by George Zamora
SOCORRO, N.M., June 30, 2004 – New Mexico Tech doctoral candidate Sam Earman is investigating the possible use of natural tracers, such as stable isotopes of oxygen and hydrogen, as a means of improving estimates of groundwater recharge attributable to snowfall and snowmelt.
“Although snow is recognized as an important contributor to the groundwater in New Mexico’s aquifers, our knowledge of what portion of the groundwater in various aquifers originated as snowmelt is not good,” Earman says.
Stable isotopes of oxygen and hydrogen are widely used in hydrogeology and other fields as natural tracers, but using these isotopes to study snow and snowmelt is not a widespread practice among hydrogeologists, although research in this specific area has increased over the past few years.
“Some of the methods currently used to estimate the contribution of snowmelt to groundwater recharge may yield values that are too low,” Earman says. “Alteration of the stable isotope signature of snow during snow metamorphism has the potential to cause groundwater recharge signatures to differ significantly from fresh snow signatures.
“This study uses natural tracers—substances that are naturally present, rather than added—in snow and groundwater to get improved estimates of the importance of snow in groundwater recharge,” he adds.
A major portion of the research study involves using a network of stations set up in various mountaintops in New Mexico and Arizona with different types of precipitation collectors. Some of the collectors are designed to preserve the isotope signature of fresh snowfall, while others allow varying degrees of alteration and then maintain the isotope signature of the melted snow.
Improving estimates of the proportion of groundwater recharge derived from snow will serve to improve estimates of total groundwater recharge,” Earman says. “In turn, these improved estimates of groundwater recharge will allow water planners to make better decisions regarding our water resources.”
Earman’s ongoing research work in this area is funded in part by a New Mexico Water Resources Research Institute Student Research Grant.