Over the last fifteen weeks, my Sundays have started at 4am with a hastily-prepared breakfast and a drive to OSU’s campus to meet my field techs and pick up a university SUV, already packed high with sampling equipment. My goal each week was to measure the amount of sediment and carbon present at three sites, each within the 25-ish miles between Iron Gate Dam and the confluence at which the Shasta River meets the Klamath. Additionally, I wanted to measure the amount of oxygen being consumed at each site, and I brought back large jars of water with dissolved oxygen sensors submerged in the jars, taking measurements every 15 minutes as unseen microbes feasted on the carbon present in the samples.
The reason I wanted to learn these things is because dissolved oxygen is necessary for fish to breathe in rivers. In fact, it’s important for many water-residing beings, including microorganisms – tiny living things that are invisible to the naked eye. While these organisms are small, they are abundant, and many of them LOVE carbon. When I say carbon here, I mean the once-living but now-dead stuff. Tiny particles of dead plants, animals, and algae that eventually blends into the silt and clay you might see on the bed of a lake, and was very abundant at the bottom of the Iron Gate and Copco reservoirs. When the reservoirs were drained, this sediment was flushed downstream, creating miles of an all-you-can-eat buffet for these microbes.
The objective of my weekly trips was to study how much oxygen these microbes were actually consuming downstream of the dam, and if it contributed to dissolved oxygen levels low enough to kill fish.
The first few weeks of January went by quickly as I honed my methods and sampled the Klamath, bringing back jars of clear water for lab analysis and getting to know the six undergraduate students/emerging researchers we were able to bring onto the project. Drawdown for Iron Gate Dam commenced the same day I began sampling, and my expectations were undefined. Would there be a sediment pulse? Would I notice if there was? Would I miss it by spacing my trips out every seven days?
The week of January 28th answered those questions. That was the week that our water samples suddenly looked like chocolate milk with too much syrup. Our lab equipment couldn’t even filter the samples, and we spent the first weeks of February revising our methods to adapt to the high concentrations of silt and clay present in the water. We saw dozens of dead fish washed up on the banks, and no sign of other wildlife save for an occasional duck or two in the river.
Photo taken by Rebecca Wheaton
However, the widespread and enduring lack of oxygen that some feared didn’t really materialize. There were two periods when oxygen dropped to lethal levels for fish for a short distance downstream of the lowest dam. Oxygen levels then recovered to non-lethal levels in time periods measured in hours rather than days and weeks. One of the key things I’m trying to understand is why those drops in oxygen occurred when they did, and why the river recovered so quickly.
Data accessed from KRRC (2023)
While DO recovered quickly, the high sediment concentrations in the river lasted for several weeks, and by the time March arrived, our equipment was degrading. Silt had clogged life jacket zippers and electronic ports. I was spending 30 minutes each night scrubbing my nail beds and getting the smell of the carbon-rich sediment out of my skin and hair. Then, as March rolled on, the water began clearing little by little. Each week we started to return to the lab with cleaner samples, and now, at the very end of April, I am able to see straight through the water we collected, as if I poured it from a (slightly dirty) tap. The sediment and carbon present in each week’s samples have grown less and less abundant, and as I wrap up the project, I find myself reflecting on the resilience of the Klamath River.
It has been a privilege to watch this incredible force of nature restore itself over time, finally unencumbered by the four dams that held its natural regime captive for so many years. While it still has a long way to go, we are now seeing families of ducks swimming on the river, aquatic plants beginning to emerge for their Spring season, and fish – alive and well - finally reclaiming their habitat once again.
References:
Klamath River Renewal Corporation (KRRC). 2023. Klamath River Renewal Project Data Management System. Maintained and published by RES, LLC. Accessed at: https://klamath-data-management-platform-klamath.hub.arcgis.com/
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