Parshall Flume Advantages

The Parshall flume is the most widely used flume for measuring the flow of water in open channels and non-full pipes. The flumes have a number of distinct operational advantages, including:

Parshall Flumes Conform to Irrigation and Treatment Plant Channels

The rectangular cross-section means that it conforms to the standard shape of irrigation and treatment plant channels. Depending on whether the channel is new or existing, all that may be required is for the channel walls to contract to direct the flow into the flume.

Operator Familiarity

Treatment plant operators and water rights regulators are most familiar with the Parshall flume. This familiarity means that it is less likely that there will be application or flow measurement errors than otherwise might be experienced when using a different flume style.

Resistance to Submergence

As Parshall flumes get larger, their ability to resist the effects of downstream conditions increases. For very large Parshall flume, the submergence transition (where the flume changes from free to submerged flow) is 80%. While not as high as some other flume styles, this submergence transition is sufficient for most flume applications.

Width / Breadth of Research

The first of the modern style of flumes, the Parshall flume has been operational properties of the Parshall flume have been investigated for nearly 100 years. This research has lead to: unified free / submerged flow equations, corrections for submergence, and corrections for lateral / longitudinal settling. No other flume type has been as exhaustively researched as the Parshall flume.

Wide Variety of Flow and End Connection Accessories

With almost 100 years of application in a variety of flow applications, a wide variety of flow and end connection accessories have been developed for the Parshall flume. In particular, the small to medium sized Parshall have a dizzying array of options available, including: flow meter mounts, inlet flow conditioners, above and below ground integrated structures, and accessibility options.

Standardization

Unlike other flume types (Palmer Bowlus), the Parshall flume is standardized in both its design and flow characteristics. The flume forms the basis of ASTM, ISO, JIS, and other national / international technical standards for measuring sub-critical, open channel flows.

Good System Accuracy

A well applied Parshall flume can be expected to be accurate to within +/-3-5%. This accuracy compares favorably with weirs and long throated flumes.

In short, the Parshall flume provides engineers, consultants, and operators excellent application flexibility along with reliable measurement accuracy.