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Wildfire ash turns Spanish mountain river black, contaminating water supply

By Thomson Reuters Oct 7, 2026 | 8:50 AM

By Susana Vera

CASAVIEJA, Spain, Oct 7 (Reuters) – A river running through a town in central Spain has turned black from wildfire ash and debris, contaminating the local drinking water and forcing ​residents to rely on emergency supplies.

In the town of ‌Casavieja in Avila province, where fast mountain streams flow into the Tietar River, the churning waters were inky black from ash-laden runoff. Residents queued at fountains and tanker trucks to fill canisters with clear drinking water, and authorities distributed water in ‌bottles.

“To ​drink, to cook, for the bathroom, for everything. ⁠Water: you only realize ⁠how much you need it once you don’t have it anymore,” said resident Miguel Angel Perez Sanchez.

Casavieja Mayor Vanessa Muñoz said torrential rains had compounded the damage caused by the fires, washing away bridges ​and carrying runoff into a reservoir that serves as a backup water source for the town.

“It affected us mainly because it entered ⁠the reservoir, which was our water supply ⁠and our emergency plan when the first rains arrived,” ​she told the regional broadcaster Castilla y Leon TV.

Santiago M. Barajas, an ​agronomist and co-founder of environmental group Ecologistas en Accion, wrote ‌on X: “The impacts of the fires continue after they have been extinguished.”

“After torrential rains, the water barely filters into the soil without vegetation and rushes away muddy at great speed, as if the ashes had ⁠made it impermeable.”

In the nearby town of Piedralaves, authorities and water utility Aqualia were working to restore normal supplies after ash washed into water catchments ⁠following recent rains, prompting ‌officials to declare tap water unfit for consumption.

The affected ⁠area lies downstream from the Burgohondo wildfire in ​Avila, one ‌of Spain’s largest blazes this year, which burned ​33,943 hectares (83,875 ⁠acres), accounting for more than 15% of the total area destroyed by wildfires nationwide, according to Environment Ministry data.

Jose Maria Manso, mayor of nearby El Barraco, said ash and sediment could eventually reach the El Burguillo reservoir, a key source of drinking water for surrounding communities.

(Writing by Emma PinedoEditing ​by Peter Graff)