Low-Flows in Deterministic Modelling: A Brief Review

Deterministic hydrological models are limited in their ability to model low-flows, but as they are increasingly being used for low-flow Studies, a review is timely if they are to be used for this purpose. The representations of the physical processes that govern low-flows are described for a selection of models developed and/or used in Canada. The models vary in the extent to which they incorporate low-flow processes, Such as drawdown of storage in lakes, stream channels and wetlands, riparian evapotranspiration, freeze-up and bank storage. Tic representation of groundwater in the models is not physically-based and the hydrologic models must be Coupled with distributed groundwater models to answer questions about groundwater withdrawals. Most models have not been rigorously tested for low-flow simulations. Considerable work remains to be done, especially in the adequate representation of low-flow processes, and in evaluation of models for low-flow studies by using low-flow specific evaluation criteria.