Anomaly in the rainfall-runoff behaviour of the Meuse catchment. Climate, land use, or land use management?
Abstract. An anomaly has been found in the rainfall runoff behaviour of the Meuse. Ninety years of rainfall-runoff simulations show a consistent underestimation of the runoff in the period between 1930 and 1965. Different authors have debated possible causes for the anomaly, including climatic variability, land use change and data errors. None of the authors considered the way in which the land is used by for instance agricultural and forestry practises. This paper focuses on the possible effects of land use and land use management on the hydrological response of the Meuse catchment. In absence of detailed information on land use over the observation period, we adopted a fully "top-down" approach to the problem. The approach consists of a dynamic evaluation of a conceptual hydrological model and the interpretation of the temporal trends of model parameters. It appears that land use has had a considerable impact on the hydrological behaviour of the Meuse catchment. The time lag of the catchment has reduced markedly over time, possibly related to more intensive drainage and river training works. Moreover we hypothesise that forest rotation has had a significant impact on the evaporation of the catchment. These results contrast with previous studies, where the effect of land use change on the hydrological behaviour of the Meuse catchment was considered negligible, mainly because there was not sufficient change in land cover to account for it. Here we hypothesise that in the Meuse it was not the change of land cover that was responsible for hydrological change, but rather the way the land was managed.