CHARACTERIZATION OF ACIDIC DRAINAGE THROUGH GROUND AND HYPERSPECTRAL REMOTE SENSING

Hyperspectral remote sensing, acquired from airborne platforms such as AVIRIS (Airborne Visible Infrared Imaging Spectrometer) and satellites such as HYPERION, is being investigated with respect to its ability to map diagnostic mineralogy within a watershed as a means of identifying the relative contributions of natural and anthropogenic sources of metals and acidity to that drainage. Ground-based reflectance spectroscopy is used to independently verify mineralogical variations throughout a watershed. In-stream and above-water-line rock and sediment samples are collected concurrently with water chemistry samples to tie the observed mineralogical variations of sediment and rock surface coatings to water quality during high and low flow periods in a drainage. A methodology is being developed to integrate the ground and airborne remote sensing data to improve environmental assessments and tracking of impacts to drainages. This project builds upon efforts by the Colorado Geological Survey to identify areas of hydrothermal alteration that contribute acidic and metalliferous water to drainages in Colorado.

Phase I (2001-2002) of this NASA-funded research project involves the Lake Creek drainage basin, a tributary to the upper Arkansas River. This drainage is impacted by natural acid rock drainage from hydrothermally altered areas in its headwaters. Minerals and mineraloids that are of particular interest are low-pH iron phases such as jarosite, ferrihydrite, schwertmannite, coquimbite, voltaite, and transitional amorphous phases. AlOH phases from neutral to high-pH environments are observed to precipitate with the iron in streams draining the hydrothermal systems. Phase II of this project (2002-2004) will focus on drainages dominantly impacted by anthropogenic sources related to the Leadville mining district. If successful in discriminating differences between sources of acid drainage, our techniques may provide a means of determining baseline remote-sensing data needed to identify natural impacts on drainages, allowing evaluation of separate impacts from mining or other anthropogenic causes.