Water management along the Bow River system is a complex process that involves a number of different stakeholders. The 2013 flood brought about a heightened awareness of the devastating impact water can have on our communities and how water management along the Bow River system could be changed to not only protect Bow River communities, but also the Downtown Core. Insight into the complexity of water management along the Bow River system starts with an understanding of the history of how existing network of hydro facilities along the Bow River system came about, as well as the complexity involved in managing the diversion and use of water along the system. In collaboration with TransAlta, CRCAG has constructed the following write-up which outlines a brief overview on the history of hydroelectric development and water management along the Bow River system, as well as the impact TransAlta facilities had during the June 2013 flood. From this, you will see the necessity of ensuring that a long-term water management agreement is reached between TransAlta and the Alberta Government, so as to provide some degree of flood protection to Bow River communities and the Downtown Core when the next, inevitable, flood occurs.
How existing infrastructure along the Bow River System came about
Calgary was officially incorporated as a municipality in 1884, with a population of 400 residents. As the population of the City increased so did its demand for electricity. Initially, the Calgary Water Power Company, a subsidiary of the Eau Claire Lumber Company, supplied hydroelectricity to the growing city. As Calgary grew, the Company was unable to meet the City’s electricity demands. The growing demand for electricity gave rise to the concept of harnessing the natural power of upstream waterfalls along the Bow River to meet Calgary’s electricity demands. In 1907, two entrepreneurs, Budd and Alexander, successfully obtained a license to develop Horseshoe Falls into a hydroelectric facility, under the company name of Calgary Power & Transmission Company (which eventually became TransAlta).
Calgary Power began constructing its first hydroelectric facility, the Horseshoe Power Plant, in 1909. However, engineers failed to take into account the unpredictable nature of the Bow River. Calgary Power witnessed the fickle nature of the Bow River when it nearly dried up in Feb/Mar 1910, and then flooded in June 1910. The irregular flow of the Bow River forced the company to redesign Horseshoe dam’s spillways and to rethink how it could meet the contracted power agreements with the City of Calgary. With the Horseshoe facility completed in 1911, it was clear that more capacity was required to fulfil the electricity contract Calgary Power had with the City of Calgary. This led to a second hydroelectric facility being constructed at Kananaskis Falls, which commenced operation in 1913.
Even with the Horseshoe and Kananaskis facilities in operation, winter flows were too low to keep up with the electricity demands of the City of Calgary. As such, Calgary Power sought to enhance the storage of Lake Minnewanka in order to augment winter flows in the Bow (a small dam was already constructed by the Federal Parks Department to improve navigation on the lake in 1908). However, Calgary Power faced opposition to the hydropower development at Lake Minnewanka, as conservation groups argued that it would detract from the beauty of the landscape and undermine tourism in the National Park. After extensive negotiations, Calgary Power received permission to raise the dam by 3.7 meters to provide winter storage. However, an application for further enlargement of Lake Minnewanka in 1914 was denied and the outcry from the conservation groups stalled the approval to further enlarge Lake Minnewanka for many years.
In the 1920’s, Calgary Power explored the possibility of developing Spray Lakes into a hydroelectric storage site, but environmental and economic issues delayed this development. As a result, Calgary Power turned its attention to construction of the Ghost Dam to meet the electricity demands of Calgarians. The completion of the Ghost Dam in 1929 gave rise to the present day Ghost Reservoir, but with the onset of the Great Depression, further hydroelectric storage development was halted along the Bow River system.
World War II created new demands related to the war effort and to meet those demands, Calgary Power was granted the ability to enhance the storage of Lake Minnewanka and to construct a diversion that would divert water from the north Ghost River into Lake Minnewanka. As such, the height of the dam at Lake Minnewanka was raised and the Cascade hydroelectric facility was completed in 1942. Following the construction of Cascade, hydroelectric facilities were built at Barrier (1947) and Spray Lakes (1951 – Three Sisters, Spray, and Rundle facilities).
In the 1950s, additional facilities along the Bow tributaries were added to increase the efficiency of the Horseshoe, Kananaskis and Ghost facilities. The additional facilities included Interlakes (between Upper and Lower Kananaskis Lakes) and Pocaterra (on Lower Kananaskis Lake). Based on the findings of a Royal Commission study, Calgary Power built Bearspaw Dam in 1954 to alleviate winter ice jam flooding in Calgary and the company also installed a generating station at the dam to recoup its costs. Therefore, the intricate system of hydroelectric facilities that we have along the Bow River system today was precipitated by increasing demands for electricity from a growing Calgary population intersecting with a business venture investment by two entrepreneurs Budd and Alexander in 1907.
The management of water along the Bow River system
Similar to many jurisdictions that are prone to dry periods, those wishing to divert and use water must obtain a water license. Water management decisions along the Bow River system are governed by the Alberta Water Act, which is administered by Alberta Environment and Parks (AEP). In Alberta, licenses under the Water Act are issued on the basis of “First In time, First In Right” – which means that the licensee’s right to divert water from the Bow River is based on the seniority of the license holder (the earlier the license was issued, the more senior the license holder). The earliest water license issued for the diversion and use of water along the Bow River dates back to the late 1880s.
As a result of the “First In time, First In Right” principle of water management in Alberta, theoretically, the most senior license holders can take the full amount of water they have been licensed to divert at a specified rate before the next most senior license holder. The whole system of diversion, allocation and monitoring is referred to as water mastering, and is administered in real-time by the Water Operations Group of AEP.
Along the Bow River, there are hundreds of water license holders and the system is now closed to new license applications since the system has reached maximum allocation. The largest and most senior licensees on the Bow River (listed in order of seniority) are:
- Western Irrigation District in Strathmore
- Eastern Irrigation District in Brooks
- Bow River Irrigation District in Vauxhall
- TransAlta (which has multiple licenses for different hydro developments)
- City of Calgary (which also has multiple licenses)
When irrigation demands are high (typically during the summer months), dialogue between the five senior licensees listed above is initiated to ensure that a mutually acceptable operational plan is put into place. In a dry year, such as 2015, discussions are expanded to ensure that there is a cooperative approach in reaching a balance of use and shortage that is shared by all senior licensees. Such an approach results in a distributed sharing of the water shortage across all license holders along the Bow River system during a dry year. In contrast, during a high flow/flood event, emphasis shifts from distributing water to users to moving water through the river system. The Alberta River Forecast Centre works closely with all the operators of water management structures, including TransAlta and the City of Calgary, to provide timely forecasts and warnings. Therefore, water management along the Bow River system itself is a complex process that involves finding a balance to meet the demands of all license holders along the Bow River system.
How water was managed along the Bow River system during the June 2013 flood and future upstream flood mitigation for the Bow River
The devastating 2013 flood brought about a heightened interest of how water is managed along the Bow River system and questioning around how TransAlta operated its facilities during the 2013 flood. In June 2013, none of TransAlta’s dams were at risk of failure or breach. The Hydro System Control Centre and the Hydro scheduling staff moved to TransAlta’s emergency operations centre where they continuously monitored water levels and flow releases on a 24-hour basis. There was also a TransAlta representative moved into the City of Calgary’s Emergency Operations Centre throughout the duration of the flood to ensure clear and rapid communication between the two groups.
Much of TransAlta’s reservoir operations are based on data from four Water Survey of Canada (WSC) stream gauges and seven TransAlta owned gauges. By June 20, 2013, only one WSC gauge and three TransAlta gauges were operational – all others were destroyed from the rapid high flows along the Bow River and its tributaries. Despite this, TransAlta managed to operate its facilities to ensure the structural integrity of its dams and minimize the impact on downstream communities. During the 2013 flood, TransAlta held back approximately 138 million cubic meters of water. If none of the hydro facilities along the Bow River system were in place during the 2013 flood, the peak flow entering Calgary would have been ~2250 cubic meters per second (cms), which corresponds to a 1:180 flood event (see City of Calgary and Golder Associates Hydraulic Model and Flood Inundation Map reports and hydrographs below). With TransAlta operating its dams in accordance to their internal Flood Action Plan during the June 2013 flood, the peak flow entering Calgary was ~1840cms, which corresponds to a 1:75 flood event.
With the heightened interest in water management along the Bow River system, there has been great interest in leveraging TransAlta facilities for additional upstream flood mitigation. CRCAG continues to advocate for a long-term water management agreement between TransAlta and the Government of Alberta, so as to provide some degree of upstream flood mitigation to Calgary Bow River communities. In 2014, TransAlta and AEP conducted a one-year pilot project to lower the level of the Ghost Reservoir to 1189.3m in anticipation of high flows in mid-May-early July. This was estimated to shave ~100cms off of the peak flow of ~1840cms during the June 2013 event. However, even with such an operation change at the Ghost Reservoir, Bow river communities would still be inundated. CRCAG advocated for negotiations between TransAlta and the Government of Alberta to extend beyond 2014 pilot project so as to a greater degree of flood attenuation.
In 2015, TransAlta announced that they reached a one-year agreement with the Alberta Government to lower the Ghost Reservoir to ~1185m. Such an operational change was estimated to provide ~65 million cubic meters of storage for flood mitigation and would have reduced the 2013 peak flow along the Bow River to ~1450cms, which corresponds to a 1:35 flood event (see hydrographs below).
To completely eliminate flooding along the Bow River approximately three additional storage reservoirs the size of the Ghost Reservoir are required. With the large network of hydro facilities along the Bow River system there may be limited options for additional storage facilities that have a high benefit-cost ratio. Therefore, the Government of Alberta must continue negotiations with TransAlta to reach a long-term water management agreement that will protect Bow River communities. At this point, no such commitment has been made to work towards a long-term water management agreement with TransAlta to protect Bow River communities in Calgary. Given the complexity of water management along the Bow River system, modeling work must be started as soon as possible so that a timely long-term water management agreement can be reached between TransAlta and the Province, and to ensure that a balanced approach to flood and drought mitigation is achieved along the Bow River system. Moreover, it is clear that additional flood protection is required for Bow River communities beyond operational changes at TransAlta facilities. As such, an exploration into additional upstream storage options by the Province, as well as the identification of local mitigation measures by the City of Calgary, must be pursued. History has shown that there have been floods larger than the one experienced in June 2013 – it is not a matter of if Calgary will flood again, but when. Ensuring that upstream mitigation is in place before the next inevitable flood occurs will prevent billions of dollars in economic damages and ensure public safety.
