River Systems: Anthropogenic Impact

In the middle of the Triglav National Park, Slovenia, the Soča River mysteriously emerges from the carbonatic rocks and shows its magnificent colour, appearing calm and inviting. As soon as one starts to walk down the stream from its source, Soča begins to create rapids, waterfalls and clearly transforms its calmness into wilderness – something to be careful of and never underestimate.

Photo credit: David Štulc Zornik

Driving through the Trenta Valley, it is hard to stay on the road since the continuous presence and beauty of Soča drag one’s attention and, indeed, the upper part of the river is well preserved by the proud inhabitants of the villages near Soča. The crystal clear water triggers to think that the river is clean, but is it really?

I have searched a lot through the internet and, frankly, haven’t been able to find many scientific articles. However, a few of them popped out and turned out to be essential.

Velika Korita, Lepena, July 2016
Soča Village, July 2016

Firstly, I would like to focus on the construction of river dams for electricity production. Have you ever wondered where the power for your lamp comes from, or if it makes any difference to leave it switched on for more than you actually need? I hope you have because believe me, I have shared living spaces with many people, and they sort of didn’t get it (sometimes it is best to ignore and humans are very good at it). One of the ways to get energy is hydropower. Dams have these huge turbines that are moved when water flows through, and their movement generates power. Sounds very cool and ingenious, but what about the animals and plants that have suddenly been cut out from their natural habitats?

It has been researched that below the Ajba and Podsela dams, the oscillations of water temperature, dissolved oxygen and oxygen saturation are much larger than at unregulated sites upstream. In the Soča River, the impact of prolonged periods of reduced flows, a lack of sediment supply from upstream and changes in physicochemical variables has caused high periphyton biomass, proliferation of green algae and increases in the number of periphytic algae species below the dams (Smolar-Žvanut et al., 2014).

Credit: Jan Pirnat

Secondly, there is a chemical factory called TKK in Srpenica, that produces polyurethane foam bottles. The TKK buildings are situated right next to the river Soča. In an article that I have found, the researchers focused on the possible accidental scenarios that could happen. One of them could be an LPG leakage (LPG is used as a foam creating agent in the spray bottles). Its storage area, and of other raw materials, are at the northern edge of the industrial area and are close (approx. 10 m) to a precipice toward the Soča river. In case of a vapor cloud explosion, the car tanks could lose control and roll from the precipice into the river. The content would flow into the river within 2 hours and approx. 100 meters downstream. Because the riverbed is rocky, there would be complete mixing and homogenization of the dissolved and suspended MDI or polyol. The half-life of MDI decomposition by hydrolysis in the clod Soča river water is estimated at 2 hours. Such possible accident at TKK resulting in major pollution of the river Soča would have consequences for both water/environmental quality and water use. The Salmonidae sp., which are one of the most abundant fish species in the Soča River, would be the most affected of this possible accidental scenario.

Credit: TKK d.o.o.

Thirdly, in Idrija Mercury Mine, one of the biggest mercury mines in Europe and in the world, half a millennium of mercury production has increased mercury content in all of its environmental segments. It has been estimated that around 45550 tones of mercury were emitted into Idrijca River from 1867 to 1991. The Idrijca River flows into the Soča River which then flows into the Upper Adriatic Sea. The average concentration of Hg in the first section amounts to 603 mg/kg with individual contents up to 4121 mg/kg! At the Idrijca-Soča confluence, the average is 213 mg/kg, while the average in the Soča river sediments is 57 mg/kg (M. Gosar, 2008). It is not surprising that the sediments found along the Idrijca and Soča rivers are mercury-rich, as well as the sediments of the Isonzo (= Soča in italian) and Adriatic Sea delta.

Moreover, since the Adriatic Sea, especially the Upper Adriatic Sea, has a slow water turnover, meaning that the currents move slowly, the sediments remain relatively stationary along the delta Grado. This is one of the reasons for which the algal communities and fish populations living within the Adriatic Sea have a much higher content of mercury in their vegetal and body tissues, respectively.

Credit: M. Gosar, 2008

Many times, we are forward-sighted which is good because it keeps us going on, but at times, it is good to slow down and look outside the box. I have been spending time in the Slovenian mountains, working and enjoying the green and blue around. Even though my summer wasn’t spent on the sea side as it should be for a future marine biologist, I have been wondering non-stop about the essence that surrounds me and the human impact in these upper parts. I had the chance to talk to many people and meet some activists last year already, and something had to be written on white. This platform got the name for a reason – because we want to share the passion for the Oceans and not only, we want to share the passion for the Entire Earth.

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