Hydrological drought types in cold climates : Quantitative analysis of causing factors and qualitative survey of impacts

For drought management and prediction, knowledge of causing factors and socio-economic impacts of hydrological droughts is crucial. Propagation of meteorological conditions in the hydrological cycle results in different hydrological drought types that require separate analysis. In addition to the existing hydrological drought typology, we here define two new drought types related to snow and ice. A snowmelt drought is a deficiency in the snowmelt discharge peak in spring in snow-influenced basins and a glaciermelt drought is a deficiency in the glaciermelt discharge peak in summer in glacierised basins. In 21 catchments in Austria and Norway we studied the meteorological conditions in the seasons preceding and at the time of snowmelt and glaciermelt drought events. Snowmelt droughts in Norway were mainly controlled by below-average winter precipitation, while in Austria both temperature and precipitation played a role. For glaciermelt droughts, the effect of below-average summer air temperature was dominant, both in Austria and Norway. Subsequently, we investigated the impacts of temperature-related drought types (i.e. snowmelt and glaciermelt drought, but also cold and warm snow season drought and rain-to-snow-season drought). In historical archives and drought databases for the US and Europe many impacts were found that can be attributed to these temperature-related hydrological drought types, mainly in the agriculture and electricity production (hydropower) sectors. However, drawing conclusions on the frequency of occurrence of different drought types from reported impacts is difficult, mainly because of reporting biases and the inevitably limited spatial and temporal scales of the information. Finally, this study shows that complete integration of quantitative analysis of causing factors and qualitative analysis of impacts of temperature-related droughts is not yet possible. Analysis of selected events, however, points out that it can be a promising research area if more data on drought impacts become available.