Water Measurement

Examples of Alternative Measurement Methods

Electricity Records Dedicated to the Pump

Description:  If a pump has a dedicated meter, the electricity used on the meter, in kilowatt hours, can be correlated to a water volume using a pump test.  If a dedicated meter is not present or available, a device called a sub-meter can be installed by qualified electrician. This method requires a log book and occasional data entry to track usage over time.

Accessories:  Log book; sub-meters by Kill A Watt™, Leviton™ and other manufacturers.

Advantages: The Kill A Watt™ electrical meter shows how much power a pump is using.The Kill A Watt™ electrical meter is for various indoor uses with standard 110V 15A wiring systems.The meter costs about $20 at home improvement stores. Indoor/outdoor commercial-grade sub-meters are $200 to $300 with some more sophisticated (3phase-240V-200A) systems with monitoring data ports are $400. Once the kilowatt-hours to gallons relationship is determined and calibrated, accuracy is relatively good under steady-state conditions.

Disadvantages: Measurement is indirect. A change in source water level, pipe length, pump speed or other factors that change the pump pressure “head” will affect the calibration. Large capacity electrical sub-meters should be installed by a qualified electrician.

Total Facility Electricity Records minus Estimated Non-Pump Electricity

Description: This method involves estimating the amount of non-pump electricity used at a facility, and subtracting it from the total electricity recorded at the facility’s electrical meter. The difference is the power used by the pump, which can be correlated to a water volume.

Accessories: Electrical meter, “Smart” meter

Advantages: This method does not require an electrical meter “at the pump.”

Disadvantages: This method may not work well when the amount of electricity used by the pump is small relative to other electrical loads “on the meter”. A change in source water level, pipe length, pump speed or other factor that changes the pump pressure “head” will affect the calibration.

Power Generation Estimates

Description: Power generated in watts, kilowatts, or megawatts using a turbine is correlated to the volume of water flowing through the turbine at a given head pressure. This method requires power generation meters and record-keeping to track power generation.

Accessories: Electronic data logger, data telemetry.

Advantages: Flow rate and quantity of water used can be approximated without the purchase of a flow measuring device.

Disadvantages: Requires calibration to develop a rating curve(s). Turbine and generator efficiencies affect the accuracy of calculated flow rates and volumes.

Remote Satellite Imaging

Description: Use of satellite imagery to estimate consumptive use of crops.

Advantages: State-of-the-are method for approximating crop evapotranspiration of consumptive use.

Disadvantages: Commercial satellite imagery is often more costly than other types of measuring devices.  Satellite imagery at the required resolution may not be available in a timely fashion to estimate water use for Statement reports by July 1 of the following year.  This method provides an estimate of crop consumptive use, but not the amount diverted from the stream.

Crop Duty Estimates/Consumptive Use Estimates

Description: The total volume of irrigation water required to grow a particular type or variety of crop, including consumptive use, evaporation and seepage from ditches, canals and water application.

Accessories: Farm advisor contacts, publications, and resources (e.g.: University of California Division of Agriculture and Natural Resources).

Advantages: The water used can be estimated without purchasing a measuring device.

Disadvantages: Crop duties depend on a number of variables being consistent, if not constant, including: soil moisture, average daily temperature during the growing season, precipitation, method of irrigation, groundwater percolation, soil type, crop type and variety, and availability of nutrients. Since these factors vary seasonally and by location, a crop duty in one area may not be applicable in another area.

Other Water Duty Estimates Other Than for Crops

Description: The approximate amount of water used “per person” by occupants of a household, or some other unit, such as water use per head of livestock. Amounts for households vary depending on the structure, fixtures, weather, location, and whether there is ornamental lawn watering.

Accessories: Daily log book; Various duty estimates can be found in Appendices I, II and III of the Division of Water Right’s booklet, How to File an Application.

Advantages: Quantity of water can be estimated without the purchase of a measuring device.

Disadvantages: Housing structures have varying levels of plumbing fixtures, habitation, and use; therefore, a water duty for one household is often different than another.

Modeled/Estimated Flows

Description: Flow estimated using a computer model or estimated based on a water balance.

Accessories: Model or flow balance spreadsheet.

Advantages: Relatively easy to use.

Disadvantages: Flows are estimated.

Bucket and Stopwatch

Description: This method involves filling a bucket of known volume and using the stopwatch to determine the time the bucket takes to fills. The volume of the bucket divided by the time it takes to fill gives the flow.
Accessories: Daily Log Book; Bucket and stopwatch.

Advantages: Easy to use.

Disadvantages: Provides the flow at one point in time.

Engine Fuel Use

Description: Water diversion pumps using diesel or gas engines that run continuously typically use x gallons of fuel to pump y amount of water. If the amount of fuel use can be correlated to the amount of water pumped using a calibration procedure, a relationship may be developed between the amount of fuel used and the amount of water pumped. This can give a reasonably good estimate of the amount of water pumped based on the amount of fuel used to run the diversion pump(s).

Accessories: Daily Log Book

Advantages: No special water measurement devices needed.

Disadvantages: Determination of the amount pumped based on fuel usage is an indirect measurement of the “amount of water taken from the source” and may or may not give an accurate rate of diversion. A water measurement device is needed to develop a fuel to water-volume relationship (calibration).

Staff Gage and Floodable Acreage

Description: For water use(s) involving the deep flooding of land (such as duck clubs or rice checks), the amount of water applied to the land can be determined volumetrically. For example, a 5-acre rice check filled 24 inches or 2 feet deep will take 10 acre-feet to fill (excluding the water used to saturate the soil).

Accessories: Daily Log Book and some type of permanent or temporary staff gages placed at key locations within the flooded area.

Advantages: No special water measurement devices used.

Disadvantages: Does not account for initial and ongoing soil percolation losses, resulting in the under-estimate of the volume of water diverted to fill the containment area; diminished accuracy and precision of water diversion measurement.

Float and Stopwatch

Description: This method involves using a float and a stopwatch to estimate the velocity of flow by measuring the time it takes for a float to move a given distance. Since the float is near the top of the cross-sectional flow, it does not represent average velocity. The average velocity can be determined by multiplying the velocity at the top of the cross-sectional flow by 0.8 (Vavg = Vfloat x 0.8). To determine the discharge, you will need to measure the area of flow in the channel and multiply times the average velocity (discharge = velocity x area).

Accessories: Daily Log Book; Float and stopwatch.

Advantages: Easy to use.

Disadvantages: Provides the flow or volume discharged at one point in time.