How are kajons and ditches similar?

El Cajón Dam (Honduras) - El Cajón Dam (Honduras)

This article is about the dam in Honduras. For other dams named El Cajón, see El Cajón Dam.

The El Cajón Dam , officially known as Central Hidroeléctrica Francisco Morazán , is a hydroelectric power plant located in western Honduras. The dam dams the Comayagua River, which gets its large volume from two major tributaries, the Humuya River and the Sulaco River. El Cajon is a double arch dam that uses parabolic geometry in horizontal and vertical axes to distribute the weight of the backwater to rock walls that act as supporting pillars. Overall, the dam is the fifth tallest dam in America and the 16th tallest in the world, as well as the tallest arched dam in the Western Hemisphere and the sixth tallest in the world.


The El Cajón Dam is 180 km from Tegucigalpa, the capital of the country, and 80 km from San Pedro Sula, the main industrial city of Honduras.


Harza Engineering of Chicago, Illinois, USA began the site survey in the 1960s. The first construction work began on June 15, 1980. A multinational team of designers, builders and engineers included members from Italy, Germany and Switzerland. The technical design was developed by Motor Columbus [now Colenco] from Switzerland. Italian companies were responsible for the construction of the underground engine room, while Italian and German companies were responsible for the dam construction and ancillary works. Once completed, the dam became the largest piece of infrastructure in Honduras, and it took over half a million cubic meters of concrete to build. Due to its double-curved arch construction, this dam is relatively thin compared to the Hoover Dam (gravity dam construction), which spans a similar valley profile but uses about four times as much concrete.


A finite element design was used for the components of the dam. The dam is 282 meters long and 48 meters thick at the bottom. The top is 7 meters thick and wide enough for the small back road that crosses the dam. About 170 meters from the bottom of the dam, three meet 14.5 m 2 large Drain pipes from water that has passed through the turbines of the engine room. Near the top of the dam is an overflow made up of four large square pipes, each 14 meters wide, which are opened when the flow through the dam cannot be handled by the lower drainpipes.


The reservoir created by El Cajón extends over 94 km 2 with a maximum capacity of around 5,700 million m³. The reservoir displaced approximately 4,700 people. While the reservoir's main purpose is to power El Cajón's turbines, flood control is another great benefit. Prior to the dam's completion, annual flooding in the Sula Valley severely disrupted trade for the people of Honduras. During the rainy season, the reservoir can hold back a ten-meter-high layer of water and then slowly drain it to avoid catastrophic flooding. Agriculture has also benefited from this. In the past, the Comayagua flow decreased significantly to around 20 m during the dry season 3 / s. The dam now provides a year-round flow of around 100 m 3 / s, which had a significant economic impact on the region.


Eight large turbines with a vertical axis are located in an underground housing on the left side of the limestone valley. The construction took place in two steps. First, four turbines were installed in the room; which at that time was already quite large: 110 m long, 30 m wide and 49 m high. In the second construction phase, the length was extended by a further 65 meters to accommodate the remaining four turbines. Each turbine rotates at 300 rpm and drives its own generator, which can produce 75 megawatts. Completion of the second stage brought the total output to 600 megawatts. The electricity generated there is then transmitted to a central station at 230 kV.


Originally, electrical monitoring devices were installed that are commonly used in modern dams. However, due to the high sulfur content in the surrounding rock and water, all devices corroded and failed. With the exception of portable monitoring devices, El Cajón now relies solely on mechanical devices to check its performance.

  • Mechanical extensometer to measure the deposit and linear deformation are aligned in the horizontal and vertical directions. These devices are distributed horizontally across the dam at various distances, with a group every 30 meters.
  • V-notch weirs are used to measure infiltration through the curtain of the dam. One is in a ditch at the bottom of the dam in the lower right
  • Force balance accelerometer is used to measure movement of the dam, which is an indication of deformation. These devices are useful in monitoring damage from seismic events.
  • Inverted pendulum - These devices measure the vertical deformation of the dam. One end of a thin wire is attached to an anchor grouted under the dam in solid rock, while the other end is attached to a floating station attached to the dam. The movement of the float relative to the anchor alerts the dam operator to possible movements.
  • Direct pendulum - This device works similarly to the inverted pendulum except that the anchor is on top and the float tank is on the bottom. There are 21 direct and indirect pendulums in El Cajón.
  • Bourdon pressure gauge are used to measure the static pressure of the water contained in the reservoir.
  • Geodetic surveying stations are at fixed reference points in the vicinity of the dam. "Object" points are installed on the front of the dam (look carefully, you can see the yellow drums). Surveyors use equipment such as theodolites and total stations to compare changes in the distance and elevation of the object points on the embankment to the reference points. The information gathered gives dam operators a picture of how the dam is settling or whether facial movement is occurring.
  • In the abutments of the dam are Inclinometer installed to monitor slope stability. The device measures the linear deformation.
  • Seismograph are used to monitor the vibration of the structural elements due to geological activity. With El Cajón lying on three fault lines, seismic information gathering is critical in making decisions about the dam's operation.

The important role these devices play came into focus after a 7.1 magnitude earthquake that began 200 miles north of Tegucigalpa and massively damaged many infrastructure parts on May 28, 2009. These devices were critical in determining the internal deformation of the structure.



  • ENEE (Empresa Nacional de Energia Electrica), 2009, "Central Hidroelectrica 'El Cajón'", Honduras, CA (Translated from Spanish into English by Missouri S&T)
  • McCully, Patrick (1996). Silenced rivers. Ecology and politics of large dams . London: Zed Books.
  • Rodriguez, 2009, "El Cajón reports on the earthquake in Honduras"
  • VOA News 2009 "Honduras Earthquake Kills 4", (July 21, 2009 2009 )