See the new “How Do I … ?” link on the left. There are so many posts on this blog, it is getting harder to find stuff. Click on the link, or right-click then “Open link in new tab”, and the big questions are linked to the appropriate blog posts.
Photo on the right: Intermountain Environmental Inc. Nuway Ramp Flume with stilling well, 20 cubic feet per second (cfs) capacity. Shipped disassembled including fasteners; stilling well not included (but inexpensive to add).
20 cfs irrigates 400 to 2,000 acres of crops, trees, pasture, or hay, depending on where you are. As a Professional Engineer with wide experience installing and operating flow measurement devices, I can solve your headaches, heartburn, and trouble meeting the Water Board’s Regulations, diverting 20 cfs, for as little as $6,000 with one of these flumes. These flumes can go in an almost flat ditch, needing a water drop of less than 4″, and still maintaining accuracy of plus or minus 5%, twice what is needed by the Water Board. Smaller flumes cost less; even larger diversions could use 2 of these side by side.
Frank Crowe, farmer/rancher and the neighbor of some readers of this blog, has been doing research for 7 months on all possible flow measurement and datalogging devices. He has found some lower-cost options, including the Nuway flumes, that in past years, I did not think would work well. After checking into them, I know many of these can save you headaches, anguish, trouble, and some money. Technology has improved and computing costs have come down to make smaller, less expensive data loggers very useful for diversions. For example, the eTape sensor and Track-It datalogger shown here, and similar equipment from other manufacturers, will work well for many diversions:
Frank checked into the smallest Nuway flume, for 3.5 cfs, and found that the cost is fairly low at $580. With a size of about 12″ wide, 15″ high, and 48″ long, it will be easy for one person to assemble and would be possible to install by hand, without a backhoe.
Most diversions will have to comply using standard, accepted methods of measurement and recording data. Following up on Frank’s research, I contacted Intermountain Environmental, Inc. in Utah and asked Josh Hanks about their 10 cfs and 20 cfs galvanized flumes. They cost $1,017 and $1,995 respectively. Shipping would be less than $300. Josh provided detailed information, including how these flumes have performed in the field. They are designed and built to be plus or minus 5% accurate, well within the Water Board’s regulation of +/- 10% accuracy as certified in the field. Many installations have worked with soil backfill only, instead of poured concrete. Installations will probably require a mass-concrete anchor, and may need steel plate inlet wingwall extensions, or outlet wingwalls added.
The bottom line, what does it cost for me to solve your problem, and to purchase, install, attach a datalogger, and certify the device to the satisfaction of the Water Board? For the largest flume, which can measure up to 20 cfs, in a typical location with vehicle access, I can have these working right, logging data, and certified for you, for $6,000 to $9,000. Telemetry and/or solar power, if needed or required by the Water Board, could add another $1,000 to $4,000.
Done! No more headaches, turmoil, or trouble for you, and I will have the pleasure of helping you keeping your business working well.
What is the cheapest flow measurement device to install, that is durable, accurate, and easy to maintain? The California Department of Water Resources (CDWR) Red Bluff office wrote a memo in October of 2010, detailing findings on flow measurement devices over decades of watermaster service. Part of the memo is summarized here – not direct quotes:
Economics of Flow Measurement Devices
CDWR watermasters helped water right holders to install and operate a variety of structures over eight decades. Physical factors such as flow range, ditch width and slope, soil type, whether or not a site is protected from livestock, and access to the site, play a large role in picking the right device. Cost is also important, including design, installation, replacement, operation, maintenance and repair.
The following chart shows the relative costs that the watermaster service and water right holders have experienced for various devices. The chart shows that pre-built weirs are the least expensive to install and repair. Flumes are the least expensive to operate, but are the most expensive to design and construct or install.
Some considerations for the proper use of weirs are:
Always seal leaky flashboards with sediment, horse manure if available, and if necessary, sheet plastic. Use newer flashboards, replaced every year or two, and trim boards on site to ensure a level top board, and reduce gaps prior to use.
1.5 inch (2″ nominal lumber e.g. 2″ x 8″) flashboards are not measurably less accurate than a thin steel plate metal with sharp edges, provided that the head on the weir is great enough to cause separation of the water from the upstream edge of the flashboard. The air bubble on top of the board is easy to see when the weir is working right. The minimum required head is around 0.25 feet. As an example, CDWR watermasters compared the use of flashboards to
sharp-crested weirs on November 20, 2008, as they have done several times in the past. Differences were recorded and weirs with flashboards had flows that were both slightly less and slightly more than the flows calculated for sharp-crested weirs. Any difference is well below the margin of error when taking into account all possible errors. In summary, 1.5-inch flashboards provide results indistinguishable from sharp-crested weirs for the use of measuring diverted flows.
CDWR measures weir heads with weir sticks, as specified in the USBR Water
Measurement Manual, 3rd Edition, 2001, on Page 13-4. CDWR has checked the use of weir sticks numerous times and found the difference between the head measured with a weir stick and that at a staff gage nearly always to be 0.00 feet (the same to the hundredth of a foot).
Even when diverters are careful, the amount delivered may occasionally be somewhat more than the water right as streamflows vary due to diurnal fluctuation, changes in upstream diversions, and from increased flows due to storm events. However, more than half the time when flows are not at the legal amount, they are less than the water right amount for the following reasons:
Floating debris sometimes accumulates on the upstream side of a diversion headgate, reducing flow.
Water right holders who grow hay shut off their diversions to cut, dry, bale and haul hay for several days, reducing their total volume of diversion.
Irrigation season damage to ditches requires diversions to be reduced or stopped during repairs.
Weed growth or sediment in the ditch reduces the hydraulic capacity of ditches.
A local farmer, rancher, and apiarist, whose name you likely know, referred me to a pretty smart ranching friend of his who has been researching more cost effective flow measurement and data collection schemes. This retired aircraft engineer has found data collection devices with installed costs in the $500 – $600 range, instead of $1,200 up to $20,000. I’ll publish their names if they agree later; they should have a chance to read this before they put their names on it.
They aim to save themselves and all of you some of your hard-earned money. I really want to see what data collection setups are available, hopefully this week there will be an all-in-one system that meets State requirements and is not such a budget-buster. There are also be some pre-fabricated flow measurement devices that can be easily dropped in a flat ditch where a weir (the least expensive device) won’t work, saving money compared to a formed-up flume.
From my years at DWR, my coworkers and I dealt with the trade-off between high accuracy and durability, at a high cost, and reasonable accuracy and lower durability for less money. This was always the tension, whether acquiring surveying equipment, portable flow measurement devices, or flow gaging components like data collectors, bubbler pressure sensors, or GOES satellite radios.
You have probably seen this triangle before – it is useful for planning prrojects. For the purposes of evaluating data collectors at diversions, Time is the owner’s, contractor’s, or engineer’s level of effort to make a diversion comply with the law. Scope is meeting the Water Board requirements – the length of that side cannot change. Everyone, including me, wants to reduce the Cost side of the triangle. Reducing Time means getting the labor, equipment rental, engineer’s report, and certification done cheaper – it’s the other way to reduce cost.
What is the effect of reducing cost? The size of the triangle equals quality, and that goes down. How much loss of quality is acceptable? In the case of data collectors, quality equates with the durability – maybe the device will only last 2 years instead of 4, or maybe it is twice as likely to quit working in the middle of an irrigation season. If quality goes down too much, then the data collection scheme will not meet Water Board requirements.
On the other hand, computer technology and sensors have improved over the years. Computing costs a tiny fraction of what it once did. Sensors have come down in cost a little, while their quality has improved somewhat. Maybe we can get just-fine data collection at half the cost – we’ll see!
In Part 1, How Do I Comply With Water Board Regulations? , we looked at what water flow measurement devices will meet and exceed the Board’s requirements. The questions right back to me were: 1) Yeah, but which dates apply to me? and 2) Yeah, but what about monitoring and collecting data and reporting? How do I do that?
Who has to have a certified, accurate device by January 1, 2017? How often is it monitored?
This is the “worst case” if I am not already compliant – less than 6 months from today! The first to have to report are those who divert 1,000 acre-feet or more per year, or store 1,000 acre-feet or more per year. The reporting has to be hourly, or 8,760 data points per year. The average rate of diversion for 365 days is 1.38 cubic feet per second (cfs) (which I had rounded to 1.40 cfs in previous posts). That’s equal to 620 gallons per minute (gpm), or 2.74 AF/day.
What if all the flow is diverted just for the irrigation season? Let’s use 6 months for simplicity – the average rate of flow is 2.76 cfs. Available flows drop as the summer proceeds, so what size of water right are we really looking at? Let’s say flows decline evenly from 100% at the beginning, to 50% of available flows at the end of 6 months. The right that would divert 1,000 AF per year under these conditions is 3.68 cfs. The summary is, if my water right is, say, 4 cfs or more, then it is very likely I will be in this category. The weir shown above is a 4′ weir, capable of measuring up to 4 cfs very accurately, at plus or minus 5% (sometimes better) accuracy with new lumber. A headgate like the one to the left is easily capable of passing 4 cfs and, if the gate is used as a measurement orifice, the accuracy can be 5%, certainly within plus or minus 10% if care is used with an older gate.
I can get that 4′ weir shown above installed and working for somewhere between $2,000 and $10,000 – depending on how difficult the access is to the site, whether native materials can be used, or 3/4″ base rock and 12″ protective rock have to be hauled in, and whether I already have a backhoe or excavator to install it. The headgate will cost more than that, maybe $3,000 to $12,000. A larger bulkhead or box is required, and good gates can cost quite a bit.
A larger diversion will have to use a larger weir or orifice, or more likely a flume or acoustic measurement device. That makes sense – the larger the flow, the more complicated it is to measure.
How do I report hourly flows? I sure can’t run out to the diversion every hour, so that means I have to use some kind of automated flow measurement device. The G.E. Panametrics acoustic Doppler meter on the left is an option, and it or an in-line propeller meter, or an inline mag-meter, will be necessary for some configurations of diversions (pumped or very flat). The price starts at $5,000, though. If I have enough fall (drop in water elevation), I would sure rather put in a weir, orifice, or flume. A weir or flume can use a water level measurement device and data collector like the water level logger above on the right. That Global Water device is relatively durable, takes readings as often as desired, and can store data for months. It costs a little over $1,000. Oh, and if the orifice is submerged, so that the hole is underwater both upstream and downstream, then I will need two water level loggers, for $2,000.
Some folks at the Water Board are talking about telemetered data, meaning the data is sent to a remote location, or even available online. This would only be necessary if there were a great possibility that the diversion would be tampered with, or if it is a large diversion having a big impact on the amount of flow left in the stream. This has little benefit for anyone at most diversions. I would only install it if the need were very clear to me and everyone else. The added cost can be anywhere from $1,000 for short-range radio, to $20,000 or more for a full-on gaging station like you see on streams. The annual cost of operation and maintenance goes up, too.
How do I read the data on these devices, so I can report it to the Water Board? Well, that takes some expertise. If I have 5 diversions from a creek, I’ll make sure my foreman knows how to do it, and handle it myself. If I have 1 or 2 diversions, then it’s more cost effective for me to have a professional do it, and to maintain it periodically. Reading that data takes a laptop to hook up to the USB port, and the software that comes with the device, and the expertise to look at the data and make sure it’s reasonable. The data that is recorded is “stage”, or water surface elevation. Using the correct weir, orifice, or flume equation, or table from the Water Measurement Manual, the stages have to be converted to flows. For hourly flows, that means 8,760 data points per year, which will require a spreadsheet like Excel to make the conversions. A BIG caution is that if the boards are changed, it has to be written down and then a different zero-flow datum used to convert stages to flows starting when the change was made.
2. Who has to have a certified, accurate device by July 1, 2017? How often is it reported?
The “next worst case” is for those diversions from 100 AF to 1,000 AF per year – irrigation water rights of about 0.35 to 3.5 cfs. These have to be recorded daily. The measurement devices are the same, but smaller. It is possible someone might grab a reading every day…but it is more likely that these will also have some kind of automated water level logger. More on these later. Have a great weekend!
Yesterday I met with some nice folks up in Hat Creek and Old Station. A big question right now is, how do I comply with Water Board regulations? Also, what exactly do I need to do for a measuring device? And, where can I find out that what I do will be acceptable, so I don’t get dinged after I did what I was supposed to?
Weirs are the least expensive, long-lasting, accurate devices. This weir was prefabricated and shipped from Briggs Manufacturing. Installation takes a few hours, and with new 2″ lumber, accuracy is plus or minus 5 %. That is better than the Water Board’s requirement of 10 % accuracy.
An orifice is often exactly the same as a weir, with the boards set as an orifice. Instead of the water going over, it goes through an exactly-sized hole. The accuracy is plus or minus 5 % if it is set up carefully. The cost is the same as for installing and operating a weir.
Here is another kind of orifice – a headgate. If it is a square headgate, or a new, round (Waterman) headgate, then the area of the opening can be determined with plus or minus 5% accuracy. An older headgate or one with a less-than-perfect opening can still be 10% accurate, within the Boards’s standards.
This is a Parshall flume. It uses no boards, so no debris can pile up. It is nearly maintenance-free. Flumes cost more to install, and if they settle and get out of level they lose accuracy. However, you’ll see many of these in Northern California. There are some prefabricated flumes just coming into production that will be easier to install and will include data collectors.
How do you know which one will work for a particular diversion? Someone with expertise can check the ditch, grade, soil-type, flow range, and other information and tell you within a couple of days what will work best, with an engineering report and cost estimate. Rights To Water Engineering does this for $300 to $500, and can install the device if you like, with an operations manual.
Filing Statements of Use with the Water Board is now all by computer through the Internet. That’s one of the things Rights To Water Engineering, and some other folks do at a reasonable cost. If that’s your worry then contact us and we can point you in the right direction or help you out with reporting.
This is the quick summary on compliance! Contact me at (530) 526-0134 or RightsToWaterEng1@gmail.com, and read this blog for more detailed information. Have a great weekend!
Build measurement devices level, leak-proof outside and at boards inside, and replace old boards for accurate flows and to avoid fines for noncompliance.
Some operational considerations for flow measurements are the same as for your house. When it was built, the foundation was made level. Sure there can be transitions – changes in level where steps will be built – but the whole foundation had to be perpendicular to gravity. Otherwise, the whole house would be tilted, nothing would fit together correctly, doors would not swing easily, windows might get stuck open, or worse.
It’s the same when measuring flow. For any manually-measured device, like a weir, orifice, or flume, structures have to be installed level and replaced when they are no longer level. More particularly for this discussion, weir and orifice boards must be level. If the bottom of the weir box is not level, some adjustment can be made with the bottom board so that the top board is level.
A house is sealed against the weather, so air doesn’t blow through the cracks and water can’t leak inside the house. If roof shingles come loose, the damage may cost hundreds of dollars by the time the ceiling shows a wet spot.
Weirs, orifices, flumes, or any other device cannot leak around the edges. Otherwise some flow is not measured – so the reported diverted amount would be less than the amountactually going past. Inside the device, the boards have to be sealed. They might be sealed with plastic and gravel, as shown below, or just well-fitted. If the soil is sandy, it is easy to dump shovelfuls of sand along the backs of the boards until the sand fills the cracks. As long as the boards are not changed out, they will stay sealed for the season.
Boards wear out, too. Fortunately, lumber is inexpensive for the few boards needed in a weir or orifice. They should be replaced each year, or every 2 years at the most. Everyone knows why – boards warp, shrink, twist, and otherwise change so they won’t fit welltogether anymore. Besides fit, an old board can’t be leveled; one end will be level but the other end will not because of the warp or twist.
All of these considerations might seem like common sense, but 2/3 of diversions out in the field fail in at least one of these 3 tests. Maintenance and replacement of measurement devices is not fun, but it’s like a house. If a home is not built level and leak-proof, and rotted wood replaced, then damage only gets worse faster so it’s not a nice place to live. In the case of surface water diversions in California, not only do these factors affect flow measurement, but they can affect compliance with the law, make neighbors upset, and possibly incur fines for inaccurate devices or misreported flows.
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 install 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.
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.
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
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.
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: