Paleohydrologic Reconstruction of Three Shallow Basins, Slave River Delta, NWT, Using Stable Isotope Methods

• Main Author: Mongeon, Cherie
• Format: Text
• Language: unknown
• Published: Scholars Commons @ Laurier 2008
• Subjects: Physical and Environmental Geography; Athabasca River; Peace-Athabasca Delta; First Nations; Slave River
• Online Access: https://scholars.wlu.ca/etd/870; https://scholars.wlu.ca/context/etd/article/1869/viewcontent/MR38718.PDF

p>The long-term natural hydrological variability of the Slave River Delta (SRD), NWT, is not well documented and needs to be further developed to provide temporal context to understand and evaluate impacts of Slave River (SR) floodwater influence and climate variability and change on contemporary hydro-ecological doncidiotns of the SRD. The SRD has broad ecological and cultural significance, as it provides extensive habitate for wildlife and is important for local First Nations community who have an historical connection with the delta and its resources. Concners have been raised over recently reported drying trends in the SRD over the past few decades and have largely been attributed to the regulation of the Peace River (PR), which supplies the SR with ∼65% of its annual flow. Modern lake water balances (2003 to 2005) of three lakes from different hydrological settings within the SRD were assessed with oxygen (δ18O) and hydrogen (δ2H) stable isotope analyses. Contemporary lake water balance was used to constrain paleohydrological interpretations of cellulose-inferred δ18O from lake sediment cores. Past hydro-ecological conditions of each lake was also reconstructed using bulk organic carbon and nitrogen elemental and stable isotope analyses. Lead-210 (210Pb) and caesium-137 (137Cs) analyses were conducted to establish sediment core chronologies. Results from lake water δ18O and δ2H analyses of SD20, an evaporation-dominated basin, indicate seasonal precipitation, snowmelt runoff and evaporation predominantly control the water balance of this lake. An ∼215-year cellulose-inferred δ18Olw, δ13C and δ15N record of SD20 provides paleoclimatological evidence that recently reported dry conditions in the SRD are not outside of the range of natural variability for the delta. SD20 paleohydrological records follow a similar pattern as PAD5, a climate-driven basin in the Peace-Athabasca Delta (PAD), and align with paleoclimate records reconstructed from tree-ring sequences from the Athabasca River headwaters. Results ...