Volumetric Water Measurement

How to Operate a Rubicon Slip Meter in Flow Mode (English) 

How to Operate a Rubicon Slip Meter in Gate Position Mode (English) 

How to Operate a Rubicon Slip Meter in Flow Mode (Spanish)

How to Operate a Rubicon Slip Meter in Gate Position Mode (Spanish)


TID has deployed several different types of water metering devices over the last four seasons in response to the Water Conservation Act of 2009, also known as SBx7-7. In simple terms, this law requires all agricultural water suppliers serving more than 25,000 acres to charge customers within a specific volumetric accuracy range. The law defines the accuracy requirements based on the type of device measuring a parcel’s flow. The only way to bill by volume per the State’s requirements was to make a significant investment in new metering equipment and modify the way our customers order water. Many of you have probably noticed the requirement to order on every sidegate opened. This is directly related to SBx7-7. The District has also modified the way it tracks and accounts for water in an effort to comply.

Prior to deploying these meters, TID’s delivery/measurement facilities were adequate based on the historical allotment system. The new volumetric billing and accuracy requirements of the law meant we could no longer use the allotment system or bill from historical measurements. This triggered a Corrective Action Plan process specified by the California Department of Water Resources (DWR). The implementation of this Plan resulted in the meters you see in our system today. TID’s goal is to rate every active parcel/sidegate combination receiving water in an effort to comply with SBx7-7. Details of the original Corrective Action Plan from 2012 are outlined in Appendix F of TID’s Agricultural Water Management Plan. Some plan specifics have changed over time but the overall accuracy requirements of the law still applies. Updating of the current plan is scheduled for completion in 2020.

Volumetric Accuracy vs. Flow Accuracy

There is a very important distinction between volumetric accuracy and flow accuracy as it applies to a gravity system such as ours. On gravity deliveries, it is virtually impossible for the flow delivered through a standard sidegate to remain exactly the same throughout an entire irrigation. This ever-changing flow can be created by many variables/changes in conditions. The list below does not show all of the conditions affecting flow but it does describe the most common variables for every gravity/surface water delivery in our system.  

These items are normally outside of TID’s control because they exist on private property or are not within our right-of-way.

  • Moving from one check to another on your property
  • Moving closer to or farther away from the canal within your pipeline or ditch
  • Different elevations of checks within your parcel…sometimes a 1” difference in ground elevation causes flow variability
  • Changing conditions of your property such as floating for harvest, pre-irrigation on ripped ground, heavy weeds, mature crops etc.
  • Different stem heights or valve sizes of your own field valves/gates
  • Not opening the same number of valves/gates in each of your checks   
  • The existence of structure boxes, road siphons, debris etc. within the section of line you use while irrigating
  • Utilizing any kind of pump that discharges directly into your pipe/ditch  

These items are normally within TID’s control because they are within our canal right-of-way.

  • Any water elevation change within our canal
  • Any change in stem opening at the canal sidegate
  • A plugged grate or debris in front of your sidegate

How does this variability affect flow accuracy and volumetric accuracy? The variability requires us to take multiple measurements during different periods of your irrigation so we can average all of the flows together and compute a single average flow rating for your parcel/sidegate combination. The examples in the following graphs illustrate this variability. The first graph shows an entire irrigation on a single parcel measured by a Rubicon FlumeMeter. The flow steps you see on the graph (yellow line) are from the irrigator switching checks on their parcel.

The next image shows graphs from the same irrigation but illustrate how single flow ratings can be inaccurate when looked at individually. When these single flows are averaged together, they virtually match what the Rubicon computed as the average flow. This is why you may notice some of our employees taking multiple measurements on the same parcels. Simply put, the more measurements we have on a single parcel, the more accurate the billed flow will be.

Graph 2

Meter Types and Measurement Strategy

These constantly changing conditions coupled with delivering large gravity flood heads along with smaller micro/drip heads meant we needed to use the appropriate meter for a particular delivery criteria. Depending on the delivery, we have five types of meters in the following quantities:

  • Rubicon SlipMeters - 120 permanent sites
  • Rubicon FlumeMeters - 59 meters, 46 are mobile
  • Hach Velocity Meters - 4 hand-held mobile meters
  • Sontek Meters - 1 permanent & 1 hand-held mobile
  • Fuji Transit Time Meters - 4 meters for pumped/booster deliveries
  • Down looker – 1 in an ID structure

With well over 1,100 active sidegates in our system, installing permanent flowmeters at each site would be extremely expensive resulting in much higher water rates for our growers. For that reason, we only installed permanent meters on sidegates serving more than 250 acres with a few exceptions depending on location and canal operations. The remaining sidegates would be measured by mobile Rubicon FlumeMeters, Hach velocity meters, Fuji transit time meters and Sontek meters. We are able to have permanent real time measurement data now on more than 72,000 acres after installing meters in only 135 locations. The remaining 75,000 acres would be measured by the other mobile meters. Utilizing this strategy, we are able to volumetrically measure over 1,100 sidegates serving more than 147,000 acres by purchasing only 190 meters overall.      

Rubicon SlipMeter

Slip Meter

Click Here to Enlarge Photo - credit Modesto Bee

The Slip Meter is a fully automated gate that can be operated in flow mode or gate position mode. Flow mode allows the gate to automatically open or close itself to deliver an ordered flow as long as there is enough water in the canal and the pipeline/ditch capacity will allow it. When the meter is in gate position mode it operates just like a standard sidegate by opening to a requested height in inches. Data is sent back to TID in real time allowing WDOs and water managers to see what is happening in the field almost instantly from their PCs or mobile tablets.  Customers served by SlipMeters have the ability to see their actual flow while they irrigate by logging into their TID online water account. Contact the Irrigation Call Center at 883-8456 for details on how to find your flow. You can also learn how to operate SlipMeters by contacting your WDO or by watching our short how-to-videos at the top of this page. Here is an example of SlipMeter data sent back to us through our SCADA network. Click graph to enlarge.

single graph

Rubicon FlumeMeter Rotations

Irrigators with a large aluminum frame installed in front of their existing sidegate will be measured by a Rubicon FlumeMeter. Click image below to enlarge.

FlumeMeters are rotated from gate to gate and require no interaction from the customer. They are simply just a meter sending flow and canal elevation back to TID in real time. Once all parcels being served by a specific sidegate are measured, the meter will be moved to a different site and the process will be repeated. By using this rotation method, we will be able to measure over 32,000 acres with only 46 mobile FlumeMeters. 

Sprinkler Systems and Pumps

In most cases, irrigators utilizing any type of drip, micro or solid-set sprinkler irrigation systems will be measured by portable hand-held meters while some will be rated by Rubicon SlipMeters and FlumeMeters. When this project was first developed, the District planned to install magnetic meters along with full scada/radio equipment at all 400 known systems within TID. To verify cost and feasibility, we performed an inventory of every system and installed measuring equipment at ten sites. The inventory found more than 500 systems and the test sites verified it would cost us more than $4,000,000 to install meters & scada District wide. The inventory also found that most systems had two sources of water. One was TID canal water & the other was groundwater. After taking all of this into consideration, it didn’t make sense to spend over $4,000,000 while having the potential of billing a customer for their own pumped groundwater.

Fuji Transit Time Meter

Fuji Transit Meter

The Fuji transit time meter was chosen as the alternative measurement device for pumped deliveries. They are extremely accurate and have a laboratory certified accuracy of ±1.0 percent. Fuji meters are easy to use and most ratings can be completed from start to finish in 15 minutes. Measurements are performed by trained WDOs at a significant savings when compared to the original plan of installing meters and scada/communications equipment at over 500 locations. We can measure virtually every system in the District with only four of these meters over a period spanning two seasons.

Other Forms of Flood Measurement

On pipelines and ditches not receiving a FlumeMeter or a SlipMeter, TID will use a portable hand-held meter manufactured by Hach (pronounced Hawk) to rate their flows. Trained members of our Water Distribution Department will measure these deliveries by placing the meter sensor inside a vent pipe or within an open ditch during multiple irrigations to determine an accurate average flow. 

Sontek Meter

The Sontek meter (pictured below) will be permanently installed inside designated pipelines and open ditches. This type of permanent meter will be less obvious to irrigators because the hardware is not visible at a sidegate. Sontek meters will be installed in a location upstream of all field valves so all parcels can be measured. If irrigators notice a pole with a communications antenna installed near a pipeline or ditch, one of these permanent Sontek meters is likely being used.

Sontek Meter #2

2017 Billing

In the interest of fairness, TID plans to rate as many customers as possible before changing their billed flows in 2018. Prior to the start of the 2018 irrigation season, information will be provided to all active parcels comparing their historical flow with their new flow. This information will also include a comparison in dollars to help you understand how this new flow change can potentially affect your operations. Some flows will decrease, some will increase and others will see no change at all.

There will also be a series of informational meetings scheduled in your area so District staff can better answer your questions. The locations, dates and times of these meetings will be mailed to you as they become available.  For additional information about water billing, visit TID's Water Rates page or call the District's Irrigation Department at 883-8356.