Tuesday, February 24, 2009

Guest column: Following a murky trail

Storm water may lead to pollutants muddying up Kenai creeks

The Kenai Watershed Forum has discovered that in the past several years, No Name Creek and another unnamed creek in Kenai have shown a trend of elevated turbidity levels. Turbidity is a way of measuring the cloudiness of water and can be caused by natural sources, like glaciers, or human sources, such as storm drains. Extremely high turbidity levels can kill salmon, and elevated levels can make it difficult for salmon to find food or migrate.

So where exactly is all the turbidity coming from? To answer that question, KWF employees spent last summer walking the streets of Kenai to establish where water travels during a rainy day before it enters creeks. As one astute observer pointed out, water flows downhill. Indeed, Kenai does not have any pumping stations, so all storm water travels by gravity to the outlets. However, Kenai’s storm-water system was implemented in pieces as the city grew, so storm water sometimes follows more of an illogical pattern, depending on the construction of roads rather than natural topography.

To find out the path of storm water and the pollutants it can carry, KWF used a Global Positioning System unit to determine the coordinates of culverts, manhole covers and storm-drain inlets and outlets.

A construction level and observations on rainy days were utilized to clarify which direction storm water travels through ditches and gutters that eventually drain into No Name Creek and the unnamed creek.

Once the series of storm drains and gutters were mapped out, this data was used to build a drainage network in a Geographic Information System. This digital drainage network provides a better understanding of how the different areas of Kenai are linked to No Name Creek and the unnamed creek. In a few weeks, monitoring equipment will be placed where the storm water connects to the stream and water samples will also be collected. Using the GIS, monitoring equipment and water-quality collection in unison will help narrow down potential sources of water pollution that are being flushed into two of Kenai’s creeks and harming salmon habitat.

Jennifer McCard is a watershed scientist at the Kenai Watershed Forum.

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