Groundwater-dependent ecosystems: recent insights from satellite and field-based studies
Groundwater-dependent ecosystems (GDEs) are at risk globally due to unsustainable levels of groundwater extraction, especially in arid and semi-arid regions. In this review, we examine recent developments in the ecohydrology of GDEs with a focus on three knowledge gaps: (1) how do we locate GDEs, (2...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2015-10-01
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| Series: | Hydrology and Earth System Sciences |
| Online Access: | http://www.hydrol-earth-syst-sci.net/19/4229/2015/hess-19-4229-2015.pdf |
| _version_ | 1819259606800531456 |
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| author | D. Eamus S. Zolfaghar R. Villalobos-Vega J. Cleverly A. Huete |
| author_facet | D. Eamus S. Zolfaghar R. Villalobos-Vega J. Cleverly A. Huete |
| author_sort | D. Eamus |
| collection | DOAJ |
| description | Groundwater-dependent ecosystems (GDEs) are at risk globally due to
unsustainable levels of groundwater extraction, especially in arid and
semi-arid regions. In this review, we examine recent developments in the
ecohydrology of GDEs with a focus on three knowledge gaps: (1) how do we
locate GDEs, (2) how much water is transpired from shallow aquifers by GDEs
and (3) what are the responses of GDEs to excessive groundwater extraction?
The answers to these questions will determine water allocations that are
required to sustain functioning of GDEs and to guide regulations on
groundwater extraction to avoid negative impacts on GDEs.
<br><br>
We discuss three methods for identifying GDEs: (1) techniques relying on
remotely sensed information; (2) fluctuations in depth-to-groundwater that
are associated with diurnal variations in transpiration; and (3) stable
isotope analysis of water sources in the transpiration stream.
<br><br>
We then discuss several methods for estimating rates of GW use, including
direct measurement using sapflux or eddy covariance technologies, estimation
of a climate wetness index within a Budyko framework, spatial distribution of
evapotranspiration (ET) using remote sensing, groundwater modelling and
stable isotopes. Remote sensing methods often rely on direct measurements to
calibrate the relationship between vegetation indices and ET. ET from GDEs is
also determined using hydrologic models of varying complexity, from the White
method to fully coupled, variable saturation models. Combinations of methods
are typically employed to obtain clearer insight into the components of
groundwater discharge in GDEs, such as the proportional importance of
transpiration versus evaporation (e.g. using stable isotopes) or from
groundwater versus rainwater sources.
<br><br>
Groundwater extraction can have severe consequences for the structure and
function of GDEs. In the most extreme cases, phreatophytes experience crown
dieback and death following groundwater drawdown. We provide a brief review
of two case studies of the impacts of GW extraction and then provide an
ecosystem-scale, multiple trait, integrated metric of the impact of
differences in groundwater depth on the structure and function of eucalypt
forests growing along a natural gradient in depth-to-groundwater. We conclude
with a discussion of a depth-to-groundwater threshold in this mesic GDE.
Beyond this threshold, significant changes occur in ecosystem structure and
function. |
| first_indexed | 2024-12-23T19:12:41Z |
| format | Article |
| id | doaj.art-ca91078774ff41dd9c645755a1e0c373 |
| institution | Directory Open Access Journal |
| issn | 1027-5606 1607-7938 |
| language | English |
| last_indexed | 2024-12-23T19:12:41Z |
| publishDate | 2015-10-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Hydrology and Earth System Sciences |
| spelling | doaj.art-ca91078774ff41dd9c645755a1e0c3732022-12-21T17:34:24ZengCopernicus PublicationsHydrology and Earth System Sciences1027-56061607-79382015-10-0119104229425610.5194/hess-19-4229-2015Groundwater-dependent ecosystems: recent insights from satellite and field-based studiesD. Eamus0S. Zolfaghar1R. Villalobos-Vega2J. Cleverly3A. Huete4National Centre for Groundwater Research and Training, University of Technology Sydney, P.O. Box 123, Sydney, NSW 2007, AustraliaNational Centre for Groundwater Research and Training, University of Technology Sydney, P.O. Box 123, Sydney, NSW 2007, AustraliaNational Centre for Groundwater Research and Training, University of Technology Sydney, P.O. Box 123, Sydney, NSW 2007, AustraliaSchool of Life Sciences, University of Technology Sydney, P.O. Box 123, Sydney, NSW 2007, AustraliaSchool of Life Sciences, University of Technology Sydney, P.O. Box 123, Sydney, NSW 2007, AustraliaGroundwater-dependent ecosystems (GDEs) are at risk globally due to unsustainable levels of groundwater extraction, especially in arid and semi-arid regions. In this review, we examine recent developments in the ecohydrology of GDEs with a focus on three knowledge gaps: (1) how do we locate GDEs, (2) how much water is transpired from shallow aquifers by GDEs and (3) what are the responses of GDEs to excessive groundwater extraction? The answers to these questions will determine water allocations that are required to sustain functioning of GDEs and to guide regulations on groundwater extraction to avoid negative impacts on GDEs. <br><br> We discuss three methods for identifying GDEs: (1) techniques relying on remotely sensed information; (2) fluctuations in depth-to-groundwater that are associated with diurnal variations in transpiration; and (3) stable isotope analysis of water sources in the transpiration stream. <br><br> We then discuss several methods for estimating rates of GW use, including direct measurement using sapflux or eddy covariance technologies, estimation of a climate wetness index within a Budyko framework, spatial distribution of evapotranspiration (ET) using remote sensing, groundwater modelling and stable isotopes. Remote sensing methods often rely on direct measurements to calibrate the relationship between vegetation indices and ET. ET from GDEs is also determined using hydrologic models of varying complexity, from the White method to fully coupled, variable saturation models. Combinations of methods are typically employed to obtain clearer insight into the components of groundwater discharge in GDEs, such as the proportional importance of transpiration versus evaporation (e.g. using stable isotopes) or from groundwater versus rainwater sources. <br><br> Groundwater extraction can have severe consequences for the structure and function of GDEs. In the most extreme cases, phreatophytes experience crown dieback and death following groundwater drawdown. We provide a brief review of two case studies of the impacts of GW extraction and then provide an ecosystem-scale, multiple trait, integrated metric of the impact of differences in groundwater depth on the structure and function of eucalypt forests growing along a natural gradient in depth-to-groundwater. We conclude with a discussion of a depth-to-groundwater threshold in this mesic GDE. Beyond this threshold, significant changes occur in ecosystem structure and function.http://www.hydrol-earth-syst-sci.net/19/4229/2015/hess-19-4229-2015.pdf |
| spellingShingle | D. Eamus S. Zolfaghar R. Villalobos-Vega J. Cleverly A. Huete Groundwater-dependent ecosystems: recent insights from satellite and field-based studies Hydrology and Earth System Sciences |
| title | Groundwater-dependent ecosystems: recent insights from satellite and field-based studies |
| title_full | Groundwater-dependent ecosystems: recent insights from satellite and field-based studies |
| title_fullStr | Groundwater-dependent ecosystems: recent insights from satellite and field-based studies |
| title_full_unstemmed | Groundwater-dependent ecosystems: recent insights from satellite and field-based studies |
| title_short | Groundwater-dependent ecosystems: recent insights from satellite and field-based studies |
| title_sort | groundwater dependent ecosystems recent insights from satellite and field based studies |
| url | http://www.hydrol-earth-syst-sci.net/19/4229/2015/hess-19-4229-2015.pdf |
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