Landslide risk? This was the precise, tense maneuver of 40 centimeters per day to fill the Hidroituango reservoir to the 420 level

NewsThe reservoir rose 12 meters at a controlled pace. EPM monitored stability and ANLA confirmed compliance with environmental regulations. Hidroituango Reservoir Photo: EPMJOURNALIST11.11.2026 06:01 Updated: 11.11.2026 06:01 A single miscalculation in the rate of ascent could have triggered a catastrophe of major proportions in the Cauca River canyon. With the specter of landslides looming over the slopes and a bitter political dispute ignited by an alleged regulatory "whim" worth 36 billion pesos, Empresas Públicas de Medellín (EPM) faced a new technical challenge of great magnitude: raising the water 12 meters drop by drop. The reservoir of the Ituango hydroelectric plant reached a decisive operational milestone this Monday, November 9, arriving at elevation 420 meters above sea level (masl), the project's maximum design and generation level. Hidroituango elevation 420 Photo: The operation, carried out by EPM after obtaining a temporary environmental authorization valid until mid-2027, allows a substantial expansion of the water body's storage capacity, which accumulated around 390 million additional cubic meters of water. This volume is equivalent to the energy generated by a 130-megawatt thermal plant or the energy consumption of a city like Medellín for 15 days. Its 79-kilometer extension runs through the Cauca River canyon up to the jurisdiction of Santa Fe de Antioquia. The technical maneuver to raise the reservoir from elevation 408 — where it had historically been operating — required a highly meticulous process to gain those 12 vertical meters without compromising safety. EPM explains the importance of reaching elevation 420 Photo: EPM Raising the water level abruptly carried imminent risks of instability and landslides on the mountainsides, reviving memories of the past contingency. For this reason, EPM scheduled a controlled ascent rate of only 40 centimeters per day starting September 25. During the weeks of filling, if the water inflow exceeded the speed permitted for a safe ascent, the spillway of the hydraulic complex was immediately activated to release the excess. This gigantic discharge infrastructure, composed of a 405-meter-long channel — equivalent to the size of four soccer fields together — allowed absolute control of the flow while the indispensable water resource accumulated. The execution of the procedure addressed not only the physical and structural aspects of the dam — a monumental rockfill work 225 meters high, taller than landmark buildings such as the Torre Colpatria — but also a rigorous social and environmental contingency scheme. Hidroituango Photo: EPM In the areas of the reservoir and the upper river basin, analyses of traditional activities such as fishing and gold panning were carried out, coordinating wildlife management plans that included the relocation, transfer, and continuous monitoring of biological species. In parallel with the gradual rise of the impounded river, work was rigorously carried out to remove the remaining vegetation layer in the reservoir basin, accompanied by periodic verification visits from the environmental authority. Behind every centimeter the water level rose was the uninterrupted surveillance of EPM's Technical Monitoring Center. This technological complex analyzes in real time the information from more than 3,600 instruments installed in the dam structure. The system makes it possible to know up to 40 hours in advance any variation in the flows that will enter the reservoir, measure possible ground settlements, evaluate millimetric infiltrations, and monitor the stability of the slopes, supported by permanent boat patrols and drone inspection patrols. Hidroituango Reservoir Photo: EPM Upon completing the ascent phase, the plant began a rigorous period of evaluation and testing to verify that the reservoir is capable of operating stably within its design fluctuation range, located between elevation 405 and elevation 420. EPM verifies the technical response of the gates, the stabilization of all mechanical and geotechnical variables, and the absence of unforeseen leaks, with the aim of gathering the information required by the National Environmental Licensing Authority (ANLA) to consolidate the definitive regulatory process. The administrative decision to allow filling to the maximum elevation was accompanied by strong statements about the technical demands imposed in the past. Hidroituango Reservoir Photo: EPM Environment Minister Fabio Arjona Hincapié highlighted the change in the government's stance regarding the project's technical progress, stating that "there was no technical reason to prevent the elevation from rising." The head of the environmental ministry questioned the previous delays in licensing and argued: "The only reason we sought, tried to scrutinize, was the possibility of an impact on water quality from the flooding of plant biomass, which, although it was removed, was not necessary. There, 36 billion pesos were invested that were not required, simply out of a whim. Because in this government we work with information and awareness. We do not work with hypotheses or environmental hysterias that only delay projects," said the minister. For its part, the authority in charge of environmental control confirmed the strict compliance with safety and environmental impact requirements by the hydroelectric plant's operator. ANLA Director Sergio Arturo Piñeros Botero backed the viability of the procedure carried out by EPM: Environment Minister and ANLA Director Photo: EPM "We can affirm today that EPM, as the operator of Ituango, has complied with the ascent operation standard. The reservoir's quality levels remain within the margins. The flooding of 33% of the vegetation layer has not had an impact on quality. It was verified that there is no variation in the natural filtrations of a dam, which in these cases are very efficient." With elevation 420 now reached, Hidroituango will continue operating under constant surveillance of its infiltration and slope pressure variables. The project's spillway will remain enabled as the primary safety mechanism to buffer potential rises of the Cauca River, ensuring that the reservoir does not exceed the permitted margins while the country takes advantage of the maximum storage capacity to sustain national energy demand in the face of the challenges of the El Niño phenomenon. Follow all the news from Colombia on Facebook and Twitter, or in our weekly newsletter. EL TIEMPO NEWSLETTERSSign up for our newsletters and receive news in your email according to your interests. Stay informed about what really matters to you. EL TIEMPO GOOGLE NEWSFollow us on GOOGLE NEWS. Always stay up to date with the latest news, coverage, stories, and analysis directly on Google News. EL TIEMPO WHATSAPPJoin the El Tiempo channel on WhatsApp to stay up to date with the most relevant news as it happens. EL TIEMPO APPStay informed with the EL TIEMPO app. Receive the latest news, coverage, stories, and analysis directly on your device. 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