Measuring Water Use & Flow Meter Requirements

Flow Meter Requirements 1. Systems with widely fluctuating discharge rates or

How do I get my method approved ?
when variable speed pumps are used.
Minnesota Statutes § 103G.281, Subdivision 2, 2. Systems with alternating zone coverage, such as
golf course irrigation systems. Each year permittees are required to sign an affidavit
requires all installations for appropriating water to be
3. Instances where the permit holder has a history of compliance on the water use report indicating
equipped with a flow meter to measure the quantity of
of providing inaccurate pumping reports or has failed to compliance with the law requiring a flow meter or an
water appropriated within the degree of accuracy
submit water use fees and reports. approved measuring device. The affidavit of
required by rule (10%). The commissioner may
4. Situations where the adequacy of the resource is compliance and the annual report of water use are
approve alternate methods of measurement based
a concern or there is a history of well interference due by February 15 of each year.
on the quantity of water used, the method of
appropriating or using water and any other problems.
Permittees using a method of measurement that has
information supplied by an applicant.
not been approved must submit a written request for
What methods are approved ? approval of an alternate method. Requests should
Why require Flow Meters ? include a detailed description of the proposed method
The following methods are approved for measuring (i.e. diagrams, calculations). Requests for approval of
The law is aimed at improving the accuracy of water water use: an alternate method should be sent to DNR Waters,
use reporting and has many benefits. Careful Permits Unit, 500 Lafayette Road, St. Paul, MN
monitoring of water withdrawals can be used to: 1. Flow meters with a totalizer. 55155-4032. Only methods that measure water use
provide valuable information for management of the 2. Flow rate meters used with timing devices.† ‡ within 10 percent accuracy will be considered for
resource, detect well and pump problems, improve 3. Timing devices (hour meters and electric approval. Records of water use must be kept for all
irrigation efficiency, and determine pumping plant meters). † ‡ methods of water use.
efficiency. As a management tool, accurate flow 4. Vehicle gallon capacities (i.e. water trucks).†
monitoring can help to conserve both energy and Failure to have an approved method is a violation of
water resources. Accurate data is necessary to † Daily records of water use and time pumped must Minnesota Statutes and permit conditions and is
evaluate the capability of the resource to sustain be kept for these methods. punishable as a misdemeanor with fines up to $700
water withdrawals and is also important for ‡ Methods 2 and 3 are require d to have a constant and/or 90 days in jail.
investigation of well interference complaints. pumping rate.
General
Does everyone need a flow meter ? What if I am using a gravity flow system ?
To obtain information about the purchase and/or
All new permitted installations will be required to have Special instructions regarding gravity flow operations installation of a flow meter, contact a licensed well
flow meters unless prior DNR approval has been are available by calling DNR Waters and requesting driller, irrigation equipment dealer or plumbing supply
given for an alternate method. Existing systems may the "Measuring Appropriations from Gravity Flow company.
be allowed to use an approved alternate method. Installations" information sheet. (continued on next page)
Depending upon the type of system, water use and
quantity of water used, the commissioner may Which methods are not approved ?
approve alternate methods for measuring water use.
Requests for approval of alternate methods must be
submitted in writing to DNR Waters. Proper record The following methods are not approved for measuring
water use:
Minnesota DNR Waters
keeping is required for all approved methods of
determining water use.
1. Rain gauges or other methods using application 651-259-5700
When is a flow meter required ? rates, such as irrigation systems that are set to apply a
certain amount of water per acre or pass.
This information is available in an
Flow meters are required when alternate methods 2. Buckets used to measure discharge rates.
alternative format upon request
cannot provide an accurate measurement of water 3. Fuel consumption by gasoline or diesel engines.
use. Flow meters will be required where the following 4. Estimates using a set volume of water per
 1994 State of Minnesota, Department of Natural Resources
circumstances exist: person or animal.
Calculating Monthly Water Use • gph per 100' of trickle tube* feet/100 Typical Discharges for Single Large
= gpm Nozzle Sprinkler Guns
To calculate monthly water use from: • Open discharge pump's manufacture curve.
Sprinkler Straight or taper bore nozzle sizes (inches)
A. Flow Meter: Subtract the reading at the ESTIMATING DISCHARGE OF A CENTER Pressure 0.8 1.0 1.2 1.4 1.6
beginning of the month from the reading at the end (psi) Sprinkler discharge in gpm
PIVOT WITH CORNER UNIT
of the month. If the meter is in cubic feet, multiply the 60 145 225 330 445 585
monthly use by 7.48 to convert the usage into 70 155 245 355 480 630
A good average discharge flow rate estimate for a
gallons. 80 165 260 380 515 675
center pivot with a corner arm can be determined by
90 175 275 405 545 715
taking the average of the discharge rate when the
B. Timing Device: Multiply the hours pumped for 100 185 290 425 575 755
corner arm is fully extended and fully retracted.
the month by the pump rate (in gallons per minute, 110 195 305 445 605 790
The water discharge from a center pivot with a corner
gpm) times 60 (minutes). [Example; 150 hrs x 800 120 205 320 465 630 825
swing arm varies depending on the postion of the swing
gpm x 60 min/hr = 7,200,00 gallons].
arm, usage of flow control/regulators, and the slope of the Ring Nozzle Sizes (inches)
pump performance curve. 0.9 1.1 1.3 1.5 1.7
Hourly timing device options:
1. An hourly time clock connected directly (psi) Sprinkler discharge in gpm
to irrigation pumping plant system.
STEPS TO ESTIMATE GPM FOR A 60 110 185 275 385 510
2. Kilowatt Hours: Monthly hours of pumping TRAVELING GUN 70 120 200 295 410 550
determined by dividing monthly electric 80 130 215 310 435 585
usage by electric meter's monthly power 1. Determine nozzle size to nearest 1/100th of an 90 135 225 325 460 620
demand rate (Kw). [Example: 3000 Kwh inch and nozzle type (bore or ring): [ex: 1-1/4" = 100 140 240 340 485 655
of electricity was used in the month of 1.25 inches taper & bore nozzle]. 110 150 250 350 510 690
June and the electric meter recorded a 2. Determine average operating pressure at the 120 155 260 360 530 720
peak demand for the month of 25 Kw, base of the sprinkler. If pressure varies between
then the total hours pumped is found by first and last travel runs, take the average
dividing 3000 Kwh by 25 Kw, which yields between the first and last runs: [ex: 1st run = 95 Table Sources: Nelson Irrigation Corp. - sprinkler
120 hours pumped for the month. To find psi, last run = 85 psi, average = (95 + 85)/2 = 90 charts. Rain Bird, Agri Products Division - sprinkler
water use take 120 hrs x 300 gpm x 60 min/ psi]. charts. SCS National Sprinkler Irrigation Book -
hr = 2,160,000 gallons]. 3. Select the appropriate discharge table (bore or Chapter 15.
ring nozzle) listed below and find the estimated
gpm for your nozzle size and average operating *Prepared by: Jerry Wright, Extension Agricultural
* Approved Alternatives for Estimat- Engineer, University of Minnesota, 1990.
pressure or use gun manufacturer's published
ing Water Pumping Rate from discharge table.
Agricultural Irrigation Systems If your nozzle size or operating pressure values Equal opportunity to participate in and benefit from pro-
follow between the table numbers, make an grams of the Minnesota Department of Natural Resources
interpolation between the smaller and larger is available to all individuals regardless of race, color,
The following alternate methods are approved by the national origin, sex, sexual orientation, marital status,
numbers to get a more accurate estimate of
Department for agricultural irrigation systems. status with regard to public assistance, age or disability.
flow: [ex: have 1.25" bore nozzle @ 90 psi; table
Discrimination inquiries should be sent to: MN/DNR,
gives at 90 psi 405 gpm @ 1.2" and 545 @ 1.4"; 500 Lafayette Road, St. Paul, MN 55155-4031; or the
• Pumping flow rate test.
then to estimate the gpm for 1.25" nozzle Equal Opportunity Office, Department of the Interior,
• Center pivot/linear system's manufacturers
calculate as follows: Washington, D.C. 20240.
nozzling chart.
- for a center pivot with a corner swing unit,
gpm = 405 gpm + [(1.25" - 1.2")/(1.4" - 1.2")] * (545 The DNR Information Center phone numbers:
refer to the following section.
gpm - 405 gpm) Twin Cities: (651)296-6157
• Traveling gun nozzling chart.
= 405 + (0.05/0.20) * 140 MN Toll Free: 1-888-646-6367 (or 888-MINNDNR)
• Lateral line irrigation systems nozzling chart.
= 405 + 0.25 * 140 Telecommunication Device for the Deaf:
= 405 + 35 = 440 gpm (651)296-5484
1-800-657-3929 MN Toll Free