Shannon L. Bartelt-Hunt
George A. Hunt
Daniel D. Snow
Date of this Version
PhD Dissertation, Modeling Watershed Sensitivity to Climate Change in Systems Affected by Discharge of Mine Tailings, University of Nebraska-Lincoln, Civil Engineering, December, 2021.
For more than a century, a large volume of gold-mining tailings was deposited in Whitewood Creek and the Belle Fourche River, tributaries to the Cheyenne River in western South Dakota. Much of it still remains, and field and historical evidence indicates continued remobilization of tailings-containing alluvium in these bedrock-dominated channels. Both long-term, natural fluctuations in climate and anthropogenically driven changes can impact regional precipitation, temperature, hydrologic patterns, and ecosystem functions. Such changes have the potential to affect both the transport and distribution of arsenic-laden sediments and mechanical erosion that can undermine the stability of channel-bed and overbank material.
This study reevaluates published literature and simulates future climatic conditions with Global Change Models downscaled to hydrologic models to detect trends and determine if they differ from historical time series data or exhibit non-stationarity. Arsenic concentrations vary in solution with relatively small shifts in pH and Eh, allowing for the sorption/desorption on sediment and mobilization into the dissolved or aqueous phase.
Published data suggest that the presence of competing anions are also important factors in controlling arsenic release. Carbonates in the alluvium and locally occurring bedrock control the formation of acidic conditions. This river system continually adjusts to historical and recent changes to achieve a “new equilibrium” from the cessation of mining discharge; geomorphic changes linked to regional continental glaciation; stream channel readjustment due to discharge velocity changes in the Oahe Reservoir; and channel instability. Knowing the relationship between streamflow and sediment transport and assessing a stream’s sediment transport capacity are important to planning and managing river corridor protection and restoration. These are also significant considerations in predicting potential exposure of contaminant sediments to human, ecological, and biological receptors. It appears climate change may be exerting an influence on hydroclimatic variables in the Lower Cheyenne River Basin, difficult to pinpoint in a qualitative assessment. In general, water resource managers should build resiliency into their designs to adaptably account for potential future impact of climate variability.
Adviser: Dr. Shannon L. Bartelt-Hunt