Читать книгу Hydrogeology - Kevin M. Hiscock - Страница 25

Focusing on the upper 2 km of the continental crust in which most hydrogeological observations are made, Gleeson et al. (2015) combined multiple approaches using geospatial datasets, tritium age dating of groundwater and numerical modelling to show that less than 6% of the groundwater in the uppermost portion of the Earth's land mass is less than 50 years old, representing modern groundwater that is the most recently recharged. Gleeson et al. (2015) found that the total groundwater volume in the upper 2 km of continental crust is approximately 22.6 × 10⁶ km³, of which 0.1–5.0 × 10⁶ km³ is less than 50 years old. The distribution of this modern groundwater is spatially heterogeneous, with very little in arid regions. Although modern groundwater represents a small percentage of the total groundwater storage on Earth, the volume of this component is still very significant, equivalent to a water depth of about 3 m spread over the world's continents.