Despite land-use planning and export of treated sewage effluent from the basin, the lake is becoming increasingly eutrophic (having an excessive richness of nutrients), with primary productivity increasing by more than 5% annually, and clarity decreasing at an average rate of 0.82 feet (0.25 m) per year.[81] Until the early 1980s, nutrient-limitation studies showed that primary productivity in the lake was nitrogen-limited.