Eastern Mineral and Environmental Resources Science Center
Development of Mineral Environmental Assessment Methodologies
Task 2 - Development of Mineral Environmental Assessment Techniques at the Watershed Scale
Development of Numerical Models
Performing a mineral environmental assessment over a broad region would require an ability
to estimate baseline water quality conditions in mineralized watersheds having little or no
available water chemistry data. Knowledge of baseline (premining) water quality is essential
in order to assess the potential environmental impacts of future mining. Previous work has
identified numerous factors that might influence the natural generation of low-pH, metal-rich
surface water and groundwater (acid-rock drainage, or ARD). This work has largely
focused on lithology and hydrothermal alteration type, and suggests that these mineralogical
factors are of primary importance. However, the relative importance of climatic, hydrologic,
and geologic factors controlling the subsurface flow of water and oxygen essential for sulfide
oxidation remains uncertain. The purpose of this subtask is to use numerical modeling
methods to determine relative importance of the many variables controlling ARD production,
and to identify a limited number of "super variables" of primary importance in predicting the
occurrence of ARD on the watershed scale. Knowledge of these super variables would be
critical in successfully performing a mineral environmental assessment because data are
typically scarce, particularly over broad regions, demanding that efforts be focused on the
acquisition of only the most essential data coverages.
- Identify numerical modeling codes best suited for simulating the generation and transport
of natural acid-rock drainage (ARD) and for performing the required modeling experiments.
- Determine relative importance of the many factors potentially controlling ARD production
using numerical modeling experiments. Emphasis will be placed on assessing climatic,
hydrologic, and geologic factors that control the subsurface flow of oxygen and water as
apposed to mineralogical factors, which have been studied far more extensively. Identify
"super variables" of primary importance predicting the occurrence of ARD.
- Identify potential proxies or surrogates for super variables identified. Emphasis will be
placed on those super variables for which direct measurements are rare, meaning that
broad data coverages would be difficult or impossible to obtain.
Statement of Work
Model sensitivity studies will continue to be performed using primarily
TOUGHREACT to obtain final model test results. A report will be drafted
on results of the sensitivity studies. Modeling efforts with the incorporation of existing data from well-characterized sites will continue to help establish
reasonable ranges for model inputs.
- Manning, A.H., Bove, D.J., and Verplanck, P.L., 2009, The role of
groundwater recharge processes in the formation of natural acid-rock drainage in
mineralized mountain watersheds, EOS Trans., AGU, 90(52), Fall. Meet. Suppl., Abstract
- Manning, A.H., Caine, J.S., Verplanck, P.L., Bove, D.J., and Kahn,
K.G., 2009, U.S. Geological Survey research in Handcart Gulch, Colorado: An alpine
watershed with natural acid-rock drainage, in Webb, R.M.T., and Semmens, D.J., eds., Planning for an uncertain future—Monitoring, integration, and adaptation, Proceedings of the
Third Interagency Conference on Research in the Watersheds: U.S. Geological Survey
Scientific Investigations Report 2009-5049, p. 97-102.
Posters and Presentations
The use of firm, trade, and brand names is for identification purposes only and does not constitute endorsement by the U.S. government.
- Johnson, R.H., Manning, A.H., and Friedel, M.J., 2009,
Evaluating the Utility of Watershed-Scale Numerical Models in the U.S. Geological
Survey's Mineral Environmental Assessment Project: Presentation at the National Ground
Water Associations's Ground Water Summit, April 19-23, 2009, Tucson, AZ.
- Manning, A.H., Todd, A., 2010, An investigation of the potential impacts
of climate change on water quality in mineralized mountain watersheds: poster presented at
the 2010 USGS Climate Change Conference, March, 2010, Denver, CO.
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