A NATIONAL-EXTENT HYDROGEOLOGICAL FRAMEWORK FOR THE UNITED STATES: FIRST STEPS

The U.S. Geological Survey (USGS) Integrated Water Availability Assessments (IWAAs) Program is designed to deliver nationally consistent assessments of water supplies for human and ecological needs, and to identify factors that influence water availability. IWAAs studies are being conducted at regional and national scales. In support of these studies, a National-Extent Hydrogeologic Framework (NEHF) is under development.

A wide range of existing data and tools are relevant to the development of the NEHF. Relevant types of data can include lithologic, structural, stratigraphic, mineralogic, geochemical, and hydraulic properties. Relevant tools can include general purpose geographic information systems and special-purpose three-dimensional visualization and data-manipulation software.

The spatial resolution (lateral and vertical) of the NEHF is intended to be flexible. The framework needed for predicting groundwater contributions – both water and solutes – to streams needs to focus on shallow depths, and needs to account for properties near the water table and in proximity to streams. The framework associated with the human use of groundwater needs to: identify the depth zones tapped by wells for various purposes; account for regional properties relevant to extraction of groundwater by wells; and account for regional properties that affect the suitability of groundwater (water quality) for the intended purpose. The framework related to the potential development of, or impacts from, brackish/saline water needs to focus on deeper groundwater, generally below the depth of most existing water wells. The spatial resolution required would likely be highest for the first example and lowest for the third.

It is anticipated that a broad-brush approach will be implemented at a national-scale and that a comprehensive, detailed approach will be applied in selected regions. It is anticipated that the NEHF will be a “living model” and that approaches and methods developed for assimilating data into selected regions will be useful for future efforts. The NEHF will also include links to sources of information upon which the NEHF is based and to information that could be relevant to future refinements.