Land use, water quality and ecological responses in Lake Colac – trends from Australia

Abstract

Purpose

Recently, Colac Otway Shire in Australia released its management plan for Lake Colac, claiming over‐enrichment of the lake with nutrients and degraded water quality. This paper aims to investigate these claims by establishing a correlation between key water and ecological indicators and land uses.

Design/methodology/approach

The paper examines the correlation between impairment and stressors in Lake Colac. This was achieved by identifying the likely sources of pollutants into Lake Colac; identifying any existing monitoring program; and characterizing the water and sediment inputs. The likely impacts of increased nutrients and sediment levels on indigenous flora and fauna were also examined. The use of meiofauna (very small benthic metazoan animals) was investigated as an indicator of degraded sites. Plankton diversity as a measure of water health was also assessed.

Findings

Water quality in Lake Colac was found to vary both temporally and spatially, and exhibited low attainment against acceptable trigger values/objectives. At current levels the lake can be classified as poorly degraded. Likely sources of pollution were identified to be related to land uses in the catchments. The biota of the lake, investigated at four study sites, yielded a sparse, benthic macrofaunal assemblage that was dominated by oligochaetes. In contrast, an abundant and taxonomically diverse meiofaunal assemblage was noted. Future meiofaunal analyses are likely to resolve suitable biotic indicator species of free‐living nematodes in response to land use and waterway threats specified in the study.

Originality value

This work will provide a better understanding of integrated environmental systems to enable development of best management practices, thus transforming the way the land and water are used in the future. Following the present work, other key water and ecological indicators (increased dispersion and dominance of biological species) at five additional sites were studied. Alternative management options for the effluent generated at Colac Sewage Treatment Plant and possible ecological effects of each option were also evaluated. More recently, a sediment characterization study was also carried out at sensitive sites representative of locations where build up of sediments and algae outbreaks are reported. This will enable classification of sediment and evaluation of dredging options.

Citation

Khalifé, M., Gwyther, J. and Aberton, J. (2005), "Land use, water quality and ecological responses in Lake Colac – trends from Australia", Management of Environmental Quality, Vol. 16 No. 4, pp. 362-379. https://doi.org/10.1108/14777830510601235