Many streams along the Minnesota coast of Lake Superior have been listed as impaired from
high turbidity, suspended sediment, or high fish mercury concentrations. Both total suspended
sediment (TSS) and total mercury have been shown to be strongly correlated to turbidity in many
disturbed watersheds. Total suspended sediments, phosphorus, and total mercury loads were
estimated in four western Lake Superior watersheds from 2005-2006 using automated in-stream
turbidity measurements. Regression models were developed relating this near-continuous
turbidity data to grab sample measures of mercury, suspended sediments and nutrients during
differing flow regimes. Suspended sediment and phosphorus loads estimated using the turbidity
surrogate were compared to those made using FLUX software, a standard assessment technique
based on discharge and grab sampling for TSS. Stream specific turbidity vs. TSS measures were
strongly correlated (r2 = 0.6 to 0.95; p < 0.05) and total mercury also showed a close
relationship with TSS (r2 = 0.82, n = 23; p < 0.05) for all four streams. Continuous turbidity
monitoring appears to be a reasonable surrogate for both suspended sediment and total mercury
concentration, providing information when manual sample collection is cost-prohibitive or
logistically difficult, and across a wide range of flows.
University of Minnesota M.S. thesis. December 2010. Major: Water resources science. Advisors: Richard P. Axler and George E. Host. 1 computer file (PDF) vii, 74 pages. Ill. (some col.)
Ruzycki, Elaine M..
Estimating sediment, nutrient and mercury loads from four western Lake superior watersheds using continuous in-stream turbidity monitoring..
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