Oregon Water Science Center Hydrologic Studies

USGS Collection of Basic Ground-Water Records in Oregon

Contact: Dan Polette

LOCATION: Willamette, Deschutes, and Rogue Basins

BACKGROUND

The Oregon Water Science Center Collection of Basic Records (CBR) index well network is part of a national network of wells designed to monitor water-level fluctuations in response to climatic changes. This network is useful for:

• Placing data collected during short-term projects in long-term climatic perspective,
• Providing a current index to drought conditions,
• Making long-term estimates of natural recharge and its temporal variability, and
• Removing climatic effects from water-level records affected by human-induced changes.

APPROACH

A list of 17 index-well candidates was submitted to the USGS Western Region Ground-Water Specialist in May 1997. These candidates were selected with the assistance of several USGS and Oregon Water Resources Department (OWRD) colleagues with special knowledge of the hydrogeology of different parts of the State. The candidate wells were selected on the basis of the following criteria:

• Open to a single, known hydrogeologic unit,
• Known well construction,
• Located in unconfined aquifers or near-surface aquifers that respond to climatic fluctuations,
• Essentially unaffected by nearby pumping and likely to remain so,
• Long-term accessibility,
• Not susceptible to going dry,
• Representative of a broad area,
• Existence of previous records, and
• Existence of lithologic or geophysical logs.

The cost of operating a statewide network is not feasible in the current funding environment. Therefore, the proposed wells were selected in areas where ground-water issues are of concern (intense ground-water development and urgent resource-management questions). These areas are coincident with USGS ground-water studies in the upper Deschutes Basin, the Willamette Basin, and the Rogue Basin. The wells are completed in a variety of geologic units and reflect a wide range of climatic conditions.

The Office of Ground Water selected 6 of the 17 candidates to be included in the Oregon CBR. The Oregon Water Resources Department (OWRD) measures two of the wells on a quarterly basis. USGS personnel also measure the wells quarterly, but approximately 45 days after the OWRD has measured the wells; therefore, they will be measured approximately eight times per year. The remaining wells are measured by the USGS. One well is measured bimonthly. The other wells have continuous recorders installed.

Water-level measurements are recorded to the nearest 0.01 foot. For quality assurance, two successive measurements must be within 0.01 ft before the measurement is recorded. Measurement equipment (steel and e-tapes) is frequently checked for accuracy and designated only for use with the CBR index well network. Measurements are entered into the USGS National Water Information System (NWIS) data base.

Hydrographs of water levels in wells of the CBR index-well network, as well as tables of the measurements used to construct the hydrographs, are available online through the link below. The information is accessible through an interactive map that shows the locations of the observation wells. Clicking on the well symbol will generate a period-of-record water-level hydrograph for that well, as well as a link to a table of water-level measurement data for the well. Alternately, there is a list of basin wells below the basin maps with links to hydrographs (PNG, JPG, and GIF formats) and data tables (TXT files).

Download CBR water-level hydrographs and data.