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Explain This To Me: Where does the Treasure Valley’s water come from?

Water is a hot topic in the Treasure Valley and across the Mountain West as our population grows and our climate continues to get hotter. 

At BoiseDev, we get many questions about the basics of water, both what flows through the valley in miles of irrigation canals and what comes out of your faucet at home. To help readers, we put together this basic guide to how our region’s water system works, where different types of water are sourced from, and how much we use throughout the year. 

No “city water” in Boise 

The inside of Veolia’s water treatment plant on Marden Lane. Photo: Margaret Carmel/BoiseDev

Unlike other localities, the City of Boise nor any other local government doesn’t provide water for the majority of Ada County. 

Instead, French-owned corporation Veolia (formerly SUEZ) is the water provider. They are regulated by the Idaho Public Utilities Commission, which determines what rates the company can charge, the boundary of their service area, and whether or not the company can purchase other providers (like Eagle Water Company). Veolia’s water is also regulated by the Idaho Department of Environmental Quality, just like a public utility. 

This private ownership dates back to Boise’s early roots. Until the 1870s, a system of wells and irrigation ditches fed the newly settled city. This worked for a while, but as Boise grew, the city battled flooding from all of the irrigation systems, and the community started looking toward a centralized water system. But those upgrades don’t come cheap. 

Brothers Hosea and Benjamin Eastman began searching for a water source. They found one in Hulls Gulch, where they eventually filled a reservoir with spring water and piped it into downtown Boise to service their Overland Hotel and several other residences. By 1889, they had found more water in the foothills and began applying for permits to service the entire city as a private company. Boise Water Works was incorporated in 1890. 

In 1928, Boise Water Works became Boise Water Company. General Waterworks Corporation acquired it in the 1940s, which later merged with United Water in 1994. This company was purchased by Suez, a French-owned water company, in 2015. The name changed for the latest time earlier this year when Veolia purchased Suez after years of talks. 

Where does your water come from?

If you turn on the tap in Boise, your water most likely comes from one of Veolia’s 83 active wells. 

These wells go between 200 and 1,100 feet deep to tap into the region’s aquifer system, which is fed from snowmelt traveling down through the mountains and under the earth for years before it comes out of the ground and into your tap. This is a much deeper network of water supplies than private wells, which are usually only drilled between 60 and 100 feet deep and fed by the rain cycle and agricultural watering recharging the area. 

Veolia’s water output changes drastically depending on what time of year it is. The system demands roughly 23 million gallons of water per day in the winter, but it spikes up to 97 million gallons per day in the summer months to feed the demand for watering lawns and gardens and filling swimming pools. 

Roughly two-thirds of the company’s water supply comes from groundwater wells, while the other 25-30% comes from the Boise River. Like any farmer or household with water rights to the Boise River, Veolia has rights to pull water stored up at Lucky Peak Reservoir that is released into the Boise River Basin to give water to their customers. This means that in years like 2021, when irrigation shuts off early due to drought, and everyone has to turn to Veolia’s water supply to water lawns instead of cheaper pressurized irrigation from the canal, the company is also unable to pull from the river either, and has to meet all demand from groundwater. 

But, even with the big swing between winter and summer in demand for water, domestic water use (including lawn watering) is only 2% of the Treasure Valley’s water use, as of the latest available estimates. Agriculture is far and away the most significant water user in the region and throughout the state. 

What is this canal doing in my backyard?

Lucky Peak might be a fun place to spend the day on a boat, but it’s a vital resource powering the Treasure Valley’s water supply. 

The valley’s 1,170-mile-long irrigation system is fed by three dams above the city, Anderson, Arrowrock, and Lucky Peak. These dams store water from the Boise River behind them, which is then slowly let out to flow through the floor of the valley clear to eastern Oregon throughout the summer. The more rain and snowmelt we get in the spring, the more full those reservoirs get and the longer the irrigation season can go on. Up to 1 million acre-feet of snowmelt water can be stored in the reservoir systems to feed the Treasure Valley’s farms.

Walking around Boise and other places in the Treasure Valley, it’s not uncommon to see canals and ditches snaking through your neighborhood. Some of them are large and are walled in with steep concrete walls, while others are smaller and can look like natural creeks at first glance. This network, which canal companies and water districts control, carries the water from the Boise River out to homeowners and farmers. 

If a canal is on your property, even if you don’t have a water right to use it, it is your responsibility. You cannot fill it in or reroute it beyond paying to put it in a pipe underground. And if you don’t have a right to that water, you cannot pump out of it to water your garden. Because, as Deputy Boise Water Master Daniel Hoke told BoiseDev, that would be stealing. 

“If you’re in the irrigation entity, they would control that, but very basically whatever water is running in the ditch that is all accounted for, and that water is being used by somebody,” he said. “If you go out there and stick a pump in there and start pumping water out, you are stealing somebody else’s water. You have to have a water right permission to use it.”

During the hottest days of the growing season in June and early July, roughly 5,000 cubic feet per second of water is released out of Lucky Peak to come down into the Treasure Valley. This is nearly all for agricultural uses, although some subdivisions have access to water their lawns or gardens. Irrigation water is far cheaper than Veolia rates, allowing homeowners to keep their trees and other plants healthy for a low cost, even in the middle of a high desert summer. 

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Margaret Carmel - BoiseDev Sr. Reporter
Margaret Carmel - BoiseDev Sr. Reporter
Margaret Carmel is a BoiseDev reporter focused on the City of Boise, housing, homelessness and growth. Contact her at [email protected] or by phone at (757)705-8066.

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