HILL SLOPE GROUNDWATER CHEMISTRY IN CALIFORNIA'S ANGELO COAST RANGE RESERVE, EEL RIVER WATERSHED

In the California Coast Range baseflow supports summer flows in rivers that are the habitat of endangered salmonid fish and provides water to downstream human populations. This study investigates groundwater chemistry variations in the Angelo Coast Range Reserve protected natural area including the Eel River Critical Observatory. This research focused on differences between wells, creeks, and springs. In August 2024, we measured temperature, pH, dissolved oxygen, specific conductance, alkalinity, hardness, and ion content across the Elder Creek watershed, a tributary of the Eel River. We found strong positive correlations between pH, alkalinity, and hardness in springs and wells. Wells showed higher ion concentrations—especially sodium, magnesium, calcium, and sulfate—compared to springs and creeks, suggesting mineral dissolution during prolonged interaction with weathered bedrock. While creeks exhibited decreasing hardness at higher pH levels likely due to precipitation of calcium carbonate minerals. Elevation of sites within the watershed were not correlated with spring flow rate or electrical conductivity. Spring flow rate correlates to electrical conductivity potentially due to variations in catchment size. Larger catchments can provide more water to the spring as well as produce longer flow paths that allow more time for water-rock interactions. These findings provide a valuable baseline for comparing to developed regions and assessing water quality in unaltered coastal environments. Groundwater chemistry helps with determining hill slope flow dynamics and also with predicting climate change impacts on baseflow and water supply.