Irrigation Season Is Here. What Does That Mean for the River?

April 17, 2020
Irrigation Season Is Here. What Does That Mean for the River?

Spring has sprung and canals all over Central Oregon are filling with water diverted from local rivers and streams. Over 700 miles of canals will carry this water throughout the region’s irrigated lands bringing back life after a frozen winter.

If you are a regular visitor along the banks of the Deschutes River (downstream from Bend) or many of its tributaries, you’ll notice a significant drop in flows that coincides with the beginning of irrigation season each spring.

To understand this correlation, let’s take a trip back in time. The Deschutes River, named so by French trappers for its many chutes or falls, was once thought of as a “peculiar river” in that its flows were relatively stable year-round. This is not the case with many other rivers due to their primary dependence on snowmelt. The Deschutes is distinct because of its dual source of flows: groundwater and snowmelt. During its 250-mile course winding north to the Columbia River, the Deschutes is replenished by significant underground springs.

Today, the river functions vastly different from its original state. When settlers arrived, seeking farmland and a new future, water rights to access flows from the Deschutes and its tributaries were handed out in abundance. So abundant, in fact, that there were more rights to access water from the river than there was water instream. To meet these needs, water managers began to store winter flows in Wickiup and Crane Prairie Reservoirs, releasing them in the spring and summer to meet demands. This practice dramatically altered the flows in the river from relatively consistent year-round to seasonally fluctuating dramatically.

So, what does this all mean for the canals and instream flows? As canals turn on in the spring, instream flows are diverted from the river. Water levels in the Middle Deschutes (from Bend to Lake Billy Chinook) drop from 400 - 475 cubic feet per second (CFS) to 60-100 CFS in mid-April when districts turn on. This reduction in flows is detrimental to fish and wildlife who depend on the river. As flows drop and temperatures rise throughout the summer, the water in the Middle Deschutes can reach near-lethal levels for native fish populations.

The Middle Deschutes has seen a four-fold increase in flows over the past 25 years. This has been thanks to partnerships between the DRC and irrigation districts in Central Oregon. While we are proud of the progress we’ve made so far, there is still further to go. The Oregon Department of Fish and Wildlife recommends a rate of flow of at least 250 CFS. The DRC plans to continue to partner with districts on conservation projects and instream leasing to increase these flows.

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