Marshall County: Hendrickson Marsh

DSC_0085[1]Every wetland is part of a landscape, connected to the air, water, soil, sun, and life around it. These open systems connect the pieces of the world around us, transcending any arbitrary boundary drawn by humans.


Hendrickson Marsh is an excellent example of such an open system, most immediately in that it straddles two counties: most of the site is in Story County, but a so-called “control structure” regulating water depth is located in Marshall County. (The county line runs vertically in the middle of the topo map above). The water is impounded by a large concrete dam pictured below, with the specific water depth determined by the height of two separate controllers. On the left in the photo is a large steel roller gate, and to the right of it is a tall, narrow weir with stacked planks called stop-logs. (I don’t suppose modern structures ever actually use logs anymore, but we still use that term.) By stacking the logs higher, the water behind the dam is made deeper.

DSC_0088[1]Of course, most of that water flows here from upstream–the topographic map helps set the context. The wetland is at the confluence (joining) of several streams, including Indian, Willow, and Dye Creeks. The land area (basin) drained by these creeks forms the watershed for this wetland. Rainfall and snow melt in the watershed flows downstream, eventually gathering here. Human activities in the watershed will affect the quality of that water. If we dump waste on the ground, or leak fluids onto a parking lot, or disturb the soil surface, it can impact both this wetland and the water leaving it for places beyond. Those streams drain a watershed which is in turn, part of a larger watershed, and so on. Eventually these join the Skunk River, rolling along down near my hometown. Just like the blackbirds, herons, frogs, willows, and other life I saw at Hendrickson Marsh, “we all live downstream.”

Author: Paul Weihe

Associate Professor of Biology at Central College, traditional author (Textbook of Limnology, Cole & Weihe, 5th ed.; Waveland Press), and now...blogger!

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