouldn’t make any difference” because of “canyon effect.” Our findings contradict that.
- Solar radiation (down-bound long wave radiation) is far more important than air temperature in determining river temperatures. Solar radiation warms both air and the water in the river. That means that shade from canyon walls and riparian vegetation is important in maintaining cooler water in the river. Air temperature in Redmond is also an important factor in determining the goal for temperature management for dam discharge, yet air temperature has little effect on water temperature.
The Selective Water Withdrawal Tower at Round Butte Dam (the uppermost dam of the three dam complex at Pelton-Round Butte) has intake portals in the top 30 feet of the reservoir, and at 265 feet of depth. To better understand the water quality effects of Tower operations and selective water withdrawal, we sampled surface water and water at depth in front of the Tower, as well as in the river below the dams.
The data we gathered demonstrated many things, and also raised more questions that we will be attempting to answer through the water quality sampling we started in February of this year. Our results from 2015 shed light on a number of critical factors, including that:
- Surface water withdrawn from Lake Billy Chinook, for much of the year, consists primarily of water from the Crooked River Arm of the reservoir.
- Water from the Crooked River Arm is warmer, and of poor water quality (the Crooked River water quality above the reservoir is rated as “poor” by Oregon Department of Environmental Quality). Plus, the water in the Crooked River Arm supports the densest level of algae growth in the reservoir. In contrast, water from the Metolius River, which, because of its colder temperature constitutes most of the water at the depth of 265’, is of high quality (based on ODEQ data, as well as our own data).
Questions we are hoping to answer in 2016 include (but are not limited to):
- What is the “nutrient load” entering Lake Billy Chinook from the three tributaries, and when does it get discharged from the dam complex into the lower Deschutes River? Algae in the upper water of the reservoir actually help decrease nutrient levels during summertime growth, but nutrients in surface water discharged in late fall, early winter and spring are not likely attenuated by that algae, and probably contributes significantly to the growth of nuisance algae that has been documented in the lower river. So we are now tracking nutrient levels at the surface and at depth in the reservoir and below the dams.
- Is the surface water in the Crooked River Arm of Lake Billy Chinook too toxic for migratory juvenile fish survival during major algae blooms due to high pH, high temperature and/or other variables?
- Is operation of the dam complex in compliance with the water quality requirements of the Pelton-Round Butte Section 401 Certification under the Clean Water Act and the Federal Energy Regulatory Commission license?
We would also like to announce that we are (finally!) getting some of our raw water quality data posted on our website. We are open-sourcing the data for all to view or use. It will take some time to get everything posted, but we will be working on this going forward.
We hope to post updates on our work throughout the year. So please stay tuned.
Deep and heartfelt thanks to our donors and supporters for making this work possible!
Deschutes River Alliance: Cooler, cleaner H2O for the lower Deschutes River.
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