Mitigating the Impacts of Climate Nonstationarity on Seasonal Streamflow Predictability in the U.S. Southwest

Seasonal streamflow predictions provide a critical management tool for water managers in the American Southwest. In recent decades, persistent prediction errors for spring and summer runoff volumes have been observed in a number of watersheds in the American Southwest. While mostly driven by decadal precipitation trends, these errors also relate to the influence of increasing temperature on streamflow in these basins. Here we show that incorporating seasonal temperature forecasts from operational global climate prediction models into streamflow forecasting models adds prediction skill for watersheds in the headwaters of the Colorado and Rio Grande River basins. Current dynamical seasonal temperature forecasts now show sufficient skill to reduce streamflow forecast errors in snowmelt‐driven regions. Such predictions can increase the resilience of streamflow forecasting and water management systems in the face of continuing warming as well as decadal‐scale temperature variability and thus help to mitigate the impacts of climate nonstationarity on streamflow predictability. Key Points Seasonal temperature forecasts from climate prediction models are skillful over the headwaters of the Colorado and Rio Grande river basins Adding temperature information to current operational seasonal streamflow forecasts in snowmelt‐driven basins improves forecast skill Temperature forecasts help mitigate impacts of nonstationarity on U.S. Southwest streamflow predictability under increasing temperatures