Browsing by Author "Sadek, MA"

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    Evaporative isotope enrichment as a constraint on reach water balance along a dryland river
    (Taylor & Francis, 2008-03) Gibson, JJ; Sadek, MA; Stone, DJM; Hughes, CE; Hankin, SI; Cendón, DI; Hollins, SE
    Deuterium and oxygen-18 enrichment in river water during its transit across dryland region is found to occur systematically along evaporation lines with slopes of close to 4 in H-2-O-18 space, largely consistent with trends predicted by the Craig-Gordon model for an open-water dominated evaporating system. This, in combination with reach balance assessments and derived runoff ratios, strongly suggests that the enrichment signal and its variability in the Barwon-Darling river, Southeastern Australia is acquired during the process of evaporation from the river channel itself, as enhanced by the presence of abundant weirs, dams and other storages, rather than reflecting inherited enrichment signals from soil water evaporation in the watershed. Using a steady-state isotope mass balance analysis based on monthly O-18 and H-2, we use the isotopic evolution of river water to re-construct a perspective of net exchange between the river and its contributing area along eight reaches of the river during a drought period from July 2002 to December 2003, including the duration of a minor flow event. The resulting scenario, which uses a combination of climatological averages and available real-time meteorological data, should be viewed as a preliminary test of the application rather than as a definitive inventory of reach water balance. As expected for a flood-driven dryland system, considerable temporal variability in exchange is predicted. While requiring additional real-time isotopic data for operational use, the method demonstrates potential as a non-invasive tool for detecting and quantifying water diversions, one that can be easily incorporated within existing water quality monitoring activities. © 2008, Taylor & Francis Ltd.
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    Stable isotope tracing of water exchange along a dryland river
    (Goldschmidt, 2006-08-27) Gibson, JJ; Sadek, MA; Stone, DJM; Hughes, CE; Hankin, SI; Cendón, DI; Hollins, SE
    Deuterium and oxygen-18 enrichment in river water during its transit along the Barwon-Darling River, a dryland region in southeastern Australia, is found to occur systematically along evaporation lines with slopes of close to 4 in 2H-18O space. This is largely consistent with expected trends for an open-water dominated evaporating system. When combined with reach balance assessments and derived runoff ratios, this strongly suggests that the enrichment signal and its variability is acquired during the process of evaporation from the river channel itself, as enhanced by the presence of abundant weirs, dams and other storages, rather than reflecting inherited enrichment signals from soil water evaporation in the watershed. Using a steady-state isotope mass balance analysis based on monthly 18O and 2H, we use the isotopic evolution of river water to re-construct a picture of net exchange between the river and its contributing area along eight reaches of the river from July 2002 to December 2003, including the duration of a minor flood event. As expected for a flood-driven dryland system, considerable temporal variability in exchange is predicted. For 65% of all reach-months evaluated the river was apparently gaining water along its course; about 10% of these times it was also undergoing substantial volumetric drawdown. Overall, a broad systematic decline in the percentage of gaining intervals is noted from the upstream to downstream reaches, with most reaches gaining water substantially more than half of the time. One reach, known to be an intensive cotton-growing area, was found to be fairly balanced between gaining and losing periods. While a more detailed analysis is required to carefully verify the quantities of water exchange, a first assessment of monthly runoff ratios for the reach catchments suggests that the inflow estimates are reasonable. The technique, while requiring additional quantitative ground-truthing, demonstrates potential as a non-invasive tool for detecting and quantifying water diversions, one that can be easily incorporated within existing water quality monitoring activities.
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    Stable isotope tracing of water exchange along a dryland river
    (Goldschmidt, 2006-08-27) Gibson, JJ; Sadek, MA; Stone, DJM; Hughes, CE; Hankin, SI; Cendón, DI; Hollins, SE
    Deuterium and oxygen-18 enrichment in river water during its transit along the Barwon-Darling River, a dryland region in southeastern Australia, is found to occur systematically along evaporation lines with slopes of close to 4 in 2H–18O space. This is largely consistent with expected trends for an open-water dominated evaporating system. When combined with reach balance assessments and derived runoff ratios, this strongly suggests that the enrichment signal and its variability is acquired during the process of evaporation from the river channel itself, as enhanced by the presence of abundant weirs, dams and other storages, rather than reflecting inherited enrichment signals from soil water evaporation in the watershed. Using a steady-state isotope mass balance analysis based on monthly 18O and 2H, we use the isotopic evolution of river water to re-construct a picture of net exchange between the river and its contributing area along eight reaches of the river from July 2002 to December 2003, including the duration of a minor flood event. As expected for a flood-driven dryland system, considerable temporal variability in exchange is predicted. For 65% of all reach-months evaluated the river was apparently gaining water along its course; about 10% of these times it was also undergoing substantial volumetric drawdown. Overall, a broad systematic decline in the percentage of gaining intervals is noted from the upstream to downstream reaches, with most reaches gaining water substantially more than half of the time. One reach, known to be an intensive cotton-growing area, was found to be fairly balanced between gaining and losing periods. While a more detailed analysis is required to carefully verify the quantities of water exchange, a first assessment of monthly runoff ratios for the reach catchments suggests that the inflow estimates are reasonable. The technique, while requiring additional quantitative ground-truthing, demonstrates potential as a non-invasive tool for detecting and quantifying water diversions, one that can be easily incorporated within existing water quality monitoring activities. © 2006 Published by Elsevier Ltd.
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    Stable water isotope investigation of the Barwon–Darling River system, Australia
    (International Atomic Energy Agency, 2012) Hughes, CE; Stone, DJM; Gibson, JJ; Meredith, KT; Sadek, MA; Cendón, DI; Hankin, SI; Hollins, SE; Morrison, TN
    The Murray-Darling Basin is the largest river basin in Australia and is host to agriculture, recreation, water supply reservoirs and significant biodiversity. Through land use practices and climate change there is the potential for significant disruption to the natural hydrological system of the basin. The Barwon-Darling River, in the upper part of the Murray Darling Basin, is primarily in a semi-arid landscape which is subject to significant evaporation, yet evaporative losses from the river remain poorly described. The stable isotope composition of groundwaters has become widely used over the past several decades as an indicator of the circumstances and geographical locations of aquifer recharge, though applications to surface water budgets have been far less extensive. A global isotopic observation initiative, the Global Network for Isotopes in Rivers (GNIR), focussed in Australia on the dryland Barwon-Darling River system. We report on drought driven isotopic signatures in the Barwon-Darling River during 2002-2007 and estimate that the amount of water lost by the Barwon-Darling River system due to evaporation may be up to 80% during severe drought periods. Runoff ratios have been commonly estimated to be between 0.1 and 1% and there is evidence of groundwater exchange with the river. This work highlights the role of stable water isotopes in assessing the amount of water lost from the river by direct evaporation, and in quantifying groundwater inputs and ungauged losses from the river. © The Authors