Yuma Ag and You: Colorado River water flow

Bobbi Stevenson-McDermott       August 7, 2016 Publication

The Colorado River is a wonderful playground for Yuma County residents, out of state visitors and winter visitors. Unless your river activities take place strictly on the lower river below Imperial Dam, you may not realize that there is an ongoing daily changed in the river water level above Imperial Dam.

The reason for the fluctuations in the upper river is the change in irrigation demand from summer to winter crops. Generally, the highest flows, measured in cubic feet per second (CFS) take place in May, June and July. The lowest flows are in December and January.

A cubic foot per second is defined as 450 gallons per minute of flow. The Bureau of Reclamation, the water master of the Colorado River, is tasked with delivering the amount of water ordered by each Irrigation District in Yuma County and the Imperial Irrigation District each day. To accomplish this, each farmer who utilizes irrigation district water delivery places his individual water order for his farm three days in advance of the time he needs it. The six local districts send a sum total order to the Bureau of Reclamation. The irrigation water is released out of the upriver dams, ending up at Parker Dam. Each day’s release takes 2 – 3 days to move from Parker Dam to Imperial Dam, where the water is distributed into the various irrigation district systems.

For the week of August 1, 2016, the Monday release is 10,000 CFS; Tuesday 10,100 CFS; Wednesday 9500 CFS; Thursday August 4, 7500 CFS; Friday 9500 CFS; Saturday 9800 CFS and Sunday 9900 CFS.

Every Thursday is the lowest release for the week, so starting late Thursday the water begins to drop in the river, with the lowest flows on Saturday. If you are a recreational water user, skiing, fishing, pleasure boating, or jet skiing, less water means more sandbars or exposed debris to avoid. You may ask why the releases are not kept at a uniform flow? Farmers are people too, with families and other responsibilities. Irrigations are scheduled so that they can also enjoy other activities on weekends. By Monday morning, water releases are at their full flow for the week.

With all the irrigation districts working together there is very little waste in water delivered to the Yuma area, because it all has a predetermined location for delivery. As usual, the only thing that disrupts the delivery plans is Mother Nature. Most rainfall does not affect the irrigation deliveries because not enough water falls to meet the plant needs. Only when there are heavy storms, 1 to 3 inches of rain or more, is there too much water in the system. Since most farmers apply 3 to 4 inches of water across a field when irrigating, heavy rains make the irrigation water unnecessary. At that point, the Bureau of Reclamation diverts water into Senator’s Wash and Brock Reservoir in California to try to prevent excess water going down the river. The stored water is then released in the coming days until it reaches the static level for each facility.

The reason it is important to Arizona to not send too much water below Imperial Dam involve the international agreements with Mexico and the metering of water delivered at the Southern International Border.

Many people who have lived in Yuma for years do not realize why the river above Imperial Dam varies in flow. During the months of December and January, as little as 3000 CFS flow to Imperial Dam. The weather is cool, the produce doesn’t grow as rapidly and not as much water is used.

To enjoy a quiet day on the river with maximum water flows, go play Monday thru Thursday!