Water Quality Monitoring on the Free-Flowing Klamath River

The Klamath River returned a free-flowing condition after four dams were removed in 2024. The dams formed physical barriers that were impassable for salmon and other migrating fish. Two years later, natural sediment flows and temperature fluctuations have also been restored, and water quality in the river has dramatically improved. These changes have already made the Klamath much more hospitable for migrating fish, and the improvement in water quality is also benefiting the people up and down the river.

Swiftwater Films’ recently created a video in partnership with RES, the restoration contractor that has jump-started recovery in the river system post dam removal. The new video walks through the sediment and water quality monitoring efforts that demonstrate enormous improvements in the reconnected river.

Nutrient rich, stagnant water captured in the reservoirs behind the old dams heated up in summer months and fostered toxic algal blooms that were hazardous to humans and animal life. Warnings were often posted about the dangers of contact with river water due to elevated levels of a toxin called Microcystis. If a dog jumped into the water, the consequences could prove fatal. That’s how bad the water was.

Millions of cubic yards of sediment were impounded behind the dams. In a free-flowing river, sediment flows through the system, constantly renewing salmon nesting habitat and redistributing this important material throughout the river system. After an initial surge of released sediment during the dam removal process, the river is now moving sediment the way a river should, rebalancing and refreshing fish nesting habitat in the process. With sediment now moving through the system at a natural rate, there is also a decreased likelihood of any toxins accumulating the way they did when the dams were in place.

While experts expect to see some spikes in turbidity, or cloudiness in the water, (caused by increased amounts of sediment in the water) when high winter flows come through, those spikes are expected to increase naturally as flow increases and decrease naturally as flow decreases.  That pattern is precisely what you expect to see in a healthy river system.

Water quality sampling before and after dam removal, including testing of sediment composition, has yielded encouraging results.  For one thing, the algal blooms have all but disappeared and the low dissolved oxygen that contributed to fish disease is much improved.

Sediment sampling was done before dam removal to establish baseline measurements. This testing showed that the sediments trapped behind the dams did not pose a toxicity hazard, with no pesticides present in 2009 or in 2023. Recently, sediment samples were taken above the former reservoirs, within the areas the former reservoirs covered, and all the way down to the estuary where the river meets the ocean. These samples are being tested for toxins and metals to compare to the baseline levels. Various metals are present naturally in the Klamath watershed so it is expected that some level of metals will be present in the samples.

Temperature variation in river water has also been restored to its natural cycle. While it’s true that salmon generally need cold water, especially in the fall when the adults return to the river to spawn, slightly warmer water at the right time of year can be beneficial for juvenile fish growth as well as for the food fish eat, like macroinvertebrates.

The reservoirs acted as giant heat sinks, releasing water at the wrong temperatures at the wrong times (the orange line in the chart). In the year following dam removal, river water warmed about three weeks earlier in the spring and cooled about three weeks earlier in the fall (the red line in the chart).  The natural temperature rhythm has returned.

All indications so far point to a recovering, healthy river system. We appreciate the ongoing work of Shane Anderson and Swiftwater Films in chronicling key milestones in the recovery of the Klamath River.