At DHI, we have experience in hydrodynamics and morphological modelling of reservoirs and the impact of sedimentation on the service life of these reservoirs. Our dedicated MIKE 21 Hydrodynamics Flow Model (HD FM), complemented by the MIKE 21 Mud Transport (MT) module allows for the prediction of sedimentation rates within the reservoir and the annual maintenance dredging required. With MIKE 21 MT, we can simulate the change in bed thickness of the main reservoir, along with the volume of sediments accumulated behind check dams.
The numerical modelling of the reservoir serves as the primary tool to assess the current sedimentation issues and to investigate various mitigation solutions. These, in turn, require substantial amounts of data and to be supported by a dedicated site survey campaign. Given the rapid pace of development in the catchment, the hydrodynamic and sediment transport models are challenging to calibrate. The sediment input into the model is supplemented by DHI’s in-house equipment SediScat Pro, which proved to be successful in estimating the particle size distributions at various locations within the tributaries and the reservoir body.
Besides appraising the impact of land clearing on the sedimentation rates, we have also provided the following services:
- Evaluation of current best practices in reservoir sediment management
- Review of the current dredging and desilting operations
- Numerical modelling to provide a platform to assess the current sediment loading and test the practicality of various mitigation and management options
- Development of a sustainable sediment management plan for Ringlet Reservoir
In total, eight different mitigation options were developed based on improving the retention performance in the upper parts of the reservoirs, increasing the reservoir flushing and introducing sediment bypass tunnel. The improvement in sediment management oversees a reduction of reservoir deposition of between 14% and 54% over the baseline conditions. The established sediment management strategies ensure that the long-term resilience of this critical infrastructure facility is safeguarded.