Eagle River Water Quality Report Card

5-year data period: 2018-2022

The Water Quality Monitoring and Assessment Program (WQMAP) is an important behind-the-scenes component of Eagle River Coalition that seeks to coordinate with partners for efficient long term data collection and archiving, as well as review and report results and watershed conditions to basin stakeholders (including the public).

The Water Quality Report Card is a periodic review of data through the lens of statewide water quality standards to help program partners understand where concerns may exist or where additional data collection could be beneficial. Colorado’s Water Quality Control Division organizes the basin’s streams into subsegments called Assessment Units that are used to consider water quality conditions on shorter stream lenghts of similar characteristics.

The Report Card Assessment Table below considers what data is available for a given stream reach, and how that data compares to statewide standards. The state assigns a variety of existing or potential uses (drinking water, recreation, fisheries/aquatic life, and agriculture) to streams. Each use class has specific water quality standards assigned to it. Monitoring activities tend to occur where pollution or human impact is most likely, therefore not all stream segments have data collected regularly.

The Eagle Watershed has many pristine wilderness streams with few human impacts; the presumption for these is that water quality is very good and scarce monitoring resources can be better spent focusing on locations of concern like near towns, below mining-impacted areas, and on popular recreational reaches.

 

For an in-depth tour of watershed issues, check out the Report Card Story Map here.

Assessment Table

Water Quality Assessment Table

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Ratings explanation:

  • Good: Ambient conditions <= 50% of water quality standard level.
  • Acceptable: Ambient conditions > 50% of water quality standard, but no observations exceeding standard.
  • Concern: Ambient conditions > 50% of water quality standard, and the maximum observed value exceeded the standard.
  • Poor: Ambient conditions exceeded the water quality standard.
  • Poor Resolution: Too many censored result values for accurate statistical characterization

 

Chronic water quality conditions are assessed using ambient conditions values, which are estimated using statistical aggregations of available data on a stream reach.  Ambient conditions are specifically defined as the 50th percentile of the ranked data for total metals and 85th percentile for all other chemical parameters.

Monitoring Locations  2018-2022

 

THE FINE PRINT: Methodology

 

1. Data sources

Multiple agencies and organizations collect water quality data across the Eagle River watershed. Insufficient metadata may lead to inappropriate data use, or misinterpretation of results and represents a significant barrier to data analysis. The existence of multiple non-standardized data formatting approaches represents another barrier to data analysis, as reformatting data sets may require a significant time investment. Therefore, selection of data sources that minimize formatting concerns and provide adequate data annotation represents a critical step when conducting water quality evaluations. To this end, the Eagle River Coalition aggregated only a subset of the data produced by active data collection efforts in the watershed for use in this report.

To ensure that readers of this report retain the ability to cross-reference statistical summary information against raw data from the selected data source(s), Eagle River Coalition utilized only data stored in public electronic data repositories and available from the Water Quality Portal. All data utilized for analysis in this report came from either the USGS NWIS database, or the EPA STORET database—both accessible through the National Water Quality Monitoring Council Water Quality Portal (www.waterqualitydata.us). Use of these electronic repositories greatly simplifies data formatting concerns during analysis. Additionally, the requirements by the NWIS and STORET repositories for storage and publication of minimum metadata sets with any stored water quality data value provide an avenue for evaluation of data reliability.

The fact that not all data collection entities across the watershed store data in either NWIS or STORET and because some data entry into STORET experiences a significant lag time between data collection and publication (e.g. Colorado Watershed Assembly River Watch data) there are some inherent disadvantages to using the selected data sources.

 

2. Data Analysis

Data used in this report was derived from surface water samples collected along 305(b) stream segments in the Eagle River watershed over five water years spanning the time period between January 1, 2018 and December 31, 2022. This iteration of the Report Card collated and analyzed 38,564 data observations of 214 different monitoring parameters collected at 92 sites by 8 organizations. Prior to analysis, water quality data was grouped according to 305(b) stream segments.  Data aggregation according to the 305(b) segment aligns with the State of Colorado’s assessment methodology for identification of impaired waters. Data did not exist over the time period of interest for all 305(b) segments. This resulted from either a lack of recent sample collection at some locations, or the lag-time between sample collection and data publication noted above. Not all parameters collected by different monitoring groups are used in state assessment contexts, therefor not all parameters (individual analytics or indicators of water quality) are reported in the assessment table.

Analysis of data collected for each chemical water quality parameter produced summary statistics useful for qualitative interpretation and ranking. Summary statistics included the minimum observed value, the median value, the maximum value, the date when the maximum was observed, the 15th percentile of the data, the 50th percentile of the data, and the 85th percentile of the data. Where a sufficient number of observations existed and were evenly distributed over the review period, a non-flow corrected Seasonal Mann-Kendall trend test identified significant trends in specific parameter values over the past 5 years. In order to conduct this analysis, data were initially binned according to season (e.g. December-February, March-May, June-August, and September-November). This binning strategy reflects with typical hydrologic milestones observed in the Eagle River watershed. Trends analysis results identified statistically significant (at the 95% significance level, or p-value < 0.05) monotonic upward or downward trends.

Assessment of water quality conditions relied on comparison of collected data to WQCD water quality standards for particular water uses on a given water body. Data analysis utilized EPA recommendations for water quality parameters where no WQCD standard exists. Water uses and associated water quality standards for a given segment corresponded to 305(b) water use type classifications and narrative or numeric standards outlined in CDPHE Regulation #31 and Regulation #33. Aggregation of data for a particular 305(b) segment did not attempt to distinguish differences in water quality conditions between multiple data collection locations on that segment. Quantitative analysis of numerical data relied on the R statistical computing environment (http://www.r-project.org/).

 

3. Levels of Concern Ratings

Methods for data evaluation followed CDPHE Regulation #93 for attainment of water quality standards, as quoted below:

“Attainment of chronic chemical standards, in both streams and rivers, and lakes and reservoir systems, is based upon the 85th percentile of the ranked data, […]. Percentile values are calculated by ranking individual data points in order of magnitude. Hardness-based metal standards are evaluated by comparing the 85th percentile against the assigned hardness-based equation using the mean hardness. Total recoverable metals are evaluated against the median value, or the 50th percentile. Dissolved metals are evaluated against the 85th percentile. Dissolved oxygen (DO) is evaluated at the 15th percentile for streams. Minima pH is evaluated against the 15th percentile, maxima at the 85th percentile. […]”

“Sample data that are below detection limits will, in general (except coliform data), be treated as zeroes for assessment of attainment. […]”

“Attainment of the E.coli standard is assessed using the geometric mean of representative stream samples. […] E.coli data that are reported as less than detect will be treated as a value of one to allow calculation of a geometric mean. […] Evaluation of the E. coli standard is over multiple fixed two-month intervals. The evaluation intervals are: January/February, March/April, May/June, July/August, September/October, and November/December. […]”

“Biological and/or physical assessment protocols may support a determination of non-attainment of numeric standards or, alternately, nonattainment of narrative standards and classified uses. […] In general, a determination that an assigned aquatic life use is not supported will be consistent with the protocols established in WQCC Policy 10-1, ‘Aquatic Life Use Attainment, Methodology to Determine Use Attainment for Streams and Rivers.’ […]”

Calculation of mean hardness values for assessments using hardness-based standards utilized all hardness data collected on a given segment over the entire observation period. Comparison of observed water quality data against water supply use protection standards did not consider the location of the observed arsenic, nitrate, or nitrite data in relation to any drinking water supply intakes. Neither did this assessment attempt to calculate standards for manganese, iron and sulfate using pre-2000 existing water quality conditions. Rather, in keeping with the intention of this report as a coarse-screening tool for assessing water quality conditions throughout the watershed, table value standards (TVS) were used for assessment of water supply use protection on each stream segment.

Categorical use-protection rankings were assigned to each parameter evaluated against State of Colorado water quality standards or EPA recommendations. In general, if the ambient levels of a given water quality parameter (defined as the 50th percentile of the ranked data for total metals and the 85th percentile for all other chemical parameters) exceeded the relevant water quality standard, the segment received a ‘Poor’ use protection rating for that parameter. If the ambient quality did not exceed the standard, but did exceed 50% of the standard concentration and the maximum observed concentration exceeded the standard, the segment or site received a ‘Concern’ use protection rating for that parameter. If neither the ambient quality nor the maximum observed concentration exceeded the standard, but ambient conditions did exceed 50% of the standard concentration, the segment or site received an ‘Acceptable’ use protection rating for that parameter. A use protection rating of ‘Good’ was awarded when ambient conditions did not exceed 50% of the standard for a given parameter. When the number of censored values in a data set equaled the number of water quality samples, the segment or site received a “Poor Resolution” rating.  This ranking system generally aligns with the “Concern levels” adopted for use by the USGS in the Comparison of 2011–12 water years and historical water-quality data, Eagle River Basin, Colorado (http://co.water.usgs.gov/infodata/eagle_summaries/).