STABLE ISOTOPE RESPONSE OF LOCAL AND REGIONAL SPRINGS TO EXTREME WEATHER EVENTS

Isotopic data from a new large database of springs of Western North America was used to determine the effects of extreme climate events on local and regional springs. The stable isotopes 18O and 2H of water can be indicators of the season and elevation of precipitation which recharges aquifers. Springs with a local precipitation source have an isotopic signature similar to the precipitation of the same elevation. Springs with a regional precipitation source have an isotopic signature of the elevation of the precipitation where the aquifer is recharged, sometimes at elevations significantly higher than the elevation of the discharge of the spring. Multiple years of data collection from two, high-elevation, local springs and several low-elevation, regional springs provided information on the ranges of seasonal variability of isotope ratios. A locally sourced, ephemeral hillslope spring, sourced from a shallow karst aquifer, recharged from an extreme summer monsoon precipitation event with a significant 18O and 2H fluctuation. Non-karstic local springs, and regional springs did not fluctuate with the extreme monsoon event.