Diagnosing drought using the downstreamness concept: the effect of reservoir networks on drought evolution

To effectively manage hydrological drought, there is an urgent need to better understand and its human drivers. Using the “downstreamness” concept, we assess the role of a reservoir in the emergence and evolution of droughts in a river basin in Brazil. In our case study, downstreamness concept shows the effect of a network of reservoirs on the spatial distribution of stored surface water volumes over time. We demonstrate that, as a consequence of drought and recovery, the distribution of stored volumes became spatially towards upstream locations, which affected the duration and magnitude of hydrological both upstream (where drought was alleviated) and downstream (where drought was). The downstreamness concept thus appears to be a useful entry point for spatiotemporally explicit assessments of hydrological drought and for determining the likelihood of from meteorological drought to a human-modified hydrological drought in a basin.