Recharge and Flow in the Medicine Lake Volcano-Fall River Springs Groundwater Basin, California

摘要

Isotopic measurements of the 34 m~3/s discharge from the Fall River Springs of northern California indicate recharge from 50 km upgradient in high elevation regions of Medicine Lake Volcano. Age determinations suggest less than 20-year travel time. Data demonstrate Klamath Basin further north cannot be a recharge source. Mass balance calculations support that annual precipitation on the volcano supplies observed spring discharge, requiring 50％-75％ recharge rates. Radiocarbon and δ~(13)C of dissolved inorganic carbon indicate 30％-40％ is derived from magmatic CO_2. Measured excess 3He is also consistent with the presence of magmatic gas derived from the Quaternary Age Medicine Lake Volcano.