Do Waterfalls Dry Up? Rain, Snow, Springs and Dams

Some waterfalls do dry up, and the ones that do share a feed, not a climate. A waterfall runs on four kinds of supply: rain, snowmelt, springs, and a human decision about a dam or a power canal. Each has its own calendar, and each fails in its own way. Where winter storms fill the river, the summer can leave it at a quarter of its average. Where snow is the store, winter is the low season and May is the flood. A spring changes the flow less, but it still changes it. And where engineers divert the water, the schedule belongs to a power company and a treaty, not to the sky. This guide gives one measured example of each, with the gauge, the period and the source, so you can see what a month-by-month claim is made of. For the chart itself, go to our guide to when to visit waterfalls.

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It runs out when whatever fills the river stops arriving. That is rarely the whole story, because most waterfalls sit on rivers with more than one source. The useful question for a trip is narrower: in which month does the supply change, and by how much? Gauges beat guesses. Every figure below comes from a stream gauge or from a park's own page, read on October 27, 2026, and the notes say where a number is shakier than it looks.

Two cautions. USGS says its monthly statistics come from approved daily means and may not match its official publications. And we have not checked whether withdrawals upstream of the Waimea gauge shape its low months, so read the number as a record of the river, not as a measurement of any one waterfall. For a visit, the practical reading is that drier slopes can look very different in July than in January photos, while the wetter valleys keep a steadier flow.

Ask which month a listing photo was taken in. A waterfall photographed in its wettest month is not a promise about the day you arrive.

The Montmorency River, which feeds the falls near Quebec City, is a snow river. The Water Survey of Canada station on it, 0.6 kilometers below the Marches Naturelles dam, has a 1991-2020 monthly mean of 8.5 m³/s in February and 115.3 m³/s in May. That is more than thirteen times as much water in the flood month. April averages 55.9 and June 42.4, and July to December sit between 22 and 39. Winter is low because the precipitation is stored as snow, which is our reading of the record and not a sentence from the agency. The station is on the river below a dam, not at the falls, and we have not checked how much the dam shapes those figures. Take it as the shape of the year. A record, not a promise. Our Montmorency Falls tours from Quebec City page lists the day trips that go there.

Yosemite National Park describes the same shape in words. Its waterfalls page, last updated May 12, 2026, says Yosemite Falls flows approximately November through July, with peak flow in May, and tells visitors to look for the ice cone at the base of the upper fall during winter. Yosemite is not in our catalog, but it shows how an operator talks about a snow-fed fall: a window of months, a peak, and an edge season on each side. What happens at the cold end of that window is the subject of our guide to frozen waterfalls and snowmelt.

At Niagara it does. Niagara Parks says that in winter 75% of the water flowing from Lake Erie along the Niagara River is diverted about a kilometer before the Falls, which leaves a winter flow of approximately 85 million liters a minute over them. From April 1 through October 31 about 50% is diverted, and the summer flow is generally measured at 170 million. You can read both figures on its frozen falls page. The river itself barely moves. The USGS gauge at Buffalo, which measures the Niagara River as it leaves Lake Erie, has monthly means between 5,836 and 6,342 m³/s over 1991-2020, from about 3% below the annual mean to about 5% above. So the river has no spring peak, and the flow over the Falls is regulated into a summer setting and a winter setting. Both statements are true. They measure different things. The treaty behind the minimums has its own page: Niagara Falls, erosion and the 1950 treaty.

Victoria Falls shows the other end of the scale, a big river measured every day. The Zambezi River Authority publishes flows at its Victoria Falls station, and on October 26, 2026 the page gave 296 m³/s, against 223 on the same date a year earlier. The same page gives a long-term mean annual flow of 1,100 m³/s and a record low annual mean of 390, in the 1995/96 season. Setting a late-October day beside an annual mean tells you very little, which is why the guide to a closed or dry waterfall shows how to read these bulletins. For the two banks of the river, see which side to choose.

Not automatically. More water arrives with the rain, and so do mud, closed trails and cloud. A Vietnam tourism site, which we could not confirm is the national authority, says September and October give the best combination of water volume and rice-harvest scenery at Ban Gioc, and that from December to April the falls lose most of their volume. A travel blogger writes that Tumpak Sewu in Java gains considerable volume in the rainy season, typically November to March, while the trails turn muddy and slippery. Both are secondary sources, so read them as local advice and not as measurements. They agree on one point: the month with the most water is rarely the month with the easiest access.

Single years matter more than months. On May 16, 2023, NP Krka recorded 254 centimeters at Skradinski buk, the highest level since measuring began. The previous high was 223 cm in December 2005, and the lowest was 5 cm on October 3, 1990. The park closed Skradinski buk and Roški slap and canceled all boat excursions, in a month that is not among its usual high ones. In October 2026 the concessionaire of Iguazú National Park reported 17.7 million liters per second on October 26, 11 times the historical mean it quotes, after heavy rain in the Iguazú basin. Floods like these are events, not seasons, and the closures that follow them are covered in if the waterfall is closed or dry. Our Niagara Falls tour pages are a steadier bet, since the flow there is managed.

Less than it looks. For our own season matrix we compared monthly rainfall at the nearest weather station with the USGS gauge on the same island, and the two agreed on the month's class (peak, usual or low) in between 3 and 9 months out of 12, depending on the river. The match was best on the wetter side of Kauai and worst on the leeward Waimea and at Oheo Gulch on Maui. Where no gauge exists we use rainfall and say so. For Krka, the rainfall proxy reproduces the park's November high and August low but misses March, which the park lists as a high month. A chart built on rain is an approximation. The matrix marks which rows rest on gauges and which on proxies, and the method page gives the thresholds and the limits.