U.S. Geological Survey

Oregon District Active Projects

OR156 Ground-Water Resources Evaluation of Jackson County, Oregon

Study area

PROJECT CHIEF: Leonard L. Orzol

LOCATION:Jackson County, Southwestern Oregon

PROJECT EXTENT:Jackson County

TOTAL AREA IN SQUARE MILES: 2,800

PROBLEM

Jackson County is one of the fastest growing areas in Oregon. Its natural beauty and mild climate have promoted the development of many small (2 to 10 acre) ranches; the area is gaining a reputation as a high-quality retirement community, and the county is predicting 100,000 new residents by the year 2000. Ground water is the principal source of domestic water for the ranches. Continued growth and development will depend, in part, on the continued availability and potability of Jackson County's ground-water resources. According to planners and concerned citizens, two major ground-water problems presently exist: (1) poor ground-water quality and (2) inadequate ground-water supply. An additional problem is the lack of data and information regarding the distribution and source of contaminants or harmful trace elements. Well density in some parts of the county is very high and increasing; in some locations deep, narrow cones of depression occur each year during the dry season. However, very little data exist to determine whether long-term water- level declines are taking place or if the aquifers fully recover during the winter recharge season.

OBJECTIVE

We will select wells for an observation well network to define and document natural and anthropogenic changes in ground-water levels in the major aquifers. We will complete the basinwide ground-water study begun in the 1970's to gain an understanding of the regional ground-water flow system. And finally, based on the data and interpretations available from work done to satisfy these first two objectives, we will design a long-term study which will quantify the ground-water and surface-water resources and water quality to the extent needed for proper management of the system.

APPROACH

The sites composing the observation well network will be selected using available maps of 1978 well density. These wells will be inventoried and about 45 will be selected for measurement and sampling every two months until February-March 1990. These and historic data will be used to describe the general year-to-year changes in water levels. To assess the regional flow system we will map the thickness of the alluvial aquifer and general distribution of other aquifer units and their lithologic makeup. We will prepare a water table map and, if feasible, a water-level change map during 1988-90. We will gather ground-water quality data to aid in describing the horizontal and vertical distribution of mineralized water in each of the principal aquifer units. Data and interpretations will be used to write a proposal for future work to quantify the ground-water flow system to the extent needed for future purposes.

PROGRESS AND SIGNIFICANT RESULTS

Maps of the thickness, extent, and elevation of the major geological units have been processed into ARC/INFO coverages. Preliminary geologic plates (for proposed map report) have been processed and presented to the Jackson County Commissioners. All water-level measurements for the monitoring well network (about 40 wells) have been entered into the GWSI data base for the years 1990 to 1992.

A summary of the water levels in the observation well network were presented to the public and members of Ground-Water Advisory Committee of Jackson County. Progress of the proposed expansion of the well network was discussed. The USGS has been measuring 80 wells (sites) since June 1994 (ahead of schedule).

PLANS FOR FISCAL YEAR 1995

Create review copies of the geologic plates (for five coverages) and begin the review process. Well monitoring for the network of 40 wells will continue and the data will be entered in the GWSI data base. Well water quality has already been collected for Jackson County wells. A search will be conducted into the QWDATA data base and missing water quality will be added. Finally, an outline or work plan to publish the collected data (water level and water quality) will be developed. Two additional objectives are incorporated into this project:
1. Do a preliminary inventory of water use for the County using available data from the State and Jackson County, and
2. Help design and populate a GIS data base that includes data from USGS and other sources.
Continue measuring 80 wells (sites) every two months and record measurements into the GWSI data base. Meet with the County Commissioners to summarize water levels in the observation well network sometime in early 1995.

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Last modified: Thu Jun 29 08:43:15 1995