Toward a Sustainable Management Concept for Coastal and Island Aquifers
Toward a Sustainable Management Concept for Coastal and Island Aquifers
Presented on Tuesday, December 3, 2019
Despite widespread acknowledgement of the “paradox of safe yield” among groundwater hydrologists, there nevertheless remains a need to give practical answers—including “hard numbers”—to managers, planners, and regulators of groundwater resources, who must deal with the fundamental question, “How much water can safely be drawn from this aquifer?” Coastal and island aquifers present a particular challenge because while the volume of water that can be withdrawn is unlimited, the salinity of the water increases as more water is withdrawn. Production potential is thus limited by both rate of replacement of the fresh water component and the rate of decline in water quality. Limiting variables include the rate of recharge, the extent of natural and induced freshwater-saltwater mixing within the aquifer, the spatial variability of water quality across the part of the aquifer accessible for development, available production techniques, and the acceptable limits on product salinity for specified uses. This presentation describes our efforts to develop a methodological approach for evaluating sustainable limits for drinking-water production in coastal-island aquifers. We propose the heuristic application of classical economic models applied to the harvesting of natural resources such as petroleum reservoirs, mineral deposits, fisheries, and forests, in which quality of the raw material declines—and production costs, for any given technology, increase—as extraction increases. Supporting concepts are examined, including alternative production technologies, best-practice production systems, and ultimate natural limits for renewable resources. The proposed paradigm provides a rational approach for providing useful answers to policy-makers and water resources managers who need to know what the practical limits are to the production of drinking water from a given coastal-island aquifer. Attention is also given to the complementary management of both supply and demand for assessing and meeting the needs of a given community.
John Jenson, PhD
Water & Environmental Research Institute of the Western Pacific, University of Guam
Dr Jenson is Professor of Groundwater Hydrology, and Director of the University of Guam's Water & Environmental Research Institute of the Western Pacific (WERI). His current research interests include development of the Carbonate Island Karst Model and its application to numerical modeling and sustainable management of island karst aquifers.
Nathan Habana, PhD
Water & Environmental Research Institute of the Western Pacific, University of Guam, Mangilao, Guam
Dr Habana is Assistant Professor of Groundwater Hydrology at the University of Guam's Water & Environmental Research Institute of the Western Pacific (WERI). His duties at WERI include serving as Coordinator for the Guam Hydrologic Survey Program, which compiles and analyzes basic data on Guam’s freshwater resources. His current research interests include modeling of vadose and phreatic transport, and the management of salinity and nitrate contamination in island aquifers.