An upstream–downstream/observation–model approach to quantify the human influence on drought.

Disentangling the meteorological and human drivers of drought is a critical challenge. A key difficulty is identifying natural conditions against which human impacts can be analysed. Here, a combination of approaches is used: a hydrological model is developed for an upstream unmodified location and is then applied to a downstream site subject to irrigation-related abstractions: i.e. an upstream–downstream/observation–model approach. The relative importance of climate change is also investigated. The study location (the Lindis River, New Zealand) has a continental climate, and the lower river frequently runs dry during summer. Output from the hydrological model indicates that despite the warm and dry summer conditions there is a substantial influence of abstractions on Lindis River low flows – without abstractions, dewatering would likely be rare rather than regular. Increases in precipitation associated with climate change could reduce the occurrence of dewatering, but this eventuality will be strongly influenced by water management strategy. [ABSTRACT FROM AUTHOR]