Massive lake drained for hydropower leaves dry bed and no fish

This lake used to be about a kilometre wide

Reuters/Dado Ruvic

By Maria Bolevich

A large artificial lake in the Balkan state of Bosnia and Herzegovina totally vanished this month and with it an estimated 2 million fish.

Following rains and snowmelt, Jablanica lake has now started to reappear, but the ecological damage might take years to repair, say environmental groups and local fishers.

Water levels in the lake are usually regulated to keep enough water to generate hydroelectricity and to avoid floods in the city of Mostar, which lies downstream. So it came as a surprise to local people, especially fishers, to see the lake completely drained last week, and with it all its __life gone, too.

Normally, the lake is 30 kilometres long, around a kilometre wide with a depth of about 70 metres. Water levels had dramatically dropped twice before, during droughts in 2005 and 2012, but never by this much.

The discharge was carried out largely last month by power firm Elektroprivreda BiH, which says it was needed to maintain electricity production during a dry and especially cold period when energy demand was above average.

Endangered fish

The lake was home to some ten fish species, including the endangered Adriatic trout (Salmo obtusirostris) and vulnerable Adriatic dace (Squalius svallize). It is also part of the Neretva river system, a biodiversity hotspot with many endemic species.

It is clear that the lake’s disappearance has diminished the local wildlife habitat, says Alen Soldo at the University of Split in Croatia. Aquatic species that can’t relocate would have died, while the rest would have had to migrate.

But a huge influx of fish into waterways already occupied by other fish would also cause long-term damage to animal numbers and biodiversity in those surrounding areas, he adds.

Fully draining the lake has completely degraded its ecosystem, agrees Senka Barudanović, a biologist at the University of Sarajevo in Bosnia.

Impact unclear

But Samir Đug, from the University of Sarajevo, who visited the site to evaluate the damage, says it’s not yet clear what damage has been caused to wildlife.

And there might be a silver lining, he adds. Đug says the fishers should take advantage of this situation to clean the lake by removing now-exposed waste before all the water comes back.

The whole episode points to a bigger problem in the region: a lack of integrated management of water resources, says Petra Remeta, the freshwater programme manager of environmental campaigners WWF Adria.

Anes Podić from environmental NGO Eko Akcija agrees. There has been no monitoring of how  changes in lake water levels affect wildlife, he says. Elektroprivreda BiH is ignoring the consequences for plants and animals, he adds.

Elektroprivreda BiH said in a press release that the discharge didn’t cause an ecological disaster, and added that water is already returning, as it did in 2012, when low levels also didn’t hurt fish stocks.

Read more: Many of world’s lakes are vanishing and some may be gone forever