, Volume 176, Issue 1, pp 1–5 | Cite as

Social choice, risk and determinism in water quality management

  • Peter Cullen
Water and water science management


In attempting to predict the likely water quality of a lake following some intervention to control nutrient inflow, or in attempting to predict the likely water quality in a proposed new impoundment, it is important to appreciate the probabilistic nature of such predictions. The OECD-Vollenweider models require an estimate of phosphorus inflow to the water body, and these inflows will be partly at least a function of runoff from the catchment. Since the rainfall, and hence runoff varies so much from year to year in climates such as Australia, it seems unwise to base predictions on some average rainfall or runoff value, when the long term average may be experienced only very rarely. A better approach seems to be to look at the range of runoff values, and apply the OECD-Vollenweider model to dry, normal and wet periods, and develop trophic state predictions for each such hydrologic state.

Since water quality is probabilistic, rather than deterministic as implied by the models, then levels of acceptable risk have to be established. Is it acceptable for an impoundment to have a cyanobacteria bloom one year every decade? These are questions of social choice, and require the public to be involved in choosing between the various possible performances of the water body. The trade-off between cost and acceptable water quality is not one that can be made by professionals alone. In such questions of social choice society can expect professionals to assist them to understand the various trade-offs, not to make political choices under the guise of technical analysis.

Key words

Flow regime climate nutrient loadings eutrophication management 


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Copyright information

© Kluwer Academic Publishers 1989

Authors and Affiliations

  • Peter Cullen
    • 1
  1. 1.Canberra CAESchool of Applied ScienceBelconnenAustralia

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