A Risk Analysis Approach to Groundwater Quality Management in the Upper Santa Cruz Basin

Abstract

Potential groundwater contaminant sources in the upper Santa Cruz basin include copper mines, irrigated agriculture, and urban wastewater. Risks to human health are posed by groundwater contaminants. Analysis of these risks provides useful information to decision makers for comparing groundwater quality management alternatives. Alternatives include preventing the input of contaminants at their sources, preventing migration of contaminants in groundwater to withdrawal points, removal of contaminants at the points of groundwater withdrawal, relocation of withdrawal points, importation of water, and compensation for those who suffer damages. The framework for risk analysis is composed of hazard identification, hazard estimation, risk estimation, and identification and evaluation of risk response alternatives. Potential contaminants identified range from inorganic ions to complex organic molecules. Hazards have been estimated in terms of fate of potential contaminants in the environment and their toxicity. Risks to groundwater quality and human health in time and space are described with the use of a groundwater contaminant transport model. Because information for the analysis is incomplete, the estimation of risks is not without uncertainties. Major uncertainties remain in data on contaminant concentrations and toxicology of contaminants. The results of the risk estimation, including the uncertainties, may be used to evaluate the groundwater management alternatives.