| Sedimentation
Klamath River
With drawdown of the four US dams slated for removal on the Klamath River now completed, the river is reshaping itself by removing decades worth of accumulated sediment. During March and April 2024, NOAA Fisheries and the US Bureau of Reclamation worked with tribes and other basin partners to release water from the Link and Keno dams farther upstream to create a flushing flow that doubled the river volume, picking up sediment and flushing it downstream and into the ocean. Such measures offered the river its best opportunity
to move sediment that had built up behind the Iron Gate, Copco No 1 and 2, and JC Boyle Dams over the last 60 to 100 years. The goal was to maximise the amount moving down river while reducing risk to fish released from hatcheries and others migrating in the river. Studies anticipated that sediment mobilising in the first months of dam removal would muddy the river, as turbidity naturally rises with higher winter flows. Although it was anticipated this would have some short-term impacts on fish this year, the strategy of concentrating the movement of sediment over a few months will avoid impacts on fish spawning and hatching in future years. “The river is undoing a century of being impacted by these dams, and that may look messy right now,” said Shari Witmore, a fisheries biologist in NOAA Fisheries’ Klamath Branch. “It’s moving all that sediment faster and more efficiently than we ever could, so what we are seeing is a very good thing.”
Hydropower cascades Sediment deposition has become “an extremely
constraining factor for large reservoir groups” according to research by Jun Li et al. Admitting that it can be difficult to estimate and understand sediment deposition when designing and managing reservoirs, the authors say it is nonetheless important because the joint operation of cascade reservoirs not only affects the utilisation efficiency of a specific reservoir, but it can also affect: The sediment boundaries of other reservoirs in the group. The comprehensive benefits of the entire cascade reservoir system. The regional water ecological environment.
www.waterpowermagazine.com | July 2024 | 31
Sediment deposition is a key factor to be considered when designing and monitoring the operation of multi-reservoirs, and in-depth research is required to ensure that cascade reservoir benefits are optimised. In their research, Li et al focus on the Baihetan Reservoir in China which was constructed as part of the second stage of building four cascade power stations in the lower Jinshajiang River, with initial water storage officially beginning in April 2021. Previous studies on sedimentation here were mostly based on the use of simulation predictions during the design stage, and relatively minimal research on actual sedimentation has been conducted. In this study, rich hydrological and topographic observation data from the Baihetan Reservoir area were used to analyse the characteristics of sediment deposition during the initial period since its inception. The results showed that water entering the reservoir was mainly derived from the upper mainstream, with ten times the amount of sediment derived from the mainstream received from tributaries and uncontrolled areas of the reservoir.
Above left: The international, interagency team during a field site visit to the Río Coca in Ecuador during January 2024. The team includes members from the Electric Corporation of Ecuador, US Army Corps of Engineers, and USGS (Pablo Espinoza, Electric Corp. Ecuador (CELEC))
Above: USGS scientists Amy East and Molly Wood at the US Embassy in Quito, Ecuador (Eddy Santana, U.S. Department of State)
Below: Rio Coca in Ecuador, near the location of the erosion front, which is migrating upstream toward the intake of the Coca Codo Sinclair hydropower facility. Taken January 2024 (Molly Wood, USGS)
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41
