Hydrological Shifts Threaten Water Resources

TLDR

Recent shifts in watershed hydrology, often triggered by multi‑year droughts and now observed on multiple continents, reveal a tendency for reduced streamflow relative to precipitation, posing acute challenges for water planning under climate change and exposing limitations of commonly used hydrological models. The commentary urges hydrologists to investigate the causes of shifting hydrological behavior and integrate dynamic realism into operational models to address the implications of future climate‑driven drying for water planning and management. Reliance on current hydrological models can underestimate hydroclimatic risk, leading to unexpected reductions in water supply compared to projections.

Abstract

Abstract Recent shifts in the hydrological behavior of natural watersheds suggest acute challenges for water planning under climate change. Usually triggered by a multi‐year drought, these shifts involve a tendency for less annual streamflow for a given annual precipitation, and this behavior has now been reported on multiple continents. Future drying under climate change may induce similar unexpected hydrological responses, and this commentary discusses the implications for water planning and management. Commonly used hydrological models poorly represent these shifts in behavior and cannot be relied upon to anticipate future changes. Thus, their use may result in underestimation of hydroclimatic risk and exposure to “surprise” reductions in water supply, relative to projections. The onus is now on hydrologists to determine the underlying causes of shifting behavior and incorporate more dynamic realism into operational models.