Surface-water-quality data from selected sites in Washington affected by Mount St. Helens eruptions; March 27 - September 30, 1980

The volcanic eruptions of Mount St. Helens have resulted in the collection of many forms of hydrologic data. Chemical data collected from March 27 to September 30, 1980, to document the effects of the various volcanic events (mudflows, pyroclastic flows, deposition of ash) on the quality of surface water at selected sites in the State of Washington are presented in the report. (USGS)