Underwater sensors help scientists monitor water

Measuring water quality in lakes and streams traditionally starts with a time-consuming trip with a bucket to get a water sample for the laboratory.

Now University of Minnesota water researchers have found a way to skip that step.

In an ongoing study of urban creeks and watersheds that is focusing this summer on Lake Pamela in Edina, the university is taking thousands of water-quality readings a day using underwater sensors that relay the data by cell phone to the U's St. Anthony Falls Laboratory.

The study promises to "move environmental monitoring to the next level and improve our understanding and management of water resources," said Deb Swackhamer, co-director of the university's Water Resources Center.

State and watershed officials already monitor area streams, wetlands and lakes for herbicides, chemicals from houses and cars, fecal coliform and other pollutants swept in by rainfall. But sensor measurements can speed up the pace and expand the scope of that monitoring, so officials can get a faster and more accurate picture of how well water cleanup efforts are working, said Bill Arnold, associate professor in the U's Department of Civil Engineering.

One sensor can send in as many as 1,500 measurements a day, said Arnold, who is heading up the sensor study.

"It's a tremendous increase in the amount of data available," he said. "It gives us a more accurate feeling of how much pollution is going through and how well the pollution removal systems are working.''

The sensors measure the depth and flow of the water as well as its turbidity, temperature, salinity, pH, and nitrate and oxygen levels. In Lake Pamela, five sensor stations will be used, sampling water before and after it goes through settling ponds on its way to the lake as well as in the lake itself.

Ultimately, this kind of data collected from a variety of area lakes could be used to create a water information network to give water users -- boaters, swimmers and fishermen as well as scientists -- up-to-date information on water conditions and quality. It could also help guide engineers in developing future designs for holding ponds and storm water drainage systems.

Remote monitoring could be especially valuable during storms or spills or other events when it's difficult for people to reach the water, Swackhamer said. And because the sensors detect pollution that could be missed between weekly or monthly bucket samplings, carefully positioned sensors could provide an early warning about unexpected contaminants, she said.

Judging by the popularity of the Department of Natural Resources website on lake water conditions, she expects public interest in the data to be high.

The electronic sensors themselves are not new, but U scientists are among the first to use them for water-quality research, Swackhamer said.

The U is keen on the testing because it has more than 100 faculty members for whom water is a primary area of research as well as a graduate program in water resources science, Swackhamer said.

The testing, now entering its third summer, is focusing on the watersheds of Minnehaha Creek and Shingle Creek. The National Science Foundation, the U.S. Geological Society, the Minnehaha Creek Watershed District and the Mississippi Watershed Management Organization and other agencies have provided nearly $600,000 for the work.

Each station costs about $10,000. They are being used for about three months in several locations. The next step in testing will be to install one of the sensor stations in a specific spot for an extended period of time. The longer goal is to install 100 sensor stations over the next decade, the U said.

Laurie Blake • 612-673-1711