Making the water last
Facing historically low water levels at Ochoco Reservoir, the manner in which Ochoco Irrigation District provides water will change for the remainder of the season.
"The district normally operates on what is known as a demand system," explained OID Manager Russ Rhoden. "This mode of operation has the board set an acre foot allocation per acre in the spring of each year, and patrons order water as needed."
During normal water years, Rhoden said the allocation is typically set at 3 acre-feet per acre with an increase made in the late summer or fall. This year, the allocation was set at 2.5 acre-feet per acre with no planned increase.
However, this is not a normal water year – in fact it is one of the most unique water years the district has faced in the past 20 years. Mountains in the Central Oregon area had a very low snowpack following a drier and warmer than normal winter, and the spring and summer months have followed the same trend, particularly in July when all but a few days have had highs in the 90s and approaching 100.
In fact, Rhoden had to go back to 2001 to find a comparable year and even that year looked better in certain ways. Both years, on July 24, the Ochoco Reservoir inflows from Mill Creek and Ochoco Creek are at zero cubic feet per second. The reservoir level was lower at this time in 2001, 13,827 acre-feet, compared to 16,239 acre-feet this year, but the outflow from Ochoco Canal are 74 cfs versus 40 cfs in 2001 and outflow from Ochoco Creek is 15 cfs compared to 11 cfs in 2001.
Driving the discrepancy in outflows is the fact that the majority of crops OID customers are irrigating this year are grass hay and alfalfa hay, both of which demand a lot of water. In 2001, there was a more diverse mix of crops, and water demand was not as high.
He points out that the rate of water demand is fairly constant, unlike more typical years where the need for water sees more peaks and valleys.
"We really don't see it falling off," he said of the demand, adding that the hay crops could likely demand the same level of water into late August.
Because of the declining reservoir level and the continued demand for water this season, the OID manager and board decided to switch to a rate base system, effective Aug. 1, in hopes of conserving as much water as possible.
"It is just something we have to do in order to have enough water to get through the season," said board member Brian Barney.
"On a rate base, irrigators will be given a flow rate that they can order 'on' and 'off' per acre," Rhoden explained. "The rate the board approved is the same rate as in the district's water right certificate, which is 5.6 gallons per minute."
He went on to note that OID has made such a change in the past, but not since the 1990s. He and board members, some of whom are farmers, hope the change will enable the district and its customers to manage their water well and conserve as much of what is left as possible.
Rhoden said he and the OID board will monitor the situation closely throughout the remainder of the irrigation season and make adjustments to the rate of delivery as needed with the goal of ensuring customers can irrigate through Sept. 28.
"The district appreciates your help and cooperation on this change of delivery method," he said.