Comparison of ⁸⁵Kr and ³H Apparent Ground‐Water Ages for Source Water Vulnerability in the Collyer River Catchment, Maine¹

Abstract

Apparent ground‐water ages as determined by the noble gas isotope 85Kr and the water isotope 3H are compared. Refined gas extraction methodology at the wellhead permits efficient collection of Kr for 85Kr isotope enrichment. 85Kr isochrones elucidate areas of much younger ground‐water ages than 3H. Declining 3H activities in the catchment prevent its correlation with the youngest measured 85Kr ages. Source water for most drinking water supplies in the Collyer River catchment is recharged within 40 years BP (2004). Mean‐age (τ) transport modeling suggests uncertainty of ground‐water ages is greatest in the central basin area.

Groundwater Quality

“…Recharge temperatures or ages were simulated by three models, indicating the occurrence of diffusive degassing (Cey et al, 2008). Apparent groundwater ages could be determined by the noble gas isotope 85 Kr and the water isotope 3 H. The data indicated that source water for most drinking water supplies in the Collyer River catchment, Maine, was recharged within 40 years (Sidle, 2008). Direct current electrical resistivity could be used for assessing ground water/surface water interactions within streams.…”