Alternative water supply, storage, and treatment (AWSST) systems, which utilize aquifers to supply, store, and naturally treat water, are increasingly being implemented globally to address water scarcity and safety. The failure of some AWSST systems to meet water quality expectations was caused by conceptual model error, in which local hydrogeological conditions were less favorable than recognized or considered during project feasibility assessments, economic analyses, and design. More successful implementation of AWSST projects requires that conceptual model error be explicitly and rigorously addressed. Recommended approaches to addressing conceptual model uncertainty include more detailed aquifer characterization, recognition of a wide suite of possible alternative conceptual models, and then screening the models as to whether or not they are plausible and relevant in terms of materially impacting predictive results. Subjective professional judgement remains the basis for assigning probabilities to relevant conceptual models (contingencies).
© 2016, National Ground Water Association.