Measure It Right – All Water Rights

My Ditch Is Too Flat / Too Shallow To Measure With a Weir

The simplest measurement device to install is a weir. Vertical side walls with board slots, or channel iron bolted onto the concrete, hold 2″ x 4″ boards. The boards need to be stacked 12″ to 18″ high, and the channel depth needs to be 24″ or deeper. Here is a 3′ wide weir with a 12″ board height:

But, what if the ditch is less than 24″ deep? The ditch shown below is about 18″ deep, and it must convey flow that comes near to the top of its banks. The ditch here is about 10′ wide and is passing 20 cfs:

The solution was to install a Watchman Replogle flume that is nearly as wide as the ditch – 8′ wide. It is installed on a concrete base so it stays level and does not tip. The flume floor is 3″ above the bottom of the ditch, and the maximum depth upstream of the ramp is 15″. In other words, the top of the flume as the same elevation as the top of the bank:

The flume is conveying about 12 cfs in these photos. It does so with a total accuracy better than +/- 10%.

The maximum ditch flow is 30 cfs. Will the flume convey that maximum flow, without overtopping? The photo below shows the flume conveying a flow of 30 cfs. Yes, it still measures flow accurately, without overtopping.

Here is the same size of flume in a different location, at a lower flow. Even with the low flow, the depth of water is the same all the way across the flume:

Here is another version of the same flume. The ditch here has plenty of depth, so overtopping was never an issue. So, why is a low-head flume installed here? This ditch is very flat and there is a possibility of restricting the flow into the ditch as it enters from a low pipe. Measuring the flow this way ensures accurate measurement without flooding the incoming pipe:

Write It Down (Or Possibly Lose A Water Right)

I got a call from a distraught diverter. “My grandfather has irrigated this land since at least 1910, from _______ Creek. Everyone knew about it at the time, we get 1.2 cubic feet per second for 105 acres of pasture up here. Nobody was worried about filing on water rights back then, so we didn’t file at the Water Board until a few years ago. But a new guy moved in next door and he says we don’t have a water right, it’s all his water. We do have a well but we don’t use it until late in the season when the creek flow drops way down. The neighbor claims we only use the well and never use the water from the creek. Then he went and filed a complaint with the Water Board saying we never used water, which is a lie. We got some letters from the state, we figured they were just the regular reminders and we were really busy. It turns out one of the letters said the Water Board wanted to come to the ranch and see if we really divert water. Now we have a letter that says we have to ‘cease and desist’ within 30 days or pay $500 per day fines! What can we do about this?”

I asked, “Did your grandfather, parents, or you write down notes when you were irrigating? Do you have photos at the diversion showing you were taking water? Did you measure the flow somehow?”

“No, we don’t have anything like that. But everyone around here used to know who used the water! It wasn’t a problem until there were new owners.”

Have you heard the saying, “Write it down, or it never happened.”? That is true in everything – conversations, phone calls, purchases,

From one legal website, here is a list:

What Types of Contracts are Required to be in Writing? Contracts that are for the transfer or sale of land, are for the sale of goods over $500, cannot be fully completed within one year of signing (according to the contracts terms), are related to marriage, involve a promise to pay another person’s debt (“surety contracts”), or will continue beyond the lifetime of a party performing the contract.

Water rights definitely belong on the list!

When I was a bureaucrat, I learned early on to document the work I was doing, document processes so I and others could do some technical process faster next time, and document all important conversations. When email came around, I learned to email things to myself to have a record. Then, 5 or 10 years later when questions came up, I had a dated electronic document to answer with.

So what happened with that diverter who called? The diverter called the Water Board staffer who wrote the letter and arranged a visit to the property. I went out and took photos, measured the diversion, put in a temporary measurement device, and wrote a report detailing all that the diverter told me. Two Water Board engineers visited and wrote up a report. Then nothing happened for three years. The diverter is still using water from the creek, and now is measuring the amount of water and reporting it every year. Hopefully the state won’t take any further action, but we don’t know.

The lesson is, keep records! Even if something happened 100 years ago, write down now what you know about your water right, the diversion rate, the acreage irrigated, number of livestock. When a complaint comes, it’s a lot easier to refute when you can just hand over a written account.

Using Circular Headgates as Submerged Orifices

If you have a circular headgate, how can you use that as an orifice to measure flow? It’s easy if the gate is fully open – orifice equations from the USBR Water Measurement Manual can be used. The area of a circle is PI*r^2.

Here are the orifice equations for a rectangular headgate – the same equations are used for a circular headgate, or really a headgate of any shape:

A = the area of the orifice
g = gravity, 32.2 ft/sec^2
h1 = the upstream depth in feet
h2 = the downstream depth in feet

The first equation with the coefficient of 0.61 is for a gate on a wall. The second with the
coefficient of 0.70 is for a circular gate at the end of a pipe.

The difference between h1 and h2 can also be measured down from the top of a
wall with a level top.

Now, how do you get the area of a partly open circular headgate? There is a long equation with a good description at: https://mathworld.wolfram.com/Circle-CircleIntersection.html However, it sure is easier to get it from a table:

There you go. Based on the change of stem height, you can calculate how much the headgate is open. Convert that to a percentage. For example. A 2.0′ diameter headgate open 0.5′ is 25% open. Then use the table’s 50% row to where it intersects the 2.00 foot diameter column to get an area of 1.913 square feet.

H-S Flumes For Accurate Measurements Of Small Flows

What if you have a small diversion, but grass or debris would interfere with a standard weir? A weir has to have unobstructed, free-flowing water over

the crest so measured depths accurately relate to a calculated flow. A weir with debris problems has to be cleared whenever flow is measured, which increases the time requirement.

When weirs have low flows, they trap debris more frequently, and they are less accurate when the depth over the crest drops below 0.2 feet (2.4 inches). Then the only way to measure flow is with a narrow suppressed weir, or with a contracted weir, typically half or less the maximum width. A V-notch weir can be used for measurement of low flows.

Changing the weir boards for different flows requires someone with experience,

who will recognize when the depth over the weir is 0.2 feet or less and then use a contracted weir board. However, people are busy when irrigating, and even busier when flows drop. Weirs are often neglected during the time they need more frequent maintenance visits.

A good flume for passing debris and measuring low flows is the HS flume. These are accurate right down to zero flow. For the maximum flow, they require more

**1.0-foot HS flume, for flows of 0.00 to 0.80 cfs**

material than a rectangular Winflume, Montana, or Parshall flume. However, they are more accurate than other flumes at very low flows – testing by the University of Minnesota found an average accuracy to be +/- 3.2% for ideal approach conditions. They will pass debris down to zero flow – the flume shown here has an opening of 0.05 feet, or 5/8 inch at the flat bottom, and the opening increases with height.

Why aren’t HS flumes common in California? I suspect that the early adoption of Parshall flumes here established the standard. I have seen a few hundred flumes, but I had never seen an operating HL (wide, high flow), H, or HS flume, prior to my installations.

Why go to the trouble of using an HS flume, if Parshall flumes are readily

available? A Parshall flume may be +/- 10% accurate down to perhaps 5% of its maximum flow. Below that, the accuracy decreases. An HS flume is +/- 10% accurate down to 1% to 2% of its maximum flow. If the flow regime is predominantly low with occasional high flows, it is important to measure those low flows with the best possible accuracy. Some places where low flow measurement is critical include field runoff where pollution is proportional to flow, small water rights, and dam leakage.

HS flumes are easier to construct than a Parshall, too. The HS flume bottom is flat, and it has 3 vertical planes. The photos of the Parshall flume here show

that it has 3 horizontal planes, and 5 vertical planes. An HS flume takes less time to build, and can be put together fairly quickly in any farm or ranch shop. Parshalls are complex enough that they are purchased, including design and shipping costs.

Do Something Wrong, Instead Of Nothing Right

Do something wrong, rather than nothing at all. Have you ever heard that before? I have heard it from Army veterans, a boss, even an elder of a church. George Patton said, “A good plan violently executed now is better than a perfect plan executed next week.” A non-military way to say that is, “A poor plan now is better than no plan at all.”

What it means to you and me is, if action is necessary, do something, maybe ANYthing, rather than freezing in place or ignoring a problem. This is obvious when you see a tornado 5 miles away, for example; either drive away from it if you are in a car, or take shelter if you are on foot. If you have a plumbing leak in the house and no parts to replace broken pipe, then put a bucket under it, or turn off the valve, and call a plumber. All of us have seen a TV show (or maybe had it happen to us) where the bad guy pointed a rifle and said, “Don’t move”. What do we all say to the TV? “Don’t just stand there, run!”. Doing nothing is a much worse choice, if the result for freezing in place is death or injury.

What about water rights – how does doing something wrong help? Everyone knows by now that surface water diverters need measurement devices, so put in a weir box and boards and measure your flow before the threats come from the Water Board, your watermaster, your ditch tender, or your neighbor. Even just stick horizontal boards in a ditch and seal the sides with plastic – something to take positive action to reduce future pain.

Remember to file the information for the measurement device with the Water Board, either via your annual report of diversions, or using the Water Right Form and Survey Submittal Portal.

Take a look at the blog posts below. There is enough information and how-to directions, that you should be able to do it well enough to satisfy the Water Board. Check out these posts:

There is a philosophy based in law and a lot of experience, that says don’t put any controls on yourself until the court or government makes

you. Why remodel your house to accommodate the wiring or plumbing, if you aren’t selling the house and everything works okay right now? Who would put a lot of money into an old truck to make it pass smog, if it just might pass a smog check the next time it has to be done? What farmer would change how he irrigates or ranches if everything still operates and the bank will keep making operating loans?

All of the Water Board deadlines have passed to install measurement devices, or file Alternative Compliance Plans. If you haven’t got your device or plan done yet, get a Request For Additional Time done as soon as possible.

Be proactive. Take some inexpensive, temporary action. Educate yourself for free with some time in the Internet. Even a small, less-than-perfect improvement in your measurement device, flow and water use record keeping, can pay back a lot more when you have to deal with potential Water Board fines, a court case, or even just an angry neighbor in the future.

Installing Reservoir Staff Gages

How is a staff gage installed in a reservoir? The typical way is to drive a piece of 2″ galvanized pipe into the ground, deep enough to so it isn’t easy to push over. If cattle will be in the reservoir to get water, then the pipe needs to be really well installed. A gas-powered post pounder can be rented at Rental Guys, Home Depot, or similar places.

Most reservoirs are deeper than six feet, so it’s best to maximize the length of pipe installed. The length of pipe that can be installed by hand is usually about 6 feet. For a 6-foot tall pipe, about 3 feet of pipe needs to be in the ground, so the total pipe length is 9 feet.

Then the staff gage is attached to a 2″ x 8″, using screws or small bolts. Staff gages vary in width from 1″ to 4″; the usual USGS Style C staff gages are 2-1/2″ wide. Once the staff gage is screwed on, the board is U-bolted to the pipe.

That’s it…except for the surveying part. The top of staff gage needs to be at the same level as the spillway crest, so the maximum water surface elevation can be measured. How is the surveying done? An autolevel is close enough for most reservoirs, or two installers can use a very accurate survey level.

If the reservoir is deeper than your staff gage length (6 feet as shown here), and most are, then staged staff gages will be needed. For example, a first gage is installed at the top, going from, say, 6 feet to 12 feet. The second, lower staff gage is installed from 0 feet to 6 feet, and 6 feet is exactly the same elevation on both staff gages. In the photo below, there are 3 staged staff gages to measure 18 feet in elevation: 0 to 6 feet, 6 feet to 12 feet, and 12 feet to 18 feet. The top of the third, lowest staff gage can be seen in the bottom right corner.

More commonly, staff gages like the USGS Style C are purchased in 3.33 foot lengths. This is convenient because staff gages are installed closer together.

What if a pond is full, or mostly full? It is still possible to install a staff gage, but it will be harder. Boats or rafts will be needed, and the pipe with the board already attached has to be put in place and held vertical while being driven. If the total depth is greater than 6 feet, then a longer pipe, board, and staff gage will be needed, and the combined weight will be that much greater. Hint: tie a rope and buoy to the pipe so ~~when~~ if it slips and sinks, it can be pulled up again.

What about installing a staff gage along the slope of a dam, to avoid having to wrestle a pipe and board for a deep installation? This can be done by attaching a length of rebar or pipe to the dam face using concrete stakes or similar method. The slope distances measured are converted to vertical depths. However, this won’t stand up well to cattle or elk traffic, and it is more liable to be vandalized if the reservoir has easy access.

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Converting Logger Pressure to Depth & Storage/Flows

If you have a pipeline as part of your diversion, then an in-line meter with an integrated data collector can be installed. The data files from these units are

McCrometer McPropeller inline meter with data collector

easily readable in Excel, and the files can be sent directly to the Water Board to meet the requirements of SB 88.

What if you don’t have a pipeline? Then your flow needs to be measured in the open ditch with a weir, flume, or orifice. These devices measure the flow but they don’t record the data. To continuously record data, a submersible logging instrument must be used to measure the water pressure at the bottom of the box. These logging instruments are commonly put into stilling wells that are inside or outside the measurement device.

Flume with attached stilling well for water level logger

How are water pressure logger measurements converted to diverted flows or reservoir storage? Why does anyone even have to have an electronic pressure logger? Onset Computer, PMC, In-Situ, , and other manufacturers sell data loggers and water level loggers, not pressure loggers, so why is this post talking about measuring pressures at all?

Bluetooth Hobo Logger, cabled to recorder and barometric compensator unit – least expensive option for a single location

Loggers record pressure, because that is the easiest physical attribute to measure. A data logger in water does not know how deep it is, and it does not

know how much flow is going by, or how much water is being stored in a reservoir. Pressures relate directly to static (standing) water depths, and then equations convert the depths to flows, or to reservoir storage volumes.

How is pressure converted to depth? It’s an easy calculation – water that is one foot deep has a pressure of 0.4335 psi at the bottom. So, if your logger measures 1.60 psi, then the calculation to get depth is 1.60 psi / 0.4335 psi per foot = 3.69 feet of depth.

Note that water level loggers can be of two types. The least expensive are completely submersible, and do not compensate for barometric pressure. For an idea of the readings of barometric pressure in a measurement device, a 2 foot deep logger records a pressure of 0.8670 psi. Atmospheric pressure at sea level is about 14.7 psi, and high in the mountains may be 12.0 psi. Air pressure is much greater than those measured in ditches. Usually two of these loggers are used at once, one in the water, and one out of the water measuring only air pressure. This also eliminates the variability in pressure due to weather changes.

The second type of data logger compensates for barometric pressure at the same time water pressure is being recorded. That way, the water and air pressure data sets do not have to be combined before conversion to depths. These loggers were always more expensive until the Bluetooth Hobo water level logger came along; as of February 2019 I found that it is the least expensive option for a single location.

Now that you can calculate any depth, how do you convert depths to reservoir storage? That requires an Area-Capacity curve, also known as an Elevation-Storage curve. The points can be picked off the curve. For example, in the curve below, a depth of 8.5 feet would correspond to an elevation of 2,802.5 feet, and a reservoir storage volume of 30 acre-feet.

An owner of a reservoir with a capacity over 10 acre-feet must collect monthly storage values. That’s easily done by hand. However, a reservoir with a capacity of 50 AF requires weekly measurement; over 200 AF requires daily measurement; and over 1,000 AF requires hourly measurement. That is really tedious to do by hand.

This is where an Excel spreadsheet can make the task a whole lot easier! The spreadsheets shown below are just for this. The first sheet helps translate a graph into a table of elevations and storage volumes. The second sheet translates collected pressure values into depth and storage values, for as many data points as needed.

For diversion ditches from a stream, how are pressures converted to flows? The logger is in a stilling well, usually a pipe connected to the inside or outside wall of the weir, flume, or orifice. It measures pressure, which is easily converted to depths.

As with reservoirs, Excel spreadsheets make the conversion process a whole lot easier. The sheets below have the rating curve for a suppressed weir, and the second sheet converts pressure to actual water depths over the weir boards. Even for thousands of hourly readings, the hourly flow volumes are quickly calculated and are ready to send to the Water Board:

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Flow/Volume Data and Data-Heads

SB 88 requires diverters to measure diverted water flow and/or volume, then report the measurements. For small to medium-sized diversions and reservoirs, there is a often transducer measuring and recording pressure. The pressure data has to be converted to depth and flow, or depth and volume. Data may be hourly, daily, weekly, or monthly. Whatever the frequency, the Water Board wants data files uploaded with annual Reports and Supplemental Statements.

Where’s the manual for how to do this, for any of several data loggers, and for meters, weirs, flumes, and orifices, and flumes? It exists in pieces and parts. Each data logger manufacturer has a manual for each product. Sometimes products are similar, and sometimes very different, as are the manuals. The long-existing measuring devices, weirs, flumes, and orifices, are described and general measurement instructions listed in the U.S. Bureau of Reclamation Water Measurement Manual.

When it comes right down to it, a person has to be a “data-head” to enjoy collecting the data, and going through all of it to find bad results, missing data, and odd trends. Then stage and flow have to be calculated and checked against periodic readings taken during visits to the reservoir or stream. Data have to be listed in a format to upload with the Report or Supplemental Statement to the Water Board, and summed monthly to fill out the online form.

If you enjoy educating yourself and taking on new tasks, then you can be a data-head. If not, then you’ll need to have an employee do it, or more likely hire an expert. Data Head

Who are the experts? There are engineering firms, manufacturers, vendors and others who can download data for you. It still comes down to the person helping you That person who does the work has to have done data reduction, calculations, checking, and quality control in the past.

Make sure you get help from someone who knows data inside and out! If the Water Board has any questions, your data-head can explain and defend every bit of it for you. He or she will already know the answers to any questions that come up.