Riñihuazo
Encyclopedia
The Riñihuazo is the name given to the damming of Riñihue Lake
on 22 May 1960, after a landslide caused by the Great Chilean Earthquake blocked its outflow. According to the chronicler Mariño de Lobera a similar event occurred after the 1575 Valdivia earthquake
.
During the Great Chilean Earthquake, several landslide
s near Tralcán
Mountain blocked the outflow of Riñihue Lake
at (39°45′00"S 72°30′00"W). Riñihue Lake is the lowest of the Seven Lakes chain and receives a constant inflow from the Enco River
. The blocked San Pedro River, which drains the lake, passes through several towns and the city of Valdivia before finally reaching Corral Bay
.
Because the San Pedro River was blocked, the water level of Riñihue Lake started to rise quickly. Each meter the water level rose was equivalent to 20 million cubic meters, which meant that 4800 million cubic meters of water would release into the San Pedro River (easily overpowering its flow capacity of 400 cubic meters per second) if it rose above the first, 26-meter-high dam. This potential disaster would have destroyed all the settlements along the course of the river in less than five hours, and had more dire consequences if the dam suddenly broke.
About 100,000 people lived in the affected zone. Plans were made to evacuate Valdivia, and many people left. To avoid the destruction of the city, several military units and hundreds of workers from ENDESA
, CORFO
, and MOP started an effort, called the Riñihuazo, to control the lake. Twenty-seven bulldozer
s were put into service, but they had severe difficulties moving in the mud near the dams, so dykes had to be constructed with shovels. A proposal by some US military to blow up the dams with missiles from a helicopter was rejected. The work was not restricted to the lake; drainages from other parts of the Seven Lakes were also dammed to minimize the flow into Riñihue Lake. These dams were removed later, with the exception of Calafquén Lake, which still retains its dam.
By 23 May, the main dam had been lowered from 24 to 15 meters, allowing 3000 million cubic meters of water to leave the lake gradually, but still with considerable destructive power. The settlements of Los Lagos
, Antilhue
, Pishuinco
and the riverside areas of Valdivia were partially flooded. The team led by engineer Raúl Sáez
finished two months after beginning the works.
Riñihue Lake
The Riñihue Lake is a lake of glacial origin in eastern Valdivia Province, southern Chile. It is surrounded by several mountains. The eastern side receives the waters of the Panguipulli Lake, by the Enco River its main contributor. It is the last of the Seven Lakes chain. In the west is it cut...
on 22 May 1960, after a landslide caused by the Great Chilean Earthquake blocked its outflow. According to the chronicler Mariño de Lobera a similar event occurred after the 1575 Valdivia earthquake
1575 Valdivia earthquake
The 1575 Valdivia earthquake was an earthquake in Chile that caused the subsequent flood of Valdivia much like the 1960 Valdivia earthquake caused the ensuing Riñihuazo flooding. It occurred at 14:30 local time on December 16, 1575. It had an estimated magnitude of 8.5 on the surface wave...
.
During the Great Chilean Earthquake, several landslide
Landslide
A landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rockfalls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments...
s near Tralcán
Tralcan
Tralcán is a triangular shaped mount near Riñihue Lake, Chile. It is located south of the outflow dividing western Riñihue in two arms. Despite been sacred for the huilliches for centuries, the mount became famous when several landslides near Tralcan dammed the Riñihue Lake, after the Great...
Mountain blocked the outflow of Riñihue Lake
Riñihue Lake
The Riñihue Lake is a lake of glacial origin in eastern Valdivia Province, southern Chile. It is surrounded by several mountains. The eastern side receives the waters of the Panguipulli Lake, by the Enco River its main contributor. It is the last of the Seven Lakes chain. In the west is it cut...
at (39°45′00"S 72°30′00"W). Riñihue Lake is the lowest of the Seven Lakes chain and receives a constant inflow from the Enco River
Enco River
Enco River is a river in Panguipulli commune in southern Chile. By flowing from Panguipulli Lake to Riñihue Lake Enco River carries the water of the six upper lakes of the Seven Lakes area into Riñihue, the last lake in the chain...
. The blocked San Pedro River, which drains the lake, passes through several towns and the city of Valdivia before finally reaching Corral Bay
Corral Bay
Corral Bay is a bay in the mouth of the Valdivia River, southern Chile. Its main towns are Corral and Niebla. The mouth of the bay is between Juan Latorre point and Morro Gonzalo, with a width of 5.5 km. All the year the bay is transited by merchant, transport and fish boats...
.
Because the San Pedro River was blocked, the water level of Riñihue Lake started to rise quickly. Each meter the water level rose was equivalent to 20 million cubic meters, which meant that 4800 million cubic meters of water would release into the San Pedro River (easily overpowering its flow capacity of 400 cubic meters per second) if it rose above the first, 26-meter-high dam. This potential disaster would have destroyed all the settlements along the course of the river in less than five hours, and had more dire consequences if the dam suddenly broke.
About 100,000 people lived in the affected zone. Plans were made to evacuate Valdivia, and many people left. To avoid the destruction of the city, several military units and hundreds of workers from ENDESA
Endesa (Chile)
Endesa Chile is the largest electric utility company in Chile. It was created as a subsidiary of the state-owned CORFO in 1 December 1943 and was privatized in 1989. As of April 2009, it is owned by Enersis with a 60% stake, which in turn is 61% owned by Endesa International SA, a wholly owned...
, CORFO
CORFO
Production Development Corporation is a Chilean governmental organization that was founded in 1939, by President Pedro Aguirre Cerda, to promote economic growth in Chile...
, and MOP started an effort, called the Riñihuazo, to control the lake. Twenty-seven bulldozer
Bulldozer
A bulldozer is a crawler equipped with a substantial metal plate used to push large quantities of soil, sand, rubble, etc., during construction work and typically equipped at the rear with a claw-like device to loosen densely-compacted materials.Bulldozers can be found on a wide range of sites,...
s were put into service, but they had severe difficulties moving in the mud near the dams, so dykes had to be constructed with shovels. A proposal by some US military to blow up the dams with missiles from a helicopter was rejected. The work was not restricted to the lake; drainages from other parts of the Seven Lakes were also dammed to minimize the flow into Riñihue Lake. These dams were removed later, with the exception of Calafquén Lake, which still retains its dam.
By 23 May, the main dam had been lowered from 24 to 15 meters, allowing 3000 million cubic meters of water to leave the lake gradually, but still with considerable destructive power. The settlements of Los Lagos
Los Lagos, Chile
Los Lagos is a Chilean city and commune in Valdivia Province, Los Ríos Region.-Demographics:According to the 2002 census of the National Statistics Institute, Los Lagos spans an area of and has 20,168 inhabitants . Of these, 9,479 lived in urban areas and 10,689 in rural areas...
, Antilhue
Antilhue
Antilhue is a village in Chile, South America. It is located in the commune of Los Lagos on the shores of Calle-Calle River just east of Valdivia. Two petroleum-fueled power plants, Antilhue I and Antilhue II, with a combined pruduction capacity of 101.3 MW, are located near the village....
, Pishuinco
Pishuinco
Pishuinco is a hamlet in the commune of Valdivia, Chile. It lies at the northern end of the Calle-Calle River between the city of Valdivia and Antilhue....
and the riverside areas of Valdivia were partially flooded. The team led by engineer Raúl Sáez
Raúl Sáez
Raúl Sáez Sáez was a noted Chilean engineer who also served as Minister of Finance in Chile in 1968.-Early life and education:...
finished two months after beginning the works.