The site after the Kachov Reservoir, or a chance to renaturalize the Great Lug

Wielkiego Ługu

The destruction of the Kachov Dam and the resulting sudden decommissioning of the dam reservoir was an environmental disaster, which we wrote about inWater Mattersin June. The Ukrainian authorities have already announced its reconstruction. The arguments raised are familiar to readers of our site from plans to cascade the Vistula related to energy, shipping, fishing, etc. Some also argue that the lack of a reservoir will contribute to the desertification of the Great Lug, or Lower Dnieper Valley. Meanwhile, Ukrainian scientists studying the Great Lug steppes and the nature of the Dnieper River take a different view.

A brief history and characteristics of the Great Lug

Ukrainian scientists are aware of the ecological damage caused by the sudden drainage of the reservoir, flooding in the Dnieper valley and the influx of fresh and polluted water into the Black Sea, as they are the ones who prepared the June report, cited by subsequent services. At the same time, they know that the state in which the nature of the Dnieper River and its surroundings has been since cascading was its degradation, and the destruction of the Kachovsky Reservoir and, before that, Oskolsky Reservoir (in 2022) is an opportunity to restore the state close to nature. The Great Riparian, once a unique part of the Wilderness, has not been wild for a long time, and its nature until recently was an artificially formed ecosystem of a relatively shallow dam reservoir, more of an extensive farm pond than a riparian.

The remnants of the Great Lug are protected (that is, they were, before the Russian occupation) as the “Vlykyj Luh” national park. It covers the slopes of the former floodplain rather than the valley itself. A section of them is a Ramsar network area. The forest component is partly anthropogenic in nature, as the Zaporozhian Cossacks, who ruled the area (albeit informally) for hundreds of years, planted trees as natural fortifications of the sietch. The Great Lug was a combination of steppe, forest and swamp vegetation, especially rushes. It was shaped by floods, and the substrate is not only alluvial and peaty, but also karst.

Not surprisingly, the idea of cascading the Dnieper River, implemented at the turn of the Stalin and Khrushchev eras, aroused the horror of naturalists who did not share the Michurinsky (then in force in the worst – Lysenko – version), vision of shaping nature. Their voices, however, did not get through the censors. In Poland at the time, analogous plans to cascade the Bug and Vistula were being developed, although they were less successful.

Social and economic impact of flooding of the Great Lug

The construction of the reservoir not only destroyed the nature of the Great Lug, but also made life more difficult for the people living in its vicinity. Apart from the bridge over the dam, the only way to cross it was by ferry. Without it, it would have been much easier to build several additional bridges. It turns out that the reservoir’s role as a drinking water reservoir was not irreplaceable. After the destruction, it was fairly quick to rebuild the intake system in such a way that there is no shortage of water. The Dnieper carries enough of it without piling up. By the way, the risk of blooms has decreased.

At the time of its creation, the reservoir was heralded for its versatile use, verging on science fiction. Rice fields were to be built in the littoral zone, cotton plantations on the shore, and the reservoir itself was to be a model fishery farm with sturgeon farming at the forefront. All in accordance with Michurin’s agronomy. In the name of this, not only wild fields but also 500,000 hectares of farmland were flooded, and another 100,000 hectares were placed in a new flood zone. The zone, moreover, has also become dangerous due to numerous landslides and flooding.

The fishery declined very quickly. Sturgeon disappeared completely, predatory species, which were supposed to dominate the fishery, marginalized themselves. Siltation and lack of current eliminated the most valuable fishery species, whose place was taken by foreign, ubiquitous species. In ten years, between 1956 and 1966, fish catches in Kherson declined almost tenfold. Then came the blooms and chemical pollution. As long as sediment collected on the bottom, the latter was not a significant problem, but if the basin were refilled, the newly dissolved contaminants would prevent gastronomic use of the fish for some time. It seems that fishing on the naturally flowing Dnieper could be as effective as it was on the reservoir.

Counterintuitively, the reservoir has also made shipping more difficult. The sluicing reduced the capacity of the waterway, and smaller vessels could not use the waterway in windy weather due to wave action. In winter, the reservoir froze faster than the river. Large-scale shipping in Ukraine has declined, as it has in other regions of Europe. Between 1980 and 2009. Cargo shipments across the Dnieper decreased tenfold and passenger shipments sixteenfold, falling to a marginal 1,500. individuals. The Kachovsky reservoir was to be one of the last sections of the planned E40 Gdansk-Odessa waterway.

Before the war, the chances of implementing this plan were slim due to nature conservation requirements in Poland and technical difficulties in the swampy Pripyat valley in Belarus. It should be noted that Ukraine’s candidacy for the EU will make conservation requirements there more stringent as well. Since the outbreak of the war, they have dropped to zero. On a Ukrainian scale, the role of the Kachov power plant is also not crucial. The entire cascade produced only 5-7% of Ukraine’s energy, and the cost of maintaining it is higher than the profit.

The steadily declining water flow is not insignificant. In 1971. 80 km3 were released from the reservoir, while in 2018. already only half that value. Erosion made the reservoir shallower and wider, and evaporation accounted for an increasing share of its water balance. Climate change would only exacerbate this phenomenon.

Chances for the return of the Great Lug

After the ecological disaster that was undoubtedly the draining of water from the reservoir, nature is recovering quickly in a new form. Despite initial opinions, there has been no desertification of the area. Admittedly, as usual in degraded habitats, invasive species initially predominate, but willow riparian forests are recovering just a month after the wave passes. The site after Oskol Reservoir became a bird sanctuary during the year. Scientists predict that in the first stages of succession the site after the Kachov Reservoir will be covered with ruderal vegetation. While the seed bank of aquatic and marsh plants exists, meadow and forest plants will have to come here from the neighborhood, which will certainly take some time.

It is assumed that for the time being there will be no striping characteristic of riparian forests, as the water-covered soils have become uniform. Sooner or later, however, the differences will become apparent, which may be helped by several floods. This includes differences in soil salinity.

Scientists believe that this is an opportunity to implement plans to increase Ukraine’s forest cover without harming agricultural areas. Forests are not expected sooner than in a few or a dozen years, and even so, the former Great Lug may only resemble the former Great Lug after 2-3 generations of pioneer trees have passed.

Although the Mykhurin Doctrine is no longer in effect in Ukraine, there are voices for the reconstruction of the dam and reservoir. The loudest came from the Ukrhydroenergo company. Biologists at Kherson University, however, hope not to restore the Kachov Reservoir but the Great Lug.

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