Colombia’s Two Largest Rivers, Cauca and Magdalena, are Drying Up

As a consequence of the El Niño phenomenon, the two Colombian main rivers, Cauca and Magdalena, see their flow levels decline. The first alerts had been issued at the beginning of this month, but in recent hours, reports on the situation have raised concern.

The entity that has been warning about the situation is the Institute of Hydrology, Meteorology and Environmental Studies (IDEAM), which has confirmed the progressive and widespread decline in water levels and flows across broad sectors of the rivers, whose records at the beginning of August were below the historical averages for that period of the year.

At that time, IDEAM’s hydroclimatic monitoring established a critical schedule regarding the behavior of the two rivers during the second half of 2026: For August and September, it forecast a period of greater impact, with reductions and negative flow anomalies projected between 20% and 60% in the basin.

For October, it forecast the gradual beginning of the year’s second rainy season, which could generate a temporary recovery in water flow, although areas with levels below the usual ones will persist.

The Magdalena, below normal

In the long-term outlook (September 2026 to January 2027), projections from the Standardized Multivariate Drought Index (MSDI) warned of the sustained risk of moderate, severe, and extreme drought at several points across the national territory.

Monitoring of the Magdalena River‘s levels showed the persistence of below-normal conditions and an expansion of the stretch where this situation is occurring. Initially, the greatest reductions were concentrated between Puerto Wilches (Santander) and El Banco (Magdalena), where during the second quarter and the beginning of the third quarter, sustained declines and levels that reached categories far below normal were observed.

Low levels remained in this sector and, in addition, greater persistence of below-normal values was observed at stations located upstream, between Purificacion (Tolima) and Barrancabermeja (Santander). In the Purificacion (Tolima)-Puerto Salgar (Cundinamarca) stretch, the stations showed a trend of levels that remained in low ranges during recent weeks, without showing a sustained recovery toward normal values.

This situation continued downstream, in the Puerto Salgar (Cundinamarca)-Barrancabermeja (Santander)-Puerto Wilches (Santander) sector, where recent records continued to be below the values expected for this time of year. The signal was particularly persistent at the stations of Penas Blancas (Yondo, Antioquia), Barrancabermeja (Santander), Puerto Wilches (Santander) and Sitio Nuevo (Santander), which show current levels in the lower ranges of their historical behavior.

In addition, Corantioquia warned that this condition is generating water stress in ecosystems and affecting communities and fishermen in the Antioquia Magdalena Medio region. For this reason, the environmental authority recommends saving water, prioritizing human consumption and maintaining permanent monitoring of water levels and flows.

Low Cauca levels affect Hidroituango

IDEAM pointed out critical stretches of the Cauca River: Municipalities and sectors between Yotoco (Valle del Cauca) and San Jacinto del Cauca (Bolivar). Stations with records of reduced flows include Juanchito, Mediacanoa, La Victoria, La Virginia, Irra, La Pintada, Bolombolo, Puerto Valdivia and Las Varas.

This Friday, Aug. 28, Empresas Publicas de Medellin (EPM) reported that the reduction in the flow of the Cauca River to historic minimum levels has caused Hidroituango, the country’s largest electricity generation complex, to operate at half capacity.

The energy manager, Alberto Mejia, said that since the end of July, the country’s second-largest tributary, which supplies the hydroelectric plant, has fallen to flows of 250 cubic meters per second, a level that represents a substantial decrease that has forced it to operate with only two of the four generation units it has.

The serious issue is that Hidroituango is the main supplier of the energy consumed by the country, through its installed capacity of 1,200 megawatts, equivalent to 11% of what the country consumes. When operating at maximum power, it will be able to generate twice as much, supplying 17% of the consumption of the entire Colombian territory.

“The [Pacific] Ocean is at 1.8 degrees Celsius at this moment of warming and will probably reach three. So, if today we are already at historic minimum levels with an ocean ahead at 1.8, plus the historic minimums, they will probably be more intense,” Mejia said, recalling forecasts that the temperature will rise by practically more than 3 degrees in total.