Forecasting Water Supply In Colorado River May Benefit Water Resource Management

Oct 27, 2020

View of the Colorado River at Lee's Ferry, November 2016. Water supply records from this location provide a record of the natural history, prior to downstream withdrawals. Low water supply puts communities and industries at risk.
Credit National Park Service

What if I purchase an early season ski pass– will it pay off with good snow this winter? Yoshimitsu Chikamoto, a climate scientist at Utah State University Utah had an idea to use climate modeling to help him decide.

Weather forecasting targets a short term, days to weeks, mostly based on atmospheric conditions. Forecasting climate patterns a year in advance is more complex, said Chikamoto.  

“Weather forecasting needs the atmospheric model. In the climate model the atmospheric model is one component of the climate that also needs ocean and sea ice, and the land," Chikamoto said.

Chikamoto and his research team used dynamic climate modeling to try to predict water supply in the Colorado River. They found ocean surface temperatures have a larger impact on predicting drought than atmospheric processes like precipitation. What that means is that even after a good winter snowpack Utah may experience summer drought. Chikamoto said oceans provide a long-term memory that can be used to forecast drought.

This annual drought forecast is to help managers allocate water supply strategically and economically. This is especially important to the southwestern U.S. that depends on the Colorado River supply each year.

“Water resource managers need to make a plan to use this [each] year in terms of allocation. So how much water is allocated to this community or how much irrigation [do] we require?” Chikamoto said.

Forecasting with climate models is too expensive to do each year, so the team developed an operational version that can be updated each year, giving a three-year forecast.

“Our research proves we can predict Colorado River supply on multi-year timescales,” Chikamoto said. “And then next step is we try to do the operational forecast to provide a corollary, about what does happen in the future.”

Chikamoto said future work may lead to refinements to help land managers optimize crops and wildfires in drought years.

As for buying that discounted season ski pass– Chikamoto laughed–  perhaps we are closer to a good decision.