How Do The Rocky Mountain Glacier Lakes Get Their Famous Blue Or Green Colour?
As much as a local might try to convince you that each year the lakes are drained and the bottoms are painted or that dye is added to the water, neither is the case. The lakes in the mountains that have vivid blue and green colours are glacier fed. As the melt water from a glacier starts to flow in the spring time it carries with it glacier silt or rock flour. The silt is created when rocks underneath the surface of the ice are grinding from the movement of the glacier. The rock flour is very light and stays suspended in the lake water for a long time. The sunlight that reflects off these particles is what gives the lakes their spectacular turquoise blue or green colour.
When Is The Best Time To See The Turquoise Colour Of The Glacier Lakes?
In the late spring when the glacier lakes first thaw they don’t have a lot of colour yet. As more silt enters the lakes from the glacier melt water they start to take on the famous turquoise blue or green colour that visitors come from around the world to see. The months of July and August are when the flow of the melt water levels are at their highest and consequently this is when the lakes have the most intense colour. As summer ends the melt water flow starts to slow down. In September and early October there is still some colour, but as the glacier silt starts to settle in the water the intensity of colour diminishes with it.
The colour of a lake can appear different from one day to the next or even from hour to hour. The intensity or brilliance of the colour varies depending on the lighting conditions. There needs to be sunlight, even the most colourful lake is not going to look very spectacular on an extremely gloomy or cloudy day. The angle of the sunlight hitting the water and the angle of viewing also have an affect on the colour. Often you’ll notice how much more vivid a lake looks when viewed from above. This is probably one of the reasons Peyto Lake looks so surreal from the viewing platform high above it.
The photos below of Lake Louise are an example of how the same body of water can have a very different look depending on the lighting conditions and the time of year.
Lake Louise in early July
Lake Louise in August
Lake Louise in the first week of October
Taken the same day as the photo above about an hour apart. You can see how the angle of the sunlight is enhancing the brilliance and colour of the water.
Lake Louise in the last week of October 
When Do The Glacier Lakes Thaw?
People often want to time their trip to the Rocky Mountains to see the spectacular water colour that the glacier lakes are known for. They especially want to know when the world famous Lake Louise thaws. What is surprising is the number of people that travel from around the world and arrive only to learn they came too early! Some of them booked with travel agents who should have known better or at least did some research.
Lake Louise thawing in the month of May.
Visitors may get the wrong impression because they have seen or heard of the spring time weather in other parts of Canada such as the west coast where the cities of Vancouver and Victoria are located. By April those areas are usually enjoying warmer temperatures and all the beauty of springtime flowers. Winter lasts much longer in the higher elevation of the mountains.
Lake Louise and many of the other high elevation lakes such as Peyto Lake, Bow Lake, Moraine Lake and Maligne Lake do not thaw until the first week of June or later. In a warmer than average spring they might be thawed by the last few days of May but it doesn’t occur any earlier than that. From personal experience while living in the area we have seen Lake Louise free of ice as early as May 27th and as late as June 22nd.
The elevation of a lake has one of the largest influences as to when it thaws. Generally the higher the lake the longer it takes to be free of ice. There are other factors such as the orientation of the lake, how much sunlight it receives and the angle of sunlight it receives due to the shade of the mountains.
Some of the lower elevation lakes in the valley bottoms thaw much earlier. Vermillion Lakes near the town of Banff can start to thaw in April and nearby Minnewanka Lake is usually thawed by the start of May.
Each Glacier Lake Has Its Own Distinct Colour
As explained earlier the colour of a lake can vary and fluctuate for a variety of reasons, but each glacier lakes does have its own unique colour. You can see the differences between bodies of water such as Petyo Lake known for its surreal blue colour, Lake Louise for it’s turquoise water and Emerald Lake obviously named for its green hue. The melt water that creates Cavell Pond at the bottom of Mount Edith Cavell in Jasper is so heavy with silt that at times it’s a completely opaque green.
Famous Or Note Worthy Lakes Of The Canadian Rocky Mountains
Lake Louise
Elevation: 1750 meters (5740 feet)
Lake Louise is one of the most well known lakes of the Rocky Mountains. It’s located in Banff National Park, 40 minutes west of the town site of Banff. Canoeing on its turquoise waters and strolling along the shoreline trail are the most popular activities. Visitors come from around the world to see Lake Louise. In the peak summer tourist season between dawn and dusk there can be up to 15,000 visitors that come to its shoreline. It’s a beautiful setting back dropped by Mount Victoria and the hanging Mount Victoria glacier. On average it usually thaws in the first week of June, but it can be later.
Moraine Lake
Elevation: 1910 meters (6265 feet)
Moraine Lake is located at the end of Moraine Lake road which is accessed from the same road that leads to nearby Lake Louise. The lake is lined by the towering mountains known as the Valley Of The Ten Peaks. It’s image was made famous when featured on the back of a past $20 Canadian Bill. The road to Moraine Lake is closed to all vehicle traffic from approximately mid-October to the end of May depending on the conditions. The lake has a very low water level and is still frozen when the road first opens in June. It thaws quickly and the water level rises as the glacier melt water flow increases. The water level crests by late June.
Bow Lake
Elevation: 1920 meters (6299 feet)
Bow Lake is located along the Icefields Parkway (Highway 93N) that runs between Lake Louise and Jasper. It’s approximately a 30 minute drive from Lake Louise. The Bow glacier melt water feeds Bow Lake and through a series of waterways this same water travels an incredible distance across several provinces to Hudson Bay. A popular hike in the area is to the falls that flow off the Bow Glacier. The trail is accessible from behind the Num Ti Jah Lodge on the north side of the lake. There’s an elevation gain of 280 meters, allow 2.5 hours for the return trip. The lake has a very short summer season and can often be frozen until mid-June or later.
Peyto Lake
Elevation: 1880 meters (6170 feet)
Peyto Lake is also located on the Icefields Parkway about 5 mintues further north from Bow Lake. It’s colour is so incredibly vivid that many people see images of the lake and can’t believe they have not been photoshopped. Yes, Peyto Lake is really that blue! Peyto Lake shows an excellent example of how a delta is formed when back filling occurs from the dumping of glacier silt. You can see the massive delta on the left hand side of the lake. (not visible in the photo) It now covers almost 1/3 of the former length of the lake. Peyto Lake usually thaws by mid June, but in some years it can take longer.
Lake Minnewanka
Elevation: 1500 meters (4920 feet)
Lake Minnewanka is located just north of the Banff town site. It was originally a series of lakes that became one of the largest lakes in Banff National Park when the water levels were raised by Hydro dams. The Lake Minnewanka Loop is just one of the many scenic drives in Banff National Park. Boat tours are available when the lake thaws (usually by the beginning of May) and continue through until early to mid-October.
Vermillion Lakes
Elevation: 1400 meters (4592 feet)
Vermillion Lakes sit at the edge of the Banff town site. They are some of the earliest lakes to thaw in the area. They serve as a shallow wetland for many birds and attract a variety of wildlife. Vermillion lakes are most known for the beautiful photos reflecting Mount Rundle. It’s a popular spot for tranquil walks along the shoreline and for canoeing.
Maligne Lake
Elevation: 1675 meters (5494 feet)
Maligne Lake is located southwest of the town of Jasper at the end of the scenic drive along Maligne Lake road. It’s the largest lake in Jasper National Park. Spirit Island located within the lake is one of the most recognizable postcard photos in Canada. It’s reachable only by taking a boat tour offered at the lake front or by long day of self canoeing or kayaking. The lake is usually thawed by the beginning of June.
Medicine Lake
Elevation: 1436 meters (4710 feet)
Medicine Lake is located 21 km’s along Maligne Lake road in Jasper National Park. It’s a unique lake that disappears and reappears each year. As the Maligne River swells with runoff in the spring the water backs up and forms Medicine Lake. The water constantly drains through an underground system of caves. It’s only when the runoff into the lake exceeds the rate of drainage that a large body of water remains. In late summer as the flow decreases the lake starts to disappear leaving behind a giant mud flat. The cycle repeats itself again the following year. The lake starts to fill up by early summer and by late summer/early fall the water level is starting to decrease until it disappears.
Cavell Pond
Elevation: 1750 meters (5742 feet)
Cavell Pond is located in Jasper National Park, approximately 45 minutes drive from the Jasper town site. It’s just too spectacular not to include in the list even though it’s not a lake by definition. It’s located at the base of Mount Edith Cavell and can be accessed by taking a short hike on the Path Of The Glacier Loop. The colour is a stunning opaque green. Angel Glacier can be seen above the pond with it’s wings spread across the face of the mountain. Cavell Road is closed for the winter. Depending on conditions it opens in early July and remains open until mid-October.
Emerald Lake
Elevation: 1309 meters (4294 feet)
Emerald Lake is located in Yoho National Park south of the town of Field in the province of B.C. It’s approximately 40 minutes drive west of Lake Louise. This lake holds up to its name as it has a very green colour. It can get busy with tour buses during the summer months, but overall it sees a fraction of the people that visit nearby Lake Louise. Canoe rentals are available from the boathouse near the parking lot. It’s usually thawed by the end of May or early June.
Lake O’Hara
Elevation: 2115 meters (6938 feet)
Lake O’Hara is located in Yoho National Park. The parking area is located off the Trans Canada Highway just a few minutes west of the B.C./Alberta border. The setting is stunning but it is not easily accessible. No public vehicles are allowed to drive to the lake area. You must reserve a ticket on a bus run by Parks Canada. To protect the delicate environment a strict limit of people are allowed in each day. The bus runs from June to early October. The only other way to access the area is by parking at the lot near the highway and walking in along the 11km gravel fire access road. From Lake O’Hara there are hiking trails to many other beautiful lakes in the region such as McArthur Lake, Oesa Lake and Opabin Lake. These lakes sit at a very high elevation and can still be frozen well into June and may have some ice present as late as July or August.
Grassi Lakes
Elevation 1500 meters (4920 feet).
Grassi Lakes are located along Spray Lakes Road near the town of Canmore. They are a set of small but vibrant coloured lakes that sit at the end of one of the most popular and easy hiking trails in Canmore. Up above the lakes are ancient pictographs that have been dated to over 1000 years old.
Waterton Lakes
Elevation: 1274 meters ( 4180 feet)
Waterton Lakes are located in Waterton Lakes National Park in southwest Alberta, approximately 3 hours drive southwest of Calgary. The area is much less visited than the other parks in the Rocky Mountains such as Banff and Jasper. The most remarkable view of the lakes can be seen from the Bear’s Hump accessed by a short but steep hike near the town site of Waterton.
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