From: Robin Blackstone, ENN
Published May 2, 2014 10:29 AM

Local residents chronicle lake water quality

Long-term water quality trends in Midwestern lakes yield good news in the form of little change in water clarity in the regions 3,000 lakes. But what makes this news unique is that the data to make this determination was collected by non-scientists and local residents from the area’s towns and villages.



The data to support the study, which is published in the journal PLOS ONE, has come directly from lakefront homeowners, boaters, anglers and other interested members of the public with a vested interest in the water quality of these aquatic resources.

Noah Lottig, of University of Wisconsin-Madison's Center for Limnologya and co-author of the paper, says ecologists are looking at big-picture issues including land use changes and the effects of climate on various scales. This particular study has been conducted with the help of local residents.

"This study highlights research opportunities using data collected by citizens making important environmental measurements," says Elizabeth Blood, program director at the National Science Foundation (NSF) Directorate for Biological Sciences. "Their efforts provide scientists with data at space and time scales often not available by other means."

Tens of thousands of Secchi disk readings demonstrate water clarity

Non-scientists using a circular, plate-sized instrument called a Secchi disk took the water clarity measurements they sought. These water clarity measurements had been logged and documented on state agency records and online databased.  

Secchi disks, used in the aquatic sciences since the mid-1800s, hang from a rope and are lowered into the water until their distinct black-and-white pattern disappears from view. This distance marks the "Secchi depth" for water clarity. Previous studies have shown that local residents' Secchi readings are nearly as accurate as scientists' measurements, says Lottig.

Lake associations and other groups have used the disks for decades to document conditions in their respective waters.

With a dataset covering more than 3,000 lakes and stretching back to the late 1930s, the team decided to ask questions about long-term change.

Before and after the Clean Water Act

The Clean Water Act provided a useful frame of reference. Signed into law in 1972, the act set water quality goals for all U.S. waters. Thanks to the data collected by residents, Lottig's team had access to water clarity measurements for decades before and after the act came into effect. Somewhere in that data, the researchers reasoned, they might detect a landscape-scale shift over time to clearer (often an indicator of cleaner) water.


Secchi Disk in use image via Craftsbury Outdoor Center.

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