SCIENTISTS FIND GOOD NEWS REGARDING MIDWESTERN LAKES

FROM:  NATIONAL SCIENCE FOUNDATION 

Clarity for lake researchers' water quality questions

Studies of trends in Midwestern lakes benefit from help of local residents
Scientists engaged in a study of long-term water quality trends in Midwestern lakes found some good news: little change in water clarity in more than 3,000 lakes.

Look deeper, and the research becomes something more: a chronicle of a new source of data for scientists, data from residents of towns and villages surrounding the lakes.

The results are published in a paper in the journal PLOS ONE.

The paper co-authors analyzed almost a quarter of a million observations taken over seven decades on 3,251 lakes in eight Midwestern states.

Enter local residents

But the researchers didn't collect those data. The observations came from lakefront homeowners, boaters, anglers and other interested members of the public wanting to know more about what's going on in "their" lakes.

Noah Lottig, a co-author of the paper and a scientist at the University of Wisconsin-Madison's Center for Limnology, says that ecologists are looking at big-picture issues--such as how changes in land use or climate affect ecosystems--at state, national and continental scales.

This time, the help of local residents was key to the findings.

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

Water clarity from a Secchi disk reading--or tens of thousands of them

Lottig and freshwater scientists from across the United States combed through state agency records and online databases. The water clarity measurements they sought were taken by non-scientists using a circular, plate-sized instrument called a Secchi disk.

Used in the aquatic sciences since the mid-1800s, Secchi disks hang from a rope and are lowered into the water until their distinct black-and-white pattern disappears from view, a distance that marks the "Secchi depth."

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

Previous studies have shown that local residents' Secchi readings are nearly as accurate as scientists' measurements, says Lottig.

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.

While there was a slight one percent yearly increase in water clarity for the lakes, Lottig says, "most of the lakes are just chugging along, not changing much through time."

While some lakes improved, others did not. Taken as a whole, there was no major change in clarity at the landscape scale.

Lottig is part of the "Cross-Scale Interaction" or "CSI Limnology" project, an effort to collect global data on water chemistry and aquatic biology that will add needed context.

Townspeople weigh in

For Ken Fiske, collecting data has been well worth the effort.

In 1985, Fiske saw an announcement for volunteers for a new Wisconsin lake monitoring program. Fiske had been coming to northern Wisconsin from his home in Illinois for years and had recently bought property on the shoreline of Lake Adelaide.

"My interest was in finding out what the quality of water in Lake Adelaide was and seeing what we could do to maintain it," he says.

For the next several years, Fiske went on a monthly five-hour drive to Lake Adelaide to take measurements. Eventually, he found some neighbors to help. Some 30 years later, the group is still going strong.

"We've been doing it long enough that it makes the results meaningful," Fiske says.

Scientists are harnessing efforts like Fiske's to try to answer questions about not just one lake, but 3,251--or more--of them.

-- Cheryl Dybas, NSF
Investigators
Noah Lottig
Emily Stanley
Related Institutions/Organizations
University of Wisconsin-Madison

NSF ON ROCKY MOUNTAIN BARK BEETLES AND WATER QUALITY

Photo:  Rocky Mountains. Credit:  Wikimedia, Williams Jim, U.S. Fish and Wildlife Service. 

FROM:  NATIONAL SCIENCE FOUNDATION 

Earth Week: Bark beetles change Rocky Mountain stream flows, affect water quality

What happens when millions of dead trees, killed by beetles, no longer need water?

On Earth Week--and in fact, every week now--trees in mountains across the western United States are dying, thanks to an infestation of bark beetles that reproduce in the trees' inner bark.

Some species of the beetles, such as the mountain pine beetle, attack and kill live trees. Others live in dead, weakened or dying hosts.

In Colorado alone, the mountain pine beetle has caused the deaths of more than 3.4 million acres of pine trees.

What effect do all these dead trees have on stream flow and water quality? Plenty, according to new research findings reported this week.

Dead trees don't drink water

"The unprecedented tree deaths caused by these beetles provided a new approach to estimating the interaction of trees with the water cycle in mountain headwaters like those of the Colorado and Platte Rivers," says hydrologist Reed Maxwell of the Colorado School of Mines.

Maxwell and colleagues have published results of their study of beetle effects on stream flows in this week's issue of the journal Nature Climate Change.

As the trees die, they stop taking up water from the soil, known as transpiration. Transpiration is the process of water movement through a plant and its evaporation from leaves, stems and flowers.

The "unused" water then becomes part of the local groundwater and leads to increased water flows in nearby streams.

The research is funded by the National Science Foundation's (NSF) Water, Sustainability and Climate (WSC) Program. WSC is part of NSF's Science, Engineering and Education for Sustainability initiative.

"Large-scale tree death due to pine beetles has many negative effects," says Tom Torgersen of NSF's Directorate for Geosciences and lead WSC program director.

"This loss of trees increases groundwater flow and water availability, seemingly a positive," Torgersen says.

"The total effect, however, of the extensive tree death and increased water flow has to be evaluated for how much of an increase, when does such an increase occur, and what's the water quality of the resulting flow?"

The answers aren't always good ones.

Green means go, red means stop, even for trees

Under normal circumstances, green trees use shallow groundwater in late summer for transpiration.

Red- and gray-phase trees--those affected by beetle infestations--stop transpiring, leading to higher water tables and greater water availability for groundwater flow to streams.

The new results show that the fraction of late-summer groundwater flows from affected watersheds is about 30 percent higher after beetles have infested an area, compared with watersheds with less severe beetle attacks.

"Water budget analysis confirms that transpiration loss resulting from beetle kill can account for the increase in groundwater contributions to streams," write Maxwell and scientists Lindsay Bearup and John McCray of the Colorado School of Mines, and David Clow of the U.S. Geological Survey, in their paper.

Dead trees create changes in water quality

"Using 'fingerprints' of different water sources, defined by the sources' water chemistry, we found that a higher fraction of late-summer streamflow in affected watersheds comes from groundwater rather than surface flows," says Bearup.

"Increases in stream flow and groundwater levels are very hard to detect because of fluctuations from changes in climate and in topography. Our approach using water chemistry allows us to 'dissect' the water in streams and better understand its source."

With millions of dead trees, adds Maxwell, "we asked: What's the potential effect if the trees stop using water? Our findings not only identify this change, but quantify how much water trees use."

An important implication of the research, Bearup says, is that the change can alter water quality.

The new results, she says, help explain earlier work by Colorado School of Mines scientists. "That research found an unexpected spike in carcinogenic disinfection by-products in late summer in water treatment plants."

Where were those water treatment plants located? In bark beetle-infested watersheds.

-- Cheryl Dybas, NSF
Investigators
Reed Maxwell
Eric Dickenson
Jonathan Sharp
Alexis Navarre-Sitchler
Related Institutions/Organizations
Colorado School of Mines