The dynamic relationship between ground water and the Columbia River: using deuterium and oxygen-18 as tracers

Deuterium and oxygen-18 were used as natural tracers to investigate the hydraulic relationship between the Columbia River and the Blue Lake gravel aquifer near Portland, Oregon. A time series of stable-isotope data collected from surface and ground waters during a March 1990 aquifer test confirms that the river and aquifer are hydraulically connected. Calculations based on simple mixing show that the river contributed 40-50% of the yield of three wells after 5-6 days of pumping. Data collected during August 1990, show that the river contributed 65-80% of the yield of one well after 22 days of pumping and indicate that the contribution of the river was still increasing. ?? 1992.