2022 Early Hearing Detection & Intervention Virtual Conference

March 13 - 15, 2022

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5/23/2019 | 11:45 AM - 12:00 PM | A DAY IN THE LIFE OF LAKE MICHIGAN: A COMPREHENSIVE ESTIMATE OF TRIBUTARY NUTRIENT LOADS | 151 DEF

A DAY IN THE LIFE OF LAKE MICHIGAN: A COMPREHENSIVE ESTIMATE OF TRIBUTARY NUTRIENT LOADS

Despite efforts to reduce nutrient loads to the Laurentian Great Lakes since the 1970’s, inputs of nitrogen and phosphorus continue to cause coastal eutrophication and degrade ecosystems. Tributaries that deliver nutrients directly into the Lakes are a key focus for managing loads. However, there is uncertainty in aggregate contributions of tributaries due to limited monitoring data of small and mid-sized watersheds. We used a synoptic, lake-wide sampling approach paired with modeled estimates of discharge to estimate total nutrient input from Lake Michigan's tributaries. Over a 6-day period in July 2018, we collected water from 265 tributaries (97% of Lake Michigan's watershed area) for total and dissolved nutrient analyses. For each tributary, discharge was modeled for the 24-hour period around the sampling event. Tributary nutrient loads spanned many orders of magnitude (e.g., <1 to >100 kg nitrate per day). Although tributary size is an important driver of load, high nutrient concentrations allow some small tributaries to contribute disproportionately large loads. Our comprehensive snapshot approach to estimating nutrient loads provides context for evaluating nutrient loads at large spatial scales using limited local data.

Phosphorous
Landuse
Nitrogen

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Presenters/Authors

Robert J. Mooney (), Center for Limnology, University of Wisconsin - Madison, rjmooney@wisc.edu;