Drought could cause Treasure Valley irrigation to end a month earlier

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Treasure Valley farmers and other water users are likely considering a shortened irrigation season as high temperatures continue to cook the area.

In a normal year, water flows through southwestern Idaho from a network of three reservoirs in the hills above Boise through an extensive network of irrigation canals to water the crops up in October. But, this year, the brutal punch of a dry spring and record summer temperatures have brought the Boise River Basin to near record highs. This means that the irrigation could stop flowing in September, about a month earlier than normal.

[The Boise River: nature, development, and water quality shape its future]

Boise Watermaster Rex Barrie, who manages the Boise River irrigation system, recently warned irrigators and other water users, such as the Suez Water Company, to conserve the water so the supply can expand the as long as possible. He said this year’s low numbers are on track with 1977, the lowest runoff year on record for the Boise River basin.

He said some irrigation districts require their users to alternate watering on odd and even days, and residential users should slow down watering their lawns.

“The more water we can conserve, the more we can extend our season,” said Barrie. “In agriculture, there are crops that must be watered. If they don’t have water guys lose yield and loss of yield leads to loss of income, and it’s hard. When it comes to city dwellers watering your garden, the grass is extremely tough. It may turn brown, but when you start watering it again, it will start to green again.

Lower than average tank levels

This drought started unusually, with a typical snowpack that normally marks the start of a good hydrological year. But, without the typical spring rains and several over 100-degree days in June and the July heatwave evaporating the water, the network of reservoirs feeding the Boise River system did not fill up. Bureau of Reclamation figures show 2021 volumes in the Arrowrock, Anderson and Lucky Peak reservoirs well below average.

A graph from the Idaho Bureau of Reclamation showing the average water volumes in the Arrowrock, Anderson, and Lucky Peak reservoirs over time.

Typically, the three reservoirs would contain 704,000 acre-feet of water at this point in the season, according to Bureau of Reclamation hydrologist Ryan Hedrick. This year, there were only 478,000 acre-feet in the system at the end of July.

The way water is distributed to users is based on a complex legal system of water rights. At the start of the season, as long as there is sufficient water, all users who have water rights can divert all of the water allocated to them in the canals. As the water supply becomes depleted, water users are assigned a smaller and smaller percentage. Eventually, the Watermaster begins to restrict their rights to divert the river based on the priority date. The most recent water rights are closed first, and the order goes back in time, to the oldest rights in 1864.

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Currently, Barrie only releases water to customers with water rights granted in 1871 or earlier. However, customers with storage rights are still entitled to the water retained in the reservoirs. Barrie is responsible for releasing the appropriate amount of water from Lucky Peak to meet the orders of the various irrigation districts and other customers each day.

Irrigators get the biggest volumes from the river

One of the Boise River’s biggest customers is the New York Canal, which diverts 2,000 cubic feet of water per second every day. This water supplies five different irrigation districts, including one across the border from Oregon. Bob Carter, project manager for the New York Canal Boise Project, told BoiseDev that heat had been an “unknown factor” in 2021, leading to high demand since the floodgates opened.

Idaho fishing
A fisherman along the Boise River. Photo: Don Day / BoiseDev file

“We’ve been at full capacity since day one and demand is high just because of the heat and the dry spring,” Carter said. “Customers are concerned about the condition of some crops towards the end, so they like to have that extra water. Sugar beets and corn consume a lot of water. Some people say they will get by and get by, but others will be more concerned with the choice of culture.

Suez is also diverting water from the Boise River to supply its drinking water distribution system for the Treasure Valley, but not as much as the irrigators. On July 19, Suez diverted 14 cubic feet per second from the Boise River, far less than the New York Canal. When their storage capacity is exhausted, the system will have to rely entirely on pumping groundwater to meet the valley’s drinking water needs.

Suez consumes up to a billion gallons

With less water in the canals, less water recharges aquifers for residents to drink. And in turn, there is more pumping of groundwater to meet the demand. Last month, staff from the Idaho Water Resources Department told BoiseDev that the valley has plenty of groundwater to meet current demand, but that raises long-term questions about how the water moves through the valley.

“This feedback loop bothers me,” Hedrick said. “You have to look at the growth in the value of the number of more people who are drilling wells and depleting this aquifer than before.”

Suez recently urged customers to reduce their water consumption by watering lawns only two or three times a week, avoiding watering during the heat of the day, and directing the sprinklers to the grass instead of the sprinklers. sidewalks. The company has so far used a billion gallons of water more than expected in 2021, with use rising 15% in July, according to company spokesperson Katie Birkenstein.

“The summer has been unusually hot and dry, and the wise use of water has never been more important in the Treasure Valley,” Birkenstein wrote in a press release. “As a water supplier to nearly a quarter of a million people, SUEZ closely monitors water use in order to guarantee a sufficient supply for everyone. “

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