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As we have seen before, a Modified Parshall Flume (aka USGS Portable Parshall Flume) is a Parshall flume with the discharge section removed. Removing only the discharge section still allows for submergence calculations to be performed – unlike the true Montana flume where…

There is a common misconception of what does and does not constitute a Montana flume.  For some, a Montana flume is a Parshall flume with the discharge removed.  For others, it is a Parshall flume with the throat and discharge removed.

In investigating the original data developed by Dr. Ralph Parshall on his namesake flume, Dr. Fred Blaisdell observed a wave action phenomena that developed when using traditional 45º wing walls to transition flow into a Parshall flume.  The phenomena developed as the…

In conjunction with the State of Utah, the Utah Water Research Laboratory conducted a statewide study to determine the accuracy of flow measurement devices in Utah.  Their investigations showed that 2/3rd of the devices (flumes, weirs, electromagnetic and ultrasonic flow…

The streamlines through a Parshall flume are assumed to be both parallel to the flume walls and continuous (Parshall 1936).  Many things can disrupt parallel streamlines as they enter the flume, including:  upstream debris, bank vegetation growing into the upstream…

For a short-throated flume to accurately measure flow, it is desirable to keep the flume’s dimensions with +/-2% of nominal.  But what happens when they aren’t?  For Rectangular Cutthroat flumes, investigations have shown that corrects for throat width can…

Recently research has conducted into the aeration efficiency of Parshall and Venturi flumes.  Unlike most other devices that are used to aerate river systems and which require stepped spillways or drop structures, Parshall flumes may be used to increase dissolved oxygen (DO)…

The 1-inch Parshall Flume is the smallest of the 22 standard Parshall flume sizes. The small size means that it is relatively limited in its use. 1-inch Parshall Flumes cannot be used on unscreened sanitary flows as they will clog. The 3-inch Parshall Flume is the smallest…

The 3-inch Parshall Flume is one of the last flumes developed in the Parshall series. The flume can be used equally well to measure sanitary flows as well as surface waters. It is important to note that the 3-inch Parshall flume is the smallest Parshall Flume size that can be…

The 9-inch Parshall Flume is a popular size in the Parshall Flume family. The flume is equally at home measuring surface waters, wastewater flows, and water rights.

The 12-inch Parshall Flume is one of the most popular sizes of the Parshall Flume family. The flume is equally at home measuring sanitary wastewater at a municipal treatment plant as it is measuring water rights on The Western Slope. Applications The flume is regularly used to…

For years Openchannelflow has offered staff gauges integrated into our flume, weir, and manhole products.  Over time, though, we have been asked to expand our offerings to include free-standing staff (level) gauges. Openchannelflow staff gauges are availalbe in a range of:…

On the face of it, mounting a staff gauge on a weir plate to get the head / flow rate seems like a good idea.  It works for on a flume, why wouldn’t it work on a weir? The problem is, as we have seen earlier, the water level in a weir pool draws down as the flow…

A common problem in using weirs to measure water flows is reading the flow level too close to the weir plate.  To understand why this is a problem we need to look at what happens as flow travels through the weir pool and then over the weir crest. In a properly formed,…