@AZwater: Feds predicting short-term improvement on the #ColoradoRiver system… and longer-term challenge #COriver

From</a the Arizona Department of Natural Resources:

Part Two of the federal government’s annual August analysis of conditions on the Colorado River system are out, and – just like Part One – the results depict a mixed bag of decreasing risk in the short-term and rapidly increasing risk in the longer-term.

River-system modeling by the federal Bureau of Reclamation is showing a much lower chance of a Lower Basin water shortage in 2019, a result of the extremely wet, snowy early winter that created higher than average snowpack on the western slopes of the Rocky Mountains.

The modeling depicts a 15 percent chance of a shortfall in Colorado River allocations beginning in January 2019, a 16 percent drop in shortfall expectations in April of this year, and a substantial drop from expectations of a year ago, when the chances of Lake Mead falling into shortfall as soon as January 1, 2018, stood at even odds.

Lake Mead falls into “shortfall” once lake levels recede to under 1,075 feet. By the terms of a 2007 agreement among the states, Arizona and Nevada would begin taking substantial cutbacks in their delivery allocations from Lake Mead at that point.

Unfortunately, the modeling – known as the Colorado River Simulation System, or CRSS – also depicts increased risk of shortfall starting in 2020.

Chances for a Lower Basin shortage increase to 42 percent in 2020, according to the modeling, and continue rising to a better-than-even chance of a shortage in 2022.

The Bureau’s River Operations Group, which conducts the modeling survey, cites a lower starting elevation at Lake Powell as the principle culprit for the quick-rising shortfall likelihood in Lake Mead.

Lake Powell serves as a regulator of water flowing downstream from the Upper Basin states of Colorado, Utah, Wyoming and New Mexico to Lake Mead.

As recently as March, analysts had been hopeful that the initially strong Upper Basin winter snowpack might produce a huge “equalization” release this year from Powell to Mead – perhaps as much as two million acre-feet above the 8.3 million acre-foot annual average.

An abnormally dry and warm late Spring, however, provided less runoff into Lake Powell. That resulted in the lower-than-anticipated Spring elevations in Powell, which nixed the hoped-for “equalization” into Mead.

Indeed, the Lower Basin water picture quickly darkens, according to the analysis.

Between 2020 and 2022, the probabilities of a shortage at Lake Mead increase by at least 10 percent a year over predictions laid out in the Bureau’s April analysis.

The Bureau’s April and August data analyses are key to making plans for water releases for the coming year.

In particular, the August 24-Month Study projections for anticipated elevations at the beginning of the next calendar year are used by the Secretary of the Interior to set the operating tiers for Lake Powell and Lake Mead.

The first part of the Bureau’s August data analysis – its determination of anticipated water-level flows in the Colorado River system – concluded that Lake Mead would end the 2017 calendar year at an elevation of 1,083.46 feet.

That determination put Mead more than eight feet above the point that Arizona and Nevada would be required to take delivery shortfalls, according to the terms of the 2007 agreement.

As Arizona Department of Water Resources Director Tom Buschatzke noted regarding the data released last week, much of the positive news coming out now about Lake Mead can be attributed to conservation efforts.

“The collective efforts of Arizona, California, Nevada and Mexico to conserve water in Lake Mead from 2014 through 2017 have created an additional 14 feet of elevation in the lake,” said Buschatzke.

Yampa River streamflow drops to below average

Yampa River at Steamboat Springs gage March 1 through September 4, 2017.

From The Craig Daily Press:

With the Yampa River flowing well below normal during most of the week preceding Labor Day, the city of Steamboat Springs has closed down commercial tubing in the river where it flows through the city and is asking the public to voluntarily follow suit by refraining from private tubing, paddling SUPs, swimming and fishing…

It’s not unusual for commercial tubing to be suspended by the first week in September, but the United States Geological Survey was reporting earlier this week that the river had dropped significantly below 100 cubic feet per second, the median flow for the date. Ironically, the stiff rain showers that cooled Steamboat the night of Aug 31 had temporarily boosted river flows by Sept. 1…

City of Steamboat Water Resources Manager Kelly Romero-Heaney said commercial tubing would not be restored unless river flows return to 85 cfs. But the boost in flows from the rainfall of Aug. 31 is expected to be short-lived; the National Weather Service forecast for the upper Yampa River Valley called for a 20-percent chance of isolated storms the afternoon of Sept. 1, followed by sunny to mostly sunny skies through Sept. 7

The city and the Colorado Water Trust had been collaborating since earlier this summer on boosting the flows in the Yampa with water procured from the Upper Yampa Water Conservation District’s Stagecoach Reservoir, and that effort will resume.

Romero-Heaney said efforts to boost the Yampa’s flows will likely continue until early October, when the managers of Lake Catamount, downstream from Stagecoach, begin releasing water as they draws down the reservoir in anticipation of spring runoff in 2018…

The USGS reported at midday Friday that the Yampa was flowing at 97 cubic feet per second, just below median for the date. The lowest Sept. 1 river flow measured at the Fifth Street Bridge, was the 24 cfs, reported in 1934.

The mechanism of tree death due to #drought

California’s hotter drought has already killed millions of trees, particularly in low-elevation forests. (Photo credit: N. Stephenson, USGS)

From Water Deeply (Jane Braxton Little):

New research into how drought kills trees has helped reveal a potentially huge climate consequence of an increase in dead and dying forests that one scientist cautioned could result in a “carbon death spiral.”

[…]

“If we understand the mechanisms of how trees die, we can make predictions and prioritize areas for management,” he said.

First we need to understand how healthy trees function. They get water from the soil, pulling it up through their roots through xylem, one of two specialized transportation tissues in vascular plants. The water flows into tree trunks and branches to leaves or needles. Sunlight turns the nutrients in water to sugar and sap, which nourish new growth.

When there is less water in the soil, trees pull harder. When they pull too hard they break the column of water in the xylem, creating air bubbles known as embolisms. This causes “hydraulic failure.” And this is what killed all of the trees studied by the research team of 62 scientists, said Adams.

But another process also causes trees to die when their response to drought deprives them of carbon.

“Trees aren’t stupid,” Adams said. To prevent losing precious water to the atmosphere through their needles and leaves, trees close the pores scientists call stomata. That keeps the water in the tree, but stomata do more than prevent water loss. They also let carbon dioxide in, allowing trees to carry out photosynthesis.

When trees close their stomata to wait out a drought, they are no longer making any food through photosynthesis. Instead, they are relying on stored sugars and starches. If the drought lasts long enough, they use up everything they have stored, and they die.

Carbon starvation contributed to tree mortality in at least 60 percent of the cases the researchers studied. They still don’t understand the critical threshold for carbon starvation but know it plays a significant role in trees dying.

Mountain pine beetles

Scientists also know bark beetles contribute to tree mortality. That sticky resinous sap used to pitch out beetles is made from carbon. When trees become carbon-starved they are not only unable to metabolize the nutrients for survival; they are also unable to muster the carbon they need to defend themselves against beetles.

The connection between physiological stress caused by drought and defending against bark beetle attack is still an active area of research, Adams said. Entomologists have tended to approach tree mortality in the West through beetles, while physiologists have come at it from the drought perspective…

He and his colleagues analyzed drought-induced mortality in 26 tree species. They examined data from 19 recent experimental and observational studies from around the globe. The research will help scientists and land managers more accurately predict how trees will respond to environmental stresses that include insect damage and disease as well as drought, said Lina Patino, a section head at the National Science Foundation’s Division of Earth Sciences, which cofunded the study.

@USBR Begins Animas-La Plata Project Repayment Negotiations with Ute Mountain Ute Indian Tribe

Lake Nighthorse August 2017 via the US Bureau of Reclamation.

Here’s the release from the US Bureau of Reclamation (Marc Miller):

The Bureau of Reclamation is initiating negotiations on a proposed repayment contract for the Animas-La Plata Project with the Ute Mountain Ute Indian Tribe for the Tribe’s statutory allocation of project water. The first negotiation meeting is scheduled for Wednesday, September 13, 2017, at 1:30 p.m. at the Dolores Water Conservancy District office, 60 Cactus Street, Cortez, CO 81321.

The contract to be negotiated will provide for storage and delivery of project water and provisions for payment of operation and maintenance costs of the project.

All negotiations are open to the public as observers, and the public will have the opportunity to ask questions and offer comments pertaining to the contract during a thirty minute comment period following the negotiation session. The proposed contract and other pertinent documents will be available at the negotiation meeting, or can be obtained on our website at: http://www.usbr.gov/uc/wcao/index.html, under Current Focus or by contacting Marc Miller with Reclamation at 185 Suttle Street, Suite 2, Durango, Colorado, 81303, telephone (970) 385-6541 or e-mail mbmiller@usbr.gov.