The Demographics of Water

The Demographics of Water: A Review of Water Ages in the Critical Zone

Sprenger, Matthias (Albert-Ludwigs-Universität Freiburg; IDAEA-CSIC; University of North Carolina)
Stumpp, Christine (BOKU-University of Natural Resources and Life Sciences)
Weiler, Markus (Albert-Ludwigs-Universität Freiburg)
Aeschbach, Werner (University of Heidelberg)
Allen, Scott T. (ETH Zürich)
Benettin, Paolo (Swiss Federal Institute of Technology)
Dubbert, Maren (Albert-Ludwigs-Universität Freiburg)
Hartmann, Andreas (Albert-Ludwigs-Universität Freiburg; University of Bristol)
Hrachowitz, M. (TU Delft Water Resources)

2019-01-01

The time that water takes to travel through the terrestrial hydrological cycle and the critical zone is of great interest in Earth system sciences with broad implications for water quality and quantity. Most water age studies to date have focused on individual compartments (or subdisciplines) of the hydrological cycle such as the unsaturated or saturated zone, vegetation, atmosphere, or rivers. However, recent studies have shown that processes at the interfaces between the hydrological compartments (e.g., soil-atmosphere or soil-groundwater) govern the age distribution of the water fluxes between these compartments and thus can greatly affect water travel times. The broad variation from complete to nearly absent mixing of water at these interfaces affects the water ages in the compartments. This is especially the case for the highly heterogeneous critical zone between the top of the vegetation and the bottom of the groundwater storage. Here, we review a wide variety of studies about water ages in the critical zone and provide (1) an overview of new prospects and challenges in the use of hydrological tracers to study water ages, (2) a discussion of the limiting assumptions linked to our lack of process understanding and methodological transfer of water age estimations to individual disciplines or compartments, and (3) a vision for how to improve future interdisciplinary efforts to better understand the feedbacks between the atmosphere, vegetation, soil, groundwater, and surface water that control water ages in the critical zone.

critical Zone
stable isotopes
terrestrial water cycle
tracer hydrology
travel times
water ages

http://resolver.tudelft.nl/uuid:c9457fe2-d945-406b-8b63-807f2915057a

https://doi.org/10.1029/2018RG000633

8755-1209

Reviews of Geophysics, 57 (3), 800-834

Institutional Repository

review

© 2019 Matthias Sprenger, Christine Stumpp, Markus Weiler, Werner Aeschbach, Scott T. Allen, Paolo Benettin, Maren Dubbert, Andreas Hartmann, M. Hrachowitz, More Authors