Using high temporal resolution δD, δ¹⁸O to determine groundwater and surface water interactions in tropical catchments

Rockett, Nicholas (2015) Using high temporal resolution δD, δ¹⁸O to determine groundwater and surface water interactions in tropical catchments. Masters (Research) thesis, James Cook University.

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Abstract

This Master thesis focuses on the deployment of newly developed instruments capable of monitoring the isotopic composition of water continuously and in-situ in a remote, pristine, rainforest location in the Daintree region of Far-North Queensland. Over a series of four rain-system events, towards the end of the tropical wet season 2013, two Picarro, Cavity Ring-Down Spectrometers, incorporating Diffusion Sampling units (DS-CRDS), were operated simultaneously over an extended period, to measure rainwater and creekwater isotope values at sub-minute temporal resolution. Over the series of experiments, successful methods and operational strategies were developed to cope with the often-challenging conditions faced. One storm occurrence was successfully monitored by both CRDSs during a field trip in early March 2013. Two significant rain events occurred during the transition of this system: one very intense flood event, recording a fall of 7.55 ‰ VSMOW in rainwater values and a second, less intense event, over a protracted period, with a fall of 9.68 ‰ VSMOW. The second instrument simultaneously recorded creek water isotope values, recording a fall of 1.6 ‰ VSMOW over the course of the second event. Comparison of rain intensity and ambient air temperature with isotope value, over the two events showed no significant positive correlation, confirming previous research. The simultaneous monitoring results, from the second event demonstrate the superiority of high temporal resolution methods in monitoring and modeling the water cycle and streamflow generation. Comparing mean isotope values for both event and creek water, real time values for event-water/mean values for creek-water and real time values for event-water/ 15-minute discreet values for creek-water, indicated that high resolution, in conjunction with the extra component, can highlight subtle changes to creek contribution over time. Using statistical mean values to calculate relative contribution of event water to discharge results in an input of 0.03 %. When calculated using the mean contribution values of real time analysis, the event water contributions are: 3.88 %, using mean fixed value creek/groundwater and 5.53 % using mean 15-minute values for creekwater and fixed value groundwater. These results suggest that higher temporal resolution monitoring components may produce greater accuracy in discharge contribution values.

Item ID: 41340
Item Type: Thesis (Masters (Research))
Keywords: creek water; creeks; Daintree rainforest Daintree; environmental tracers; groundwater flow; groundwater; hydrogeology; Queensland; rain; rainfall; rainwater; surface water hydrology; surface water; Thompson Creek; tropical rainforests; tropics; water isotopes
Date Deposited: 02 Dec 2015 04:31
FoR Codes: 04 EARTH SCIENCES > 0406 Physical Geography and Environmental Geoscience > 040603 Hydrogeology @ 50%
04 EARTH SCIENCES > 0406 Physical Geography and Environmental Geoscience > 040608 Surfacewater Hydrology @ 50%
SEO Codes: 96 ENVIRONMENT > 9609 Land and Water Management > 960903 Coastal and Estuarine Water Management @ 50%
96 ENVIRONMENT > 9611 Physical and Chemical Conditions of Water > 961103 Physical and Chemical Conditions of Water in Fresh, Ground and Surface Water Environments (excl. Urban and @ 50%
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