Response of Shallow Hypertrophic Lakes to Reduced Nutrient Loading

The responses of N and P concentrations in a chain of four heavily eutrophicated shallow lakes after the complete diversion of all sewage effluents are compared to predictions using a simple hydraulic dilution model. P responded closely to predictions using a sediment retention coefficient of zero. N response was less accurately predicted, probably due to denitrification losses and to less accurate N input data. Internal P loading from the sediments is shown to be correlated to wind fetch over lake surface in the predominant wind direction divided by lake mean depth. Chlorophyll a concentrations were related more to total N than to total P concentrations, indicating that N was the primary limiting factor.