Climate-change-driven deterioration of water quality in a mineralized watershed.
A unique 30-year streamwater chemistry data set from a mineralized alpine watershed with naturally acidic, metal-rich water displays dissolved concentrations of Zn and other metals of ecological concern increasing by 100-400% (400-2000 μg/L) during low-flow months, when metal concentrations are highest. SO(4) and other major ions show similar increases. A lack of natural or anthropogenic land disturbances in the watershed during the study period suggests that climate change is the underlying cause. Local mean annual and mean summer air temperatures have increased at a rate of 0.2-1.2 °C/decade since the 1980s. Other climatic and hydrologic indices, including stream discharge during low-flow months, do not display statistically significant trends. Consideration of potential specific causal mechanisms driven by rising temperatures suggests that melting of permafrost and falling water tables (from decreased recharge) are probable explanations for the increasing concentrations. The prospect of future widespread increases in dissolved solutes from mineralized watersheds is concerning given likely negative impacts on downstream ecosystems and water resources, and complications created for the establishment of attainable remediation objectives at mine sites.
US Geological Survey, Denver, Colorado, United States. atodd@usgs.gov
Andrew S
AS
Todd
Andrew H
AH
Manning
Philip L
PL
Verplanck
Caitlin
C
Crouch
Diane M
DM
McKnight
Ryan
R
Dunham
D057231:Climate Change; D005618:Fresh Water / Q000032:analysis*; D062070:Hydrology; D008670:Metals / Q000032:analysis*; D008903:Minerals / Q000032:analysis*; D060753:Water Quality; D015032:Zinc / Q000032:analysis
D008670:Metals; D008903:Minerals; D015032:Zinc