DEL080 – 11201600/11201703 Sediment management and Ecology in Rivers with reservoirs

Geplaatst op: 29 maart 2021

Aanleiding van het project

The construction of dam operating regimes always presents a trade-off between power generation, water supply and/or flood protection on the one hand and ecological quality of the reservoir and the river downstream of the dam on the other hand.
Sedimentation in reservoirs decreases their lifespan and has severe impact on the reservoir purposes. The trapping of sediment, in reservoirs, creates shortages in sediment supply downstream. This has implications for river morphology and creates ecological problems (changing temperatures, sediment starvation, blocking fish migration, altering habitats, etc). The shortage of sediment creates different bed characteristics which might not be suitable for fish. The use of sediment management practices, such as flushing or sluicing to transport more sediment to the downstream, has not been fully investigated with respect to their consequences in improving habitat suitability.
However, with the expansion of building reservoirs in cascading systems, sediment management becomes less effective and costly. The synchronization of sediment management in cascading systems needs to be explored further. To assist managers in selecting the most cost-efficient eco-friendly dam and reservoir management regime, knowledge and development of tools to diagnose the challenges and to provide the managers with integrated solutions is needed.
Deltares together with Jpower are aiming to improve the knowledge related to ecology and sediment management in rivers with reservoirs. A 2D-model (Delft3D) has been developed and coupled with RTC-tool (Real Time Control Tool) in order to mimic the real time dam operation of a single reservoir. This has been used to optimize the sediment management in the reservoir and the river downstream. However, because of the need to synchronize and optimize downstream ecology in combination with sediment management for river with cascading dams, it is vital to look for large scale system operation measures that integrate

Doel van het project

The aim of this project is to further deepen and broaden our knowledge and develop our tools (add-ons or coupling) to be able to link the dam operation with respect to ecology and sediment to:
1) efficiently flush the reservoirs (to increase their lifetime) in a cascade, 2) reduce erosion problems and increase the sediment supply within and downstream of a dam cascade and 3) create a good and sustainable habitat and ecosystem downstream by integrating the habitats requirements in the dam operation.
This allows an assessment of the ecological and sediment implications of dam and reservoir management scenarios to determine the optimal cost-efficient management strategy, for green and sustainable development of rivers systems with reservoirs.

Omschrijving van de activiteiten

1. Literature survey on ecological implications of reservoir management.
2. Implement new cohesive sediment transport formula in Delft3D and couple it with RTC-tools.
3. 2D-morphodynamic- and water quality modelling of Funagira Reservoir in the Tenryuu River with Delft3D (to simulate different sets of reservoir conditions and gate operations using non-cohesive sediment and cohesive sediment in suspension). 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. Best Feedback approach from and to HABITAT model will be investigated and recommended
4. Improve the workflow in HABITAT with scripting in Python to i) automatically update and run habitat suitability models for several years using input from Delft3D-models, and ii) automatically setup a model structure with pre-defined response curves.
5. Perform habitat suitability modelling using the new developments to assess the ecosystem downstream of Funagira Dam.
6. Perform sediment management in cascading system using 2D modelling approach

Verwachte resultaten

 HABITAT model application for Funagira reservoir and the river downstream
 Python scripts for improved workflow in HABITAT, and including meta-information;
 New formula implemented in Delft3D sed-mor module.
 2D morphodynamic and water quality model of Funagira reservoir and downstream reach that can be coupled to habitat model.
 Memorandum with the results of the pilot application for Funagira dam.
 Python scripts will be uploaded to the HABITAT wiki.
 Update to Deltares publicwiki.

Innovativiteit

High-resolution modelling tools such as Delft3D and HABITAT model are still not yet commonly used in the hydropower sector to quantify and mitigate the environmental impacts of dam operation, and particularly not for dam cascades. Previous studies (Tenryuu River, Mekong River, Koshi River, etc) show that proper integration of sediment and ecological management measures require dynamic coupling of 2D/3D modelling tool. Existing tools do not provide enough functionality to use them in practice, where 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 integrate ecological and sediment management to optimize the dam operation. These technologies allow dam operators to adjust the general sediment management strategy while more accurately predicting the environmental consequences (on short and long term).
To allow quick ecological calculations of the habitat suitability in order to build the meta-model, the workflow in HABITAT will be optimized through Python scripting. For several years now, the functionality of Python scripting in HABITAT is available. This is due to generic developments in DeltaShell. Until now, this functionality has been largely neglected due to limited knowledge on Python by HABITAT users and the lack of predefined scripts to be used in analyses. However, this functionality can be used to automate the model setup, create uniformity in response curves and speed up calculations.

Valorisatie

The tools and the framework in this project become directly available to Deltares specialists to be applied in future projects for greener and more sustainable reservoir management, which may give us an advantage in acquisition. Furthermore, the processed visualizations in this project will be used as a marketing product demonstrating the capabilities of Deltares and their tools, both by Deltares and J-Power. As Delft3D and HABITAT are open source, all improvements made to model ecological and morphological behaviour in reservoirs will be available to the worldwide community. Last but not least, the integrated sediment and ecological management based on numerical models is economical and leads to optimal reservoir operation. The outcome is expected to be useful tool to assess and improve the environment and ecological values for reservoirs and hydropower dams.

Link naar projectresultaten…