Different drought types and the spatial variability in their hazard, impact, and propagation characteristics

Abstract

Abstract. Droughts often have a severe impact on environment, society, and economy. Only a multifaceted assessment of such droughts and their impacts can provide insights in the variables and scales that are relevant for drought management. Motivated by this aim, we compared hazard and propagation characteristics as well as impacts of major droughts between 1990–2019 in Southwestern Germany. We bring together high-resolution datasets of air temperature, precipitation, soil moisture simulations, streamflow and groundwater level observations, as well as text-based information on drought impacts. Various drought characteristics were derived from the hydrometeorological and drought impact time series and compared across variables and spatial scales. Results revealed different drought types sharing similar hazard and impact characteristics. The most severe drought type identified is an intense multi-seasonal drought type peaking in summer, i.e. the events in 2003, 2015 and 2018. This drought type appeared in all domains of the hydrological cycle and coincided with high air temperatures, causing a high number and variability of drought impacts. The regional average drought signals of this drought type exhibit typical drought propagation characteristics such as a time lag between meteorological and hydrological drought, whereas propagation characteristics of local drought signals are variable in space. This spatial variability in drought hazard increased when droughts propagated through the hydrological cycle, causing distinct differences among variables, and regional average and local drought information. Accordingly, single variable or regional average drought information is considered to be not sufficient to fully explain the variety of drought impacts that occurred. In addition to large-scale drought monitoring, drought management needs to consider local drought information from different hydrometeorological variables and could be type based.

Advances and gaps in the science and practice of impact‐based forecasting of droughts

“…Traditionally, the concept of drought propagation in the literature has been depicted as a unidirectional flow, progressing from meteorological through agricultural to hydrological drought (Figure 4). However, in reality, when accounting for complexity of the water cycle and interlinked human activities (Human-water feedbacks challenge), the propagation does not always complete the entire cycle (Tijdeman et al, 2021), or could even progress in the opposite direction (Figure 4). In view of the growing complexity of drought processes, and increasing interactions with the human systems, several scholars have recently introduced the term anthropogenic drought (AghaKouchak et al, 2021).…”