Water Quality at "The Lake"

The University of Missouri Limnology Laboratory’s long-term monitoring on Lake of the Ozarks (LOTO), begun in 1976, resulted in three journal articles, all published in the proceedings of the International Society of Limnology. The first paper, published in 1981, described water quality in LOTO prior to the impoundment of Harry S. Truman Reservoir. In 1988 a second study evaluated changes in water quality associated with the completion of Truman Reservoir. A final paper published in 2000 examined seasonal water quality patterns. A brief summary of these three articles follows.

Limnological characteristics of Lake of the Ozarks, Missouri. 1981. J.R. Jones and J.T. Novak.

The purpose of this 1976–1979 study of summer water quality in LOTO was to establish baseline data prior to the impoundment of Truman Reservoir. Three main channel sites, were monitored, one each in the Gravois Mills, Grand Glaize and Niangua arms. Major findings included identification of a strong longitudinal gradient in water quality within the main lake channel. Average phosphorus concentrations at the 59-mile marker were three times higher than values at the dam (92 vs. 31 µg/L), with the 39-mile marker site having intermediate levels of 56 µg/L. Secchi transparency values were lowest up-lake (averaging 0.5 meters), moderate at the mid-lake site (1.2 meters) and deepest near the dam (2.0 meters). Interestingly, chlorophyll levels were similar across the three main lake sites, ranging from 14.2 µg/L at the up-lake site to 10.5 µg/L at the dam.

The chlorophyll concentrations at the 59-mile marker were low relative to phosphorus levels, averaging 0.15 unit of chlorophyll for each unit of phosphorus. In contrast, the ratio of chlorophyll to phosphorus at the dam site averaged 0.34. The inefficient use of phosphorus by algae at the up-lake site was attributed to high levels of inorganic suspended sediment, which reduced the penetration of sunlight into the lake and thus limited algal photosynthesis. While inorganic suspended sediment data were only measured in 1979, elevated turbidity readings and shallow Secchi transparency values at the up-lake site during 1976-1978 support the conclusion that suspended sediments reduced available light and limited algal growth.

Other findings included the relation between flow and lake water quality. Nutrient and turbidity levels were elevated and Secchi transparencies shallower in LOTO during years with high inflow. Also, data collected in the three tributary arms indicated water quality in the Gravois Mills and Grand Glaize arms was comparable to the dam site, while the Niangua Arm had slightly higher phosphorus values and shallower Secchi readings.



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