Evaluation of Low Order Stream Quality in Central Iowa

摘要

This research describes procedures and results obtained to evaluate the baseline(existing) watershed quality in the low order streams in a tri-county area in central Iowa. The five streams evaluated were located in the Upper Skunk River Basin. Field work was conducted over a three-year period from 1992 to 1994, and sampling conducted at 12 locations. The field procedures used physical (habitat), chemical (surface and sediment pore water quality), toxicological (daphid and algal bioassays), and biological (macroinvertebrates and fish) techniques. Habitat quality was the highest in the larger drainages. Non-farm streamside vegetative buffers were greater at the larger drainage sites. Significant associations were found among the macroinvertebrate community indices, surface and sediment pore water quality and drainage area. Correlations were also found between habitat quality and the biological community indices. Based on our measurements, lowest watershed quality was present in the upper drainage reaches. This study found that elevated concentrations of sediments and nutrients were associated with degraded biological communities found in low order agricultural streams.