00:00Despite popular belief, qualifying the Nile as the longest river in the world may be a mistake.
00:06To measure the length of a river, it is not enough to calculate the distance between its starting point and its arrival point.
00:13Rivers are complex systems, made up of various affluents that count for a lot in their total length.
00:20In fact, if we take into account these affluents, the total length can be multiplied by 3, as is the case for the Mississippi River.
00:27From its birth in Itasca to New Orleans, where it ends, the river measures a certain length.
00:33But if we take into account the Missouri River, things change completely.
00:38This divergence fuels many debates about the length of the Nile compared to that of the Amazon.
00:43Although Google recognizes the Nile as the longest river in the world, it may not be entirely accurate.
00:49To understand this, it is necessary to represent the rivers as the veins of a human body.
00:53It would be inaccurate to assume that an individual of 2 meters high has only 2 meters of veins, right?
00:58The veins intersect in the whole body, like a vast network.
01:02Watercourses function according to the same principle, and we cannot consider only the length of the main river.
01:08The vast network of affluents is just as important.
01:11Atmospheric rivers are fascinating meteorological phenomena.
01:15Air currents that carry an incredible amount of water vapor from the Amazon rainforest,
01:20from North America to the north of Argentina.
01:23These air routes are essential to the humidity, which is of great importance for our landscapes.
01:30Their influence extends to the regions of the Midwest, Southeast and South of Brazil,
01:36shaping the specific precipitation regimes of these areas.
01:40When these rivers meet particular meteorological conditions, such as a cold front,
01:46the latent humidity they carry can turn into precipitation.
01:51These precipitations play an essential role not only in the preservation of the various ecosystems of the region,
01:57but also in the support of the flourishing economy of Brazil, and in many ways.
02:02The importance of this phenomenon is obvious.
02:05First, it allows the irrigation of crops, guaranteeing agricultural productivity and food security.
02:11In addition, it feeds the local rivers,
02:14which allows to maintain a regular water flow and to promote aquatic life.
02:19In addition, the water collected by these rivers is sent to dams,
02:23which transform them into a reliable source of energy for the country.
02:27The amount of water transported by the air rivers can be equivalent, if not superior, to the huge flow of the Amazon.
02:33Thus, if we associate the Amazon River with its air counterpart,
02:37we get a volume of water much higher than that of an island.
02:40We also observe atmospheric rivers in the Congo Basin,
02:44where the climate is mainly shaped by the humidity emanating from the Atlantic Ocean and local forests.
02:50We witness an evaporation of 1 to 2 meters of water per year.
02:54These rivers vary in size and power,
02:57but on average, they carry a volume of water vapor comparable to the flow at the mouth of the Mississippi.
03:03In rare cases, exceptionally powerful atmospheric rivers can carry up to 15 times this volume.
03:10When these rivers reach the mainland, they release the accumulated water vapor,
03:14which leads to precipitation or snowfalls.
03:18Although atmospheric rivers are presented in different forms,
03:22those that have a strong water vapor retainer and intense winds can cause extreme precipitation and even floods,
03:29especially when they linger on hydrographic basins, subject to rain.
03:34A well-known example of an atmospheric river is the Pineapple Express,
03:38a system capable of transporting the humidity of tropical regions located near Hawaii to the west coast of the United States.
03:46Such events can disrupt transport, trigger mudslides and cause significant material and human destruction.
03:54However, all atmospheric rivers do not pose such risks.
03:59Many of them are relatively weak systems that provide precious precipitation and are essential for good water supply.
04:08In addition, they play a crucial role in the hydrological cycle of the planet.
04:13In addition to the risk of flooding, atmospheric rivers also contribute to the increase in snowfall.
04:19Atmospheric rivers were the cause of the violent winter storms that hit the west coast of the United States,
04:25from the state of Washington in southern California, between 2010 and early 2024,
04:31causing precipitation ranging from 28 to 63 cm in some regions.
04:36Water vapor currents can therefore be considered rivers.
04:40Is it possible to put something else under this term?
04:43Surprisingly, there is a phenomenon that, although devoid of water, falls into this same category, the weds.
04:49These are, traditionally, what are called river valleys.
04:53Weds are found in slightly inclined areas, almost flat, of the deserts.
04:58Unlike traditional rivers, weds do not have stable canals due to the intermittent presence of rivers.
05:05They therefore have a trellis structure due to a limited water supply and an abundance of sediment.
05:11The water that manages to reach the bed of these weds infiltrates the earth and causes a decrease in energy and large deposits.
05:19Weds can even form sediment dams, which modifies the configuration of watercourses during sudden rains.
05:26It is interesting to note that the wind also plays a role in the deposit of these sediments.
05:31When the weds are submerged or wet, the sediments pushed by the wind come to settle,
05:37which produces a mixture of sediment and aerial sediment.
05:41Rivers can be special not only because they are made up of sand or air, but also because of what covers them.
05:48In some conditions, the Scottish River Dee offers an intriguing spectacle.
05:53Frozen formations that look like water lilies.
05:57These formations, called ice crepes, appear naturally when the movement of the waves deforms the smooth and flat ice,
06:05which gives rise to these curiosities at the smooth and rounded edges.
06:09With this movement, these ice discs rise above the surface and take on the appearance of strange water lilies.
06:16In general, ice crepes have a consistency close to that of water lilies.
06:20Some media have suggested that the ice of the Dee River is formed from frozen foam.
06:25But scientists explain that even if this hypothesis is plausible,
06:29ice crepes always form because of the movement of the waters.
06:32Over time, these water lilies often end up forming large plates of ice.
06:37If the ice is thick enough and the water remains turbulent, it can bend, fracture and even form layers,
06:44which gives rise to a structure called ice crest.
06:48Now imagine a river made up not of water, but of methane.
06:52The idea may seem crazy, but on Titan, the moon of Saturn, it is a reality.
06:57Veed Floumina, a fascinating river on Titan, is thus made up of methane and liquid ethane,
07:04and has even been compared to the powerful Nile.
07:06Extending over more than 400 km, it gracefully throws itself into the Ijeya Maré,
07:11which is the second largest sea of hydrocarbons in Titan.
07:15Most of Titan's surface is made up of water ice,
07:18but Veed Floumina, by digging canyons in this frozen terrain,
07:22suggests that there is a rocky soil there.
07:25NASA scientists believe that this extraordinary river contains rapids,
07:29whirlwinds and even waterfalls, like those found in terrestrial rivers.
07:34When the Cassini probe reached Saturn in 2004,
07:37its main objective was to explore this giant planet and its moons.
07:42Scientists were particularly interested in the discovery of liquid methane on Titan,
07:47due to the unique temperature of its surface and its atmosphere.
07:51However, Cassini's first observations, focused on the equatorial region of Titan,
07:56disappointed researchers who found no signs of seas or rivers.
08:01But they had a nice surprise when Cassini's orbit moved,
08:05allowing the team to focus on other areas of the surface of the moon using radar.
08:11Surprisingly, the radar signals bounced on various angular and rough formations,
08:18sand dunes, cliffs and rocks.
08:21But when the radar reached the polar regions of Titan,
08:24the signals stopped, revealing mysterious dark spots
08:28resembling lakes, rivers and ripples similar to those found on Earth.
08:34The revolutionary discovery took place in December 2012,
08:38when Jean-Yves Radbeau, a scientist working with Cassini's team,
08:42presented an image taken in September of the same year.
08:45The image reveals a river that looks like the Nile and extends over 322 km,
08:50according to a relatively straight line,
08:52indicating a correlation with fault lines similar to those of other important rivers located nearby.
08:59This remarkable watercourse crosses rugged and inclined terrains,
09:03suggesting the existence of a tectonic movement similar to that observed on Earth.
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