Seasonal Variability In Metals Concentrations And Their Transport Mechanisms In Intermittent Streams
Presenter: Justin Headley P91
Co-Author(s): Dr. Jennifer McIntosh (advisor)
Advisor(s): Dr. Jennifer McIntosh
1Hydrology & Atmospheric Sciences
Many intermittent and ephemeral washes drain metals-rich catchments, but the natural concentrations and transport mechanisms of metals in their streamwater discharge are mostly unknown. In the 1960s, anomalously high metal content detected in southeastern Arizona streams led to the discovery of porphyry copper deposits in upstream areas of the Santa Rita Mountains. Although proposed, large-scale mining operations have yet to occur. Mine disturbances have potential to impact downstream water quality in Davidson Canyon and Lower Cienega Creek—sections of which are designated “Outstanding” by the Arizona Department of Environmental Quality. However, recent measurements of reduced water quality near active mine construction resulted in a downgrade to “Impaired” status. Characterization of current baseline concentrations and variability of metals in Davidson Canyon and downstream surface waters must be established to inform stream water quality and identify potential contamination. We hypothesize that the baseline concentrations of metals in Davidson Canyon and Lower Cienega Creek depend on the surface water’s primary source, with higher concentrations in groundwater-fed baseflow during dry periods, and lower concentrations when recent precipitation makes up a larger component of surface flow. This study aims to: (1) Evaluate trace metals concentrations in Davidson Canyon and Lower Cienega Creek baseflow. (2) Using autosamplers, collect streamwater during high-flow events for comparison to baseflow. (3) Use ion chemistry to constrain sources of water contributing to streamflow and geochemical conditions for metals transport. Understanding the current concentrations of metals and their variabilities associated with precipitation abundance could help predict the geochemical response of other intermittent streams in semi-arid climates.