Colorado Legacy Mine Lands Watershed Delineation and Scoring tool (WaDeS)
This U.S. Geological Survey (USGS) Web Application is a summarized compilation of central Colorado water chemistry datasets from previously published sources including the USGS National Water Information System (NWIS) and U.S. Environmental Protection Agency (EPA) STORET web services retrieved via Water Quality Portal (WQP), and USGS data from the Central Colorado Assessment Project (CCAP) (Church and others, 2009; Church and others, 2012). The data and scripts supporting this application are available at https://doi.org/10.5066/P9EU26J1 (Goldman and others, 2023). With consideration of the CCAP study design and more analytically comprehensive, consistent, and spatially reliable samples than the collection of historical sampling retrieved from WQP, the CCAP spatial geometry serves as the bounding coordinates for this exercise. Spatially relevant WQP data were screened to include the necessary values to calculate hardness dependent chronic and acute toxicity thresholds for aquatic life protections under Colorado Regulation No. 31 (CDPHE, 5 CCR 1002-31) for cadmium, copper, lead, and or zinc (metals). All water chemistry data that meets inclusion criteria have been summarized by monitoring location and results organized in tabular format (WQP_scores, CCAP_scores). Watershed polygons were created using Geographic Information Systems (GIS) to summarize and calculate within an area for the key conditions of metals concentrations, number and type of mine features (Horton and San Juan, 2022), and percent area of background geology with intense hydrothermal alteration (Rockwell and Bonham, 2017), on a smaller spatial scale than the available watershed polygons published in the National Hydrography Dataset. Polygons were screened for total area not to exceed thirty-five square kilometers, and then qualified based on the presence of both water chemistry data and at least one mine, adit, or mine shaft feature.
The purpose of this GIS exercise is to identify legacy mine sites within the headwaters of central Colorado that could be good candidates for future remediation work based on stream metal concentrations, the number and complexity of mine features, and the potential for high natural background metal concentrations. The first step of the process is to spatially define all headwater catchments within the region. Our approach is to delineate machine automated, repeatable, and nested watershed polygons with selective input parameters that define the size(s) of headwater streams for which calculations and classifications can occur. To visualize, data are then processed within watersheds based on metal concentrations and relative toxicity thresholds, mining activity, potential background weathering of natural hydrothermally altered geology, and these classification relationships are then broadly comparable across the landscape. Because this exercise is calculating within many digitally generated areas, specific sub watershed delineation processing methods are used and considered to be most accurate and repeatable. A system of scoring watersheds was created using Python3 scripts to calculate concentration statistics relative to chronic and acute values, number of mine features, and area percent of alteration. Additional material and descriptions of each script action can be found in the supporting ScienceBase data release, allowing users of this application to adjust calculation parameters as needed (Goldman and others, 2023). Users are advised to apply gray terrain feature when screening for watershed percent alteration score and watershed number of mine features score symbology.
Default scoring
Watershed - NMF (number of mine features within watershed)
1 - 10 score: 1
10 - 20 score: 2
>20 score: 3
Watershed - Alteration (percent area of hydrothermally altered geology within watershed)
Pct alteration < 2% score: 1
2% ≥ Pct alteration < 5% score: 2
Pct alteration ≥ 5% score: 3
CCAP and WQP - Metal score (water chemistry concentrations relative to toxicity thresholds)
Where: X = metal concentration, C = chronic threshold value, and A = acute threshold value.
X < 0.67 * C, score: 1
0.67 * C ≤ X < C, score: 2
C ≤ X < C + (0.33 *(A - C)), score: 3
C + (0.33 *(A - C)) ≤ X < A, score: 4
A ≤ X, score: 5
This screening exercise is primarily for a range of moderately elevated to acute threshold exceeding watersheds (higher concentrations). Users screening for lower concentration values should note how censored values and or values below detection limits within the WQP and CCAP datasets were removed or replaced in the process steps.
Suggested citation
McGee, B.N., Goldman, M.A., Manning, A.H., Walton-Day, K., Mast, M.A., San Juan, C.A., Wanty, R.B., 2023, Colorado Legacy Mine Lands Watershed Delineation and Scoring tool (WaDeS): U.S. Geological Survey web application, https://geonarrative.usgs.gov/colmlwades/.
References
Church, S.E., Fey, D. L., Klein, T.L., Schmidt, T.S., Wanty, R.B., deWitt, E.H., Rockwell, B.W., and San Juan, C.A., 2009, Environmental effects of hydrothermal alteration and historical mining on water and sediment quality in Central Colorado in Planning for an uncertain future - Monitoring, integration, and adaptation: U.S Geological Survey Scientific Investigations Report 2009-5049, https://doi.org/10.3133/sir20095049.
Church, S.E., San Juan, C.A., Fey, D.L., Schmidt, T.S., Klein, T.L. DeWitt, E.H., Wanty, R.B., Verplanck, P.L., Mitchell, K.A., Adams, M.G., Choate, L.M., Todorov, T.I., Rockwell, B.W., McEachron, Luke, and Anthony, M.W., 2012, Geospatial database for regional environmental assessment of central Colorado: U.S. Geological Survey Data Series 614, 76 p., https://doi.org/10.3133/ds614.
Colorado Department of Public Health and Environment (CDPHE), Water Quality Control Commission 5 CCR 1002-31. Regulation No. 31 The Basic Standards and Methodologies for Surface Water. Effective 12/31/2021. Accessed at https://www.coloradosos.gov/CCR/GenerateRulePdf.do?ruleVersionId=9874&fileName=5%20CCR%201002-31.
Goldman, M.A., McGee, B.N., Manning, A.H., Walton-Day, K., Mast, A.M., San Juan, C.A., Wanty, R.B., 2023, GIS data and scripts for Colorado Legacy Mine Lands Watershed Delineation and Scoring tool (WaDeS): U.S. Geological Survey data release, https://doi.org/10.5066/P9EU26J1.
Horton, J.D., and San Juan, C.A., 2022, Prospect- and mine-related features from U.S. Geological Survey 7.5- and 15-minute topographic quadrangle maps of the United States (ver. 8.0, September 2022): U.S. Geological Survey data release, https://doi.org/10.5066/F78W3CHG.
Rockwell, B.W. and Bonham, L.C., 2017, Digital maps of hydrothermal alteration type, key mineral groups, and green vegetation of the western United States derived from automated analysis of ASTER satellite data: U.S. Geological Survey data release, https://doi.org/10.5066/F7CR5RK7.
Water Quality Portal. Washington (DC): National Water Quality Monitoring Council, United States Geological Survey (USGS), Environmental Protection Agency (EPA); 2021, https://doi.org/10.5066/P9QRKUVJ.