reconstructing water quality histories in western reservoirs
Post on 05-Jan-2016
29 Views
Preview:
DESCRIPTION
TRANSCRIPT
Reconstructing Water Quality Histories in Western Reservoirs
Paul Gremillion, Ph.D., P.E.Associate ProfessorCivil & Environmental Engineering DepartmentNorthern Arizona University
Content
• Sedimentation in Reservoirs• Direct Indicators of Reservoir History• Proxy Indicators of Environmental Conditions• Case Studies
Sedimentation in Reservoirs
Source: Reservoir Limnology, Thornton et al.
http://www.gly.uga.edu/railsback/1121DeltaProgradation.jpeg
Direct Indicators of Reservoir History
Roosevelt Lake, Arizona
Roosevelt Lake, Arizona
Roosevelt Lake, Arizona
Direct Analysis of Sediments Can Reveal:1. Rate of loss in storage capacity.
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.
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.
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
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
Case Study: Mercury Deposition
Case Study: Mercury Deposition
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
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
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.
top related