Figure 4-15. Median TP Values at Lake Istokpoga Sampling Stations
The average HRT of 197 days was developed for the lake using the mass balance
terms described in the preceding section. Knowing the HRT for the lake, it is possible to
develop a TP concentration vs. residence time curve based on the inlet, outlet, and in-lake
measurements. The resulting curve is shown in Figure 4-16. Using the boundary
conditions of the concentration at 0 days was equal to 0.082 mg/L, the concentration at
60 days was equal to 0.0475 mg/L, and the concentration is 0.028 mg/L at 197.5 days,
then the overall rate constant, kv, was calculated as 0.016 days-1 and the background
concentration, C*, is 0.0254 mg/L.