Time series of tritium, stable isotopes and chloride reveal short-term variations in groundwater contribution to a stream

C. Duvert, M.K. Stewart, D.I. Cendón, M. Raiber

Research output: Contribution to journalArticleResearchpeer-review

7 Downloads (Pure)

Abstract

A major limitation to the assessment of catchment transit time (TT) stems from the use of stable isotopes or chloride as hydrological tracers, because these tracers are blind to older contributions. Yet, accurately capturing the TT of the old water fraction is essential, as is the assessment of its temporal variations under non-stationary catchment dynamics. In this study we used lumped convolution models to examine time series of tritium, stable isotopes and chloride in rainfall, streamwater and groundwater of a catchment located in subtropical Australia. Our objectives were to determine the different contributions to streamflow and their variations over time, and to understand the relationship between catchment TT and groundwater residence time. Stable isotopes and chloride provided consistent estimates of TT in the upstream part of the catchment. A young component to streamflow was identified that was partitioned into quickflow (mean TT≈ 2 weeks) and discharge from the fractured igneous rocks forming the headwaters (mean TT ≈ 0.3 years). The use of tritium was beneficial for determining an older contribution to streamflow in the downstream area. The best fits between measured and modelled tritium activities were obtained for a mean TT of 16-25 years for this older groundwater component. This was significantly lower than the residence time calculated for groundwater in the alluvial aquifer feeding the stream downstream (≈ 76-102 years), emphasising the fact that water exiting the catchment and water stored in it had distinctive age distributions. When simulations were run separately on each tritium streamwater sample, the TT of old water fraction varied substantially over time, with values averaging 17 ± 6 years at low flow and 38 ± 15 years after major recharge events. This counterintuitive result was interpreted as the flushing out of deeper, older waters shortly after recharge by the resulting pressure wave propagation. Overall, this study shows the usefulness of collecting tritium data in streamwater to document short-term variations in the older component of the TT distribution. Our results also shed light on the complex relationships between stored water and water in transit, which are highly non-linear and remain poorly understood.
Original languageEnglish
Pages (from-to)257-277
Number of pages21
JournalHydrology and Earth System Sciences
Volume20
Issue number1
DOIs
Publication statusPublished - 2016
Externally publishedYes

Fingerprint

tritium
stable isotope
chloride
time series
groundwater
catchment
streamwater
streamflow
water
residence time
recharge
tracer
flushing
headwater
age structure
low flow
igneous rock
wave propagation
temporal variation
aquifer

Cite this

@article{3afeeac3ff4d436f956d867c40853f8f,
title = "Time series of tritium, stable isotopes and chloride reveal short-term variations in groundwater contribution to a stream",
abstract = "A major limitation to the assessment of catchment transit time (TT) stems from the use of stable isotopes or chloride as hydrological tracers, because these tracers are blind to older contributions. Yet, accurately capturing the TT of the old water fraction is essential, as is the assessment of its temporal variations under non-stationary catchment dynamics. In this study we used lumped convolution models to examine time series of tritium, stable isotopes and chloride in rainfall, streamwater and groundwater of a catchment located in subtropical Australia. Our objectives were to determine the different contributions to streamflow and their variations over time, and to understand the relationship between catchment TT and groundwater residence time. Stable isotopes and chloride provided consistent estimates of TT in the upstream part of the catchment. A young component to streamflow was identified that was partitioned into quickflow (mean TT≈ 2 weeks) and discharge from the fractured igneous rocks forming the headwaters (mean TT ≈ 0.3 years). The use of tritium was beneficial for determining an older contribution to streamflow in the downstream area. The best fits between measured and modelled tritium activities were obtained for a mean TT of 16-25 years for this older groundwater component. This was significantly lower than the residence time calculated for groundwater in the alluvial aquifer feeding the stream downstream (≈ 76-102 years), emphasising the fact that water exiting the catchment and water stored in it had distinctive age distributions. When simulations were run separately on each tritium streamwater sample, the TT of old water fraction varied substantially over time, with values averaging 17 ± 6 years at low flow and 38 ± 15 years after major recharge events. This counterintuitive result was interpreted as the flushing out of deeper, older waters shortly after recharge by the resulting pressure wave propagation. Overall, this study shows the usefulness of collecting tritium data in streamwater to document short-term variations in the older component of the TT distribution. Our results also shed light on the complex relationships between stored water and water in transit, which are highly non-linear and remain poorly understood.",
keywords = "Aquifers, Catchments, Chlorine compounds, Groundwater, Groundwater resources, Igneous rocks, Isotopes, Rivers, Runoff, Stream flow, Time series, Tritium, Wave propagation, Alluvial aquifers, Complex relationships, Convolution model, Groundwater residence time, Hydrological tracers, Pressure wave propagation, Short-term variations, Temporal variation, Residence time distribution, catchment, chloride, concentration (composition), groundwater, headwater, rainfall, recharge, residence time, stable isotope, time series, tritium, water quality, wave propagation, Australia",
author = "C. Duvert and M.K. Stewart and D.I. Cend{\'o}n and M. Raiber",
year = "2016",
doi = "10.5194/hess-20-257-2016",
language = "English",
volume = "20",
pages = "257--277",
journal = "Hydrology and Earth System Sciences",
issn = "1027-5606",
publisher = "Copernicus GmbH",
number = "1",

}

Time series of tritium, stable isotopes and chloride reveal short-term variations in groundwater contribution to a stream. / Duvert, C.; Stewart, M.K.; Cendón, D.I.; Raiber, M.

In: Hydrology and Earth System Sciences, Vol. 20, No. 1, 2016, p. 257-277.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Time series of tritium, stable isotopes and chloride reveal short-term variations in groundwater contribution to a stream

AU - Duvert, C.

AU - Stewart, M.K.

AU - Cendón, D.I.

AU - Raiber, M.

PY - 2016

Y1 - 2016

N2 - A major limitation to the assessment of catchment transit time (TT) stems from the use of stable isotopes or chloride as hydrological tracers, because these tracers are blind to older contributions. Yet, accurately capturing the TT of the old water fraction is essential, as is the assessment of its temporal variations under non-stationary catchment dynamics. In this study we used lumped convolution models to examine time series of tritium, stable isotopes and chloride in rainfall, streamwater and groundwater of a catchment located in subtropical Australia. Our objectives were to determine the different contributions to streamflow and their variations over time, and to understand the relationship between catchment TT and groundwater residence time. Stable isotopes and chloride provided consistent estimates of TT in the upstream part of the catchment. A young component to streamflow was identified that was partitioned into quickflow (mean TT≈ 2 weeks) and discharge from the fractured igneous rocks forming the headwaters (mean TT ≈ 0.3 years). The use of tritium was beneficial for determining an older contribution to streamflow in the downstream area. The best fits between measured and modelled tritium activities were obtained for a mean TT of 16-25 years for this older groundwater component. This was significantly lower than the residence time calculated for groundwater in the alluvial aquifer feeding the stream downstream (≈ 76-102 years), emphasising the fact that water exiting the catchment and water stored in it had distinctive age distributions. When simulations were run separately on each tritium streamwater sample, the TT of old water fraction varied substantially over time, with values averaging 17 ± 6 years at low flow and 38 ± 15 years after major recharge events. This counterintuitive result was interpreted as the flushing out of deeper, older waters shortly after recharge by the resulting pressure wave propagation. Overall, this study shows the usefulness of collecting tritium data in streamwater to document short-term variations in the older component of the TT distribution. Our results also shed light on the complex relationships between stored water and water in transit, which are highly non-linear and remain poorly understood.

AB - A major limitation to the assessment of catchment transit time (TT) stems from the use of stable isotopes or chloride as hydrological tracers, because these tracers are blind to older contributions. Yet, accurately capturing the TT of the old water fraction is essential, as is the assessment of its temporal variations under non-stationary catchment dynamics. In this study we used lumped convolution models to examine time series of tritium, stable isotopes and chloride in rainfall, streamwater and groundwater of a catchment located in subtropical Australia. Our objectives were to determine the different contributions to streamflow and their variations over time, and to understand the relationship between catchment TT and groundwater residence time. Stable isotopes and chloride provided consistent estimates of TT in the upstream part of the catchment. A young component to streamflow was identified that was partitioned into quickflow (mean TT≈ 2 weeks) and discharge from the fractured igneous rocks forming the headwaters (mean TT ≈ 0.3 years). The use of tritium was beneficial for determining an older contribution to streamflow in the downstream area. The best fits between measured and modelled tritium activities were obtained for a mean TT of 16-25 years for this older groundwater component. This was significantly lower than the residence time calculated for groundwater in the alluvial aquifer feeding the stream downstream (≈ 76-102 years), emphasising the fact that water exiting the catchment and water stored in it had distinctive age distributions. When simulations were run separately on each tritium streamwater sample, the TT of old water fraction varied substantially over time, with values averaging 17 ± 6 years at low flow and 38 ± 15 years after major recharge events. This counterintuitive result was interpreted as the flushing out of deeper, older waters shortly after recharge by the resulting pressure wave propagation. Overall, this study shows the usefulness of collecting tritium data in streamwater to document short-term variations in the older component of the TT distribution. Our results also shed light on the complex relationships between stored water and water in transit, which are highly non-linear and remain poorly understood.

KW - Aquifers

KW - Catchments

KW - Chlorine compounds

KW - Groundwater

KW - Groundwater resources

KW - Igneous rocks

KW - Isotopes

KW - Rivers

KW - Runoff

KW - Stream flow

KW - Time series

KW - Tritium

KW - Wave propagation, Alluvial aquifers

KW - Complex relationships

KW - Convolution model

KW - Groundwater residence time

KW - Hydrological tracers

KW - Pressure wave propagation

KW - Short-term variations

KW - Temporal variation, Residence time distribution, catchment

KW - chloride

KW - concentration (composition)

KW - groundwater

KW - headwater

KW - rainfall

KW - recharge

KW - residence time

KW - stable isotope

KW - time series

KW - tritium

KW - water quality

KW - wave propagation, Australia

UR - https://www.scopus.com/record/display.uri?eid=2-s2.0-84957041404&doi=10.5194%2fhess-20-257-2016&origin=inward&txGid=f22c6c5fa8b38c589f8a8881d5bb6177

U2 - 10.5194/hess-20-257-2016

DO - 10.5194/hess-20-257-2016

M3 - Article

VL - 20

SP - 257

EP - 277

JO - Hydrology and Earth System Sciences

JF - Hydrology and Earth System Sciences

SN - 1027-5606

IS - 1

ER -