DEL045 1230828 Improving sediment management in river systems with reservoirs

Aanleiding van het project

Sediment management in hydropower dams is of crucial importance, both for economic and environmental reasons. Sedimentation in reservoirs may lead to loss of active storage and blockage of the inlets and consequently loss of economic value. For the ecological value (e.g. fish habitat) a proper mix and timing of sediment flushing to the downstream is important. Many hydropower authorities around the world are therefore interested in improving the sediment management of the reservoirs. J-Power, the largest power company in Japan, is actively seeking to jointly develop knowledge and techniques to improve their gate operation for better management of the sediment trapped in the reservoirs and spread of sediment downstream.

This project is a follow-up of the previous TKI project with J-Power. In addition, J-Power wants to assist to address the sediment related issues in hydropower dams in Nepal (mainly Run-of-the-River) by involving Deltares and enhancing the cooperation with local institutions and companies that are active in this field.

Doel van het project

The aim of this project is to further deepen and broaden our knowledge on how dynamic (time varying control) gate operation can contribute to the optimization of sediment management around hydropower dams to 1) efficiently flush the reservoirs (to increase lifetime), 2) reduce erosion problems downstream, 3) increase the sediment supply downstream of a dam and 3) create a good habitat/ ecosystem downstream by minimizing environmental and ecological impacts. For this we propose to carry out the following activities:

• Extend the Real Time Control (RTC) module, such that more complex regulations can be modelled using Delft3D.
• Investigate to which extend Delft3D can properly model complex flow patterns downstream of a hydropower dam (This knowledge is also relevant for other projects dealing with flow velocities in scour holes or other depressions in the riverbeds.)
• Determine and assess relevant indicators for ecology/fish habitat from the model results.
• Simulate cascading dam systems considering sediment management strategy.

Uitgevoerde activiteiten

1. Literature survey on sediment management in reservoirs, and data collection.
2. Further improvement of Delft3D and RTC tools to be able to apply the PID controller to control the reservoir water level(s) for much more flexible operation rules.
3. Funagira Reservoir in the Tenryuu River (Japan) and Kabeli hydropower reservoir in Tamur River (Nepal) shall be studied to simulate different sets of reservoir conditions and gate operations. Then perform a proper analysis to the data to come up with useful conclusion to be used in reservoirs and dams which have similar challenging conditions.
4. Explore the possibility of Delft3D to simulate complex flow behaviour like the jets and hydraulic jumps downstream of the dam.
5. Assess the impact of the new sets of reservoir operation on the ecosystem (modelling indicators for ecology/fish habitat).
6. Modelling of cascading system of dams using 2D morphodynamic modelling to perform combined sediment management techniques to series of dams, planned in Koshi basin, Nepal.

Gerealiseerde resultaten

• An improved version of Delft3D with RTC Tools to allow flexible operation of gates
• Two numerical models for the above reservoirs will be developed and adapted, such that sediment behaviour in the reservoir, across and downstream of a hydropower dam, can be studied for different gate operations.
• Numerical model will be used to study sediment management in the cascading reservoirs for different gate operations and their impacts on the whole system. This will be done with Delft3D in combination with the RTC module.
• Two scientific papers will be written based on the results (together with J-Power and other collaborative partners)
• Preparation of animations to provide insight into the morphological behaviour in the reservoir as well as downstream of the dam. Specific attention will be paid to make these visualisations realistic, informative and advertising, in order to demonstrate the advanced features and outcomes of this work.

NB. J-Power and Deltares (previously WL-Delft) have a long collaboration of 15 years. J-power wants to continue the research collaboration and to address new aspects which contribute to the improved knowledge and practice of sediment management in reservoirs

Innovativiteit

High-resolution modelling tools such as Delft3D are still not yet commonly used in the hydropower sector to quantify and mitigate the environmental impacts of dam operation. Previous studies (Tenryuu River, Mekong River, Koshi River, etc) show that proper quantification of sediment management measures, and proper indicators for habitats do require a full dynamic 2D/3D modelling tool. Existing tools do not provide enough functionality to use them in practice, and dam operators base their environmental operations mostly on trial and error. This study will not only increase the capabilities in modelling these conditions, but also introduce tools that allow smarter ways to operate the gates of a dam for more optimal sediment management strategy. These technologies allow dam operators to adjust the sediment management strategywhile more accurately predicting the environmental consequences (on short and long term).

Valorisatie

Results will be published in scientific papers together with J-Power. Furthermore, the processed visualisations in this project will be used as a marketing product demonstrating the capabilities of Deltares and their tools, applicable to the hydropower community, both by Deltares and by J-Power. As Delft3D is open source, all improvements made for modelling morphological behaviour in reservoirs will be made available to the worldwide community. Last but not least, optimizing the sediment management with the optimized gate operation based on numerical models will be economically effective for dam owners and, at the same time, may be useful to assess and improve downstream environment and ecological values for the reservoirs to be used in this project and other hydropower dams (in future projects).