Evaluation of a grid-based river flow model configured for use in a regional climate model

Regional Climate Models (RCMs) offer significant improvements over Global Climate Models in terms of their representation of rainfall at the spatial and temporal scales required for hydrological modelling. To take advantage of these improvements, we test a new implementation of a grid-based hydrological routing model coupled with a model of land-surface climatology (the Joint UK Land Exchange Scheme; JULES) against observed river flows in several major European rivers, including the Rhine, Maas, Elbe, Danube, Loire, and Seine. Our model comprises a gridded land-surface model with a probability-distributed model of soil moisture and runoff production coupled with a discrete approximation to the one-dimensional kinematic wave equation to route surface and subsurface water from cell to cell in order to estimate river flow. The model was driven with hourly output from the Hadley Centre regional climate model, HadRM3P, run over the same grid, which in turn was driven using quasi-observed boundary conditions derived from the ERA-40 reanalysis experiment for the period 1961–2002. Observed 3-h precipitation data for the period 1999–2002 were also used as model forcing to provide a clearer indication of the hydrological model performance. The results from simulations for the six rivers are presented and compared with measured river flows over the same time period. They demonstrate that the hydrological model is able to simulate flows in rivers at the resolution of the RCM with some accuracy and thus has significant potential to assess the implications of projected regional climate change on river flows.