Project Description

This study investigates long-term (1964-2007) variability in annual discharge records of 45 rivers that flow in Canada's portion of the pan-Arctic drainage basin and drain more than half of Canada’s land surface. Recent studies focusing on river discharge in northern Canada documented no trend in annual flows into the Arctic Ocean between 1964 and 2003 [Déry and Wood, 2005] and a decreasing trend into the Hudson, James and Ungava Bays basin from 1964 to 2000 [Déry et al., 2005]. This research, however, lacked information on possible changes in the variability of annual streamflow in northern Canada. Thus, the goal of this study is to better understand the variability and trends of discharge in northern Canadian rivers by examining the spatial and temporal distribution of observed annual flows into the Canadian pan-Arctic drainage system. This project is a contribution to the IPY effort as it focuses on expanding the body of evidence pertaining to hydrological variability in the pan-Arctic. As a legacy of the IPY, this study provides updated streamflow records (available here) for Canadian rivers flowing into polar seas and information on their trends and variability.

Methods

The observed daily discharge rates covering the period 1964-2007 (where and when available) are extracted from the online Hydrometric Database (HYDAT). The study period is limited to 44 years since the network of river gauges (for most rivers) degrades considerably prior to 1964. Recent (2001-2007) daily discharge data for rivers of Nunavik (northern Québec) are provided by Environnement Québec with the exception of the intensively dammed La Grande Rivière for which daily hydrometric measurements are supplied by the power generation company Hydro-Québec. Unfortunately, we do not have consent to republish all hydrometric data for La Grande Rivière; we can only publish data from 1964 - 1978 which was accessed from HYDAT. Hydrometric data for the Yukon River station at Eagle creek, an international gauging station (in Canada: 09ED001, United States: 15356000), were extracted from the United States Geological Survey (USGS; available online at http://waterdata.usgs.gov/nwis). This gauge has been considered as an international gauging station between the USGS and WSC since 1983. The information provided on this website has been aggregated, in-filled, and generated from orginal data obtained from Environment Canada, Environnement Québec, and USGS. The 2008 HYDAT data (not included in the study) has recently been added to this dababase; however, the 2008 data for the following rivers are not yet available, but will be shortly: Aux Feuilles, Boutin, Eastmain, George, Hamelin, Melezes, La Grande Rivière, Petite Rivière de la Baleine, Rupert, Burntwood, Nelson, Seal, and Ellice. The original data can be observed from their respective websites; however, the method in which we altered the orginal information is described below:

1. The flags (e.g. E = Estimated, B = Ice Conditions, A = Partial Day) shown beside applicable data on the HYDAT website have been ignored and removed.

2. Flow rates recorded by the gauge nearest to the rivers’ outlet into the pan-Arctic drainage basin are first used as the most representative for the entire river basin. In situations where there are missing data, measurements from an upstream recording gauge along the river are used if available. In these instances, the river runoff rates are adjusted to reflect the missing contributing area to total discharge such that

   
   

   R_d = R_u * A_d /A_u

   
   

   where R (m³ s^-1) denotes the runoff rate over an area A (m²) and where the subscripts u and d identify the upstream and downstream locations.

3. Several time series of river discharge are incomplete (i.e. have missing data with no upstream recording gauge), particularly in the Yukon, Northwest and Nunavut Territories at the beginning of the study period and in northern Ontario and Québec at the end of the period of interest. Data gaps are in-filled with mean daily discharge values over the period of record at each of the gauges.

4. The fraction of missing data for the time series has been calculated. However, only the fraction of missing data for the annual and daily discharge values is displayed on this website. The fraction of missing data for the monthly discharge values is not displayed; if this data is desired, it can be calclulated by using the fraction of missing data from the daily discharge values. Technically, the fraction of missing data from the daily values should be "0" or "1" (but often shown as "0.9999..") for those rivers with or without data.

   In addition, for those rivers comprised of major tributaries, the fraction of missing data is expressed as a fraction of the missing contributing area. For instance: "Joe" River has two significant tributaries, but there is no data for one tributary (i.e. Joe 1) of area A₁. To calculate the "missing" fraction of data for Joe River on that day, the following formula is used:

   
   

   Missing Data = A₁/(A₁ + A₂)

   
   

   Where A₂ is the contributing area of the other tributary (i.e. Joe 2). So the total discharge value for Joe River is composed by the sum of: the mean discharge data of Joe 1, and the unaltered data of Joe 2. Meaning we only substitute the missing discharge data for Tributary Joe 1 with the mean value for that day, and we use the unaltered data for Tributary Joe 2 for that day.

5. Given the paucity of Arctic Archipelago hydrological data, missing wintertime (January to May, inclusive) discharge records for Freshwater Creek and the Sylvia Grinnell River, Nunavut, are taken as zero (i.e. due to water freezing completely).