Inlet ortho view of a 3-inch aluminum construction USGS Portable Parshall flume showing a small rectangular stilling well (L) and staff gauge (R). The location of accessories is determined by looking down the flume in the direction of flow. USGS Portable Parshall flumes are a modification of the standard Parshall flume where the outlet is deleted. The flume should not be confused with a Montana flume, which is a modification of the Parshall flume where the throat and discharge sections are removed.