Volume

39 2001

Issue

1

Page

12

Title

Managing Submersed Aquatic Plants in the Sydney International Regatta Centre, Australia

Author(s)

D. E. ROBERTS ², G. R. SAINTY, S. P. CUMMINS, G. J. HUNTER and L. W. J. ANDERSON

Keywords

macrophyte, artificial lake, Potamogeton spp., Vallisneria americana, Hydrilla verticillata, harvesting, herbicide, fluridone

Abstract

The Sydney International Regatta Centre is a $A40 million dollar facility located at Penrith NSW, Australia. It consists of two interconnected shallow lakes, with a capacity of around 3000 megalitres. The competition lake is 2.3 km long and 170 m wide with an average depth of 5 m, whilst the warm-up lake has an average depth of 4 m and a convoluted shoreline. The two lakes are used for training, rowing, and canoeing events up to and during the Sydney 2000 Olympic games and form the rowing heart of Sydney. Adjoining these two lakes and drawing its water from them is the white water slalom course for the Olympics. When the rowing course was originally constructed, the lakes were planted with ribbonweed (Vallisneria americana var. americana Michaux), with the intent to establish a basis for a healthy aquatic plant assemblage, which was capable of "out-competing" invasive macrophyte species and nuisance blue-green algae. Over the past few years, the aquatic plant assemblages have flourished, with six additional native species colonizing the lakes. In March 1997, ribbonweed began to break away at its base and float to the surface. This defoliation caused major problems for management of the lakes and its primary users, as floating leaves interfered with rowing and swimming events. To alleviate the problem, ribbonweed was physically removed, and mechanical harvesting has been the primary management tool used to keep the plants under control. A program of monitoring was established in 1997, where spatial and temporal patterns in the distribution and abundance of submersed aquatic macrophytes were measured over two years. This program found that harvesting was ineffective, in terms of keeping plant biomass to a manageable level. In this paper we report the results of the monitoring program and present some preliminary data on a management experiment, which used the herbicide fluridone to help reduce plant growth in conjunction with physical and mechanical removal.