The start of irrigation season and water outlook

Central Oregon Irrigation District has announced that their main canals will “turn on” starting April 10.  North Unit Irrigation District is scheduled to start April 15.  Nonetheless, I drove over a main canal today and it has water in it.  So, here are some thoughts about the outlook for this irrigation season and its impact on local fisheries.  We have been very lucky with late season snowfall, but it’s not as good as it is often portrayed to be. Our reservoirs, lakes, and rivers will need a lot more than one decent winter snowpack to return to healthy conditions.

As COID states on their website, canals are dry and initial water releases are simply to saturate the ground so that the canals don’t leak too much when water deliveries to patrons begin.  The canals will increase to 50% of capacity by the end of April and reach 100% of capacity by mid-May.   This means that fishing in the Middle Deschutes near Crooked River Ranch should be good soon and get better as the weather improves.  Remember that turning on the canals reduces water in the Middle Deschutes below Bend which is bad for fish, but good for anglers as it concentrates the fish and makes them easier to target.

You can easily see how the Upper Deschutes is managed as an irrigation canal in this chart.  A few days ago releases out of Wickup Reservoir were increased to provide more water for irrigators.  Paradoxically, this is bad for fish.  These extreme and relatively sudden fluctuations erode the banks, widen the river channel, and silt in spawning grounds.  To reach historical flows, the Upper Deschutes should be running above 400 cfs, but the flows should be relatively stable.

Unfortunately, Wickiup Reservoir is only 66% full and is now releasing more water (400 cfs) than is coming in (128 cfs).  If Crane Prairie were full then more water would go to Wickiup, but Crane is only at 85% of capacity. Crescent Lake, another source of water in the Deschutes, is only 10% full.  Historically, these reservoirs would be full prior to the start of irrigation season.

Turning to the Crooked River, Ochoco Irrigation District plans to start some deliveries on April 19th but final decisions on when and how much water will be delivered are not to be made until April 17th.  The outlook for OID and the Crooked River below Bowman Dam is grim.  Prineville Reservoir is only 21% full and Ochoco Reservoir is at 17% of capacity.  Both should be full by now.  It used to be common for these reservoirs to have been dumping water for some time at this point in the year to create room for snowmelt. 

A lot has been made of our late season snow.  Luck is a wonderful thing.  Most of the reported data on snowpack is from the Natural Resources Conservation Service which states that as of April 5 the Upper Deschutes Basin is at 92% of average (median) precipitation this water year (starting October 1).  More importantly, the snow water equivalent is 162% of average.  This is good news but it is important to remember that these figures are looking at the averages for the past 30 years, a period when Central Oregon was usually in drought.

Here’s a different data source that uses a much longer time span to calculate “normal”.  According to the WestWide Drought Tracker, most of Central Oregon is in the “Below Normal” category for precipitation (bottom 33% of rankings) since 1895.

Snowpack is a primary driver of water availability in Central Oregon, and perhaps we will have many years in a row of great snowpack.  That seems highly unlikely.  Today, our lakes and reservoirs remain low, and many are unlikely to fill given irrigation withdrawals about to commence.  Flows in the Middle Deschutes and the Crooked River look to be disastrous for fish yet again this summer.  Even the Metolius River is currently flowing about 25% below the average of the past 101 years (1,250 cfs vs 1,570 cfs).

Personally, I am thankful that our water outlook looks better than it did only a few weeks ago, but we are a long way from being out of the drought and its impact on fish and wildlife.