#Snowpack/#Runoff news: North Platte irrigators should have a full water supply #ColoradoRiver #COriver

From Reclamation (Mahonri Williams):

Reclamation Issues Snowmelt Forecast for North Platte River Basin

MILLS, Wyoming — The Wyoming Area Office of the Bureau of Reclamation has prepared the April snowmelt runoff forecasts and operating plans for the North Platte River Basin. “We anticipate the North Platte Basin water contractors will have a full water supply this year,” said Wyoming Area Manager, Carlie Ronca.

The April forecasts indicate the spring snowmelt runoff will be below average. Total April through July runoff in the North Platte River Basin above Glendo Dam is expected to be 715,000 acre-feet (AF) which is 78% of the 30-year average.

As of March 31, 2018, storage content in the North Platte Reservoirs amounts to 2,190,053 AF, which is 132% of the 30-year average. The total conservation storage capacity of the North Platte Reservoir System is approximately 2.8 million AF.

Current releases are 2,700 cubic feet per second (cfs) from Seminoe Reservoir through the Miracle Mile, 1,000 cfs out of Gray Reef, and the release out of Guernsey Reservoir is expected to begin on April 23. Based on current projections, for the months of April, May, June, and July the releases out of Seminoe Reservoir are not expected to exceed 3,000 cfs, flows out of Gray Reef are expected to be in the range of approximately 1,000 to 3,000 cfs and releases from Guernsey will be in the 3,000 to 5,300 cfs range. Pathfinder Reservoir is not expected to spill this spring.

From The Nevada Independent (Daniel Rothberg):

For most of the season, the snowpack, from Tahoe to the Rockies, the source of almost all of Las Vegas’ water, was well below average. Since snowpack typically peaks around April, the dynamic set up March as a make-or-break month for water supply.

Water managers hoped for a turnaround similar to a “Miracle March” in 1991 that brought so much late-season snow it ended a massive California drought. This year, what Mother Nature brought water managers depended on what part of the state they were watching.

With cold snowstorms through March, the water picture around Tahoe and many parts of Northwest Nevada improved considerably, enough that some hydrologists have been calling it a “Miracle March.” From Tahoe to the Great Basin in Eastern Nevada, snowpack started the month of March near historical lows and ended the month closer to the average.

That said, the results, even in Northern Nevada, were varied. There are still many basins, especially outside of the Reno-Tahoe area, with snowpacks that remain well below average. Still, 2018 could have been much worse, said Jeff Anderson, who surveys Northern Nevada snow for the U.S. Department of Agriculture’s Natural Resources Conservation Services…

Southern Nevada and the Southwest were not as lucky.

Not only did the region, at the edge of the Colorado River Basin, remain abnormally dry but with only a few exceptions, little snow fell on much of the basin…

By the end of March, things had improved, especially for the basins around Tahoe. In fact, many of these basins saw significant increases in snowpack in March — the Lake Tahoe, Truckee, Carson and Walker basins saw increases of more than 39 to 45 percent of snowpack…

The answer might seem counter-intuitive. But despite a dry year — snowpack remains lower than average in almost all of the basins — Nevada’s short-term water outlook is solid for many users, Anderson said. Because last year was such a good hydrological year, ample water is stored in reservoirs throughout the state…

The lower-than-average snowpack will have the most immediate effect on water users that are not connected to the reservoir and draw their water from streams. For instance, streamflow forecasts for the lower Humboldt River, according to Anderson’s report, range from 35 to 55 percent below the average.

The key word is forecast. Nothing is set in stone. There could be more snow and other factors, such as rain falling on snow, could affect how much water ends up in streams.

And it’s important to note, said Dan McEvoy, a climatologist at the Desert Research Institute and Western Regional Climate Center, that while there was recovery, 2018 was still a dry year…

Despite the hopes of many water managers in the seven states served by the Colorado River, snowpack in the Colorado River Basin did not improve much in March. Flows into Lake Powell, the first large reservoir that captures and stores Colorado River runoff is expected to be 43 percent of the average, according to a federal forecast released April 4…

When there is low runoff into Lake Powell, federal water managers can reduce the amount of water that flows into Lake Mead, which would increase the likelihood of a shortage. Water managers across the West are still in the process of negotiating a difficult deal that would help stabilize Lake Mead, which runs at a deficit. Even in good hydrological years, more water leaves the lake than enters the lake. Nevada is ready to sign on, but the process is being slowed by internal conflicts within Arizona and California.

From Tucson.com (Tony Davis):

A cutback in Central Arizona Project deliveries in 2019 is considered highly unlikely at best. But shortage risks increase dramatically in the following years, the U.S. Bureau of Reclamation says.

Federal forecasters predicted last week that the spring-summer runoff into Lake Powell will be only 43 percent of normal this year. That’s due in part to a poor winter snowpack season and an expectation that the next two months’ weather will be about normal.

If the forecast pans out, it will be the sixth worst runoff into the lake from the river’s Upper Basin over 54 years of record-keeping.

The odds of a normal runoff season are only 3 percent today, said Greg Smith, a hydrologist for the federal Colorado Basin River Forecast Center…

Last year, spring-summer runoff into Powell was 114 percent of normal, following three years of runoff exceeding 90 percent. The high runoff provided the river enough water to survive this year’s very low runoff with minimal chances of shortage for 2019.

But overall, river flows have generally declined steadily since 2000. Lake Mead has dropped from nearly 1,214 feet in elevation at the end of 1999 to 1,082 feet at the end of 2017.

That’s due partly to continuing drought, and partly to a structural deficit between the amount of water people take from the river and what nature provides, state and CAP officials have said. A shortage will happen if Mead drops below 1,075 feet at the end of a year…

CAP manager Chuck Cullom offered a more optimistic picture. Because of continued conservation by water project users, “we expect to avoid shortage in 2019 and likely in 2020” if the weather and river runoff are favorable, he said in a written statement. Project officials expect to conserve up to 180,000 acre feet of river water this year.

The low runoff forecast comes after CAP and Arizona Department of Water Resources officials have been at odds for well over a year over how to manage the lake and river. Their disagreements dimmed hope for a three-state Drought Contingency Plan agreement to force additional conservation of river water beyond what’s already planned. Gov. Doug Ducey’s efforts to secure more state authority to conserve more water in Lake Mead have so far gone nowhere in the Legislature.

From The Greeley Tribune (Tyler Silvy) via Windsor Now:

The United States Department of Agriculture Natural Resources Conservation Service snowpack report for March, released Thursday, shows forecast streamflows between 30-70 percent of normal across the state. That’s persistently low precipitation throughout the winter — 65 percent of normal for the state…

Weld County farmers and Front Range municipalities that rely on Colorado River transbasin diversions will be in better shape, as the Colorado River Headwaters and the South Platte River basins show forecasts for precipitation 80-100 percent of normal…

Brian Werner, spokesman for the Northern Colorado Water Conservancy District, said municipalities served by the Colorado Big Thompson transbasin diversion should be in good shape. Werner said much oft that credit goes to the large amounts of water in storage. Norther Water, for example, is at 25 percent above normal…

All but the Rio Grande Basin show higher than normal reservoir storage reserves, with the South Platte at 108 percent of normal.

From the Arizona Department of Natural Resources:

Not without good reason, the nation’s media have been focusing on the dramatically thin snowpack of the Upper Colorado River Basin, which portends a meager amount of runoff into the Colorado River system.

As of April 2, the basin snowpack stood at just 72 percent of normal, heralding a runoff season that may be the sixth driest in the 55 years that Glen Canyon Dam and Lake Powell have been in place to capture the runoff.

On average, the in-flow into Lake Powell is 7.1 million acre-feet per season. Although the figure may change, this year’s projection currently stands at less than half that amount – 3.1 million acre-feet.

Bad news? Oh, yes. But where Arizona’s renewable water supplies are concerned, the 2018 story gets still worse. As opposed to the Colorado River system, the in-state river systems are setting records.

The Salt River Project is reporting that, according to provisional data for runoff in the Salt and Verde reservoir systems, the January – March runoff totals are “the lowest amounts on record dating back to 1913.”

Water Year precipitation for the State’s two major watersheds (Oct. 1 – Mar. 31) stood at just 2.88 inches, a figure that unsurprisingly graded out as “Well Below Normal.”

As a result, runoff in the watershed has been extremely poor. SRP data indicate that runoff into the Salt and Verde reservoirs in March stood at just 14 percent of median – the second-lowest amount on record.

In the wake of a December – February snowpack season that produced next to nothing in the two Arizona watersheds, three small storms after mid-March produced a snow-water equivalent of just 22,000 acre-feet, most of it at the highest elevations of the region.

Overall, total watershed streamflow this runoff season (January -May) is forecast to be near the lowest on record, which stood at 106,000 acre-feet in 2002.

SNOTEL data produced by the Natural Resource Conservation Service depict snowpack values as high as 40 percent of normal and as low as zero percent of normal.

If you seek to frolic in the snow in Arizona, you’ll be hard-pressed to find white stuff for your skis: According to satellite data, just 0.3 percent of the watershed had snow coverage as of April 1.

If winter in Arizona proved dry, early spring doesn’t hold out much hope for moisture here, either. Reports indicate that Arizona should anticipate warmer, drier weather through the first half of April, at least.

Westwide SNOTEL basin-filled map April 9 2018 via the NRCS.

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