Bow River - TransAlta agreement
In 2016, the Government of Alberta (GoA) entered into a 5-year agreement with TransAlta Generation Partnership (TransAlta) to modify operations at several TransAlta water infrastructure facilities to help protect communities along the Bow River against the impacts of both floods and drought. The agreement was extended in 2026 for the second time for an additional 5 years, now expiring on April 1, 2031.
TransAlta modified agreement
Leveraging existing infrastructure is an effective and immediate option to help protect communities, including the City of Calgary, along the Bow River downstream of Ghost Reservoir.
Terms of the agreement:
- The original 5-year Water Services Agreement began in May 2016.
- TransAlta and the GoA recently extended the existing agreement, which now is in effect until April 1, 2031.
- The modified operations period at Ghost Reservoir is from May 16 to July 7 for flood mitigation purposes.
- The modified operations period at Upper and Lower Kananaskis Lakes is year-round, and primarily for drought mitigation purposes.
- Compensation paid to TransAlta is $5.5 million per year.
Flood management
The extended agreement allows the Province of Alberta to set elevations on the Ghost Reservoir during the period of May 16 to July 7 annually, which is typically the highest flood risk period of the year.
Up to 65 million m³ of storage will be available at Ghost Reservoir for flood mitigation purposes. The amount of storage available will vary each year based on prevailing conditions. Sixty-five million m³ is a significant amount of storage, but it would not prevent flooding if we experienced a repeat of the 2013 flood event. Using available storage does, however, give operators the ability to attenuate – or lower to some degree – the peak flows experienced downstream of the reservoir and may also delay the arrival of peak flows to downstream communities.
Drought management
The agreement includes the ability of the Alberta government to have TransAlta store additional water in the Kananaskis system to be used during periods of low flows in the Bow River. This section of the agreement is in effect year-round for the duration of the agreement. Up to 40 million m³ may be available at the Kananaskis-area reservoirs for drought mitigation during periods of extreme low-flow stress on the Bow River. During times of drought, water stored in upstream reservoirs (Kananaskis system) can be released into the Bow River to maintain minimum environmental flows.
Reservoir management
Each year, the Government of Alberta works closely with TransAlta to assess and determine appropriate reservoir elevations during the control period, May 16 to July 7. Some of the key factors that are considered include current snowpack conditions in the mountains, baseline river flows, soil moisture conditions and the Provincial Water Supply Outlook. Above average snowpack in the mountains means storm events could generate higher flood flows and it also suggests a higher likelihood of being able to fill the reservoir later in the summer. Under these conditions the reservoir would be set to a lower elevation during the control period. If the overall water supply forecasts were below normal or we were experiencing a multi-year water shortage cycle, Ghost Reservoir levels could be set above the lowest threshold. It is a challenge to balance both the need for maintaining flood control storage and being able to fill the reservoir later in the summer after the highest flood risk period has passed. Current information on all reservoir elevations, river flows and proposed forecasted operations will be posted on Alberta River Basins under forecasters comments.
Ghost Reservoir
Lower water levels at Ghost Reservoir during the period of this agreement are still within the defined operating limits of TransAlta’s water license and within the historic operating range. The Ghost Lake Reservoir is a “reservoir” and will fluctuate over a broad range of elevations. In some years the reservoir will be operated near historical norms and, in potentially wet years, the reservoir will be set lower. The Government of Alberta is only able to specify target reservoir elevations on Ghost Reservoir during the control period and an overall volume target in the Kananaskis system. TransAlta considers a number of factors when deciding how to meet these targets, including factors related to riparian health, fisheries as well as commercial interests.
TransAlta compensation
Compensation paid to TransAlta is intended to offset the estimated commercial loss TransAlta will incur due to modified operations at the 4 facilities included in the agreement. These reservoirs are designed and operated to produce electricity. The lower the water level, the less electricity TransAlta is able to produce. By holding at set elevations, TransAlta’s ability to optimize for power production is also reduced.
Contact
For information about the modified operations agreement with TransAlta, contact the Information Centre: