A 30 ka paleo-climate record of the Boise area, Idaho, USA has been delineated using groundwater stable isotopic compositions. Groundwater ages are modern (cold batholith), 5–15 ka (thermal batholith), 10–20 ka (frontal fault), and 20–30 ka (Snake River plain thermal). The stable isotopic composition of groundwaters have been used as a surrogate for the stable isotopic composition of precipitation. Using δ2H and δ18O compositions, local groundwater lines (LGWL's) were defined for each system. Each LGWL has been evaluated with defined slopes of 6.94 and 8, respectively, and resulting deuterium excess values (d) were found for each groundwater system for each slope. Time dependent changes in moisture source humidity and temperature, and Boise area recharge temperatures, calculated from stable isotopic data and the deuterium excess factors, agree with previous paleo-climate studies. Results indicate that from the last glacial maximum to the present time the humidity over the ocean moisture source increased by 9%, sea surface temperature at the moisture source increased 6–7°C, and local Boise temperature increased by 4–5°C. A greater increase of temperature at the moisture source as compared to the Boise area may impart be due to a shift in the moisture source area.

In Córdoba Province, Argentina, the population uses groundwater from confined aquifer systems (CASs) for different activities. Therefore, it is necessary to carry out comprehensive studies in order to plan more sustainable use considering that groundwater renewal times can be of several thousands of years. The objective of this research is to evaluate groundwater age in confined aquifers based on hydraulic and isotopic methods. The CASs present variable extension, are multilayered and formed by thin (4–6 m) sand-pebble lenses, and are linked to Neogene fluvial paleosystems. These layers are situated at different depths (120–400 m) and interbedded with thick clay strata. The interpretations made from 2H, 18O, and 3H results and hydraulic calculations suggest that the groundwater is old. Furthermore, an age gradient was observed that increases with depth and flow direction. The 14C ages obtained for the CASs labeled A2, C, and D were 3.6–1.1 ka BP, 10.8 ka BP, and 46.0–40.5 ka BP, respectively. These results indicate that A2 and C contain groundwater recharged during Holocene cold periods, between the Little Ice Age and the ending of the Holocene Climatic Optimum and during the last glaciation. The D CAS contains paleowater that was recharged during the Pleistocene.