TY - JOUR
T1 - The Demographics of Water
T2 - A Review of Water Ages in the Critical Zone
AU - Sprenger, Matthias
AU - Stumpp, Christine
AU - Weiler, Markus
AU - Aeschbach, Werner
AU - Allen, Scott T.
AU - Benettin, Paolo
AU - Dubbert, Maren
AU - Hartmann, Andreas
AU - Hrachowitz, Markus
AU - More Authors, null
PY - 2019/1/1
Y1 - 2019/1/1
N2 - 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.
AB - 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.
KW - critical Zone
KW - stable isotopes
KW - terrestrial water cycle
KW - tracer hydrology
KW - travel times
KW - water ages
UR - http://www.scopus.com/inward/record.url?scp=85068217460&partnerID=8YFLogxK
U2 - 10.1029/2018RG000633
DO - 10.1029/2018RG000633
M3 - Review article
AN - SCOPUS:85068217460
SN - 8755-1209
VL - 57
SP - 800
EP - 834
JO - Reviews of Geophysics
JF - Reviews of Geophysics
IS - 3
ER -