Investigating flow patterns in Rantambe reservoir through two-dimensional hydrodynamic modelling

Abstract

The reservoir storage capacity is being depleted due to sedimentation, making sediment removal vital for maintaining the required capacity. Sediment deposition is a common issue in the Rantambe reservoir in Sri Lanka, and flushing is the most effective technique to remove sediments. Therefore, the objective of this research is to study the two-dimensional (2D) flow patterns in the Rantambe reservoir under different combinations of inflows and releases through power intake. The International River Interface Cooperative (iRIC), 2D flow computational model was used to develop the 2-D models for the Rantambe reservoir to generate flow patterns. The model was calibrated and validated against the field measurements carried out at selected sections of the reservoir. The results show higher accuracy; for calibration, Percentage Bias (PBIAS) is 5.2% and Mean Relative Absolute Error (MRAE) is 0.18 whereas, for validation, PBIAS and MRAE are 11.3% and 0.22, respectively. The model predictions of velocity and depth show satisfactory agreement with field observations. Therefore, the developed iRIC model of the Rantambe reservoir can be used to obtain sufficiently accurate flow patterns, velocity and water surface elevation for the effective flushing, and maintenance of the Rantambe reservoir.