Description of the Hydrometric and Meteorological Data for the Eastern Part of Hudson Bay

Description of the hydrometric and meteorological data for the eastern part of Hudson Bay

1Introduction

This document is a short description of the hydrometric and meteorological data available at Hydro-Québec for the eastern part of Hudson Bay, including James Bay. It is intended to accompany data provided by Hydro-Québec’s research institute in the context of the BaySys project.

2Hydrometric data

Figure 1 shows a map of the watersheds of rivers flowing into eastern Hudson Bay for which hydrometric data is available. The eastern part of Hudson Bay in Québec is a vast territory populated mostly by isolated natives’ communities.Hydro-Québec operates two large hydroelectric complexes on this territory: the La Grande complex, and the Eastmain-1-A-Sarcelle-Rupert complex.Throughout the years, many hydrometric stations were installed by the CEHQ[1], but for limited time spans only.These stations provide streamflow time series based on water level gauges and rating curves and are represented by green circles in Figure 1. Another source of hydrometric data is the net basins supplies (NBS) calculated at each Hydro-Québec power plant (or dam),represented by blue circles in Figure 1.Note that the sub-basin contours of the Eastmain-Rupert complex are not shown in Figure 1 for better overall visualisation, but are depicted in Figure 2. These NBS are computed with the following equation:

Where ΔS is the change in storage, I is the inflow from the upstream power plant, and O is the outflow from the current power plant. The change in storage is determined from reservoir water level measurements, and the inflows and outflows are calculated from the electric output and characteristic curves of turbines in the plants. NBS are subject to greater error than conventional streamflow measurements because of the incertitude associated with (1) the measurement of water levels in large reservoirs, (2) the modelling of storage based on water levels, and (3) the modelling of flow through a turbine based on the electric power produced. For these reasons, the time series of the La Grande complex are particularly noisy in the post-impoundment decades.Nonetheless, NBS are useful to calibrate hydrological models as they represent the natural flows from a watershed, without the influence of dam regulation.

Table 1 provides a description for each station in Figure 1 and other characteristics of the watershed (basin area, type of measurement, years with data). For every station in Table 1, the data is available at a daily time step.

Figure 1 Map of the watersheds with available hydrometric data (Google Earth Enterprise)

Table 1 Description of the hydrometric stations

2.1The La Grande complex and Eastmain-Rupert diversion

2.1.1Description of the tributaries to the La Grande complex

The La Grande complex, shown in Figure 2, drains a vast territory using a large networkof dikes, dams, canals andtunnels. Total or partial streamflows from the Caniapiscau, La Grande, Eastmain and Rupert rivers ultimately converge to the LG-1 power plant.

The Caniapiscau and Eastmain rivers were diverted during the first phase of the La Grande project, in the late 1970s and early 1980s. The Caniapiscau River initially flowed northward, and the Eastmain River (shown in blue in Figure 2) flowed westward. After the diversions, the headwaters of the Caniapiscau River flowed towards LG-4 through the Fontanges and Laforge rivers (not shown explicitly in the Figure). The Eastmain River was diverted towards the LG-2 power plant. Between 2002 and 2012, approximately 50 % of the total flow of the Rupert River (shown in yellow in Figure 2)was diverted towards the Eastmain River. The data from the 090601 station (1959-1980) and the 081002 station (1964-2004) thus represent the natural configuration of the Eastmain and Rupert rivers prior to the diversion.

Figure 2 Close-up on the Eastmain-Rupert diversions and the La Grande complex

2.1.2Net basin supplies

Net basins supplies from the La Grande complex consist of the natural contribution of the watershed comprised between two power plants (or dams). The NBS at one station thus does not include the flow from the upstream watershed. For instance, the NBS at LG-3 (948103) doesn’t include the flow from LG-4 (948076), nor does LG-4 include the flow from Laforge-1 and 2 (948064), and so on. In order to obtain the total outflow from the La Grande complex, NBS along the complex (including the Eastmain-Rupert diversion) must be summed/routed. On a daily time step though, the transit time of water must be taken into account. At the time of the redaction of this short report, the equations needed for routing the flows were not readily available, but a request has been made to obtain them.

2.1.3Regulated outflows to Hudson Bay

The regulated outflows from the LG-1 power plant are also available for the period 1995-2014 on a daily basis. Since these outflows consist of the actual amount of water exiting the power plant, they do not follow the hydrological cycle, but are rather influenced by power production and reservoir management rules. These data can be provided with the signature of a confidentiality agreement.

3Meteorology

The meteorological data consists of basin averages of the daily minimum and maximum temperatures and total precipitation. Basin averages are computed from the interpolated gridded data produced by NRCan(Hutchinson et al., 2009; McKenney et al., 2011) at a resolution of 10 km x 10 km. The data currently delivered range from 1971-2010. They shall be updated to include 2011-2013 and subsequent years as the observations are processed and made available by NRcan.

4References

Hutchinson, M. F., McKenney, D. W., Lawrence, K., Pedlar, J. H., Hopkinson, R. F., Milewska, E., & Papadopol, P. (2009). Development and Testing of Canada-Wide Interpolated Spatial Models of Daily Minimum–Maximum Temperature and Precipitation for 1961–2003. Journal of Applied Meteorology and Climatology, 48(4), 725–741.

McKenney, D. W., Hutchinson, M. F., Papadopol, P., Lawrence, K., Pedlar, J., Campbell, K., … Owen, T. (2011). Customized Spatial Climate Models for North America. Bulletin of the American Meteorological Society, 92(12), 1611–1622.

[1]Centre d’expertise hydrique du Québec, Ministère du Développement durable, de l’Environnement et de la Lutte contre les changements climatiques. The CEHQ is in charge of collecting the hydrological and hydraulic data needed by the Ministère for managing Québec’s water resources.