Water flow varies from 1,500 to 6,500 cubic meters per second seasonally. Downstream gauging stations track this 4x variation that transforms the falls from impressive to thundering.
The river's metronome
The Iguazu Falls are the dramatic expression of the Iguazu River, a 1,320-kilometer-long waterway that originates near the coast of Brazil. For most of its length, it flows across a vast basalt plateau formed by massive volcanic eruptions around 130 million years ago. The falls themselves are not static; they are a system of up to 275 individual cataracts plunging between 60 and 82 meters. This entire system is driven by a powerful, seasonally-driven pulse.
The average flow of the river is a substantial 1,756 cubic meters per second (m³/s). This figure hides a dramatic annual fluctuation. The volume is dictated by rainfall in the river's basin, 95% of which lies within Brazil. The rainy season, typically from November to March, swells the river, increasing the flow to 6,500 m³/s or more. Conversely, the dry season from August to October can reduce the flow to just 1,500 m³/s. This is a four-fold difference in the volume of water passing over the precipice each second. Gauging stations, such as the one at Capanema, continuously monitor the river's discharge, tracking these immense shifts.
Extremes of water and rock
The seasonal rhythm is sometimes interrupted by extreme events that push the falls far beyond their typical range. The most severe droughts can nearly silence the cascade. In 1978, after a prolonged dry spell, the flow diminished so completely that the massive rock faces were left exposed. A similar, though less severe, drought in 2006 saw the flow drop to just 245 m³/s.
Major floods demonstrate the river's immense power. In June 2014, following intense rains in the upstream Parana state, the falls registered a record-breaking flow of approximately 46,300 m³/s. This volume is more than 26 times the river's average discharge and powerful enough to destroy sections of the tourist walkways. These floods accelerate the natural process of erosion that shapes the falls.
The falls' structure consists of hard, resistant basalt layers on top of softer, more easily eroded sandstone. The water's force undercuts the soft lower layers, causing sections of the hard upper basalt cap to collapse periodically. This process results in the falls slowly retreating upstream at an estimated rate of 1.4 to 2.1 centimeters per year, a geological march measured one flood at a time.
💡Fun Facts
The name "Iguazu" comes from the indigenous Guarani words "y" (water) and "ûasú" (big).
During the historic drought of 1978, the Iguazu River dried up for several weeks, allowing people to walk across the normally submerged rock bed.
The record flood of June 2014 had a flow rate over 30 times the normal average, completely submerging many viewing platforms.
The number of individual waterfalls can fluctuate from 150 to over 300 depending on the river's flow rate.
Both parks are generally open daily from 8:00 AM to 6:00 PM, with last entry around 4:00 PM. Hours can vary, so check official websites.
Admission
An entrance fee is required for each park. Prices vary for residents and foreign visitors. Tickets can be purchased online in advance.
Accessibility
Both parks have made significant efforts to be accessible. Paved trails, ramps, an ecological train on the Argentine side, and panoramic elevators on the Brazilian side accommodate wheelchairs and visitors with reduced mobility. Over 90% of the trails on the Argentine side are considered accessible.
Iguazu Falls flow variationMisiones Province, Paraná, Argentina, Brazil