TALLINN – The massive death of fish in Umbusi river in the Poltsamaa rural municipality in south-central Estonia was caused by shortage of oxygen in the water resulting from an accidental discharge of silage effluent into the river.
According to the Environmental Board, there is no poisonous substance in the water and the fish are perishing due to the lack of oxygen in the water. Fortunately, fresh water is constantly coming in and the situation is expected to be resolved within hours. Until that happens, some fish mortality will continue. The dead fish are not contaminated with poison and can be composted.
The pollution was discharged into the river from a source in Kalana village, which is home to a large farm owned by Pajusi ABF, Tartu Postimees reported.
Lembit Paal, manager of Pajusi ABF, said that over the weekend, probably on the night between Saturday and Sunday, a silage silo affluent tank began to overflow.
"Debris and grit clogged the drain, the silage effluent level rose above the edge of the tank and effluent found its way into the ditch, from there to Umbusi creek and then to the river," Paal explained.
However, several people living near the river saw dead fish in the river already on Saturday and informed the Environmental Board about it, which means that the signs of major pollution appeared a little earlier.
By Sunday morning, the staff of the farm were already aware of what had happened, and during the day they managed to clear the blockage and put a stop to pollution. The ditch along which the silage juice reached the river was also closed.
However, the affluent that had reached the river had already caused significant damage. Five kilometers from Kalana, where Umbusi river crosses the Jogeva-Poltsamaa road, foamy and cloudy water and drowned river trout could still be seen in the river near the culvert on Monday.
Environmental officials and volunteers meanwhile were collecting dead fish at the Lustivere reservoir a few kilometers downstream. There were pikes, roaches and numerous perches among the perished fish.
Paal could not say how much silage juice had flowed into the river.
"The Environmental Board is assessing the extent of the damage and we have to take responsibility for it, we are not planning to hide our heads in the sand," Paal added.
He attributed the incident to human error.
"We should have noticed earlier that there was a blockage," Paal admitted, and promised that the farm operator will be more vigilant in the future.