Effects of enclosing headwaters on downstream agro-ecosystems

In agricultural areas, headwater streams are often enclosed or buried to increase the efficiency of farming and reduce soil erosion.  Our research aims to relate the degree of headwater enclosedness to the biotic structure and flow characteristics of the downstream ecosystem. Two sites in each of five streams in the Ausable River basin in southwestern Ontario were selected for this study.  These sites have varying degrees of upstream enclosedness, but are similar in other aspects of their catchment and local environments.  Fish and benthic macroinvertebrate assemblages were characterized seasonally from July 2007 to November 2008.  Water quality, discharge and habitat descriptions were also collected during this time period.  We tested the hypothesis that enclosing headwater streams affects, among other ecosystem attributes, the diversity and composition of the downstream fish and benthic invertebrate communities.   With these data we are also able to explain and account for natural seasonal variability.  The findings will provide critical information on the impact of headwater loss to downstream ecosystems, and will aid managers in Ontario in setting scientifically defensible regulations regarding future stream enclosures.