reconstructing water quality histories in western reservoirs
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Reconstructing Water Quality Histories in Western Reservoirs. Paul Gremillion, Ph.D., P.E. Associate Professor Civil & Environmental Engineering Department Northern Arizona University. Content. Sedimentation in Reservoirs Direct Indicators of Reservoir History - PowerPoint PPT PresentationTRANSCRIPT
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Reconstructing Water Quality Histories in Western Reservoirs
Paul Gremillion, Ph.D., P.E.Associate ProfessorCivil & Environmental Engineering DepartmentNorthern Arizona University
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Content
• Sedimentation in Reservoirs• Direct Indicators of Reservoir History• Proxy Indicators of Environmental Conditions• Case Studies
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Sedimentation in Reservoirs
Source: Reservoir Limnology, Thornton et al.
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http://www.gly.uga.edu/railsback/1121DeltaProgradation.jpeg
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Direct Indicators of Reservoir History
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Roosevelt Lake, Arizona
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Roosevelt Lake, Arizona
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Roosevelt Lake, Arizona
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Direct Analysis of Sediments Can Reveal:1. Rate of loss in storage capacity.
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Direct Analysis of Sediments Can Reveal:1. Rate of loss in storage capacity.2. How the rate of capacity loss may change
with climate change.
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Direct Analysis of Sediments Can Reveal:1. Rate of loss in storage capacity.2. How the rate of capacity loss may change
with climate change.3. Erosion patterns associated with wildfire.
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Proxy Indicators
Objective Analyte / Proxy
Chronology • 137Cs or 239Pu ~ 50 yrs• 210Pb ~150 yrs• 14C ~100 – 15k yrs• Event-based chronology
Primary Productivity • Diatoms• Biogenic silica• 13C (in some systems)
Anoxia • Ratios of redox-sensitive metals• Molybdenum stable isotopes• Benthic invertebrates
Fire • Charcoal• Magnetic susceptibility
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Proxy Indicators
Objective Analyte / Proxy
Hydrology • Magnetic susceptibility• Inorganic ion ratios• Particle size distributions• Compound-specific isotopes
Sediment Redistribution • Acoustic surveys• 137Cs or 239Pu inventories• Particle size distributions
Ecosystem Assemblages • Pollen• Diatoms
Atmospheric Pollutants • Chemical extraction + elemental / isotopic analysis
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Case Study: Mercury Deposition
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Case Study: Mercury Deposition
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Case Study: Watson Lake, Arizona
Objective:Collect and analyze sediment cores from Watson Lake to detect historical changes in• Nutrient loading• Primary productivity / trophic
state• Sources of nutrients
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Case Study: Watson Lake, ArizonaAnalytical Approach:• Changes in nutrient loading:
TN, TKN, TP• Changes in source of nitrogen:
Nitrogen-15• Changes in source of organic
matter: N/P, C/N, Carbon-13• Changes in primary
productivity / trophic state: Carbon-13, TP
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Conclusions
Sediment records in western reservoirs tend to be high in information content:• Magnitude and effects of erosion events.• Changes in water quality.• Changes in watershed characteristics.• Patterns of atmospheric deposition to
watersheds.