Event controls on intermittent streamflow in a temperate climate

Abstract

Abstract. Intermittent streams represent a substantial part of the worldwide stream network and their occurrence is expected to increase due to climate change. Thus, it is of high relevance to provide detailed information of the temporal and spatial controls of streamflow intermittency to support management decisions. This study presents an event-based analysis of streamflow responses in intermittent streams in a meso-scale catchment with temperate climate. According to the streamflow responses, events were classified into flow or no-flow classes. Response controls like precipitation, soil moisture, and temperature were used as predictors in a random forest model to identify temporal controls of streamflow intermittency at the event-scale. Soil moisture was revealed as the most important predictor in the catchment. However, different patterns of predictor importance were found among the three dominant geologies in the catchment. Streamflow responses in the slate geology were controlled by soil moisture in the shallow and deep soil layers, while streamflow in the marl geology was primarily controlled by the soil moisture in the upper soil layer. Streamflow responses in catchments covering both marls and sandstone were dependent on soil moisture whereas streamflow in the only catchment with pure sandstone geology depended on precipitation characteristics. In both the slate and marl geology, streamflow intermittency also showed a relationship with seasonal fluctuations of soil temperature, probably as a proxy-variable of seasonal changes in evapotranspiration as well as an indicator of freezing conditions.\n