Sediment removal as a restoration measure for the campus lakes

Abstract

The Campus Lakes, Oranga and Knighton, were formed about 1969 as a means of draining the wet, swampy land that the University of Waikato was sited on. Since Prof. Wilf Malcolm, (Vice-chancellor, 1985-1994) first expressed concern about the water quality of the Campus Lakes (Kingsbury, 1989), they have been the subject of at least four reports and one thesis. A number of approaches for improving the lake water quality have been tried or recommended, largely without success. The lakes continue to be unsightly with exotic weed growing to nuisance proportions and phytoplankton scums and blooms occurring annually, as well as discoloration from high concentrations of suspended sediments. The indigenous biodiversity values are low due to domination by pest fish and exotic macrophytes.

This report is part of a larger scale recommendation to take an integrated approach towards the management of Oranga and Knighton lakes. The focus of this study was to investigate the possibility of removal of 0.2 m of the nutrient and organic-rich surficial sediments from the two lakes, and disposal of that sediment by spreading it onto the university playing fields. The specific aims of this study were to determine contaminant concentrations (heavy metals and persistent organochlorines) in the sediments and relate these concentrations to soil environmental guideline values for human health with parkland/recreational land use.