Parshall Flumes are commonly used for a number of reasons:

• Most municipal operators are exposed to them during their initial training
• The flat bottom makes determining the water level simple and straightforward
• The Parshall Flume has a single point of measurement 
• Most flow meters come preprogrammed with flow conversions for the flume
• The Parshall Flume is the most thoroughly researched open channel primary device - with almost 100 years of research behind it
• The Parshall Flume is standardized - with dimensions and performance detailed in ASTM and ISO standards
• There are (22) standard sizes - meaning there is a Parshall Flume capable of measuring just about any open channel flow
• The Parshall Flume is economical to construct
• The Parshall Flume is accurate
• The Parshall Flume can be used to measure both open channel and non-full pipe flows