Reservoir storage loss due to grounded ice during winter operation

The immobilization of water in the form of deposited ice on the reservoir’s embankments during winter operations has received little attention in hydrological literature. In Nordic countries like Canada, this phenomenon is likely to have significant negative impacts on reservoir operation. In a previous work (Seidou, O., Ouarda, T.B.M.J., Bilodeau, L., Hessami, M., St-Hilaire, A., Bruneau, P., 2006. Modeling ice growth on Canadian lakes using artificial neural metworks. Water Resources Research 42. doi: doi:10.1029/2005WR004622); the authors developed a global artificial neural network model to predict ice thickness growth in unmonitored Canadian lakes and reservoirs. This model is used in this paper to compute a time series of ice thickness on the Gouin reservoir (Saint-Maurice River, Quebec, Canada) and the Outardes 4 reservoir (Aux Outardes River, Quebec, Canada). This and the relationship between surface water area and water level were then used to evaluate the volume of ice left on the banks of the two reservoirs during winter operation, as its water level is progressively lowered in order to release water for hydroelectric production at downstream power dams. Results show that the ratio of frozen water left on the banks to the active storage varies from 2% to 8% at the Gouin reservoir, and from 0.41% to 1.15% at the Outardes 4 reservoir depending on the water usage policy and the geometry of the reservoir.