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Phosphate very low - TP very high

Fri, 10/09/2009 - 7:37am — Karoline
I am a beginner with Ce-Qual-W2 and trying to simulate nutrients and algae blooms in a shallow, well mixed lake. By calibrating the model, most parameters fit well except of phosphate and TP. Simulated phosphate concentrations are 0 or 0.001 while input and measured concentrations range between 0.01 and 0.2. So the model does hardly simulate any phosphate. Simulated TP ranges from 3 to 80 and is way above the measured concentrations of 0.3 to 1.0. Does anyone have an idea where to start fixing this?
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Water Quality
Fri, 10/09/2009 - 3:03pm — chris

Hi Karoline, It's not unusual to have low phosphate concentrations when algae is growing and is phosphorus limited. To be safe I'd check and make sure the algae half-saturation coefficient for phosphorus is within literature values - a value of 0.003 mg/l is typical. The high TP values sounds like a boundary condition issue, and maybe the amount of phosphorus in organic matter is too high. If this is the case, the phosphorus stoichiometry of the organic matter can be adjusted (parameters BODP and ORGP in control file). Hope this helps, chris