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Coeur d’Alene Basin Environmental Monitoring Program - Surface Water

Annual Data Summary – Water Year 2018

Photographs: South Fork Coeur d’Alene River above Pine Creek near Pinehurst, Idaho , USGS site

number 12413355, September 2018. Photograph taken by Lauren Zinsser .

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.

Coeur d’Alene Basin Environmental Monitoring Program - Surface Water Lauren Zinsser, Hydrologist, USGS Idaho Water Science Center

Overview

The United States Geological Survey (USGS) operates and maintains twelve real-time stream gaging sites

and collects surface water quality samples two to four times annually at twenty monitoring sites (Figure

1) in the Spokane and Coeur d’Alene River basins (Clark and Perreault, 2017). This work is conducted in

cooperation with the United States Environmental Protection Agency (EPA) to support the Coeur

d’Alene Basin Environmental Monitoring Program (BEMP) (U.S. Environmental Protection Agency, 2002;

2012).

The Coeur d’Alene River extends across Idaho from the Montana border on the east to the Washington

border on the west. Streams within the basin have been extensively affected by historic mining activities

and are subject to ongoing remedial actions. The Coeur d’Alene River basin is mountainous, with

elevations ranging from 2,000 to 6,850 feet. About 70 percent of the annual precipitation falls as snow

during the winter (October through April), and the highest streamflows and metal loads normally occur

during spring runoff. However, warm winter Pacific storms can affect the area, bringing heavy rains and

warm temperatures that can cause rapid snowmelt and produce high streamflow rain-on-snow events.

These events can be associated with high transport of sediment and sediment-bound trace metals. In

contrast, the lowest streamflows and highest dissolved metal concentrations typically occur during

September and October (Clark and Mebane, 2014).

Selected streamflow and water quality results from the water year 2018 surface water BEMP are

presented herein. Additional water quality and streamflow data are available in the USGS National

Water Information System database, http://waterdata.usgs.gov/nwis (U.S. Geological Survey, 2019).

Highlights from water year 2018 include the following:

• Peak streamflows occurred during spring snowmelt runoff in May.

• Sampling during a February 2018 rain-on-snow event captured high total lead concentrations in

South Fork Coeur d’Alene River sites, similar to or higher than total lead concentrations

measured from 2008-2017.

• Comparisons between water year 2018 and 2008-2017 concentrations showed decreases in the

range of measured dissolved zinc and cadmium concentrations in Ninemile Creek and in the

Coeur d’Alene River near Harrison. For Ninemile Creek, this decrease likely reflects the effects of

recent, extensive upstream remediation activities. The cause of the decreases in the Coeur

d’Alene River near Harrison is unclear.

http://waterdata.usgs.gov/nwis


Figure 1. Sampling sites in the Coeur d'Alene and Spokane River Basins


Observations

Water year 2018 was characterized by several high streamflow events. Precipitation in late December

2017 caused a brief increase in streamflow. Figure 2 shows median streamflow for the streamflow

period of record and water year 2018 streamflow at continuously gaged sites in the basin. A rain-on-

snow event in early February 2018 caused streamflows to increase sharply. In water year 2018, the

maximum daily streamflow recorded in the Coeur d’Alene River at Cataldo (site 12413500) was 15,800

cfs on May 8 and occurred during spring snowmelt runoff; the maximum 15-minute streamflow

recorded at this site was 17,700 cfs on the same day. Spring snowmelt runoff throughout the basin

occurred at the same time as median runoff but was somewhat higher than median runoff at most sites

(Figure 2). The main exception was the Spokane River near the lake outlet (site 12417650) which

experienced later runoff flows than median runoff; these streamflows were likely affected by

downstream dam release operations. Spring snowmelt runoff in water year 2018 dropped off more

quickly than the median recession, indicating more rapid snowmelt and runoff than usual. Summer

baseflows throughout the basin were similar in magnitude and timing to median baseflows (Figure 2).

Figure 2. Water year 2018 streamflow at BEMP sites with continuous gaging. Colored lines show water year 2018 daily mean streamflow. Black lines show the median daily streamflow for the available streamflow period of record, which varies by site. NF, North Fork; SF, South Fork; CDR, Coeur d’Alene River. Note the vertical axis scale varies by plot.


Figures 3 through 5 show selected water year 2018 water quality results (total lead, dissolved zinc and

cadmium) visually compared to results from the previous ten years (2008-2017). Total lead did not have

consistent trends throughout the basin in water year 2018 (Figure 3). Based on visual comparison,

measured total lead at most South Fork Coeur d’Alene River sites in water year 2018 occurred across the

full range of concentrations previously measured and had somewhat higher median values. This was

driven by high total lead concentrations measured during the February rain-on-snow event. However, in

most Coeur d’Alene River sites, median water year 2018 values were similar to 2008-2017 medians.

Tributary comparisons varied, with some water year 2018 medians and ranges lower and others higher

than previous values. North Fork Coeur d’Alene River, St. Joe River and Spokane River concentrations

were similar to past measurements (Figure 3).

Figure 3. Total lead concentrations at BEMP sites in water year 2018 versus 2008-2017. Note the vertical axis scale is logarithmic

and varies by plot. NF, North Fork; SF, South Fork; CDR, Coeur d’Alene River.


Based on visual comparison, median dissolved zinc was lower in water year 2018 than in 2008-2017 in

the South Fork Coeur d’Alene River near Mullan, at several tributaries (Government Gulch, Pine Creek,

Milo Creek, seeps north of tailings), in the Coeur d’Alene River near Harrison, and in the Spokane River

at lake outlet (Figure 4). The range of measured concentrations for dissolved zinc was lower in water

year 2018 than for 2008-2017 in Ninemile Creek and in the South Fork Coeur d’Alene River at Kellogg,

and higher in the North Fork Coeur d’Alene River at Enaville. Median dissolved zinc in water year 2018

was higher than in previous years in Bunker Creek and in the Coeur d’Alene River near Rose Lake.

Generally, water year 2018 medians and ranges for dissolved zinc at the rest of the sites were similar to

previous values (Figure 4).

Figure 4. Dissolved zinc concentrations at BEMP sites in water 2018 versus 2008-2017. Note the vertical axis scale varies by plot. NF, North Fork; SF, South Fork; CDR, Coeur d’Alene River.


Based on visual comparison, median dissolved cadmium was lower in water year 2018 than in 2008-

2017 in several tributaries (Government Gulch, Pine Creek, Milo Creek), in the Coeur d’Alene River near

Harrison, and in the Spokane River at lake outlet (Figure 5). The range of measured concentrations for

dissolved cadmium was lower in water year 2018 than for 2008-2017 in Ninemile Creek and in South

Fork Coeur d’Alene River at Elizabeth Park and Kellogg. Median dissolved cadmium in water year 2018

was higher than in previous years in Bunker Creek and in the Coeur d’Alene River near Rose Lake.

Generally, water year 2018 medians and ranges for dissolved cadmium at the rest of the sites were

similar to previous values (Figure 5).

Figure 5. Dissolved cadmium concentrations at BEMP sites in water year 2018 versus from 2008-2017. Note the vertical axis scale varies by plot. NF, North Fork; SF, South Fork; CDR, Coeur d’Alene River.


Quality Control Samples

Six replicate samples and five equipment blanks were collected in water year 2018. Generally, analytical

results were in good agreement (relative percent difference less than 20%) between parent and

replicate samples. However, somewhat higher differences between copper results in several filtered

samples were observed. In the blank samples, most constituents were not detected. However, filtered

copper and unfiltered lead were detected in most blank samples, albeit at low concentrations near the

reporting limit. Given the occurrence of copper and lead in blanks, and the high relative percent

differences in copper results in replicates, the USGS will continue to evaluate equipment cleaning and

sample processing procedures in water year 2019. This evaluation will include collecting sequential

equipment blanks (blanks taken after each processing step) to identify problematic equipment and/or

procedures.

References

Clark, G.M., and Mebane, C.A., 2014, Sources, transport, and trends for selected trace metals and nutrients in the Coeur d'Alene and Spokane River Basins, Idaho, 1990-2013: Reston, VA, 2014-5204. 74 p, at http://pubs.er.usgs.gov/publication/sir20145204.

Clark, G.M., and Perreault, L.M., 2017, Quality Assurance Project Plan (QAPP) for U.S. Geological Survey Surface Water Sampling under the Coeur d'Alene Basin Environmental Monitoring Program at the Bunker Hill Superfund Site - OU2 and OU3.: Prepared for: USEPA, Region 10, p. 51

U.S. Environmental Protection Agency, 2002, The Bunker Hill Mining and Metallurgical Complex Operable Unit 3, Record of Decision, U.S. Environmental Protection Agency. 527 p, also available at https://nepis.epa.gov.

U.S. Environmental Protection Agency, 2012, Interim Record of Decision (ROD) Amendment, Upper Basin of the Coeur d'Alene River, Bunker Hill Mining and Metallurgical Complex Superfund Site, U.S. Environmental Protection Agency. 488 p, also available at https://semspub.epa.gov/work/10/664107.pdf.

U.S. Geological Survey, 2019, National Water Information System (NWIS): U.S. Geological Survey, at https://nwis.waterdata.usgs.gov/nwis.

http://pubs.er.usgs.gov/publication/sir20145204

https://nepis.epa.gov/

https://semspub.epa.gov/work/10/664107.pdf

https://nwis.waterdata.usgs.gov/nwis

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