The U.S. Geological Survey 's Hydrologic Instrumentation Facility at the Stennis Space Center, Mississippi, conducts qualification tests on water level sensing instruments. Instrument systems, which meet or exceed the Survey 's minimum performance requirements, are placed on the Survey 's Qualified Products List. The qualification tests conducted in 1987 added two instrument systems to the Survey 's Qualified Products List. One system met requirements for use at a daily-discharge station , and the other system met requirements for a special-case station. The report is prepared for users of hydrologic instruments. The report provides a list of instrument features, describes the instrument systems, summarizes test procedures, and presents test results for the two instrument systems that met the Survey 's minimum performance standards for the 1987 round of qualification tests. (USGS)