Changes in runoff regime. The Lomnice catchment case study

Abstract

Water distribution in landscape is essentially influenced by the nature of the catchment rainfall-runoff process. Firstly, this paper presents an analysis of trends in the rainfall-runoff regime of the Lomnice river basin (South Bohemia, Czech Republic), using a single and double mass curve method. Secondly, the analysis of the rainfall-runoff regime is supplemented by an analysis of the evolution of temperature and snow conditions. Finally, a water balance analysis is performed for three selected years, using the Bilan hydrological model. The aim of the present paper was to find out (1) whether any changes have occurred in the trend of the rainfall-runoff regime of the catchment since 1970, and (2) to what extent these changes may have been caused by anthropogenic activities in the catchment. The results show several changes in the runoff scheme that are not related to the amount of precipitation. This statement follows from the comparison of single mass curves of precipitation and discharges. A comparison of the hydrological balance data for the Lomnice river basin, and the Otava and the Upper Vltava (a higher order stream) river basins led to the following conclusions: (1) There has been a change in the trend of the Lomnice river runoff regime. (2) The runoff regime of the Lomnice river basin differs from the regime of the higher order river basin (the Otava, the Upper Vltava). (3) The changes in the runoff regime in the Lomnice river basin were probably caused mainly by anthropogenic activities, the influence of which disappears within the larger basin (a higher order catchment area). Therefore, when planning sustainable water resources management, it is necessary to consider the impact of human activities not only globally, but also at the local scale.