Ambient Groundwater Monitoring Network Strategies and Design

Abstract

Groundwater quality can be negatively impacted by a variety of physical features and cultural activities that are not always easily discerned by empirical observations. The detection and continued monitoring of groundwater quality constituents and contaminants requires expensive field sampling operations and laboratory analyses. Once deterioration of groundwater quality begins, it may be difficult to reverse, and treating the impacted water can be prohibitively expensive. An ambient network is a proactive strategy that uses groundwater monitoring and characterization along with scientific methods and hydrologic models to assess holistically the groundwater of a given area, usually a defined hydrologic basin. Ambient networks are designed to identify regional changes in groundwater levels and/or degradation of groundwater quality such as occurs from widespread nonpoint sources of pollution or a high density of point sources. Information gleaned from an ambient network includes determining where groundwater levels are fluctuating, locating areas of poor water quality, and identifying spatial and temporal water quality patterns. When correctly designed, the data collected in ambient monitoring programs can be statistically analyzed to make broad statements about the groundwater of a basin that have a known degree of confidence using a relatively small number of investigated sites. Several states such as Arizona and Idaho (1) have redesigned their ambient networks because of subjective, rather than statistical, selection of sites. Others such as Minnesota (2) initiated new ambient networks because the previous design failed to meet objectives.

A Spatiotemporal Characterization of Water Resource Conditions and Demands as Influenced by the Hydrogeologic Framework of the Willcox Groundwater Basin, Southeastern Arizona, USA

“…The stream deposits within the unconsolidated alluvium generally have high permeability and make the unconsolidated alluvium the most productive sequence in the basin fill aquifer system [20]. Contrastingly, the fine-grained lake-bed deposits are highly impermeable and cause locally confined aquifer conditions where it overlays the stream deposits and perched groundwater where it underlies the stream deposits [22]. Near the Willcox Playa, where extensive lake-bed deposits exist, these conditions create an area of shallow groundwater relative to the rest of the regional basin-fill aquifer system [13].…”