Abstract

Hydrographs of groundwater levels for selected wells in and adjacent to the Puyallup River watershed in Pierce and King Counties, Washington, are presented using an interactive Web-based map of the study area to illustrate changes in groundwater levels on a monthly and seasonal basis. The interactive map displays well locations that link to the hydrographs, which in turn link to the U.S. Geological Survey National Water Information System, Groundwater Site Inventory System.

Introduction

Data presented in this report are part of a larger study (http://wa.water.usgs.gov/projects/puyallupgw/), which began in February 2011 as a cooperative effort of the U.S. Geological Survey (USGS), Pierce County Conservation District, City of Tacoma, Cascade Water Alliance, area public water suppliers, and the Washington State Department of Health. The groundwater levels presented in this report are an important component in the development of an improved understanding of the groundwater-flow system in the Puyallup River watershed (PRW) study area in Pierce and King Counties, Washington (fig. 1) and its relation to surface-water resources.

Purpose and Scope

This report presents groundwater hydrographs for 169 wells from a monitoring network established by the USGS in and adjacent to the PRW. Groundwater levels were measured monthly from March 2011 through March 2013, to provide information on the groundwater-flow system and its relation to surface-water resources. Water level measurements at 129 wells were made by personnel of the USGS Washington Water Science Center using standard USGS field techniques as described by Kozar and Kahle (2013). Water levels at the remaining 40 wells were measured by various cooperators using compatible techniques.

Well-Numbering System

The USGS identifies wells in Washington State by a unique local well number that defines the location of each well within the Public Land Survey rectangular grid system for the state (fig. 2). For example, in well number 20N/04E-14B01, the ‘20N/04E’ indicates the township (20N) north of the Willamette Base Line and the range (04E) east of the Willamette Meridian. The number following the hyphen (14) indicates the section number within the township. Most range-townships in Washington are divided into 36 equal sections of 1 mi² (640 acres) numbered from 1–36. However, the Washington Territory Donation Land Claims of 1852–55 predate the Public Lands Survey and appear on maps as irregularly sized and shaped sections with assigned section numbers greater than 36. The letter following the section number (B) indicates the 40-acre subdivision (quarter-quarter) of the section, and the number following the letter (01) is a sequence number used by USGS to differentiate multiple wells in that 40-acre tract. Local numbers for deepened wells includes a ‘D1’ designation following the sequence number.

An additional unique 15-digit site identification number based on the approximate latitude and longitude of the site and a sequence number identifies wells entered into the USGS Groundwater Site Inventory System (GWSI) database. Additional detailed information about the assignment of site identification numbers is available in Lane (2007).

Well Locations and Hydrographs

All 169 wells in the PRW monitoring network are listed in table 1 and are displayed on the interactive map image of the study area at http://wa.water.usgs.gov/projects/puyallupgw/hydrographs.htm. Users can zoom in on the map image using the buttons in the upper-left corner of the image or by double-clicking the mouse within the image. A single click-and-hold on the mouse allows the user to pan the map image horizontally and vertically. Holding the cursor over a plotted well site opens a message box that displays the local well number. Clicking once on the well site opens a window containing the local well number, site id, altitude of the well, and a hydrograph of project groundwater levels collected at the selected site. Well sites also can be selected by clicking on a local well number in the drop-down list displayed above the upper-left corner of the map image.

The hydrographs accessed through the interactive map display groundwater levels measured between March 1, 2011, and March 31, 2013. The horizontal axis of the hydrograph indicates the date of the measurement and the left vertical axis indicates the groundwater levels in feet below land surface. Groundwater levels preceded by a minus sign are above the land surface. The scales on the vertical-axis vary according to the data range. The “View Additional Information” link below the hydrograph connects users to a corresponding Web page in the U.S. Geological Survey National Water Information System (NWIS), for access to a table or graph of all groundwater levels for the site.

Groundwater Levels and Changes

Several factors can influence how groundwater levels can change over time: recharge to the system, withdrawals from the system, and the hydrologic characteristics of the groundwater system. Periods of wet or dry conditions may result in groundwater-level rises and declines, respectively, as the amount of water stored in an aquifer responds to recharge and subsequent discharge over time. An increase in water withdrawn from the system may cause groundwater levels to decline, whereas a decrease in withdrawals may cause groundwater levels to rise. The amount of time required for groundwater levels to respond to these changes depends on the hydrologic characteristics of the system and may vary significantly in different parts of the groundwater system.

Acknowledgments

The authors wish to thank the many well owners in the study area for their cooperation in providing access to wells, and the Washington State Department of Ecology and public water suppliers in the study area for providing assistance in the compilation of well information.

References Cited

Kozar, M.D., and Kahle, S.C., 2013, Quality-assurance plan for groundwater activities, U.S. Geological Survey, Washington Water Science Center: U.S. Geological Survey Open-File Report 2013-1151, 88 p. (Also available at https://pubs.usgs.gov/ofr/2013/1151/.)

Lane, R.C., 2007, Guidelines for coding and entering ground-water data into the ground-water site inventory database version 4.6, U.S. Geological Survey, Washington Water Science Center: U.S. Geological Survey Open-File Report 2006-1371, 104 p. (Also available at https://pubs.usgs.gov/of/2006/1371/.)