Abstract
Abstract. Meteorological droughts like those in summer 2003 or spring 2011 in Europe are expected to become more frequent in the future. Although the spatial extent of these drought events was large, not all regions were affected in the same way. Many catchments reacted strongly to the meteorological droughts showing low levels of streamflow and groundwater, while others hardly reacted. Also, the extent of the hydrological drought for specific catchments was different between these two historical events due to different initial conditions and drought propagation processes. This leads to the important question of how to detect and quantify the sensitivity of a catchment to meteorological droughts. To assess this question we designed hydrological model experiments using a conceptual rainfall-runoff model. Two drought scenarios were constructed by selecting precipitation and temperature observations based on certain criteria: one scenario was a modest but constant progression of drying based on sorting the years of observations according to annual precipitation amounts. The other scenario was a more extreme progression of drying based on selecting months from different years, forming a year with the wettest months through to a year with the driest months. Both scenarios retained the observed intra-annual seasonality for the region. We evaluated the sensitivity of 24 Swiss catchments to these scenarios by analyzing the simulated discharge time series and modeled storage. Mean catchment elevation, slope and area were the main controls on the sensitivity of catchment discharge to precipitation. Generally, catchments at higher elevation and with steeper slopes appeared less sensitive to meteorological droughts than catchments at lower elevations with less steep slopes.
Highlights
Meteorological droughts such as the summer drought of 2003 (Rebetez et al, 2006) or the spring drought of 2011 (Kohn et al, 2014) in Europe caused low water levels in lakes, rivers and groundwater
The sorted months (SoMo) scenario generally resulted in stronger responses to the drying and the relative changes specific for the different catchments became more pronounced than in scenario sorted years (SoYe)
This indicates that during wet conditions the high elevation catchments were more sensitive to the progressive drying; during dry conditions high elevation catchments were less sensitive to the drying compared to lower elevation catchments
Summary
Meteorological droughts such as the summer drought of 2003 (Rebetez et al, 2006) or the spring drought of 2011 (Kohn et al, 2014) in Europe caused low water levels in lakes, rivers and groundwater. A prolonged lack of precipitation (meteorological drought), storage of precipitation as snow or a strong deficit in the climatic water balance can propagate through the hydrological system causing soil moisture drought and hydrological drought (Tallaksen and Van Lanen, 2004; Mishra and Singh, 2010). The consequences of such droughts are challenging: water-use restrictions have to be applied to, for instance, energy production or irrigation.
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