This text is a review of the progress made in the field of groundwater over the last few decades of the 20th century. It also considers the challenges of the future. Topics covered are: determination of aquifer parameters, resource assessment/evaluation; groundwater modelling and water well issues; chemical and isotopic characterization of groundwater; groundwater pollution, vulnerability and remediation; integrated water resources management; groundwater and mining, geotechnical and construction issues. The papers covers a wide range of groundwater issues, and should be of interest to practising professionals and graduate students in hydrological and environmental science, and to engineers and planners responsible for the development and management of groundwater resources.