Sedimentation of hydropower reservoirs is of huge concern worldwide. Currently, about 0.5 to 1% of the hydropower reservoir volume is lost every year as a result of sedimentation. The deep concern is that lost volume is larger than the added from new dams constructed. The good news is that cost-efficient measures do exist.
Siri Stokseth, Research and Development Manager and Dam Safety Coordinator, Statkraft
Experience shows that reservoirs in areas outside Northern Europe where water is already a scarce resource, often also experience considerable sediment problems.
If no measures are taken, the reservoirs will inevitably be completely buried in deposited gravel and sand, and consequently water reservoirs and intakes of hydropower, irrigation and domestic water supply will be completely lost.
The good news is that efficient technical measures exist and that they can be developed further.
On 6 and 7 June, sediment experts from among other NTNU (Norwegian University of Science and Technology), Stakraft, the International Hydropower Association and the World Bank met for a sediment seminar in Trondheim in Norway.
The seminar was followed by a workshop where concrete cases and projects were discussed.
«In my view, we are not prepared for the future. Sediment deposition is a submerged and therefore nearly invisible worldwide disaster. Sediments are filling up reservoirs. Consequently we will loose water volumes and the possibility of storing water for future generations. If we do not do it differently, we cannot claim that hydropower is neither renewable nor sustainable.»
Dr. George Annandale, hydropower consultant and special adviser to the World Bank Group
«Given the huge challenges of sustainable sediment handling in hydropower plants with large reservoirs, we should be as passionate about sediment handling as optimization of our operation and maintenance activities related to electro and mechanical components.»
Emmanuel Lopez, Emmanuel G. Lopez- VP-Chief Technology Officer- SN ABOITIZ POWER GROUP
New findings presented
During the last three years, Statkraft, NTNU and HydroCen (Norwegian Research Centre for Hydropower Technology) have carried out joint research and development projects and activities, focusing on sediment handling experiences and improvements in hydropower production including monitoring, measuring techniques and testing out new technologies and sediment measuring methods.
Studies show that sediments with hard minerals erode all types of equipment in water, and erodes and destroys more the higher the water velocity.
The worrying news is that turbines and spillway slabs have been completely worn out and destroyed by sediment erosion. The good news is that we have identified many relatively cheap ways to reduce erosion, downtime, loss of water and maintenance. By identifying “low hanging fruits” for sediment performance improvements, we have estimated a potential increased income (reduced loss) of 2-6 % of annual income of the hydropower production we analyzed.
In the seminar research and experiences in topics from hydrology & extreme flood events and sediment yield, transport and measurement challenges, deposition in reservoir and wear and resilience of turbines, included fish stress from sediment pulses were presented.