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.

Automated summary

Disentangling the meteorological and human drivers of drought is a critical challenge, requiring a combination of methods like developing hydrological models and using an upstream-downstream/observation-model approach. The study in New Zealand's Lindis River shows that irrigation-related abstractions have a substantial influence on river low flows, despite warm and dry summer conditions. Increases in precipitation associated with climate change could reduce dewatering, but water management strategy will play a significant role.