Principal Aquifer Susceptibility Study

The principal aquifer study will use regional ground-water MODFLOW models and particle-tracking predictions to estimate travel time from the water table to aquifer zones in selected principal aquifers. Zones may be related to the physical aspects of the region, such as a stream network, mountain front area, or vertical sub-section of an aquifer. Zones may also be defined by anthropogenic factors, such as regions with domestic wells or public-supply wells. The examination of zones will yield a comparatively broad, aquifer-based analysis of susceptibility that will be useful to stakeholders in making water-management decisions

Map showing Principal Aquifers.

This is a pilot study that is intended to establish a framework for evaluating susceptibility in principal aquifers. Evaluating age distributions using particle travel times is a starting point for understanding the susceptibility of aquifers and will be the starting point of this study. Any attempt to predict sources of water in an aquifer (e.g., areas of agricultural land use vs. urban land use) is sensitive to the amount of geologic heterogeneity that is represented in a model. To account for some of the uncertainty in model predictions caused by the absence of geologic heterogeneity in a model and our uncertainty of its structure, transport porosity will be varied in a group of particle tracking simulations for each groundwater model and all of the results will be evaluated collectively. Age distributions of particle advection will be evaluated for each aquifer zone using the group of results.

Publications
	Professional Paper 1737-A Hydrogeologic Settings and Ground-Water Flow Simulations for Regional Studies of the Transport of Anthropogenic and Natural Contaminants to Public-Supply Wells -- Studies Begun in 2001, edited by Suzanne S. Paschke