THE SENSITIVITY TO PHOSPHORUS AND NITROGEN LOADS, OF LAKE ROTORUA, NEW ZEALAND

The loads and outflow of phosphorus and nitrogen in 1976 and 1977 are reported. Four expressions from the literature are used to estimate expected retention coefficients for phosphorus, and are compared with measured values, the ranges being 0.50-0.66 for the literature-based estimates and 0.47-0.68 for the measurements, the values for the latter being dependent on how much of the particulate nutrient load is included. Much of the nitrogen load appears to be lost to the atmosphere. Estimates are made of the effect that changes in sewage load will have on the annual mean phosphorus and chlorophyll concentration in the lake.