Risk based decision tool for managing and protecting groundwater resources

[摘要] English: The limited number of water resources in South Africa has resulted in increasedemphasis being placed on groundwater. Groundwater supply of acceptable qualityand quantity is a very important factor in the development of communities. Theavailability of water for various uses is directly related to the management of waterquantity, quality and/or elimination of diseases.A risk can be defined as the probability that an adverse event will occur underspecified circumstances. Effective decision-making involves the management ofrisks: the identification, evaluation, selection and implementation of actions to reducerisk.The aim of the research discussed in this thesis is to develop a decision tool to aidgroundwater resource managers in the task of optimising the utilisation ofgroundwater. The decision tool will include:�?Information concerning aquifer parameters: Pumping test analysis methods havebeen developed primarily to investigate and characterise flow within idealisedconfined radial flow systems. Unfortunately these assumptions are usually invalidwith regard to the shallow fractured rock aquifers in South Africa. Notableattempts have been made to expand pumping test methodologies. A worthwhilemethod to consider when analysing a pumping test was developed by Barker(1988), where he generalised the Theis equation by including a term called thenon-integer flow dimension, thereby making it applicable to arbitrary fracturedconfined aquifers.�?Information concerning contaminant parameters: Dispersivity is a scaledependentproperty of an aquifer that determines the degree to which a dissolvedconstituent will spread in flowing groundwater. No in-depth investigation wasconducted concerning this parameter, but as it plays an important role in themovement of contaminated groundwater, it is briefly discussed.Although matrix diffusion can influence groundwater contamination, very littleresearch has been conducted in South Africa on this topic. The project therefore includes laboratory matrix diffusion experiments. The results of theseexperiments are included in the decision tool.�?A framework for risk assessments: the project introduces tools based on fuzzy logic to assist in decision-making by systematically considering all possibilities. This tool takes into account the sustainability of a groundwater resource, thepotential contamination of groundwater, human health risks and impacts ofchanges in groundwater (quantity and/or quality) on aquatic ecosystems.�?Methods to make cost-effective decisions: Negative impacts can place heavyburdens on society and economics. Cost-benefit-risk assessments are thereforeconsidered to define, compare and measure benefits and costs with regards to animpact.�?Possibilities of remediation: Remediation forms an important component of manygroundwater investigations and a few experiments were therefore conducted, theresults, of which were included in the decision tool. The results provide the groundwater manager with an indication of the possible success of a remediationproject.

[发布机构] University of the Free State