In three days the water level of the large Kakhovka reservoir fell by almost five meters following the partial destruction of the dam on the Dnipro River in the Kherson region in southern Ukraine. The water drained westward along the river, causing huge floods and forcing thousands of people from their homes. Since Tuesday 6 June, the day of the explosion, Ukraine and Russia have been accusing each other of destroying the dam, which cannot be rebuilt until the end of the war, by cutting off an important source of water and electricity that was produced from the hydroelectric plant within the infrastructure.
Dams on the Dnipro
The Kakhovka dam is just one of many dams built along the course of the Dnipro (or Dnepr), the fourth longest river in Europe and the third largest, which crosses Russia, Belarus and Ukraine. The river, which has a length of about 2200 km, passes through Ukraine for half of its course and is largely regulated by a series of artificial water basins, built over time both for the purpose of regulating the flow of the river and collect water for agriculture and for the production of electricity.
Overall there are six hydroelectric plants with as many dams, including the now unusable Kakhovka dam. Each basin depends to varying degrees on the one preceding it and is filled according to need, both for the production of electricity and for irrigation or to supply water to the population, after it has been made potable. If one considers the succession (or “cascade”) of water basins in its entirety, a volume of water exceeding 40 cubic kilometers is reached, while the surface they occupy is almost 7 thousand square kilometres.
The whole system constitutes one of the largest artificial water reserves in Europe. At full capacity, the plants along the Dnipro produce a tenth of the electricity generated in Ukraine and for this reason they have always been considered strategic.
Dams and wars
The construction of the first dam, almost a century ago, arose from the need to make the stretch of the Dnipro river navigable for about a hundred kilometers between the present-day cities of Dnipro and Zaporizhzhia. The first ones had already been developed by the end of the 19th century projects to do so, but to build it it was necessary to wait until the 1920s of the following century, when some construction techniques had been improved and above all new hydroelectric solutions were beginning to establish themselves. At the time, Ukraine was part of the Soviet Union and the exploitation of the Dnipro was part of the Soviet projects to favor its industrialization.
Construction in the vicinity of Zaporizhzhia began in 1927 and he demanded five years to complete. The course of the river was partially diverted in order to reach its bed and be able to build the foundations of the dam, which is still today the largest on the Dnipro. In 1932 it was inaugurated together with the hydroelectric power station and for the first time the river was regulated upstream, with the creation of a basin that made a stretch otherwise traversed by rapids navigable, and downstream with the regulation of the water flow towards the west.
In a short time the plant became very important and favored the development of Zaporizhzhia and also of the city of Dnipro. Electricity was mainly used to power new industrial plants for the production of aluminium, which was then used by the Soviet Air Force for the construction of military aircraft.
And the importance of the dam became evident during the Second World War, when in 1941 the Nazi army invaded Ukraine in its eastward advance against the Soviet Union. The Red Army was forced to withdraw and blow up part of the dam, in order to slow down the German army. The Russians had chosen to sacrifice one of their most important infrastructures, well known and used by propaganda to show Soviet technical and engineering superiority, in order to gain time and reorganize themselves to face the Nazi troops.
The result of the destruction of the dam was disastrous from an environmental point of view and therefore the parallel with what happened this week at the Nova Kakhovka plant does not escape. In addition, the large and unexpected flash flood downstream of Zaporizhzhia caused the deaths of 20,000-100,000 people (estimates vary widely) including civilians and Red Army soldiers who were still crossing the Dnipro. A couple of years later it was the Nazis who blew up another section of the dam, this time to hinder the Soviet counter-offensive.
In 1944, the year of the liberation of Ukraine from Nazi control, the first reconstruction works started. The war was not over yet, but the conditions existed in the area to start the construction site also thanks to the resources supplied by neighboring Russia. The situation was therefore very different from today: the Nova Kakhovka dam is very close to the front and it would therefore be unthinkable to start reconstruction work at this stage of the conflict.
It took almost five years to restore the Zaporizhzhia dam and the hydroelectric plant returned to generating electricity in 1950. In the 1970s and 1980s, the section was enlarged with the addition of a new segment to produce more electricity. Today the dam has the capacity to raise the level of the Dnipro up to 37 metres, collecting the water from the upstream basins built in the second half of the 20th century.
A huge artificial lake
Before the Zaporizhzhia Dam there are five more dams which form reservoirs in a succession starting at the border with Belarus. Construction works on the dams and associated hydroelectric power plants were completed in the 1980s, making them one of the most successful engineering enterprises of the Soviet period. Finally, downstream from Zaporizhzhia was Kakhovka, the last dam in the series, built in the first half of the 1950s.
The construction of the series of water basins solved many problems related to the supply of electricity and water to the population and to productive activities, but it was certainly not without heavy costs from an environmental point of view. Large areas of land were inundated causing major changes to their ecosystems and to that of the Dnipro itself. Territories covering over 7,000 square kilometers were covered by water, mostly forests or pasture fields. It was an area inhabited by about 3 million people, who had to abandon their homes and in many cases saw their inhabited centers disappear under the water.
Over the years along the Dnipro was observed an impoverishment of ecosystems, especially as regards fish species, with a significant loss of biodiversity often observed where artificial basins are created. The water level in the various basins changes according to the time of year, both for natural reasons related to evaporation and for the need to let more or less water flow downstream. These continuous variations, which are accompanied by significant changes in water pressure, are among the causes of the high mortality of some fish species.
Beyond the effects on the environment, the cascade of Dnipro reservoirs has long given rise to other concerns related to the safety and maintenance of the system. The presence of reservoirs close to highly populated areas increases the risk for the population of suffering floods in the event of a dam breaking, as indeed happened in the Second World War and as happened this week. The designers thought about this eventuality and built reinforced structures with greater sealing capacities than was necessary.
Each dam has the theoretical capacity of resist to severe earthquakes, bombings and the off chance that it is hit by an airplane or a meteorite. The destruction of part of the Zaporizhzhia dam was only possible by directly undermining the infrastructure, with charges placed where they would cause the most damage to its stability.
The destroyed dam
There is not much information yet on this week’s destruction in Nova Kakhovka, but various experts have supposed that it occurred following the use of explosive material in the infrastructure. A bombing from the outside would hardly have caused damage of that type and above all it would have been detected by other systems, starting with those of air defense.
The Kakhovka reservoir produced by the dam had a capacity of about 18 cubic kilometers of water (for comparison, Lake Como in Italy has a volume of 23 cubic kilometers). The water was used for irrigation of fields in a large area of southern Ukraine and especially northern Crimea, through a canal over 400 kilometers long. The dam rupture caused a huge volume of water from the reservoir to flow west within days, flooding more than 40 cities and towns along the Dnipro. In addition to the thousands of displaced people, the floods have caused the death of many animals on farms and rendered grain and seeds unusable.
To reduce the inflow of water, the system of dams upstream of Kakhovka was activated to accumulate greater quantities of water in the other basins, in order to let the flood run downstream of the damaged dam. The flow should decrease within a few days, but it will take a long time for the water to withdraw from the flooded areas, mostly flat and with waterlogged ground.
Ukrhydroenergo, the public company that manages the plant, has started the first checks to estimate the extent of the damage, but has in any case ruled out being able to intervene quickly on the dam which will have to be rebuilt in almost all of its parts. The head of the company, Ihor Syrota, he said that the reconstruction will take at least five years and has estimated that the cost will be around one billion euros. In the meantime, activities will be launched to dig wells and canals in order to bring water to areas that will no longer be able to draw from the basin. In the area, the territories east of the Dnipro are disputed or directly controlled by the Russian army and this will make reconnaissance and start-up of construction sites more difficult.