Using SIMGRO for drought analysis – as demonstrated for the Taquari Basin, Brazil

Tools were developed and tested to quantify space–time development of droughts at the river basin scale. The spatial development of a hydrological drought in river basins brings different challenges to describe drought characteristics, such as: area in a drought and areal expressions for onset, duration and severity. We used the regional hydrological model SIMGRO in a GIS framework to generate the spatially-distributed time series for the drought analysis. Droughts in different hydrological variables (recharge and groundwater discharge) were identified by applying the fixed threshold concept to the time series. The method captures the development of both the duration and the severity of the area in a drought. The GIS helps to better understand the link between areal drought characteristics and spatially-distributed catchment characteristics. Functions, like agriculture, nature or navigation in a region, need to be considered more in defining the appropriate threshold levels. It is also important to take into account varying hydrological conditions like regions with deep or shallow groundwater levels, resulting in periods with capillary rise in the unsaturated zone in the latter