PRELIMINARY ISOTOPIC AND HYDROCHEMICAL FINDINGS OF SURFACE – GROUNDWATER DYNAMICS IN AN URBANIZED WATERSHED, PORTLAND, OR

Groundwater recharge in urban settings vary significantly from natural settings due to urban water sources such as runoff derived from local, imported, and reclaimed waters. This project will evaluate various source waters within the Crystal Springs Watershed in Portland, OR to evaluate the extent in which urban source waters influence shallow groundwaters. Initial data of chloride and sulfate distinguished source waters influenced by groundwater. Groundwater, spring waters, and Crystal Springs Creek contain a relatively elevated concentration of sulfate ranging between 6.5 – 10 mg/L SO₄^-2 compared to Johnson Creek ranging between 3-4 mg/L SO₄^-2. Crystal Springs Creek and spring waters consist of relatively elevated nitrate concentrations compared to local groundwater and Johnson Creek. Crystal Springs Creek averages at 14 mg/L NO^-₃ while spring waters average at 16.5 mg/L NO^-₃. Local groundwaters average at 6 mg/L NO^-₃ while Johnson Creek has nitrate concentrations below detection limits. Initial stable isotopes of deuterium and oxygen have demonstrated distinguishable signatures between groundwaters, spring water, creek water sources which demonstrates potential to create mixing models. The data obtained from this study will add knowledge on the urban hydrologic controls on groundwater systems in relation to natural and potential anthropogenic controls.