WATER, SURFACE--Ultrasonic Ranger for Water-Level Monitoring In Reply Refer To: May 20, 1985 WGS-Mail Stop 415 SURFACE WATER BRANCH TECHNICAL MEMORANDUM 85.08 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 Supply. Verne R. Schneider Acting Chief, Surface Water Branch WRD Distribution: A, FO "This memorandum does not supersede any previous SWB Memorandum."