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 i n the central Oregon Cascades are used to understand the pattern of groundw ater flow. Standard oxygen and hydrogen isotope interpretations are used to determine the mean recharge elevation for springs. Carbon and helium isoto pes are used to measure the component of dissolved magmatic gas in the spri ng waters. Inferences from isotopic measurements are compared with temperat ure measurements made at the springs to determine whether groundwater circu lates to shallow or deep depths in the subsurface. Integrating the measurem ents of tracers derived at the surface, tracers derived from the subsurface , and temperature measurements can thus be used to derive a three dimension al picture of groundwater flow. (C) 2000 Elsevier Science B.V. All rights r eserved.