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Data Series 343

Data Series 343
April, 2008

Hydrographs Showing Ground-Water Level Trends for Selected Wells in the Yakima River Basin Aquifer System, Washington

Prepared in cooperation with the
Bureau of Reclamation, Washington State Department of Ecology, and the Yakima Nation

By M.E. Keys, J.J. Vaccaro, M.A. Jones, and R.J. Julich

Conversion Factors

Multiply By To obtain
acre 0.4047 hectare (ha)
acre 0.004047 square kilometer (km2)
foot (ft) 0.3048 meter (m)
mile (mi) 1.609 kilometer (km)
section (640 acres or 1 square mile) 259.0 square hectometer (hm2)
square mile (mi2) 259.0 hectare (ha)
square mile (mi2) 2.590 square kilometer (km2)


Selected ground-water level hydrographs for the Yakima River basin aquifer system, Washington, are presented in an interactive web-based map to illustrate the existence or lack of trends in ground-water levels and, thus, potential variations in ground-water availability in the area. Hydrographs are linked to points corresponding to the well location on an interactive map of the study area. Ground-water level data and well information from Federal, State, and local agencies were obtained from the U.S. Geological Survey National Water Information System. Selected data points were excluded from hydrographs to emphasize long-term term trends over short-term effects of human activity (such as pumping a well) and seasonal fluctuations in ground-water levels.


This report is part of a larger study, which began in June 2000, as a cooperative effort of the U.S. Geological Survey (USGS), Bureau of Reclamation, Washington State Department of Ecology (WaDOE), and the Yakama Nation (Jones and others, 2006). The purpose of the study was to develop a better understanding of the ground-water flow system, and its relation to surface-water resources in the Yakima River basin, Washington (fig. 1).

The USGS has been investigating ground-water availability in the Yakima River basin since the early part of the 20th century. During this time, the use of ground water has evolved from limited domestic and stock-water needs into more complex, modern requirements such as public-water supplies, large irrigation projects, and industrial plants. The measurement of ground-water levels has been an important component in determining ground-water availability and understanding the ground-water flow system.

Purpose and Scope

This report presents more than 220 long-term hydrographs of wells in the Yakima River basin (Jones and others, 2006). These hydrographs can be used as a general tool to identify potential water-level variations or trends and to understand how ground-water availability may be changing over time.

Well-Numbering System

The USGS assigns numbers to wells and springs in Washington that identify their locations in a township, range, and section (fig. 2). For example, given the well number 20N/15E-26N01, ‘20N/15E’ indicates the township (20 N) and the range (15 E) north of the Willamette baseline and east of the Willamette meridian, respectively. The first number following the hyphen indicates the section number, 26, within the township (where townships are divided into 36 square-mile sections). The letter following the section number, N, indicates the 40-acre subdivision of the section, as shown in figure 2, and the number following that letter, 01, is the sequence number of the well within the 40-acre subdivision. A ‘D1’ after the sequence number indicates that the original reported depth of the well has been changed; the number indicates how many times the well depth has been changed. A ‘P1’ or an ‘A’ after the sequence number indicates a group of nested piezometers, with successive numbers or letters assigned to each piezometer in the group. An ‘R’ following the sequence number indicates that the well has been reconditioned. An ‘S’ following the sequence number indicates that the site is a spring.

Ground-Water Level Data and Well Information

The USGS National Water Information System (NWIS) contains ground-water level measurement data and well information for about 10,500 wells in the Yakima River basin. The water-level data represent a combination of USGS measurements and reported information from Federal, State, and local agencies, the Yakama Nation, well drillers, and numerous private and public organizations. These data have been collected and entered for a wide variety of projects and purposes over many years. Well information for many of these and other ground-water sites in Washington also is available from the WaDOE Well Log database (Washington State Department of Ecology, 2003).

Although NWIS has accurate information for many wells (especially those visited in recent studies), some problems are known to exist for older entries. Examples of these problems include, but are not limited to, inaccurate well locations, outdated water usage information, and incorrect well-installation dates. Many wells in the database were not field visited, so information was entered into the database based on well drillers’ reports and general location information; therefore, the resulting database varies in quality and detail.

Some water levels contained in NWIS for the Yakima River basin were input during the study that began in June 2000. Data input during that study was obtained from (1) older USGS reports and field notes, (2) USGS measurements made between 2000 and 2002, (3) the WaDOE, (4) the Bureau of Reclamation, and (5) the Yakama Nation.

For this report, more than 220 Yakima River basin wells with water-level measurements spanning at least 10 years were selected from NWIS for inclusion on the website. Some wells with shorter records also were selected to represent areas or hydrogeologic units where longer periods of record were not available. When possible, wells were selected that had been measured between the mid-1990s and early 2000s when the USGS, WaDOE, Bureau of Reclamation, and the Yakama Nation were making measurements. Wells also were selected to represent a reasonable spatial distribution for the aquifer system.

Not all water-level measurements available in NWIS for a particular well may be presented on the hydrographs. For example, if most water levels for a given well were from spring months and only a few were from autumn, the autumn measurements were not included in order to emphasize the visual display of long-term trends over seasonal fluctuations. Preference was given to water levels measured during February through May because they are less affected by human activities. Similarly, water-level measurements made while the well was being pumped, as well as water-level measurements made soon after pumping, generally were not included.

Well Hydrographs

Well locations are plotted on an interactive image of the study area using Google™ Maps ( The image can be manipulated by clicking-and-dragging with the mouse to pan and double-clicking to zoom in. Alternatively, panning and zooming can be controlled with the buttons in the upper-left corner of the image. The user can hold the cursor over a well point to see a message box appear with the township-range number for that well, and click on the point to see the corresponding hydrograph and selected well information.

Each hydrograph is hyperlinked to a point on a map image corresponding to the well’s location. For each hydrograph, the well number, depth, and type of deposit in which the well is finished are indicated. The x-axis shows time and the y-axis shows depth-to-water, in feet below land surface. The y-axis is formatted with larger values on the bottom and smaller values on top, so the reader can visualize water-levels rising or declining along data points on the hydrographs. For example, if the depth-to-water values increase over time for a given well, then, visually, successive data points move downward over time on the corresponding hydrograph. Negative depth-to-water values indicate that the water level was above land surface during that measurement. Such water levels may have been measured directly or inferred from a water-pressure reading.

Ground-Water Level Trends

The hydrograph periods of record vary, so the total decline or rise in water level over the period of record may vary for wells with identical trends. For example, a well with a 20-year period of record of water levels showing a total decline of 80 feet indicates a declining trend of 4 feet per year. Likewise, a nearby well in the same unit with a 50-year period of record might show a total water-level decline of 200 feet also indicating a declining trend of 4 feet per year.

As can be seen by examining the hydrographs on the web site, rising, declining, and neutral trends in water levels were evident for different regions and hydrogeologic units in the Yakima River basin aquifer system. An improved understanding of human and natural factors controlling these water-level trends is a primary objective for the larger Yakima River basin aquifer system investigation.


The authors wish to thank the many municipal public-water suppliers, irrigators, and industrial well owners for their cooperation in providing access to their records. The authors also thank the Washington State Department of Ecology (Central Regional Office) and the Yakama Nation who provided historical measurements, without which the presentation of long-term hydrographs would not have been possible.

References Cited

Jones, M.A., Vaccaro, J.J., and Watkins, A.M., 2006, Hydrogeologic framework of sedimentary deposits in six structural basins, Yakima River Basin, Washington: U.S. Geological Survey Scientific Investigations Report 2006-5116, 24 p., 6 pls.

Washington State Department of Ecology, 2003, Well logs—Washington State well log viewer: Washington State Department of Ecology, accessed April 16, 2008, at

Send questions or comments about this report to the first author, M.E. Keys, (253) 552-1699.

For more information about USGS activities in Washington, visit the USGS Washington Water Science Center home page.

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