Hydrologic activities during the 1987 fiscal year by the U.S. Geological Survey in support of the Radionuclide Migration Program at the Nevada Test Site are summarized. These activities included monitoring groundwater levels; compiling and entering geohydrologic data into the U.S. Geological Survey computerized groundwater database; providing technical support to the Radionuclide Migration Committee and the Containment Evaluation Panel; and the planning, drilling, and sampling of the UE20n-1 hole. Groundwater levels were monitored continuously at 2 wells and intermittently at 36 selected wells, test holes, and emplacement holes. Selected monthly water-level measurements are listed for the continuously monitored wells and intermittent measurements are listed for the selected wells, test holes, and emplacement holes. Progress continued on four groundwater hydrology reports of the Nevada Test Site area. (Thacker-USGS, WRD)