Modelling seasonal flow variability of European rivers

River discharge influences many important processes in a lake ecosystem. For example, the tributary discharge is one of the major regulating factors for the lake water retention time and, hence, the retention of substances in lake water. However, river discharge depends on many more or less stochastic processes, which makes it difficult to give a reliable prediction of the discharge for a specific river at a given time. This paper presents an attempt to overcome many of those difficulties with a simple mathematical model. The model was designed to meet some specific demands for ecosystem modelling of contaminating substances. The most important of those requirements is that the model had to be based on readily available driving variables, preferably from standard maps. The presented results are based on extensive calibrations and validations using empirical data on monthly water discharge from more than 200 European rivers. It may be concluded that this model yields predictions that capture the essential components in mean monthly variations in river discharge in European rivers and that this model is driven by easily available driving variables like catchment area, mean annual precipitation, altitude, and latitude. The technique to obtain seasonal variability is based on calibrated 'norms' and smoothing functions defined from the driving variables. (C) 1998 Elsevier Science B.V. All rights reserved.