Puarenga stream alum dosing: Effects on Lake Rotorua biota 2023

Abstract

Following eutrophication in the second-half of the 20th century, Lake Rotorua currently experiences regular algal blooms reducing the recreational amenity of the lake. In 2007, an Action Plan was formulated to limit nutrient inputs to the lake, thereby improving water quality. One approach to reducing dissolved reactive phosphorus reaching the lake was the initiation of continuous alum dosing of the Puarenga Stream in 2010. The aluminium component of alum (aluminium sulphate) binds with dissolved phosphate making it unavailable for uptake by algae and limiting their growth. As a condition of the current resource consent RM18-0213-AP to alum dose the Puarenga Stream, monitoring surveys of lake water, common bully, plant material and macroinvertebrates must be conducted every 5 years to test for bioaccumulation of aluminium.