The pulse of a river

One evening several years ago, UW-Milwaukee scientist and river monitoring expert Tim Ehlinger was looking out his laboratory window when the weather flame atop the downtown Wisconsin Gas Company building caught his eye. The flame, which flickers and changes color to reflect the local forecast, gave Ehlinger an idea: Why not design a similar system to show the changing vital signs of local rivers?

That idea came to life this August as RiverPulse, a new public art display at the Marsupial Bridge on Milwaukee’s East Side. The project features an abstract design projected onto a wall near the bridge’s entrance east of the Milwaukee River. As certain characteristics of the river change, the design changes color and motion. “It’s like a mood ring for the river,” said Ehlinger.

The “mood” depicted by RiverPulse is based on real-time data collected from a device called a sonde. Placed in the water near the bridge, the sonde contains sensors that monitor the river’s temperature, flow, dissolved oxygen, conductivity, and turbidity-characteristics commonly used by scientists to assess water quality.

Those characteristics are ever-changing, Ehlinger pointed out, because rivers are dynamic systems that respond to both natural and human influences.

For example, many rivers naturally warm up in the daylight, and cool down at night. Similarly, a river’s flow may be heavier during the wetter spring months and lighter during the drier fall months.

Humans influence rivers by their use of the water and land surrounding them. The human impact tends to cause more extreme fluctuations of a river’s vital signs, said Ehlinger. “With greater fluctuations, we tend to lose less tolerant species,” he added. “So we don’t see walleye and small mouth bass, but green sunfish and carp.”

Human Impact on the Milwaukee River

Historically speaking, the human impact on the Milwaukee River has been profound. “From the 1880s to the 1970s [Milwaukee's] rivers were not taken care of,” said Chris Magruder, community environmental liaison at the Milwaukee Metropolitan Sewerage District.

Sewage was the most pressing issue of the 1880s, when Milwaukee’s sewers emptied directly into the Milwaukee River, leaving it stagnant and smelly. One consequence of that situation, said Magruder, is that dissolved oxygen, which is consumed when organic matter decays, would have been near zero, smothering aquatic life.

The river’s sewage problem was addressed in the short term with a flushing station and in the long term with a wastewater treatment plant. But as industries developed along the riverbanks during the early to mid-1900s, the waterway faced another major issue: industrial pollution.

With industries discharging chemical waste into the river with little or no treatment, the concentration of dissolved solids in the water-measured as conductivity-would have increased, said Magruder. That, in turn, likely caused physiological stress to the organisms living there, making them more susceptible to death and disease.

The Milwaukee River became noticeably cleaner after passage of the 1972 Clean Water Act, which regulates industrial and wastewater treatment plant discharges. Today, both Ehlinger and Magruder said, the main threat to water quality is polluted runoff.

Runoff is precipitation that washes over land and paved surfaces, eventually draining into rivers and other waters. Runoff carries with it the “filth” of the land-fertilizers, pesticides, animal waste, road salt, litter, loose soil from construction sites-and can impact any of a river’s vital signs.

Dissolved and suspended pollutants-reflected in measurements of conductivity and turbidity, respectively-are typically associated with runoff. A recent report on water quality by the Southeastern Wisconsin Regional Planning Commission documents increases in concentrations of both types of pollutants along much of the Milwaukee River since 1975.

Runoff can also impact dissolved oxygen, often indirectly. For example, as water becomes more turbid from polluted runoff, it also tends to warm-and because warmer water holds less oxygen than cooler water, oxygen levels can decrease.

Runoff can even affect flow and temperature. More paved surfaces lead to less water soaking into the ground and more water instead running off into surface waters during a rain event, increasing flow. Those same paved surfaces warm the water that runs over them, raising the temperature of the receiving water bodies.

Communities throughout the Milwaukee River watershed can minimize the impact of runoff on the river through so-called “best management practices” like street sweeping and the use of green roofs and stormwater detention ponds, said Magruder.

Ehlinger hopes RiverPulse will help people better appreciate the connection between human activities-both positive and negative-and the river’s vital signs. A second RiverPulse site will open upriver at Newburg’s Riveredge Nature Center in September, and sites along the Kinnickinnic and Menomonee Rivers may eventually be added, said Kae DonLevy, the project’s administrator. See riverpulse.org for more information.

RIVER VITAL SIGNS

Temperature - The hotness or coolness of water.
Dissolved Oxygen - The concentration of oxygen dissolved in water.
Turbidity - A measure of the amount of solid material (such as sediment or algae) suspended in the water.
Conductivity - A measure of the amount of solid material (such as road salt or fertilizer) dissolved in the water.
Flow - The volume of water moving through a certain area over a period of time.

Jennifer Yauck is a science writer at the Great Lakes WATER Institute. GLWI (glwi.uwm.edu) is the largest academic freshwater research facility on the Great Lakes.

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