Review papers

Refsgaard et al. (2022) review developments in hydrological modelling of catchment response over the past 60 years. Several important advancements have driven these developments. Scientists now have much better understanding of hydrological processes, leading to their improved representation in models. Another advancement is improved availability of data – more variables, at higher frequency, and observed at more places. Multi-band remote sensing data at higher spatial and temporal resolutions and algorithms to compute data of missing variables at the required scales by using the satellite data have added to the richness of databases. Scientists also have access to increasing computational power, enabling them to use larger volumes of data and an ensemble of models. However, it has also been realized that such developments have not necessarily resulted in better modelling approaches. In addition, Refsgaard et al. (2022) illustrate the importance of spatial resolution and improved data resolutions in a case study, where a model setup was run at 100 m and 500 m resolutions. While the two models perform equally well for simulation of catchment discharge, the underlying processes such as streamflow partitioning differ significantly.
The paper by Wheater et al. (2022) reviews recent developments and discusses scientific and technical challenges of large-scale cold region hydrological modelling with a focus on the Canadian community hydrological land surface scheme MESH (Modélisation Environmental Communautaire – Surface and Hydrology). Cold regions are crucial for a large part of the global population and face major and rapid changes due to global warming. At the same time the hydrology is particularly complex, because it includes cold region processes such as permafrost, frozen soil, snow and glaciers, where hydrological processes often are controlled by phase change energetics. Modelling of large river basins in cold regions are often subject to relatively sparse data coverage and application of remote sensing data has recently shown important benefits. A key conclusion is that cold region hydrology is particularly sensitive to temperature changes and that even small biases in forcing data from global climate models pose large challenges. Wheater et al. (2022) furthermore conclude that the understanding and description of hydrological processes related to permafrost and frozen soil as well as certain glacier processes poses significant challenges and scopes for improvement.