Pegasus - Managing a New Lake in an Urban Environment

Pegasus Lake is a 14 ha manmade lake in Pegasus Town, a new residential and commercial development in Canterbury. The design objectives for the lake were to provide an aesthetically pleasing lake that was suitable as a recreation facility.

Pegasus Lake was constructed in 2009, and is fed by both stormwater and groundwater. Since its completion, Golder has monitored the water quality and visual aesthetics of the lake. Through this monitoring, Golder has noted the lake’s response to: stormwater, algae growth, weed growth, microbiological contaminants, groundwater inputs, and increased urban development.

Stormwater contaminants appear to play a minor role in the lake’s water quality. Algae and weed growth appear during periods of favourable meteorological and chemical conditions which in turn lead to a rapid deterioration in clarity and colour. Pegasus staff have learned to control these changes through the management of groundwater inputs, riparian margins, lake level and maintenance.

The intended recreational and aesthetic design objectives of Pegasus Lake have at times conflicted with its ecological performance, and the result is a balancing act between an engineered system and a natural ecosystem.