2002 Denver Annual Meeting (October 27-30, 2002)

Paper No. 6
Presentation Time: 1:30 PM-5:30 PM


KENNEDY, John F.1, CLEARY, Michael1 and HAWLEY, John W.2, (1)Water Resources Research Institute, New Mexico State Univ, Box 30001, MSC 3167, Stucky Hall, Las Cruces, NM 88003-8001, (2)NM Water Resources Research Institute, New Mexico State Univ, PO BOX 30001, MSC 3167, Las Cruces, NM 88003-8001, jkennedy@nmsu.edu

The NM Water Resources Research Institute (NMWRRI) in cooperation with governmental and academic entities has recently developed GIS coverages that combine hydrogeologic data on basin-fill aquifers in the International Boundary region of southwestern New Mexico. The use of GIS technology allows for the integration of surface and subsurface data, which can be used in numerical groundwater-flow modelling and geochemical-system interpretations, to create a 3-D representation of the groundwater basin. Emphasis of recent work is on the Mesilla Basin area, which includes the heavily urbanized, Las Cruces-El Paso-Ciudad Juarez reach of the Rio Grande Valley in New Mexico, Texas, and Chihuahua (est. pop. ~2 million).

GIS coverages were created using ESRI ArcInfo® and ERDAS Imagine® software. Surface geology maps for the region where digitized using ArcInfo 8.0 on a UNIX platform and cartographically and spatially corrected using satellite and aerial imagery on a Dell® Workstation running Windows 2000 Professional and ArcGIS 8. Basemap data was acquired in digital form from the USGS. Selected borehole geophysical logs, with known geographic coordinates, where scanned into digital form using Adobe PhotoShop 6® and digitized using Adobe Illustrator 9®. The digitized logs were used to create geologic cross-sections for the basin.

The classification of mapping units for the surface and sub-surface geology was modified within the GIS to create a hydrogeologic framework model for the basin. The basin-fill hydrogeologic framework is defined on the basis of (1) composition of lithofacies assemblages (LFAs), which are organized into hydrostratigraphic units (HSUs), and (2) the nature of basin-boundary and intra-basin structural controls. Major aquifers are formed by coarser-grained LFAs associated with the ancestral Rio Grande fluvial systems. These poorly consolidated units are informal subdivisions of the Plio-Pleistocene upper Santa Fe Group and overlying valley- and basin fill. The HSUs are assigned a numerical value and this information is added to the GIS. The HSUs are matched with geologic mapping units, with some units being merged based on the HSU value, to create surface and sub-subsurface hydrogeologic maps.