Graduate Student Research Aids in Future Colorado River Basin Planning

The future is uncertain, but the agreements for water management in the Colorado River Basin are expiring in 2026, and new agreements need new solutions.

To find these solutions, decision makers have to run simulation models to evaluate alternative management options. They look at the impact of drought and declining runoff due to climate change, working to understand the availability and variability of future water resources in the basin. To run these models, they need streamflow data that reflects the uncertain future.

Working on a project funded by the U.S. Bureau of Reclamation, Utah Water Research Laboratory graduate student Homa Salehabadi developed a structured framework for assessing streamflow data to inform management options post-2026.

Planning and operation models like those being used in the Colorado River Basin require inputs of streamflow ensembles — sets of data over a period of time.

“Right now, there is no agreement on the best representation of future hydrologic conditions, and so there is no single best streamflow ensemble,” Salehabadi said.

Ensembles based on historical data may not be sufficient for the future because climate is changing. Those based on climate change models give a wide variety of projections for the future, showing uncertainty in the models.

So, under the guidance of David Tarboton, Salehabadi developed storylines, or sets of assumptions that describe plausible future conditions in the Colorado River, and sought out ensembles that matched the storylines.

The storyline approach is a way to organize all the ensemble data for decision making. It will help leaders in the Colorado River Basin make plans for plausible but uncertain future changes.

Salehabadi assembled a comprehensive set of statistical metrics to evaluate each possible ensemble and quantify the differences between ensembles, searching for those with characteristics that matched the storyline, such as persistent drought conditions.

For her project, Salehabadi developed four storylines but she couldn’t find a matching ensemble for one of them. So she and Tarboton took a new approach.

She mixed historical information with paleo-reconstructed data and combined it with estimates for future decline in streamflow to create the recipe of a new ensemble that represented a warming-driven declining streamflow future with increasing variability.

“We generated a new ensemble by considering future changes and non-stationarity along with the rich information from historical and paleo-reconstructed streamflow data,” Salehabadi said.

Salehabadi’s work, available on HydroShare, is being used by the Bureau of Reclamation as inputs in planning models. They are also using the metrics she developed to evaluate the other data they have.

Salehabadi hopes that her work can help those making decisions in the basin to find the best alternative management for the uncertain future.

“Hopefully, together we can find a way to sustainably manage and preserve this beautiful river,” she said.

For more information on Salehabadi’s work, click here.