Application of stable water isotopes to quantify the water balance of Delta Marsh
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Date
2020-08-05
Authors
Glavonjic, Marija
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Abstract
This thesis as a part of the rehabilitation project Restoring the Tradition at Delta Marsh, details stable water isotope research. Stable water isotopes are applied as a tool to quantify the water balance of the Marsh. A four-year sampling campaign for stable water isotopes was launched. Coupled with the hydraulic and hydrologic modelling, stable water isotopes assist in the understanding of contemporary water balance and the relative contribution of inflows to evaporative losses. Two hydrologically different years (2013 and 2014) are compared to offer insight into the Marsh functioning under differing climatic conditions. A contemporary isotopic framework was developed to determine correlation between end-members influencing Marsh hydrologic change. The framework has shown that the Marsh is not in hydrologic steady-state, which was previously confirmed by 2D hydraulic modelling. An isotope mass balance mixing model was established to evaluate evaporative loss (relative to inflows), and to determine residence time and water yield including marsh-lake dynamic interactions. Time series modelling was performed and confirmed that a time-dependent isotopic model is more suitable than a fraction-dependent model for modelling Marsh isotope composition. Evaporation is the most significant component in the water balance. The isotope mass balance model demonstrated that evaporation to inflow ratio was 22% in 2013 and 24% in 2014. Water residence time was found to be 99 and 140 days in 2013 and 2014, respectively. Water yield for both years was approximately 280 mm/year.
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water resources