This information is useful in planning the location and design of detention ponds or other possible treatment facilities. Measurements are commonly used to determine the amount of surface flow entering a storm sewer system, which could then be used to determine the volume available for infiltration. The Parshall flume increases flow by contracting both parallel sidewalls and dropping the floor at the flume throat. It is used to estimate the volumetric flow rate of industrial discharges, municipal sewage lines, and influent/effluent flows in wastewater treatment plants. It is therefore not entirely satisfactory for measuring widely fluctuating flow rates.
Some states require the use of Parshall flumes in certain instances by law. The depth of water at a specific place upstream of the flume mouth can be translated to a rate of flow under free-flow conditions.
It is used to calculate the volumetric flow rate of industrial discharges, municipal sewage lines, and influent/effluent flows in wastewater treatment plants. The Parshall flume is a permanently installed hydraulic structure.