The Future of Water Quality in Coeur d'Alene Lake (2022) / Chapter Skim
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1 Introduction
1 Introduction
Pages 11-46
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As seen in Figure 1-2, the CDA basin is composed of five major subbasins that are mentioned repeatedly in this report: the North Fork of the CDA River, the South Fork of the CDA River, the lower CDA River basin, the St. Joe River basin, and the so-called nearshore watershed directly surrounding CDA Lake.
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The Spokane River watershed is a subbasin of the Columbia River basin. The yellow star southeast of Spokane, Washington indicates the location of CDA Lake.
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Rather, protection of water quality in the Lake was left to a Lake Management Plan (LMP) to be implemented by the CDA Tribe, which owns the bed and banks of the southern third of the Lake, and the State of Idaho, which controls the northern two-thirds.
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. SOURCE: Generated by the committee using data from IDEQ, CDA Tribe and the USGS National Map and associated datasets.
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. The following sections describe several features of the CDA region that play a role in controlling water quality in the Lake.
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As shown in Figure 1-6, the variability in long-term average monthly precipitation between subwatersheds is smaller than the seasonal variability. The annual volume of precipitation within the CDA Lake watershed exhibits significant interannual variability.
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https://developers.google.com/earth-engine/datasets/catalog/ OREGONSTATE_PRISM_AN81m#citations. FIGURE 1-7 Trends in annual precipitation for CDA Lake region, 1979–2021.
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. FIGURE 1-8 Image of ice cover over southern CDA Lake on January 27, 2017.
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From 1991 to 2020, the range of monthly average daily maximum temperatures varied by up to 5°C in December and
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automated measurement stations and manual snow course measurement sites. Through this network of sites, the NRCS develops a basin scale analysis of snow water storage estimates for the Spokane River watershed, for which the CDA River watershed comprises the primary tributary.
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. Conversely, there was no significant trend in the date on which the peak SWE storage within the FIGURE 1-12 Annual maximum SWE in the Spokane River basin, 1983–2021.
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. The trend of decreasing peak maximum SWE in the Spokane River basin is broadly consistent with other declines in SWE metrics observed in the broader western United States (e.g., Mote et al., 2018; Hamlet et al., 2005)
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Note: As described in Chapter 3, inflow is combined flows of the CDA and St. Joe Rivers, multiplied by 1.1036 to represent the total inflow including all of the drainage area to the Lake not included in the CDA or St.
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. Several lateral lakes are adjacent to the CDA River upstream of CDA Lake (see Figure 1-3)
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According to CDA Tribe and Avista (2017) , the dam is used to control CDA Lake elevation during the part of the hydrograph when flows are decreasing, typically in June, and then it maintains the Lake level at the summer full pool elevation of 2,128 ft (648.6 m)
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. Spokane Valley-Rathdrum Prairie Aquifer The Upper Spokane River watershed overlies the SVRP aquifer, discovered in 1895 (MacInnis et al., 2009)
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The three primary drainage areas in the watershed (CDA River basin, St. Joe River basin, and the nearshore catchments)
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. FIGURE 1-19 CDA basin land-cover data in 2001.
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FIGURE 1-20 CDA basin land-cover data in 2019. SOURCE: Data plotted by the committee from the National Land Cover Database.
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. Population Growth A growing population in the watershed presents water quality risks for CDA Lake due to potential increases in both point and nonpoint source pollutants of anthropogenic origin.
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One of the issues identified within the LMP, the more recent Total Phosphorus Nutrient Inventory (IDEQ and CDA Tribe, 2020) , and the Kootenai County Land Use Comprehensive Plan (Kootenai County, 2020)
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. SOURCE: Generated by the committee using data from IDEQ, CDA Tribe, and the USGS National Map and associated datasets.
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say, "Perhaps nowhere in the history of Euro-American settlement of western North America was an area so rapidly and drastically transformed." The focus of this section is to summarize aspects of the mining activities that have had a significant impact on water quality. History of Mining Contamination Previous reports describing the ore deposits within the district provide an understanding of the range of contaminants released from the site (Balistrieri et al., 2002)
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Flood events spread particulate contamination across the CDA River basin. At the same time, increased clogging of channels with tailings from mining activities raised stream levels to the point that annual overbank flooding drove flood waters to higher levels, eventually altering stream channels (NRC, 2005)
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Substantial deposits remain in the river system and continue to be transported downstream. Figure 1-25 shows the profoundly high lead concentrations along the CDA River and within the Lake as of 2001.
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long, from Kellogg on the eastern end to Pinehurst on the western end, that had seen the most intense mining activity. Because mine tailings had been deposited in downstream beds, banks, and floodplains, and because acid mine drainage had discharged to surface waters including the South Fork of the CDA River for over a century, the contamination extended from the eastern end of the watershed, through the entire upper basin along the South Fork, into the lower basin of the CDA River, into CDA Lake, and deposited as far as the Spokane River.
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. Finalized in 2009, the LMP was developed by the State of Idaho and the CDA Tribe with the goal of protecting and improving water quality by limiting basin-wide nutrient inputs that impair water quality or impact metal ion solubility (IDEQ and CDA Tribe, 2009)
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implementation and enforcement at the Bunker Hill Superfund site. In addition to this large role, EPA reviews and approves water quality standards that have been established by the State of Idaho and Tribes under the 1972 federal Clean Water Act (CWA)
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. Coeur d'Alene Tribal Authority The CDA Tribe has authority for setting water quality standards and enhancing and protecting water quality within their reservation.
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CDA Lake is in violation of Idaho's water quality standards for some of the metals of concern in the northern half of the Lake, with zinc concentrations routinely well over the water quality standard of 36 mg/L and cadmium concentrations hovering around the standard of 0.25 mg/L. The CDA Tribe's water quality standards for these same metals are being violated at the more southern C5 location, but not at the southernmost monitoring location, C6.
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Annual mean or median dissolved cadmium and especially zinc concentrations within CDA Lake exceed the LMP targets more frequently than did dissolved lead (IDEQ and CDA Tribe, 2020)
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. The hypothesis of concern is that a decrease in oxygen levels in Lake sediments could promote the release of metals from the Lake sediments into the Lake water column, potentially leading to even worse water quality (IDEQ and CDA Tribe, 2009)
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Hence, IDEQ, EPA, and Kootenai County requested the involvement of the National Academies to analyze available data and information about CDA Lake water quality and provide insights about future conditions in the Lake. In late 2020, the National Academies assembled a committee to review historical and recent water quality data, and available modeling efforts, stemming from the 2009 LMP and other available information, with the goal of determining what near-future water quality conditions in the Lake might be.
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2021. Fifth Five-Year Review Report for the Bunker Hill Mining and Metallurgical Complex Superfund Facility (Bunker Hill Superfund Site)
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2021. Bunker Hill Mining and Metallurgical Complex Superfund Site Overview.
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2002. Modeling the relationship between land use and surface water quality.
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