Author(s): Holly Goulding; Terry Prowse
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Abstract: The Mackenzie Delta is covered in freshwater lakes that provide habitat for a myriad of species. The hydrology and ecology of these delta lakes are dominated by cryospheric processes, specifically snowmelt induced spring break-up ice jams, which typically produce the largest hydrologic event of the year. In light of limited current understanding of break-up patterns and processes in the delta, the objectives of this research are to explore the consistency of intra-delta water level variations occurring during extreme floods in the delta, determine the recurrence of these floods, and consider the influence of flood severity on the timing and duration of break-up. To complete the analysis, a break-up chronology for the period from 1972 to 2006 is assembled using a series of event-based hydrometric variables for 14 Water Survey of Canada (WSC) hydrometric stations in the delta. Historical observations and remote sensing products are used to inform and constrain the variables. Analysis of backwater level and discharge at the Mackenzie River at Arctic Red River (MARR) station and the associated spatial distribution of peak water levels in the delta are used to explain the physical rational of spatial patterns, while a return period assessment is conducted to determine the recurrence of peak water levels. Temporal patterns of extreme events are investigated through a comparison of timing and duration to averages determined for the delta. The results of the analysis highlight years of extensive delta flooding, and within the subset of larger flood years, two types of events are identified: icedominated events, with high peak water levels at MARR associated with high levels in the middelta, and discharge-driven events, with extensive high water levels in the mid and outer delta despite lower upstream peak water levels. Temporally, the break-up initiation during ice (discharge) driven events occurs earlier (later) than the delta average; no trend is detected with respect to break-up duration. These findings represent the first stage of continued investigation into the hydroclimatic controls on extreme hydrological events in the Mackenzie Delta.
Year: 2008