Characteristics of Rainfall, Snowmelt and Runoff in the Headwater Region of the Main River Watershed in Germany

In the headwater region of the Main River watershed in Germany, floods resulted from rain-on-snow events often occur in winter. Data of long-term observations at 16 gauging stations and 11 climate stations are available. Using these data, the objective of this paper is to study the characteristics of precipitation including snow depth and snow water equivalent (SWE). The importance of rainfall on the snow melt process has been assessed. Statistical analysis and trend analysis of extreme precipitation, snow depth, SWE and river discharges have been carried out. Through introducing equivalent precipitation depth from snowmelt with rainfall as a new variable, the simultaneous occurrence of snowmelt and rain-on-snow has been assessed; the characteristics of runoff including peak discharge caused by rain-on-snow have been investigated. The major climatic feature was found to be a precipitation, which as maximum in summer; and the major hydrological feature was a discharge, which was maximum in winter. By using two different models, the Unit Hydrographs at some gauging stations have been determined and compared.