Public Notice

Roosevelt County Conservation District

Board of Supervisors Regular Meeting

Scheduled for

November 7, 2017

1:00 P.M.

USDA – Service Center

508 6th Street East

Culbertson, Montana  59218


How to Estimate the Amount of Pumped Water

If you have an irrigation water permit, sometime this winter you will receive a notice from the Roosevelt County Conservation District requesting a report of the amount of water you pumped for irrigation this past growing season. Here are three methods you can use to determine the volume of water pumped for irrigation, depending on your equipment

Do you have a working flow meter?  

A working flow meter with a  volume totalizer makes filling out the form easy to do. The volume totalizer is a counter similar to the odometer in a car.  Some meters record the volume in hundreds or thousands of gallons. Determine which one usually is easy because the manufacturer will show zeros to the right of the counter.  If the meter records hundreds of gallons, it will have two extra zeros; it will show three zeros if it records thousands of gallons.  Some meters record the volume in cubic feet of water (1 cubic foot equals 7.5 gallons) and some record in acre-inches or acre-feet.  If you wrote down the numbers on the volume totalizer at the start of the season, then all you need to do is read the meter again and subtract the current number form the previous number to obtain the volume pumped. You can report water use in gallons or acre-feet. Just remember, an acre-foot of water covers an acre 1 foot deep in water and is equal to 325,800 gallons. An acre-inch is equal to 27,150 gallons.

Do you have an hour meter on the center pivot or pump?

For a center pivot system, you can calculate an estimate of the amount of water pumped using the hour meter in the pivot control panel. However, you need to have written down the hour-meter reading at the beginning of the growing season. Subtract the current reading from the previous reading to get the number of hours the pivot operated this year. You then need to know the approximate flow rate to your center pivot. This can be obtained from the center pivot sprinkler chart. Now that you know the flow rate, use the following formula to calculate the acre-feet of water that were pumped:

Volume pumped = (Hours of operation) x (gallons per minute) ÷ 5,430

For example, say your center pivot ran for 895 hours and the sprinkler flow rate is 800 gallons per minute. then the volume pumped is approximately:

(895 x 800) ÷ 5,430 = 131.9 acre feet  


No water or hour meter?