WATER, SURFACE--Ultrasonic Ranger for Water-Level Monitoring

In Reply Refer To:                                              May 20, 1985
WGS-Mail Stop 415


SUBJECT:  WATER, SURFACE--Ultrasonic Ranger for Water-Level Monitoring

The Ultrasonic Ranger (UR) has been developed by the Instrument Development
Laboratory (IDL) for use in monitoring water surfaces of streams that are
difficult to monitor by other means and where a high accuracy is not required.
The UR could have use on streams where the channel is unstable, stilling wells
silt up, or where a device placed in the stream would tend to wash out or
become covered.

The UR can monitor stages up to a range of 35 feet with an accuracy of about
0.10 to 0.15 foot.  When the UR is 35 feet above the water surface, a clear
circle 13 feet in diameter directly under the UR is required on the water
surface; therefore, the unit should not be mounted on a bridge wingwall or
pier.  The UR provides a voltage output and can be operated with a data-
collection platform and U.S. Geological Survey Minimonitor.

The accuracies noted are not acceptable on streams having stable control con-
ditions.  The UR may be used, however, at stream sites where the uncertainty
in flow is great because of the instability of the channel.  The District
Office should make the determination of whether or not to use the UR relative
to the amount of lost, incomplete, or uncertain stage record that would be
obtained if other stage-monitoring devices were used.  It is acceptable and
even recommended that a device such as the UR be used as the primary stage
monitoring instrument in places where channel and control conditions justify
its use.

The cost of the UR is between $500 and $2,000 depending on the number of
units ordered.  Additional information on the UR can be obtained from IDL.
Operating Manual No. 1-81-01 (Hydrologic Instrumentation Facility [HIF]
Catalog No. 0000901) is available at a cost of $2 from the HIF's Service and

                                           Verne R. Schneider
                                           Acting Chief, Surface Water Branch

WRD Distribution:  A, FO

"This memorandum does not supersede any previous SWB Memorandum."