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PN375 Retrospective Analysis of Processes Affecting Water Quality Due to Eruption of Mount St. Helens



The blast, debris avalanches, mudflows, and ashfall associated with the eruptions of Mount St. Helens on May 18, 1980, altered the physical, chemical, and biological characteristics of numerous streams, lakes, and aquifers. This massive disturbance of the ecosystem has provided the research community with an exceptional and unique opportunity for studies of ecological and geological processes. Despite those opportunities, the most concerted effort to date to understand post-eruption processes has been related to geomorphology, sediment transport, and regeneration of trees and other plant species. Although volcanic eruptions are generally viewed as rare events, in the Pacific Rim several eruptions may occur at intervals well within a human life span. Events during this century have included the eruptions of Lassen Peak, Mount Redoubt, and Mount St. Helens; a lahar down Kautz Creek on Mount Rainier, and a 10-fold increase in heat flow from Mount Baker. A retrospective analysis of water- quality studies over the last decade at Mount St. Helens provides valuable insight into potentially important processes for future study in the event of a major volcanic eruption.


The objectives of this study are to (1) provide a summary highlight and detailed retrospective analysis of what is known about the water-related geochemical and biological processes that were affected by the 1980 eruption of Mount St. Helens and (2) draft a strategic plan describing important study elements and hypotheses for future testing that will lead to a better understanding of the water-quality effects of future volcanic eruptions.


Review the investigations conducted after the eruption of Mount St.Helens relating to water chemistry, sedimentation, fisheries, geochemistry, microbiology, and limnology. Detail and summarize the more important processes investigated, with the intent of contrasting what was done to what could be done in future studies. Surface water, ground water, and precipitation will discussed. Some of these processes probably will include stream habitat and fish population recovery rates, effects of ashfall, changes in nutrient dynamics of lakes, streams, and estuaries due to siltation and ash covering of bottom sediments, and changes in the water-quality of lakes, streams, and rivers. Questions will be raised and some answers suggested as to how to better understand the effects of volcanic activity on dynamic processes. Hypotheses will be given for testing some of these questions in the event of future volcanic activity. Each volcanic eruption is of a different magnitude and setting, so the opportunities for research will be variable; however, a proposed strategy for examining prioritized study elements wiil be developed.


WSP 2438. Effects of the eruptions of Mount St. Helens on physical, chemical, and biological characteristics of surface water, ground water, and precipitation in the western United States, by Douglas B. Lee.

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Last modified: Tue Oct 13 16:53:22 1998