- The height of the American Falls ranges between 21 to 34 m (70-110 ft). This measurement is taken from the top of the Falls to the top of the rock pile at the base, called the talus slope. The height of the Falls from the top of the Falls to the river is 57 m (188 ft). The crestline of the American Falls is approximately 260 m (850 ft) wide
- The rapids above the Falls reach a maximum speed of 40 km/hr or 25 mph. The fastest speeds occur at the Falls: 68 mph has been recorded at Niagara Falls. The water through the Whirlpool Rapids below the falls reaches 48 km/hr or 30 mph, and at The Niagara River is a connecting channel between two Great Lakes, Erie and Ontario.
Where does the water come from?
- The Great Lakes is the world’s largest surface freshwater system in the world, about 18% of the world’s supply.
- The volume of water in the Great Lakes would cover North America in about 3.5 ft of water.
- The water flows from streams and rivers that empty into the Great Lakes, from Lake Superior down through Niagara to Lake Ontario, then into the St. Lawrence River to the Atlantic Ocean. Water always flows down to the sea, and the land slopes downward through the Great Lakes Basin from west to east – but the Niagara River actually flows north.
- Today less than one percent of the water of the Great Lakes is renewable on an annual basis (precipitation and groundwater). The rest is a legacy from the last ice age, or “fossil” water.
- There’s still water in the Great Lakes because they rely heavily on replenishment / renewal from precipitation (rain, sleet, snow, hail) and groundwater.
- The brown foam below Niagara Falls is a natural result of tons of water plummeting into the depths below. It is not dangerous. The brown colour is clay, which contains suspended particles of decayed vegetative matter. It is mostly from the shallow eastern basin of Lake Erie.
How was the Whirlpool created?
The huge volume of water rushing from the Falls is crushed into the narrow Great Gorge, creating the Whirlpool Rapids that stretch for 1.6 km (1 mi). The water surface here drops 15 m (50 ft) and the rushing waters can reach speeds as high as 9 mps (30 fps).
- The Whirlpool is a basin 518 m (1,700 ft) long by 365 m (1,200 ft) wide with depths up to 38 m (125 ft). This is the elbow, where the river makes a sharp right-angled turn.
- In the Whirlpool, you can see the “reversal phenomenon”. When the Niagara River is at full flow, the waters travel over the rapids and enter the pool, then travel counterclockwise around the pool past the natural outlet. Pressure builds up when the water tries to cut across itself to reach the outlet and this pressure forces the water under the incoming stream.
- The swirling waters create a vortex, or whirlpool. Then the waters continue their journey to Lake Ontario. If the water flow is low (water is diverted for hydroelectric purposes after 10pm each night) the reversal does not take place; the water merely moves clockwise through the pool and passes to the outlet. Below the Whirlpool is another set of rapids, which drops approximately 12 m (40 ft).
Why is the water so Green?
The startling green colour of the Niagara River is a visible tribute to the erosive power of water. An estimated 60 tons of dissolved minerals are swept over Niagara Falls every minute. The colour comes from the dissolved salts and “rock flour”, very finely ground rock, picked up primarily from the limestone bed but probably also from the shales and sandstones under the limestone cap at the Falls.
How is the water used?
The waters of the Niagara River are used by a combined Canada/United States population of more than 1,000,000 people for a wide range of purposes such as:How much water is diverted?
- Drinking water
- Recreation (boating, swimming, bird-watching)
- Industrial cooling water supply
- Receiver of municipal and industrial effluents
- Hydro-power generation (Sir Adam Beck Station in Ontario & New York State Power Authority)
The Great Lakes in general are very sensitive to high-or-low precipitation years, and this can affect the flow from Lake Erie into the Niagara River, however the levels have been regulated by the International Joint Commission (USA and Canada) since 1910.
The basis for determining the amount of water that can be diverted for power generation is contained in a treaty between the Governments of Canada and the United States concerning the “Diversion of the Niagara River”, dated 1950, and generally referred to as the “1950 Niagara Treaty”.
The treaty requires that during the daylight hours of the tourist season (0800 to 2200 hours local time, April 1st to September 15th and 0800 to 2000 hours local time September 16th to October 31st), the flow over Niagara Falls must not be less than 2832 cubic m/second (cubic m/s) [100,000 cubic ft per second (cfs)]. At all other times, the flow must not be less than 1416 cu m/s (50,000 cfs).
The treaty also specifies that all water in excess of that required for domestic and sanitary purposes, navigation and the Falls flow may be diverted for power generation.
If the river was allowed to return to natural levels, it would rise probably another 5 m.