SWAN LAKE HABITAT REHABILITATION AND ENHANCEMENT PROJECT (HREP):  POST-PROJECT 
BIOLOGICAL AND PHYSICAL RESPONSE MONITORING  

Chad R. Dolan, James T. Lamer, and John H. Chick  
Illinois Natural History Survey, Great Rivers Field Station, Brighton, Illinois  
62012

      Sedimentation of backwater lakes in the Mississippi and Illinois River 
systems is an ongoing problem.  Swan Lake is a 1,150 ha backwater lake of the 
Illinois River in which an HREP was implemented in 1993 to improve conditions.  
It was divided into three distinct units (upper, middle, and lower), and stop-
log gates were installed to manipulate water levels.  Goals were to reduce 
sedimentation rates and consolidate sediments to promote the growth of aquatic 
vegetation and improve habitat for fish and wildlife.  Pre-project monitoring 
was executed in 1992 to collect baseline data on water quality, sediment, 
aquatic vegetation, macroinvertebrates, and fishes.  Post-project monitoring 
began in 2004, two years after completion of HREP construction, and was 
completed in 2006.  Sites with consolidated sediments (penetrometer depths < 20 
cm) increased due to draw-downs, but areas that remained wet were more 
flocculent than in 1992.  Gross sedimentation rate was 798-1320 g dry 
wt./m2/day, and was similar to 1992.  Reduced turbidity was observed in the 
middle unit only, likely a reflection of increased sediment compaction.  
Submersed aquatics were absent throughout the lake during the post-project 
except in the upper unit, and substantial growth of emergent vegetation was 
observed in the middle and upper units.  Chironomids were the dominate 
macroinvertebrate during both project phases.  More fish species were collected 
in the pre- (n=40) versus the post-project (n=30).  Fish community changes 
include the addition of Asian carp, and reduction in buffaloes.  Post-project 
objectives were 1) to compile data on the same abiotic and biotic variables as 
in 1992, and 2) to compare pre- and post-project data to assess Swan Lake HREP 
successes.

Keywords:  sedimentation, backwaters, habitat rehabilitation, aquatic 
vegetation, before/after comparison