Characterizing the spatiotemporal variability of groundwater levels of alluvial aquifers in different settings using drought indices Johannes Christoph Haas1, 2 and Steffen Birk1, 2 1Institute of Earth Sciences, NAWI Graz Geocenter, University of Graz, Austria 2FWF-DK Climate Change, University of Graz, Austria Correspondence to: Johannes Christoph Haas (
[email protected]) Abstract. To improve the understanding of how aquifers in different alluvial settings respond to extreme events in a changing environment, we analyze standardized time series of groundwater levels (Standardized Groundwater level Index - SGI), pre- cipitation (Standardized Precipitation Index - SPI), and river stages of three subregions within the catchment of the river Mur (Austria). Using correlation matrices, differences and similarities between the subregions, ranging from the Alpine upstream 5 part of the catchment to its shallow foreland basin, are identified and visualized. Generally, river stages exhibit the highest correlations with groundwater levels, frequently affecting not only the wells closest to the river, but also more distant parts of the alluvial aquifer. As a result, human impacts on the river are transferred to the aquifer, thus affecting the behavior of groundwater levels. Hence, to avoid misinterpretation of groundwater levels in this type of setting, it is important to account for the river and human impacts on it. 10 While the river is a controlling factor in all of the subregions, an influence of precipitation is evident too. Except for deep wells found in an upstream Alpine basin, groundwater levels show the highest correlation with a precipitation accumulation period of six months (SPI6). The correlation in the foreland is generally higher than that in the Alpine subregions, thus corre- sponding to a trend from deeper wells in the Alpine parts of the catchment towards more shallow wells in the foreland.