The destruction of the 334.8 MW Kakhovka hydro plant, on 6 June, constitutes one of the largest man-made disasters of the 21st century. As reported on 7 June, the consequences of this catastrophe will impact almost all aspects of the life for the population, including electricity and water supply, housing, industry, ecology, health, sanitation, agriculture, wildlife, and cultural and social spheres.
The Kakhovka reservoir was 240 km-long, 23 km-wide, and had a surface area, at normal supply level, of 2155 km2. The total reservoir capacity was 18.2 km3. It was the main source of water for irrigation, industrial and domestic consumption, and fishing in the south of Ukraine. The Unified Energy System of Ukraine has lost about 5 per cent of its regulatory capacity.
The causes of the disaster, the initial and ongoing destruction, will be determined by an official investigation, in which leading hydraulic engineering specialists need to participate. Regarding the strategy for the future, according to engineers involved in the design of the dam and powerplant, three main options need to be considered, so that the optimum solution can be found for the future:
Option 1: Not restoring the powerplant
This option seems the most appropriate from an environmental point of view. It will be necessary to study the drained areas and soils, and to develop a project for the restoration of flora and fauna, identical to those downstream of the Kakhovka plant site, with account being taken of accumulated sediments (there are reports of this in the literature and in the press prior to the construction of the project). The Government will need to consider several new issues: the construction of new pumping stations for irrigating farmland; the provision of water to affected consumers; supplying the cooling reservoir at the Zaporizhzhia nuclear plant; and, the supply of water to Crimea. The construction of new pumping stations will require a constant electricity supply, which will be another challenge to be addressed, and could possibly be achieved through development of solar and wind power in conjunction with energy storage facilities. Geographically, the south of Ukraine is very favourable for the development of these types of renewable energy. One of the tasks will be to decide what to do with the existing pumping stations, which pumped water from the tributaries of the Dnipro river, where artificial dams are installed. The water consumption for various needs from the Kakhovka reservoir before its destruction, only for the major channels was more than 900 m3/s. This first option would make navigation on the Zaporizhzhia-Black Sea shipping route impossible.
Option 2: Building a cascade of smaller reservoirs with hydropower plants, instead of one large reservoir
To a large extent, this would solve the issues of electricity and water supply for the population, farmland, and industry. It should be taken into account that the Kakhovka reservoir is the lower stage of the hydropower cascade on the Dnipro river, influencing the planning of the operation of all the reservoirs upstream. The head which can be exploited would be the same (15 m) as was the head at the Kakhovka hydro plant. At the same time, there would be some areas in which the damaged environment would begin to recover.
Option 3: Restoring the Kakhovka hydro plant
To assess the extent of this task, and the methods to be adopted for the restoration, it will first be necessary to examine the remaining structures and the base of the dam after the reservoir has been completely drained. It should be recalled that the Kakhovka hydro scheme was designed in the late 1940s, and built on soft loess soils during the early 1950s. The technology at that time, and limited experience of building hydro plants on such a scale, encouraged the designers to apply additional safety factors when selecting the concrete mixes and reinforcement. Based on observations of the river flow at the site of the powerplant, it can be deduced that several sections of the spillway dam have been completely destroyed. It would not be realistic to imagine that this level of destruction would not have compromised the foundation of the hydraulic structures. Therefore, one of the main tasks during the restoration project will be to study the state of the soils and develop appropriate impervious measures. The restoration of the dam and the hydro plant will take several years to complete, and during this period a major issue will be the safe passage of floodwaters of at least 7000 m3/s, to ensure the protection of buildings remaining in the area.
Once it becomes possible for engineers to work safely at the site, the first steps likely to be taken are:
- examining of any surviving structures in the hydroelectric complex;
- studying the state of the foundation of the Kakhovka hydro plant;
- taking aerial photography across the area of the former reservoir;
- studying the composition of soils that have been drained;
- quantifying precisely the water supply needed for the population and for industrial purposes;
- optimizing solutions for power supply in the south of Ukraine for each of the recovery options;
- developing and considering a feasibility study covering the various options for the restoration of the region and hydro plants, taking into account all the data compiled.