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Scientific Investigations Report 2012–5022

Prepared in cooperation with Cascade Water Alliance

Quality of Water in the White River and Lake Tapps, Pierce County, Washington, May–December 2010

By S.S. Embrey, R.J. Wagner, R.L. Huffman, A.M. Vanderpool-Kimura, and J.R. Foreman

Thumbnail of and link to report PDF (7 MB)Abstract

The White River and Lake Tapps are part of a hydropower system completed in 1911–12. The system begins with a dive rsion dam on the White River that routes a portion of White River water into the southeastern end of Lake Tapps, which functioned as a storage reservoir for power generation. The stored water passed through the hydroelectric facilities at the northwestern end of the lake and returned to the White River through the powerhouse tailrace. Power generation ceased in January 2004, which altered the hydrology of the system by reducing volumes of water diverted out of the river, stored, and released through the powerhouse. This study conducted from May to December 2010 created a set of baseline data collected under a new flow regime for selected reaches of the White River, the White River Canal (Inflow), Lake Tapps Diversion (Tailrace) at the powerhouse, and Lake Tapps.

Three sites, one on the White River at Headworks, one on the White River at R Street, and one on the Tailrace, were equipped for continuous recording of water-quality data, and three sites (Headworks, White River Canal Inflow, and Tailrace) were sampled for discrete water-quality data. Nine lake sites were measured for physical and water‑quality properties and samples were collected for analyses of nutrients, suspended solids, and fecal-coliform bacteria concentrations. Samples from the lake also were analyzed for concentrations of chlorophyll a and organic chemicals.

Discrete samples indicated that water from the White River, White River Canal Inflow, and Tailrace sites generally was turbid, warm, chemically dilute, and well-oxygenated. Exceptions occurred at the sites when flow to the White River Canal was suspended or when little or no flow was released from the lake into the Tailrace. The quality of physical properties and concentrations in water measured continuously at the three sites generally was good and met the freshwater criteria designated by Washington State Department of Ecology for recreational and aquatic-life uses, with several exceptions. The 7-day average of daily maximum temperatures (7–DADMax) was greater than the freshwater aquatic life criterion of 16 degrees Celsius (°C) for core summer salmonid habitat on 6 days at the Headworks site and 37 days at the R-Street site during the study. The 7-DADMax temperatures were greater than the 13°C criterion for spawning, rearing, and incubation on 6 days at the Headworks site and 20 days at the R-Street site. The freshwater aquatic life criterion for dissolved oxygen of 9.5 milligrams per liter (mg/L) for core summer salmonid habitat was not met at the Headworks and R-Street sites for periods during July and August 2010. Exceptions also occurred at the Headworks site for measurements of pH, which were greater than the aquatic life upper limit of 8.5 pH units during July 2010. Aquatic life pH criteria were not met at the Tailrace site during June, July, and August 2010, when pH was greater than 8.5 pH units, and during August 2010 when pH decreased to less than 6.5 pH units.

Lake Tapps water near the surface was relatively clear, warm, and well oxygenated. The clearest water of the nine lake sites was at the Deep site with a median Secchi disk transparency measurement of 6.05 m (meters), which represents a two- to six-fold increase over historical measurements of transparency at this location. Median water temperatures were 18.2–18.9°C and maximums were from 22.9–25.0°C. Median dissolved oxygen concentrations were greater than 8.42 mg/L and minimums generally were not lower than 7.4 mg/L.

By early July 2010, weak thermal stratification developed at most lake sites into at least a warm surface layer overlying a small thermocline. A well-defined hypolimnion developed below the thermocline only at the Deep site. With the development of thermal stratification, hypolimnion water became anoxic at several sites (Deep, Tapps Island, Snag Island, and Lake Outlet). By late September 2010, an anoxic layer about 15 m thick had formed in the hypolimnion of the Deep site. Mixing during autumn overturn in late November re-oxygenated the water column of all the sites with about 10–12 mg/L of dissolved oxygen.

On the basis of pH and specific conductance measurements, Lake Tapps water is pH neutral and chemically dilute. Median pH values for water in the epilimnion and the hypolimnion ranged from 6.84 to 7.64 pH units and maximums did not exceed 7.8 pH units at any site. Median specific conductance was typically less than 70 microsiemens per centimeter at 25°C for the epilimnion and the hypolimnion.

Concentrations of nutrients and chlorophyll a in Lake Tapps were low. At most of the sites and in most of the samples from the epilimnion, total phosphorus concentrations were less than the Washington State Department of Ecology phosphorus criterion of 0.01 mg/L for maintaining oligotrophic conditions. Median concentrations of total nitrogen (unfiltered water) ranged from about 0.14 mg/L (Deep, Tapps Island, and Dike 2B sites) to about 0.18 mg/L (Allan Yorke and Lake Inlet sites). Chlorophyll a concentrations were low with median concentrations of 2.16 micrograms per liter (mg/L) or less. The majority of chlorophyll a concentrations were well below the Oregon Department of Environmental Quality action level of 10 mg/L.

Using the Carlson Trophic-Status Index and average measures of transparency, chlorophyll a, and total phosphorus data from this study, Lake Tapps generally fits within the oligotrophic classification, but with a few exceptions. At Allan Yorke, Lake Inlet, and Southeast Arm sites, the chlorophyll a and total phosphorus indexes of nearly 40 approach the upper limit of oligotrophic conditions. In addition, average concentrations of total phosphorus at Lake Inlet and Southeast Arm are at Nürnberg’s (1996) threshold concentration of 0.01 mg/L, which suggests a slight tendency towards mesotrophic conditions at these two sites during summer July–September.

On the basis of epilimnetic nitrogen to phosphorus concentration ratios of greater than 17, Lake Tapps primary production is phosphorus limited at all but two study sites. At the Lake Inlet and Southeast Arm sites, ratios of 15 and 16, respectively, for the summer period suggest either nitrogen or phosphorus (or both) may limit algal growth.

Water samples collected at the Allan Yorke, Snag Island, and Lake Outlet study sites were screened for the presence of more than 250 organic chemicals. A total of 14 compounds were detected in trace amounts (or determined to be present) at one or more of the 3 sites. The Allan Yorke site had 9 detections, the Snag Island site had 10 detections, and the Lake Outlet site had 5 detections of compounds mostly belonging to the group of wastewater indicator chemicals. Compounds detected (or with verified presence) at all three sites included the herbicide 2,4-D, the insecticide and mosquito repellant DEET, the herbicide fluridone used for Eurasian watermilfoil eradication, and the herbicide prometon. The largest concentrations of these compounds were in samples from the Allan Yorke site; the lowest concentrations were from the Lake Outlet site.

First posted March 2, 2012

For additional information contact:
Director, Washington Water Science Center
U.S. Geological Survey
934 Broadway, Suite 300
Tacoma, Washington 98402

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Suggested citation:

Embrey, S.S., Wagner, R.J., Huffman, R.L., Vanderpool-Kimura, A.M., and Foreman, J.R., 2012, Quality of water in the White River and Lake Tapps, Pierce County, Washington, May–December 2010: U.S. Geological Survey Scientific Investigations Report 2012–5022, 118 p.




Methods and Procedures

Quality Assurance

Environmental and Hydrologic Conditions During the Sample‑Collection Period

Quality of Water in the White River, White River Canal, Lake Tapps Diversion, and Lake Tapps



References Cited

Appendix A. Field Notes and Observations Recorded during Sampling of the Nine Sites on Lake Tapps, Washington, July–December 2010

Appendix B. Parameter Codes, Analytical Methods, and Reporting Levels for Analytes in National Water Quality Laboratory Schedule 1865 (Nutrients) and Schedule 1637 (Chlorophyll a and Pheophytin a)

Appendix C. Parameter Codes and Reporting Levels for Organic-Compound Analytes in National Water Quality Laboratory Schedule 2033 (Moderate-Use Pesticides), Schedule 2060 (Polar Pesticides), Schedule 1433 (Wastewater Indicators), Schedule 2080 (Human-Health Pharmaceuticals), and Lab Code 8144 (Human-Health Pharmaceuticals)

Appendix D. Analytical Results for Quality-Control Samples Collected at White River at Headworks, White River Canal, Lake Tapps Diversion, and Lake Tapps, Washington Study Sites, July–December 2010

Appendix E. Seven-Day Average of Daily Maximum Temperatures on the White River at Headworks, White River at R Street, and Lake Tapps Diversion (Tailrace), Washington, May–December 2010

Appendix F. Vertical Profiles of Water-Quality Properties with Depth for Selected Sampling Dates at Nine Sites on Lake Tapps, Washington

Appendix G. Pesticides, Wastewater Indicator Chemicals, and Human-Health Pharmaceuticals in Samples from Allan Yorke (map No. L2), Snag Island (map No. L5), and Lake Outlet (map No. L8) Study Sites on Lake Tapps, Washington, September 2010

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