The San Rafael waterfall in Ecuador has run dry.
Local officials have traced the cause to a large sinkhole that opened beneath the river that once fed the falls.
Located in Cayambe Coca Park, part of the Ecuadorian Amazon near the border with Colombia, the falls ranked as the tallest in the country at more than 500 feet.
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The San Rafael waterfall (pictured above) was the tallest waterfall in Ecuador, at over 500 feet, before a sinkhole formed underneath the river that feeds it, causing the falls to run dry
The government has restricted access to the site of the falls and surrounding area as a team investigates what caused the sinkhole, according to a report in Mongabay.
Some have pointed to a hydroelectric plant 12 miles upstream as a possible cause.
‘A waterfall that has been there for thousands of years does not collapse, coincidentally, a few years after opening a hydroelectric project,’ Emilio Cobo, coordinator at the South America Water Program with the International Union for the Conservation of Nature, told Mongabay.
‘These are processes that are in scientific papers and there is sufficient evidence that a dam can cause effects of this type on a river.’
The plant, which was built by the Chinese company SinoHydro and opened in 2016, isn’t directly on the river, but it has a diversion reservoir that’s designed to remove between 90 and 100 percent of the sediment from the river before its waters reach the plant.
Sediment acts as a protective layer in riverbeds, helping to insulate the ground below from water erosion.
Without a steady flow of new sediment from upstream, the older sediment is eventually washed away, leaving more of the riverbed susceptible to erosion, a condition researchers describe as ‘hungry waters.’
Geologist and former secretary of Natural Capital at Ecuador’s Ministry of Environment Alfredo Carrasco argues that the ‘hungry waters’ phenomenon could also have been caused by seismic activity in the region.
‘There are many quite intense earthquakes here. In March 1987, a very strong one appeared that caused tremendous damage to the trans-Ecuadorian oil pipeline that passes right through it,’ Carrasco said.
‘For me, the phenomenon is eminently of natural origin.’
Researchers are still unsure what caused the sinkhole to form, but everyone agrees the diversion of the waters to three new, smaller waterfalls will reshape the region, something already visible in satellite imagery showing the falls in 2014 (left) and 2020 (right)
In Carrasco’s theory, sediment from upstream could have been blocked by a natural dam that was formed after an earthquake, which over time would have limited the amount of sediment flowing downstream, potentially causing erosion sufficient to create the sinkhole.
Whatever the cause, researchers agree the sinkhole will radically reshape the region as the once unitary river has now been split into three smaller streams, each of which have formed their own small waterfalls along the jungle ridge.
These newer and smaller waterfalls, will bring added risk of landslides and potentially threaten the wellbeing of fish and other invertebrates that had been a part of the river’s ecosystem for years.
‘In the scientific world, many do not see rivers as ecosystems, when in reality it is a reduced surface that ends up absorbing many of the environmental impacts,’ Cobo said.
WHAT ARE SINKHOLES?
A sinkhole is a hole in the ground created by erosion and the drainage of water.
They can range in size from a few feet in diameter to the size capable of swallowing entire buildings.
They are a natural phenomenon but the process is often amplified by human processes and interference.
There are two basic types of sinkhole which are separated by how they form.
Slow developing ones are known as a cover-subsidence sinkhole and those that appear suddenly are called a cover-collapse sinkhole.
The sudden holes which seize headlines are the latter and can cause devastation and even death.
Often, it involves soluble rock, such as limestone, becoming moist and eroding rapidly.
This then leads to a swift loss of land and a sinkhole emerges.