| Summary: | This thesis investigates stable isotope signals (i.e. δ18O and δ2H) in various information carriers such as lake water and lacustrine sediments, aiming to develop and refine the use of isotope tracers in hydrology and paleohydrology studies. Located at the confluence of the Peace and Athabasca Rivers at the western end of Lake Athabasca, the PAD is a key node in the Mackenzie River Drainage system, the single large freshwater source discharging into the Arctic Ocean from continental Northern America. The delta is one of the world’s largest freshwater deltas, has hundreds of shallow lakes and wetlands, and has been regularly monitored for isotopic composition in surface water bodies over a 7-year period. Because of the hydrological significance of the delta, as well as the availability of a wealth of ancillary information collected by previous studies, the PAD serves as a natural laboratory to develop and refine the application of stable isotopes in understanding landscape hydrological conditions in present and past. The outcomes also provide critical information for the development of scientifically informed management strategies for water resources in the delta. In the study of modern processes, a novel coupled isotope tracer method was developed to characterize the isotopic composition of input water to lakes. The method is based on coupling the well-known Craig-Gordon model, which describes the evaporative enrichment process for both isotopes, with the Local Meteoric Water Line to constrain the isotopic composition of input water to lakes. The application of this method in two sampling campaigns (2000 and 2005) demonstrated significant temporal changes in source water to PAD lakes at landscape scale. The results also revealed the previously underestimated role of snowmelt to the northern part of the delta. In a laboratory culture experiment, effort was undertaken to understand the constant fractionation between aquatic cellulose and environmental water, which is routinely observed in field studies. This led ...
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