The use of temperature and the isotopes of O, H, C, and noble gases to determine the pattern and spatial extent of groundwater flow

Isotopic tracer and temperature measurements at large volume cold springs in the central Oregon Cascades are used to understand the pattern of groundwater flow. Standard oxygen and hydrogen isotope interpretations are used to determine the mean recharge elevation for springs. Carbon and helium isotopes are used to measure the component of dissolved magmatic gas in the spring waters. Inferences from isotopic measurements are compared with temperature measurements made at the springs to determine whether groundwater circulates to shallow or deep depths in the subsurface. Integrating the measurements of tracers derived at the surface, tracers derived from the subsurface, and temperature measurements can thus be used to derive a three dimensional picture of groundwater flow. (C) 2000 Elsevier Science B.V. All rights reserved.