Pollution Hotspots in the Iowa Great Lakes

Urban runoff into West Okoboji from Arnolds Park before construction of the environmental parking lot at Historic Arnolds Park. Today, runoff and pollutants are diverted from the lake by rain gardens and pervious pavements. Photo courtesty of David Thoreson.

John Wills, Dickinson County Clean Water Alliance Coordinator , lead an enlightening discussion about the Iowa Great Lakes Watershed Assessment at during "Conservation Conversations", held over coffee and rolls at Iowa Lakeside Laboratory last week.

The purpose of the assessment is to use all existing sources of data to identify and prioritize pollution hotspots in the Iowa Great Lakes watershed. It can then be used as a tool to coordinate and fund watershed improvements.

"Before we had a shoot from the hip approach, but the watershed assessment uses data from a variety of sources to help us identify and focus on hotspots- defined as those areas where the highest concentration of runoff is taking place," Wills said.

A watershed is defined as the area of land that drains into a particular water body. The Iowa Great Lakes watershed is 87,600 square acres and extends north into Minnesota. The two biggest threats to water quality in Dickinson County Iowa are too many sediments and too much phosphorus. These pollutants come from two major sources: urban and agricultural runoff. "Most people do no realize that what happens on the land affects what happens in the water," John said. "In other words, the quality of the water in our lakes reflects the type of land use." Most of the sediment and phosphorus runoff comes from agricultural practices, which represents 87% of the land use in the IGL watershed. However, acre by acre, phosphorus and sediment runoff is higher in urban areas, and urbanization is expanding in the Iowa Great Lakes.

Three priority hotspots have been identified in agricultural areas: the sub-watershed of Lazy Lagoon that feeds into West Okoboji, and the Templar Park and Reeds Run sub-watersheds, which both feed into Big Spirit Lake. The assessment identifies three urban hotspots: the sub-watershed north and east of Center Lake, the sub-watershed west of East Okoboji that includes the Iowa the Great Lakes Mall, and HW 71 from Arnold's Park to Milford.

Tools for addressing hot spots in agricultural lands include wetland restorations, reduced tillage and other conservation management programs. In urban areas, low impact development practices, such as rain gardens, bioswales, and pervious pavement can store, treat and purify water before discharging it into the lakes. "Historically, most of the precipitation that fell from the sky was absorbed into the earth, and recharged our water tables. Today, with the draining of wetlands, the paving of streets, rooftops, most water runs off into the lakes. Runoff carries all kinds of pollutants with it." Wills described a success story right in our back yard: the environmental parking lot at Arnold's Park Amusement Park. "The parking lot is over 2 acres, and is surrounded by rain gardens that absorb the run off from storm events. We have an automatic sampler that collects water before and after it enters the rain gardens. So far this summer, the rain gardens are holding all that runoff from the parking lot! None of it is discharging into West Okoboji. And that is a good thing, because our data shows that storm water runoff carries all kinds of pollutants, such as motor oil products over three times the level considered safe by the Environmental Protection Agency."

The Iowa Great Lakes Watershed Assessment can be viewed on line. Visit the Dickinson County Clean Water Alliance website at http://cleanwateralliance.net/blog/.

Conservation Conversations is held the second Friday at Iowa Lakeside Laboratory from June through September. Next month's discussion topic will be the Iowa DNR's proposed antidegradation rules.