An international team of scientists – led by Prof. Alessandro Tibaldi, from Milan Bicocca University – have been working, since November 2015, on a major collaborative research program under the aegis of the North Atlantic Treaty Organization’s (NATO) Science for Peace and Security program. The involved researchers come from Italy, the United States, the United Kingdom, Switzerland, Georgia, Azerbaijan, and Kazakhstan.
The aim of the project is to enhance understanding of the geological hazards affecting the Enguri Hydropower facility (EHF), a crucial energy infrastructure located in NW Georgia, one of the world’s most vulnerable areas, both at the geopolitical and geological level.
The EHF represents the major source of energy supply to the Republic of Georgia and the sole energy supply to the disputed region of Abkhazia; it comprises the Enguri Dam, which is the sixth tallest dam in the world, and the 15-km-long Enguri artificial water reservoir, both located in Georgian territory.
On the other hand, most of the water tunnels and the plants for electricity power production are located into Abkhazia. Any problem to this major energy power facility would bring about relevant societal and economic problems to both countries and might further destabilize the region, leaving millions of residents and hundreds of infrastructures, such as hospitals and military bases, without energy supply.
The most threatening geohazard sources for the EHF are earthquakes, floods and landslides. From the seismic point of view, it is worth pointing out that the water reservoir behind the dam occupies a deep valley carved in the southwestern Caucasus, a mountain range that has experienced earthquakes with magnitudes as strong as 7.
Earthquakes, as is well known, have the potential of triggering landslides: A major threat to the EHF is represented by the active Khoko landslide (11 million to 21 million cubic meters), which is slowly creeping downslope, and lies only a few kilometers from the dam and directly faces the reservoir.
During the first two years of the project, the scientists have carried out a monitoring campaign aimed at assessing the Khoko landslide stability and reducing vulnerability in the face of landslide-related hazard. This major effort has led to the setup of instruments aimed at measuring, at the highest possible detail, the slow but relentless downslope movements of the landlside.
One of the most relevant outcomes achieved by the team is shedding new light into the tectonic framework of the area, as attested by an impressive number of papers published in major international journals.
Moreover, the seismologists in the team have worked hard on producing an improved Macroseismic Catalogue of The Republic of Georgia, which, in the future, might play a pivotal role in enabling local authorities to effectively reduce seismic risk all across the Country.
Another possible, although extreme risk scenario is represented by the Khoko landslide mass entering the lake (either as a consequence of internal failure or due to seismic shaking) and triggering a tsunami, which in turn would lead to catastrophic consequences for towns and infrastructures located downslope of the dam.
With the purpose of assessing the extent of such an extreme event, the NATO team is currently modeling the dynamics of a possible tsunami wave overflowing the dam. Although this is no doubt an extremely rare and unlikely occurrence, it is difficult not to rembember the Vajont Dam landslide and tsunami, which, in October 1963, led to the death of 2,000 people in NE Italy.
Other, subtler sources of hazard and risk can develop gradually and unnoticed, such as the constant infilling of the bottom of the reservoir due to the water transport of sediments eroded away from the mountains. Moreover, in March 2017 the plant was closed for some weeks as consequence of significant water leakage from a 15-km-long diversion tunnel, as was declared by Levan Mebonia, the Dam’s general director, during an interview with EurasiaNet.
Federico Pasquaré Mariotto (Associate Professor, Insubria University, Varese, Italy)