Faye Hicks

Mercury Export to the Arctic Ocean from the Mackenzie River, Canada

Circumpolar rivers, including the Mackenzie River in Canada, are sources of the contaminant mercury (Hg) to the Arctic Ocean, but few Hg export studies exist for these rivers. During the 2007-2010 freshet and open water seasons, we collected river water upstream and downstream of the Mackenzie River delta to quantify total mercury (THg) and methylmercury (MeHg) concentrations and export. Upstream of the delta, flow-weighted mean concentrations of bulk THg and MeHg were 14.6 ± 6.2 ng L(-1) and 0.081 ± 0.045 ng L(-1), respectively. Only 11-13% and 44-51% of bulk THg and MeHg export was in the dissolved form. Using concentration-discharge relationships, we calculated bulk THg and MeHg export into the delta of 2300-4200 kg yr(-1) and 15-23 kg yr(-1) over the course of the study. Discharge is not presently known in channels exiting the delta, so we assessed differences in river Hg concentrations upstream and downstream of the delta to estimate its influence on Hg export to the ocean. Bulk THg and MeHg concentrations decreased 19% and 11% through the delta, likely because of particle settling and other processes in the floodplain. These results suggest that northern deltas may be important accumulators of river Hg in their floodplains before export to the Arctic Ocean.

Local spring warming drives earlier river‐ice breakup in a large Arctic delta

Pan-Arctic rivers strongly affect the Arctic Ocean and their vast lake-rich deltas. Their discharges may be increasing because of an intensifying hydrological cycle driven by warming climate. We show that a previously unexplained trend toward earlier ice breakup in the Mackenzie River Delta is little affected by winter warming during the period of river-ice growth and is unaffected by river discharge, but unexpectedly is strongly related to local spring warming during the period of river-ice melt. These results are statistically linked to declining winter snowfall that was not expected because of an intensifying Arctic hydrological cycle. Earlier ice breakup is expected to cause declining water level peaks that will reduce off-channel flows through the lake-rich delta before river waters enter the ocean. Thus, local spring warming with unexpected snowfall declines, rather than warmer winters, can drive earlier ice breakup in large Arctic rivers and biogeochemical changes in their river-ocean interface.

Hydraulic modelling of subglacial tunnel channels, south‐east Alberta, Canada

One of the key issues associated with the hypothesis of catastrophic subglacial drainage of the Livingstone Lake event is whether flows of such large magnitudes are physically feasible. To explore this issue, a one-dimensional hydraulic network flow model was developed to investigate the range of peak discharges and associated flow parameters that may have been carried by a tunnel channel network in south-east Alberta, Canada. This tunnel channel network has been interpreted elsewhere to carry large discharges associated with subglacial meltwater flows because of the convex longitudinal profiles of individual channels. This computational modelling effort draws upon established and verified engineering principles and methods in its application to the hydraulics of this problem. Consequently, it represents a unique and independent approach to investigating the subglacial meltwater hypothesis. Based on the modelling results, it was determined that energy losses resulting from friction limit the maximum peak discharge that can be transported through the tunnel channel network to 10 7 m 3 s -1 , which is in reasonable agreement with previous estimates of flood discharges for proposed megafloods. Results show that flow through channels with convex longitudinal profiles occurs when hydraulic head exceeds 910 m (Lost River) and 950 m (Sage Creek), respectively. These are considerably below the maximum head capable of driving flow through the system of 1360 m, beyond which ice is decoupled from the bed across the pre-glacial drainage divide. Therefore, it is concluded that these model results support the hypothesis of catastrophic subglacial drainage during the Livingstone Lake event.

NSERC's HydroNet: A National Research Network to Promote Sustainable Hydropower and Healthy Aquatic Ecosystems

Abstract NSERCs HydroNet is a collaborative national five-year research program initiated in 2010 involving academic, government, and industry partners. The overarching goal of HydroNet is to improve the understanding of the effects of hydropower operations on aquatic ecosystems, and to provide scientifically defensible and transparent tools to improve the decision-making process associated with hydropower operations. Multiple projects are imbedded under three themes: 1) Ecosystemic analysis of productive capacity offish habitats (PCFH) in rivers, 2) Mesoscale modelling of the productive capacity offish habitats in lakes and reservoirs, and 3) Predicting the entrainment risk of fish in hydropower reservoirs relative to power generation operations by combining behavioral ecology and hydraulic engineering. The knowledge generated by HydroNet is essential to balance the competing demands for limited water resources and to ensure that hydropower is sustainable, maintains healthy aquatic ecosystems and a vibr...

Impact of Climate Change on the Peace River Thermal Ice Regime

A one-dimensional hydrodynamic model that includes river ice formation and melting processes is developed and used to assess climate change impact on the ice regime of the Peace River in Alberta. The model employs an Eulerian frame of reference for both the flow hydrodynamics and the ice processes (ice cover formation and deterioration) and uses the characteristic-dissipative-Galerkin finite element method to solve the primary equations. Model calibration and validation results with historical data are presented; these indicate that the present model adequately simulates water temperature and ice front profiles. Higher air temperatures predicted by the CGCM2 climate model were used to generate future ice front profiles that correspond to the historical runs. This preliminary climate change impact analysis suggests that there is a significant potential for a shorter ice-covered season on the Peace River by the 21st century. At the Town of Peace River, the average total reduction in ice cover duration is 28 days (31%) under the scenario applied.

Regression and Fuzzy Logic Based Ice Jam Flood Forecasting

In Canada, ice jam events have frequently produced the most extreme and dangerous flood events on record, resulting in millions of dollars in associated damages. However, our ability to forecast such events remains quite limited. An example of this is the Athabasca River at Fort McMurray, Alberta, where severe ice jam events have been documented for over 100 years, and where breakup has been monitored intensively for the past 25 years. Despite these efforts, no reliable flood forecast model is yet available. Here, the use of Fuzzy Expert Systems is explored to examine their potential for developing long lead time ice jam risk forecasts for this site. The developed System identified seven out of twenty two years that had the potential for high water levels, including all four years where high water levels actually occurred. These preliminary results suggest that Fuzzy Expert Systems are promising tools for long range ice jam flood forecasting.

Modeling Thermal and Dynamic River Ice Processes

River ice jam formation and release both have the potential to cause flooding and present a threat to human safety. From a flood forecasting perspective, it is highly desirable to be able to predict the effects of ice on streamflow hydraulics. Although a number of models have been developed over the years that do consider ice effects, the majority of these are proprietary. This paper reports on recent developments in incorporating ice processes into the public domain River1D hydrodynamic model. The first objective in this effort was to incorporate river ice formation and melting processes and the application of these components is illustrated for the Peace River in western Canada. The model employs an Eulerian frame of reference for both the flow hydrodynamics and the ice processes and uses a Petrov-Galerkin finite element method to solve the primary equations. Model calibration and validation results with historical data are presented; these indicate that the present model adequately simulates water temperature and ice front progression. However, further enhancements are required to include certain dynamic freeze-up processes, in order to refine the ice front results. Ice jam formation and release components have also been added to the model to facilitate the ice jam flood forecasting application and these capabilities are demonstrated by modeling the large ice jam release event that occurred on the Athabasca River, AB, in 2002. Total ice and water mass and momentum equations are solved in an uncoupled sequence with ice mass conservation, with ice momentum effects considered empirically. The model is found to do a good job of modeling release wave speed and peak magnitude. Further enhancements to consider ice momentum effects more explicitly are underway.