The City of Calgary, Alberta, Canada withdraws its water from two rivers, the Bow and a major tributary to the Bow River, the Elbow. Both rivers originate in the Rocky Mountains to the west of the city. Both rivers receive substantial contributions to flow from snowpack and glacier melt; however, the Bow River, about 10 times the size of the Elbow, can have a substantial contribution from glacier melt in dry years. Like snowpack, the volume and melt timing of glaciers are sensitive to temperature change. Scientists have documented glacier recession across the globe, and this trend will likely continue if temperatures continue to rise. For a period of time, glacier-dominated systems may see an increase in runoff because of rapid melting, but in the long run less water will be stored in the glacier. As in the case of snowpack decline, it is unclear if average annual runoff will increase or decline, but there is a strong probability that in the long run glacial runoff will contribute less to river flows during the summer season than it does at present.
The Bow and Elbow Rivers are the sources of supply for the City of Calgary Waterworks’ service population of one million. Calgary does not have significant reservoir storage. The Glenmore Dam and Reservoir on the Elbow River is relatively small with a storage capacity of approximately 20 days at current rates of consumption. System reliability depends to a large extent upon consistent river flows.
The larger Bow River receives a substantial, although highly variable, portion of its summer flow from several glaciers. Two glaciers, the Bow and Crowfoot that feed the Bow River, have receded substantially over the past several decades. On average, summer flow contribution from glacier melt ranges from 4.6 to 7.5 percent. During a dry year, glacier melt can contribute as much as 47.4 percent of the August flow in the Bow River, so the future condition of the glacier will have a substantial impact on Calgary’s water.
Calgary’s utilities have collaborated with scientists to anticipate the future of glacier-fed flows. Their findings predict that average annual flows will be sufficient, but continued glacier recession will result in lower flows in August and September, when stress on water supply is greatest (Hopkinson and Young 1998). In addition to climate change, Calgary Waterworks faces a rapidly increasing customer base, as the current population growth rate of Calgary is between 2.5 and 3 percent per year.
In the past, Calgary has not had a problem with insufficient supply. In fact, the utility has never implemented water restrictions because of supply scarcity. Historically, water conservation has not been a major issue, so there is a large capacity to improve the efficiency of water use. Calgary Waterworks has taken advantage of this opportunity as a key part of the utility’s strategy to prepare for climate change and other stresses on water supply. In coming years, the utility plans to be capable of supplying an additional half million customers, a fifty percent increase in current population, with the current volume of water withdrawal. One approach to reach this goal is to reduce per capita water use by up to one-third by encouraging conservation. Another strategy involves increasing the efficiency of the water treatment process. Already treatment plant upgrades have begun which will ultimately allow the utility to fully utilize the water that it withdraws from the river by full recycling of the filter to waste and backwash water created by the treatment process. This will eliminate the utility’s discharge of water back to the river from its water treatment plant.
Decreasing per capita water use will largely depend on the cooperation of the utility’s customers and other departments of the City of Calgary, so the utility has developed a public education program that includes publications for customers and school programs on conservation issues. Conservation incentives have also received heavy attention, including programs offering rebates for water-saving appliances. Water metering is also an important demand-side tool to give consumers a monetary incentive to conserve. Calgary is currently migrating from flat rate to metered accounts, so that every home will have a meter by 2014. The case for metering is well known and, in general, comparison of customer classes in Calgary has shown that metered customers on average use 50 percent less water than flat rate customers.
The public sector of the city of Calgary is also implementing water conservation strategies. For example, the city has recently upgraded about 2000 irrigation systems for public areas to include meters. Many of these are already connected to a centralized weather-linked control system, and the plan is to eventually link all city-owned irrigation systems to central control. In addition to the direct savings in water expenditures, systems such as these are important for publicity. If the utility expects individuals to conserve water or to cooperate if the city must impose water restrictions, then it is important that citizens know the city is also committed to prudent water use. While water restrictions have not been a significant issue in the past, Calgary has realized they may soon be needed. To prepare for such a possibility, bylaws that outline how water restrictions are to be implemented in the event of a severe drought have been reconsidered and updated.
Calgary Waterworks has emphasized that public outreach will play an essential role in climate change adaptation strategies. When approaching water scarcity problems from the demand side, public cooperation is clearly vital for successful conservation. In addition, supply side initiatives, such as infrastructure investment, will also need support (and funding) from the utility’s customers. It will be much easier to gain that support from a public that is aware of the possibility of climate change and the problems it poses for the water utility.