Excerpt
The enclosure of small surface watercourses in agricultural landscapes is a practice that has not received much scientific assessment. Typically, water quality concerns and issues regarding fishery resources are realized in larger rivers and lakes. There is a tendency to overlook the smaller tributaries that contribute to these larger systems. Yet it is these smaller systems that comprise the greatest portion of the river network. Meyer et al. (2003) remind us that 50 to 80 percent of the river network is comprised of first and second order systems. These headwater systems have relatively more water in contact with the channel and therefore, have important ecosystem functions.
Headwater systems perform three functions that are broadly categorized as hydrologic, habitat/food web and physico-chemical. In an urbanizing watershed, Dunne and Leopold (1978) found that headwater streams provided the watershed with an ability to hold and store water. As the impervious area increased and small channels were replaced with storm sewers, there was an increase in both the frequency and intensity of flooding events downstream. In temperate forested ecosystems, the slower moving headwater systems have the potential to accumulate woody debris which in turn traps excess sediment (Bilby, 1981) and autumnshed leaves (Bilby …
Footnotes
Mari Veliz, is with the Ausable Bayfield Conservation Authority in Exeter, Ontario. Jane Sadler Richards is with Cordner Science in Ailsa Craig, Ontario.
- Copyright 2005 by the Soil and Water Conservation Society
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