Coming Soon, Free Ebooks on Measurement Device Installation and Flow Measurement

The All Water Rights Blog has most or all of the information needed for a farmer or rancher to install a simple measuring device that is compliant with the recent regulations of the State Water Resources Control Board.  I’ll have a couple of free ebooks by June, on how to Red_Books_Edited_3install pre-cast weirs and orifices, as well as how to use them correctly, and report flows from small diversions to the Water Board.  Actually, the ebooks will apply to larger diversions, too, except for the necessary pressure transducer needed to report hourly (and some day, 15-minute) flows to the Board.GE_PT878

There are certainly more complicated devices that require help, such as cast-concrete
Parshall and other flumes, mag-meters, acoustic Dopplers, or full-on gaging stations on rated sections of streams or ditches.

However, most diverters can (and many do) comply with the law with relatively simple devices.  That’s it for now, I just wanted to get the word out on this.

Oh, and there will be an ebook some time around August, which has a working title of “Practical And Applied Water Rights In California – The Non-Attorney Book For Diverting Your Water”.  That book will be more complete and will cost something, yet to be determined.  Let me know what YOU want to see included in a book like this.

Have a great day, pray for more rain and snow!

How Good Is Good Enough? Water Board Required Accuracy of Your Measurement Device

How accurate does your measurement device have to be?  The Water Board gives those numbers in the Fact Sheet at; see the bottom of this post for the excerpt on accuracy.

When talking about new weirs, orifices, flumes, mag-meters, and acoustic Doppler devices, plus or minus (+/-) 5% accuracy is expected of new, properly installed, regularly maintained, correctly operated devices.  What does that mean?  If your diversion rate is measured at 1.00 cubic feet per second (cfs), then you would expect the true value to be between 0.95 and 1.05 cfs.  If your diversion rate is 5.00 cfs, then the true value would be between 4.75 and 5.25 cfs.  The total accuracy is 10%, we just don’t know if measured values are really up to 5% less, or 5% more than calculated.

New devices might actually have better accuracy than +/- 5%.  Engineers never count on that because a bunch of factors, known and unknown, can stealthily make the accuracy worse.  Accuracy also depends on the measurer – some are better than others, some are better trained and experienced, and most take the job seriously but some do not.

Of course, accuracy gets worse as measurement devices age.  Why does this happen?  There are a number of reasons:

  • Settling, so the device is not level front to back, or side to side, or both
  • Cracking, so water leaks out, or the cracked wall is not straight (planar)
  • Wear, spalling, chipping, and other roughening in the device floor and walls
  • The ditch fills in downstream, causing submergence
  • Old boards that warp and leak
  • Installed staff gages wear, making them harder to read correctly
  • Etc.

The USBR Water Measurement Manual has 14 chapters, and all of Chapter 3 discusses accuracy in great detail.  That’s the “Bible” of water measurement so we would expect it to be, well, accurate in its discussion of accuracy.

It is not clear to me yet whether the Board’s accuracy numbers are +/- values, meaning the allowed accuracy is +/- 15% for diversions less than 100 acre-feet (AF) per year, and +/- 10% for diversions greater than 10 AF per year.  If so, that seems reasonable because that allows for some aging of measurement devices.  Otherwise, the Board would expect measurement devices to always be in new condition for diversions greater than 100 AF per year or storage greater than 200 AF per year.  That would be pretty expensive!

That brings up the subject of money – accuracy requirements hit your pocketbook.  First you have to either install or pay for a measurement device to be installed.  Hopefully the device will last 20 to 30 years, but high flows, getting walked on by cattle, freezing and thawing, settling faster than expected, and other events can wear them out faster.  The replacement cycle might be 10 years for some diversions, or even 5 if wear and tear is bad.


This post may be more than most people want to read on the subject of accuracy.  Still, it’s a lot shorter than Chapter 3 of the Water Measurement Manual!

That’s all for now, have a great rest of the week.

Summary of Water Rights, Flow Measurement Posts So Far

There have been 25 posts so far, on the types of California surface water rights, flow measurement devices, and how to measure diverted flows.  You’ll see new posts once or twice a week.  Please send suggestions for post topics!  We have discussed:

  1. All Water Rights, California
  2. Read Me My Rights (How do you know if you have a water right?)
  3. Reasonable And Beneficial Use Depends On Who You Are
  4. The Smartest Water Expert In California (Chuck Rich)
  5. Riparian Rules by Chuck Rich
  6. Water Rights – Why Do They Exist? Which Kinds Are There?
  7. Water Rights And Engineers
  8. California Water Right Holders Now Required To Have Measuring Device
  9. What Is Your Place Of Use?  (Where can you legally use your right?)
  10. Places Of Use – Adjudicated (Decreed) In The State Superior Court
  11. A Place For Permits And Licenses (Places of Use)
  12. Nothing Secret About It  (This is all public information.)
  13. Quick Change of Subjects: What’s a Water Right Permit Cost?
  14. Life Of Reilly: If You Can’t Measure It, You Can’t Manage It!
  15. How to Divide Up a Decreed Water Right – Part 1
  16. How to Divide Up a Decreed Water Right – Part 2
  17. Weirs – Planning, Building, Measuring Flows
  18. From weir to orifice in only an hour
  19. Chilean Water Rights at (darn near) the Driest Place on Earth
  20. Some Hope in Rain and Snow Totals
  21. Is John Stealing Water?? Orifices – Right Size and How to Measure
  22. Worried about SB 88? That’s what this blog is for! Get a device in, send a photo to the Board, record and report your diversions
  23. Flumes – installing for decades of flow measurement, Part 1
  24. Simple Weirs and Orifices, on video, and in photos!
  25. Diverters must report weekly, daily, or HOURLY starting 2017!

Simple Weirs and Orifices, on video, and in photos!

Simple to set up weirs and orifices!

On YouTube:

01a_EW_1922_01This is a corner of a diversion box built by my wife’s grandfather, Emil Wigno, in 1922.  The fleur de lis he brought with him from France.  🙂   Emil planted hay, peaches, prunes, and finally walnuts.




Hi, I’m Shawn Pike.  🙂

Now 2″ x 6″ boards, cut 1/2″ to 1″ shorter than the width of the board slots, are stacked up in the diversion box.










The weir board is cut 3-1/2″ deep.  There are 2 weirs, one 1.0′ wide, and the other 0.5′ wide.  These are contracted weirs, since water on the edge has to turn to go through.04_1_Ft_Weir


The small weir is blocked off, so the 1.0′ weir is left.  This is a 1.0′ contracted weir, and the flow can be read right out of the correct table in the Water Measurement Manual.





By simply flipping the weir board upside down, we have an orifice!  If the downstream water is higher than the hole, then the orifice is “submerged”.  If the flow out the orifice is free-flowing, then a different equation is used.  Either way, calculating the flow is pretty easy because we know the orifice area, and depths of water upstream and downstream.

Here’s the pretty photographer and videographer, in the gold-mining town of Bodie.  🙂Wiggy_At_Bodie

Is John Stealing Water?? Orifices – Right Size and How to Measure

Is John Stealing Water??  John Casey has a cattle ranch near Adin, where he grows pasture and hay to raise about 70 Angus steers.  His place is 240 acres with lower irrigated land and forest on the higher part.  He has an adjudicated water right of 2.00 cubic feet per second (cfs) from Preacher Creek, to irrigate 80 acres.

John’s downstream neighbors claim he steals water.  He says he can show that he takes only 2 cfs, or less when the flow drops down in the summer.  Can he prove it?John_Headgate_edit

As we can see, he has a square headgate at the head of his ditch.  It is 2.0′ wide, and can open up to 1.5′ high.  Right now, John says he is diverting 1.05 cfs.  His evidence is that his gate is open 0.15′, the water is 0.57′ deep on the upstream side, and the water is 0.20′ deep on the downstream side.  Is that enough to check what he says?

The box in which the gate sits has smooth walls, and the gate closes flush with the bottom when John is not diverting.  The water continues in a straight path from upstream to downstream.  That means the weir has “suppressed” sides.

This is in contrast with, for example, a hole cut in the middle of a 2″ x 12″ weir board.  The water on the sides has to make the turn to go straight through, so the hole in the board is an example of a “contracted” orifice.

Let’s look at the tables for orifices in the back of the Water Measurement Manual.  Table A9-3 is for submerged, suppressed weirs.WMM_Table_A9-3_suppressed

We can’t see the downstream side of the weir, but the water is above the bottom of the edge of the gate, so it is submerged rather than free-flowing.

This table has flows calculated for a minimum area of 2.0 square feet (sq. ft.).  However, the area of the opening at John’s headgate is 2.0′ wide x 0.15′ high, or 0.30 sq. ft.  Fortunately, the equation, Q=0.70A(2g Δh)^0.5, is listed right at the top of the table.  We can calculate the flow using that.  Q is the flow in cfs, A is the area of the orifice hole, g = the acceleration due to gravity, or 32.2 ft/second^2 (feet per second squared), and Δh is the difference between the upstream and downstream water depth.

So the flow Q = 0.70 x (2.0′ x 0.30′) x (2 x 32.2 x 0.37′)^0.5 = 1.03 cfs.  So far so good – John is taking 52%, or just over half of his right when 100 percent of flows are available.  But, how much flow is actually available right now?

Let’s use the “sum of the boxes” method.  Instead of measuring the amount of water in Preacher Creek at the top, before any diversions, and then estimating how much flow is being lost to evaporation, transpiration, and infiltration, and then estimating how much flow is subsurface above John Casey’s ranch and “pops up” out of the ground below, we’ll look at what each diversion amount is, plus the amount still in the creek after the last diversion.  This is very useful because none of the instream losses have to be estimated – we just add the diversions and flow still in the creek, and that amount IS the available supply.  Some Superior Court judges in past decades were pretty smart and actually ordered that available flows be calculated this way.

Susan_1_of_2_DecreeParaAvailWaterEqualsDiversionsSusan_2_of_2_DecreeParaAvailWaterEqualsDiversionsThe paragraph above, from the Susan River Decree, defines available water supply as what is being diverted, plus the flow passing the last diversion.

There are 4 diversions on Preacher Creek, and here are the amounts being diverted:

  • Diversion 1 (John Casey) 1.03 cfs  of a 1.60 cfs water right, 52% of his total right
  • Diversion 2 (Amy Hoss) 1.67 cfs  of a 3.80 cfs water right, 44% of her total right
  • Diversion 3 (Mark and Cindy Sample) 0.55 cfs  of a 0.88 cfs water right, 62% of their total right
  • Diversion 4 (Quint and Marcie Minks) 1.32 cfs  of a 2.50 cfs water right, 53% of his total right
  • Flow still in the creek past the Minks Diverison – Quint estimates about 0.7 cfs

The total diversion-plus-bypass flow is about 5.3 cfs.  The total rights on the creek are 9.48 cfs.  Therefore, the total available flow = 5.3 / 9.48 = 56%.

So, John is right, he is not stealing water!  He is taking 52% of his water right, when he could be taking 56% according to the “sum of the boxes” method.  Not only that, but Amy could take more, the Samples should reduce their diversion, and the Minks’s could take a tad more.  Well, that’s theoretical – Quint and Marcie Minks probably cannot seal up their dam completely, so there may be a little bit less flow actually available for diversion.

From weir to orifice in only an hour

Orifice devices are needed for flat ditches, where the fall may be as little as 0.20′ (2.4″) from upstream to downstream.  An orifice is simply a hole through which water flows, so it can be accurately measured.  The photo below shows a submerged weir, flowing from right to left.  The water in the ditch downstream (left) is above the hole in the boards.Orifice_Side_Top_2 You already noticed the amazing thing about this orifice, didn’t you?  I could tell you are savvy that way.  Yes, this is the same Briggs Manufacturing weir box as the ones in the previous post!  It has the same 2″ lumber in the upstream board slot.  Now the flow goes through a precisely cut hole in the boards, with a known area, instead of over the top of the boards.

Staff_GageInstallation is just like with the weir boxes installed in the previous post, too.  For convenience, staff gages may be attached to one side of the box so it is quick to read the water depths.  So the precast concrete box is versatile, it can be used as both a weir and an orifice.  Actually, some ditches need both a weir and an orifice.  This is especially true in a ditch where a gate or boards may be put in the ditch below the weir box, to flood hay or pasture just below the measurement device.  All it takes is a change of a couple of boards.







The big difference in measuring the flow is that, instead of “sticking” the weir boards, now the depth of the water must be measured upstream and downstream to use a weir equation or table.  The “difference in head”, or water surface elevation, gives us a value needed to read the table or use an equation to figure out the flow.  What tables or equations?  These are out of the water measurement bible, the Water Measurement Manual.  We will discuss these very soon in following posts.

This was a quick post to show how you can get 2 uses out of one device, to make your life simpler.  That’s all for now, hope you had a Merry Christmas!


Life Of Reilly: If You Can’t Measure It, You Can’t Manage It!

A friend of mine, Chris Reilly, summarizes everything you need to know about measuring flows into your surface water diversion:  “If you can’t measure it, you can’t manage it!”  Except for riparian rights and some very small water rights, diverted flows have to be measured.  Why?


Dry_DitchLegally, to ensure your neighbors, the Board, and/or a Superior Court Judge that you are diverting no more than your water right.  Practically, how do you know if you are getting as much water as you should?  As surface flows decrease through the summer, every bit less means some pasture, hay, orchards, row crops, or something else does not get irrigated.

If you have nWMM_Cover_smallever measured flow into a ditch before, well, here goes, I am going to leak the secrets right here, I’m going to violate the Unspeakable Code Of The Water Measuring Brotherhood, the ve
ry deepest, most powerful wisdom of how to measure your flow will appear on this very page.  After this, who knows if you will ever hear from me again, once this classified information is made public?  Well, not really, but few people have heard of the Bible Of Water Measurement, the
 USBR Water Measurement Manual (WMM)

Let’s look at 3 common measurement devices detailed in the manual:  weirs, orifices, and flumes.  Properly installed and maintained, these devices can measure flow within plus or minus 5% of the actual amount.  The photos below are from the WMM, which has lots of diagrams that make it easy to see the details of how each device works.  First, the weir:


You have seen these before, they’re just a level plate or board of a specific width, with a relatively still pool behind them.  That’s it!  By measuring the height of the pool above the edge of the plate or board, you can use tables or equations from the WMM to determine what the flow is.


Above is shown an orifice.  Not much to see, is there?  In this case, it is just a hole, lower than the upstream flow.  That is physically all an orifice is.  Knowing the size of the hole, and how high the water is over the center of the hole, and how high the water is down the ditch, a table or equation can be used to figure out the flow.  The gentleman above is using a square gate with a certain width.  The area changes with how high the bottom of the gate is, not hard to figure out.


The photo above shows a Parshall Flume.  These are great for measuring high flows without needing a lot of “head” or the drop in the water from upstream to downstream.  By knowing the depth at a certain point, a table or equation can give the flow amount.

We’ll go into how to use tables for specific measurement devices in later posts.  It’s enough for now to know that if you have a decent measurement device, then you CAN manage your flow, as well as proving that you are taking no more than your legal water right.

All Water Rights, California

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