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A Stream of En-Gaugement: Water measurement's ongoing evolution

By Jerd Smith

In 1881, Colorado's first State Engineer, Eugene Stimson, rode 30 miles each way on horseback between the Big Thompson River and the Cache La Poudre checking gauges he had set in the rivers. He carried a tent and a portable drafting table.

Even then, the public need for accurate water measurements was clear, especially in those regions on the Front Range where settlers, miners and farmers were battling over streams as demand for water was already outpacing supplies.

And though the prior appropriation doctrine was incorporated in the new state constitution in 1876, establishing Colorado's system of water rights, little was known then about how to measure the precious liquid and guarantee each water right holder received the correct amount.

In 1878, counties began hiring water commissioners, according to Dick Stenzel, water historian and former South Platte division engineer. They were paid $5 a day. Three years later, the State Engineer's position was created, and by statute, was handed responsibility for computing the amount of water in each stream and providing each water commissioner with a copy of the results. The water commissioners then determined who could divert. Colorado was the first state to provide for such public oversight of water distribution, but it wasn't easy.

‘The State Engineer was constantly moving during the irrigation season,’ says Stenzel. ‘He tried to hire an assistant, but the state wouldn't pay for one.’

Early measuring devices were crude and famously imprecise. Miners' inches were among the first measures used. They were calculated by forcing water through a 1-inch square opening in the floor of a box placed in the stream. As water flowed through the opening, it was timed, establishing the flow rate.

With each passing decade, Colorado's efforts to quantify water rights and distribute them fairly improved. The state's groundbreaking efforts helped lead the world into a modern era of measurement.

One of the first mechanical water meters was developed here by the second State Engineer, E.S. Nettleton, in 1884. Known as the Colorado Current Meter, and now housed in the Smithsonian Institute, the device consisted of three cups that hung from the bottom of a rod. The State Engineer or his staff would wade into a stream, lowering the meter at different points across the channel. It was considered an advancement because the cups could clear themselves of debris as they spun, where previously-used meters would quickly become clogged and cease operating.

Nettleton also installed continuous recorders on stream gauges so that commissioners and irrigators didn't have to manually measure flows multiple times a day.

In 1925, Ralph Parshall, an engineering professor at Colorado State University, patented a flume now used worldwide to measure streams. Known as the Parshall flume, it is sturdy and simple to construct. Today, the flumes are typically made from sheet metal. They are three-sided, with two walls and a floor. When the flume is installed in a stream, water is forced through in a consistent pattern that allows hydrologically-engineered rating curves to be applied to physical water measurements. The uniformity of the structure and the use of rating curves made field measurements much more precise.

Despite such advances, gauges and flumes were still installed at very few locations statewide. And Colorado's small band of water commissioners—there were only 70 in 1939—scrambled to take measurements and record data in places without such devices to ensure they could deliver water equitably.

Several regions of Colorado still wrestle with outdated water systems. In the Yampa and White River basins, for instance, stretches of the rivers' mainstems lack measuring devices, both on diversion structures and in the river. The state is pushing water right holders to install them in order to protect reservoir releases intended to reach endangered fish. The need for sufficient measuring devices will only increase if the Yampa is tapped by the Front Range or by major oil companies hoping to develop oil shale on the West Slope.
Water commissioners in the Yampa, working on remote tributaries, still sometimes calculate cubic feet per second manually, measuring stream depth by hand and calculating water speeds by tracking how long it takes a floating twig to travel between two fixed points.

Because there has always been plenty of water in the Yampa, there's been little need to determine the mechanics of the river, such as how long it takes to deliver water on certain stream segments. To solve that problem, commissioners use special dyes that color the water and allow its travel time to be visually tracked.
These days, 114 water commissioners monitor streams across Colorado's seven water divisions. The Division of Water Resources, the state's primary water regulator, has an annual budget of $27 million and nearly 300 employees. A significant part of that budget - more than $850,000 annually — is spent installing satellite telemetry on gauging stations, a technology that allows water level readings to feed into state databases at 15-minute intervals.

‘All the major diversion structures from Denver down to the state line are equipped with these devices,’ says State Engineer Dick Wolfe. ‘That's real-time monitoring. It's live on our Internet. Our water commissioners and our users utilize that on a daily basis.’

In 1881, when Stimson began work, he installed Colorado's first gauging station. Now the state owns and operates more than 480, Wolfe says, and each has a satellite telemetry system. Another 270 stream gauging stations are operated by the United States Geological Survey.

Today, Colorado is awash in water data and is racing to employ new technologies and the Internet to make it widely and quickly available. Data that was once distributed monthly in the South Platte Basin is now available to water users continuously online so that everyone who has an interest in a given stream segment, from farmers to city utility managers, can find out how much water is moving through the system and who is diverting at any given time.

‘People expect transparency of government and they like this transparency,’ says Wolfe. ‘They can see what their neighbors are diverting. But now we like to say that the division has 114 water commissioners and 3,000 volunteers, which include all the users looking at things on the Internet.’

Pressure continues to build to do more.

‘The opportunity and the demand and the need is greater now than it ever was before,’ says Stephen Smith, president of Fort Collins-based Aqua Engineering.

New automated measuring and control devices known as SCADA systems are helping streamline water deliveries. The term stands for Supervisory Control and Data Acquisition. ‘It's kind of a catch-all phrase,’ Smith says. It brings together sensors, processors and actuators into a computerized, radio-controlled system. Once seen only in industrial settings, the systems are now being used in high-stakes water regions like the South Platte, where millions of dollars worth of water must be carefully shared between fast-growing cities and farmers.

‘About seven years ago, we began taking these systems out to ditch companies and saying, 'Here's a way you can read this flume remotely and not have to drive five miles twice a day to read it,'’ Smith says.

New automated gates can also be run via SCADA systems so that when a gauge reading shows the river has fallen and a user no longer has the right to divert, the gate can be closed immediately. Water users without this technology must wait for a gauge reading and a water commissioner's call before physically going out to the field to either shut off or turn on a diversion structure. In the time that takes, thousands of gallons of water can be lost downstream.

‘The sociology of all of this is very interesting,’ Smith says. Many canal managers, for instance, have never seen SCADA systems. ‘They've always opened head gates, then read the flume, then traveled back and adjusted the head gate again. They're quite skilled at it.’ But when they see these systems work, they realize how quickly and efficiently the work can be done, Smith says. ‘I call it the 'Oh, duh' moment.’

As year-round, hour-by-hour water management gains ground, water managers continue to worry about precision. Even with satellites and hundreds of gauges, determining exactly how much water is flowing through a head gate or past a gauge at any given moment is still difficult.

A Parshall flume, for instance, has an accuracy rating of plus or minus 5 percent. New automated Rubicon Gates, manufactured in Australia, have an accuracy rating of plus or minus 2 percent, Smith says, and they have been installed in some locations on the South Platte.

‘The fact is that all of these devices have some inaccuracies,’ says Smith. ‘And though you're always going to have people who want more precision, it's good for all water users to understand there is an inherent inaccuracy in water measurement and you just have to deal with it.’

For every stretch of stream that has 2009 technology on it, there are several more whose diversion structures date back to the late 1800s. It is these structures that Wolfe says are likely to create issues in the future. ‘Irrigation and reservoir companies are going to have big challenges just to meet the cost of replacing these structures. If you're trying to manage water with them, it's very difficult. They have cracks in them, or they seep water. You really don't know how much water you're ultimately getting down the river,’ he says.
Upgrading these structures and bringing record-keeping practices up to modern standards is critical as water supplies continue to tighten in Colorado.

‘We've measured water for centuries in the world,’ says Wolfe. ‘I don't think there are questions about data collection itself anymore. I think the bigger challenges are to maintain the structures and to transmit the information quickly and accurately. These records are our legacy."

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