How Hard Is the Water in Calgary and Surrounding Areas?
Calgary and many surrounding communities are known for hard to very hard water. The reason is largely geological: the region’s drinking water originates in river systems that flow through the Rocky Mountains and foothills, where water naturally picks up dissolved minerals, primarily calcium and magnesium. The amount of these minerals determines what we call water hardness, normally expressed as milligrams per litre of calcium carbonate (mg/L as CaCO₃) or grains per gallon (GPG). As a useful conversion, 1 GPG is approximately 17.1 mg/L as CaCO₃.
What makes Calgary particularly interesting is that the city does not rely on a single water source. Calgary operates two major water treatment plants supplied by two different river systems: the Bearspaw Water Treatment Plant receives water from the Bow River, while the Glenmore Water Treatment Plant receives water from the Elbow River through the Glenmore Reservoir. Because these rivers drain different watersheds and encounter different geological conditions before reaching Calgary, their mineral concentrations — and therefore their hardness — are not identical.
Bow River and Bearspaw Water
The Bow River watershed is considerably larger than the Elbow River watershed and extends westward into the Rocky Mountains. Water entering the Bearspaw treatment system therefore reflects the geology, precipitation, snowmelt and changing river flows throughout this large drainage area.
Based on Calgary's 2025 water-quality data, water from the Bearspaw Water Treatment Plant ranged approximately from 141 to 200 mg/L as CaCO₃, equivalent to about 8.2–11.7 GPG. This places Bearspaw water predominantly within the hard-water range. The exact hardness is not constant, however, because the concentration of dissolved minerals changes as river flow changes throughout the year.
Elbow River and Glenmore Water
The Glenmore Water Treatment Plant receives its raw water primarily from the Elbow River and Glenmore Reservoir. Although geographically close to the Bow River system, the Elbow River drains a different and considerably smaller watershed. Differences in geology, groundwater contribution, runoff and seasonal river flow affect the concentration of dissolved calcium and magnesium reaching the reservoir.
This difference is clearly visible in Calgary's hardness measurements. In 2025, Glenmore-treated water ranged approximately from 181 to 274 mg/L as CaCO₃, or about 10.6–16.0 GPG. Consequently, water supplied through the Glenmore system is generally harder than water supplied through Bearspaw, with much of the measured range falling into the very hard category.
Why Water Hardness Changes During the Year
Water hardness in Calgary is not a fixed number because the Bow and Elbow Rivers change considerably with the seasons. During winter, river flows are relatively low and there is less dilution, so dissolved minerals can become more concentrated. This is why some of Calgary's highest hardness readings tend to occur during the colder months.
The opposite effect generally occurs during spring snowmelt. As mountain snow melts, substantially more water enters the river systems, increasing flow and diluting the concentration of dissolved minerals. Hardness therefore tends to decrease during this period. Through summer, river conditions begin to stabilize, while declining flows later in the year can allow mineral concentrations — and hardness — to rise again. This seasonal cycle explains why two water tests performed at the same Calgary property several months apart may produce noticeably different hardness readings.
Water Hardness Across Calgary
The treatment plant supplying a property also plays an important role. Northern and western portions of Calgary are predominantly associated with the Bearspaw/Bow River system, while southern and southeastern portions are predominantly associated with the Glenmore/Elbow River system. This helps explain why households in different parts of Calgary can experience different hardness even though they are connected to the same municipal water utility.
These boundaries should not be interpreted as absolute. Calgary's water distribution network is interconnected, allowing the City to move water between different parts of the system according to demand, operational requirements and other conditions. Central and interconnected areas can therefore receive water from different sources at different times. Location provides a useful indication of likely hardness, but the actual hardness at a particular property can vary with source and season.
Water Hardness in Calgary's Surrounding Communities
The same regional pattern extends beyond Calgary, although surrounding municipalities do not all obtain their water in the same way. Airdrie and Chestermere receive treated water through Calgary's regional water system, meaning their water characteristics can reflect Calgary's Bow River and Elbow River sources and can vary according to the part of the distribution system supplying them. Strathmore also receives treated water through the regional system, so its hardness is similarly influenced by the source and operating conditions of that supply.
Other communities operate their own systems. Cochrane draws from the Bow River, and municipal laboratory data provide an example hardness measurement of approximately 205.6 mg/L as CaCO₃, or about 12 GPG, which is firmly within the hard-water range. Okotoks uses the Sheep River as its primary water source, rather than Calgary's Bow/Elbow distribution system, so its water characteristics must be considered separately from Calgary's. High River likewise operates its own municipal water system, and its hardness should be evaluated from its own municipal water-quality reporting rather than inferred from Calgary's measurements.
Rocky View County is even more variable because water supply depends heavily on the individual community and local system. Some areas are connected to regional treated-water systems, while others rely on different municipal or local sources. For that reason, a single hardness number cannot accurately represent the entire county.
Understanding the Regional Pattern
The most important point is that there is no single water-hardness number for Calgary and the surrounding region. Hardness is determined by the source watershed, local geology, river conditions, season, treatment plant and distribution system. Even within Calgary itself, Bearspaw and Glenmore can produce substantially different hardness readings at the same time of year.
The overall pattern, however, is clear. Southern Alberta's natural geology produces mineral-rich water, Calgary's Bow River/Bearspaw supply is generally hard, and its Elbow River/Glenmore supply is generally harder and frequently very hard. Seasonal snowmelt lowers mineral concentrations through dilution, while lower river flows — particularly during winter — tend to increase them. Understanding those source and seasonal differences gives a much more accurate picture of Calgary-area water hardness than any single annual average.
