Oregon District Completed Projects
PN375 Retrospective Analysis of Processes Affecting Water Quality Due to Eruption of Mount St. Helens
PROJECT CHIEF: Douglas B. Lee
BACKGROUND
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.
OBJECTIVE
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.
APPROACH
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.
REPORTS PRODUCED TO DATE
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