Southwest US hydro outlook remains below normal, with snowmelt well underway

Southwestern snowpack levels are trending below normal and upcoming weather systems are not expected to bring significant precipitation to the region, officials said May 6 during the Colorado Basin River Forecast Center water supply webinar.

Low hydropower expectations have put upward pressure on power forwards throughout the US West.

While water supply forecasts across the region remained fairly steady month on month, they are below normal across the region, Cody Moser, hydrologist with the Colorado Basin River Forecast Center, said during the May 6 webinar, the last of the season. Current water supply forecasts across the Colorado Basin River region range from 45% to 95% of normal for the April-July forecast period.

"As you move through the season, forecast uncertainty decreases," Moser said about observed conditions improving data.

The water supply forecast at Lake Powell summarizes hydro conditions throughout the Upper Colorado River Basin, is currently 59% of normal for the April-July forecast period, Moser said.

Lake Powell affected

The water supply forecast at Lake Powell, which summarizes hydro conditions throughout the Upper Colorado River Basin, is currently 59% of normal for the April-July forecast period, Moser said.

The US Bureau of Reclamation announced May 3 that it invoked for the first time its authority to change annual operations at Glen Canyon Dam to protect hydropower generation with Lake Powell at its lowest level since being filled in the 1960s. The changes allow more water to flow into Lake Powell from upstream reservoirs, while releasing less water from Lake Powell downstream.

Lake Powell's water surface elevation is currently at 3,522 feet and will reach critical elevation at 3,490 feet, the lowest point at which Glen Canyon Dam can generate hydropower. The actions, which will last from May 2022 to April 2023, equate to about 16 feet of elevation increase for Lake Powell.

The Glen Canyon power plant has a generation capacity of 1.32 GW.

Weather impacts

"Snow melts have really started to pick up recently," Moser said. "Snow melt really took off in the last half of April."

Temperatures were 5 degrees to 15 degrees Fahrenheit above normal April 18-20, which created a pretty active period of snowmelt, Moser said.

Snow water equivalent ranges from 80% to 100% in the Upper Colorado River Basin, which is "not terrible, but not great, either," Moser said, adding the Lower Colorado River Basin ranges from 58% to 97%.

"Snow conditions are better off in the basins where snow isn't melting off yet," Moser said.

Throughout April, temperatures in the northern part of the basin were near normal, while temperatures were above normal in the southern portion, Moser said, adding that translated to near or above-normal precipitation in the north and mostly below normal in the south, with some areas less than 30% of average.

For the water year to date, the north is faring better, while the south is worse off, Moser said. Lake Powell's water year precipitation is at 90% for precipitation because of a wet October, which is influencing the data, he added.

"Soil moisture impacts runoff efficiency in spring when snow starts to melt," Moser said.

Near-term weather forecasts for May indicate continued warm and dry conditions in southern basins, with areas in the north with higher elevations that received precipitation in April expected to receive more in the coming days. Western Colorado, however, continues to have little to no precipitation in the forecast.

"That's a concern when it comes to fire weather," Moser said.

Power forwards

Power forwards continue to trend higher than 2021 packages on supply concerns and higher gas forwards, rebounding from dips in late April that brought prices below 2021 packages.

Palo Verde on-peak June is currently in the low $120s/MWh, 59% higher than its 2021 counterpart a year ago and a to-date package high, according to S&P Global Commodity Insights data. Likewise, the August package is in the low $260s/MWh, 5.5% higher but falling from a package high of $281.60/MWh in mid-April.

Bucking the trend, the July package is in the low $200s/MWh, 16% below the year-ago package.

Mead on-peak June reached a package high of $128.89/MWh May 5, as did Four Corner on-peak June of $116.31/MWh, according to S&P Global.