Summary of Trends in Six Years of the Longview Watershed Study

As is expected in a small, intermittent, silt-laden stream, macroinvertebrate diversity is low, though higher in the summer with the emergence of aquatic insects. Diversity does not appear to be increased by adding leaves, on the basis of comparing experimental samples with leaves and controls without leaves. Indications that leaves reduce dissolved oxygen and nitrate concentrations are not clear. Field experiments have been subjected to the vicissitudes of rains, floods, siltation, net destruction, and problematic chemical analysis. The complete set of methods and results can be seen in  the archive.

Longview campus Watershed Study showing trends in long term study by Stephen L Reinbold.

Table 1. Comparison of nitrate-N concentrations between experimental sites with leaves and control sites without leaves over seven years of the field study.

Table 2. Commparison of dissolved oxygen between experimental sites with leaves and control sites without leaves over seven years of the field study.

Table 3. Experimental sites with leaves and control sites without leaves, comparing number of organisms over seven years of the field study.

Table 4. Experimental sites with leaves and control sites without leaves, comparing Stream Quality Index over seven years of the field study.

Table 5. Change in nitrate-N (mg/L) from time of experimental set-up to completion of experiment. The duration was 12 weeks except in 2004 (8 weeks) and 2011 (4 weeks).

Positive values indicate decrease over time and negative values increase over time