HISTORY OF CREATION AND CURRENT STATE OF THE OVOSELSKY-ROZHKOVA DAM (KUYALNITSKY LIMAN)

Problems Statement and Purpose. The Kuyalnitskiy estuary is located within the northwestern estuary coastal region, in the interfluve of the Southern Bug and Dniester rivers. This is a closed estuary, which is separated from the sea by an embankment and has no direct connection with it. Nature management in the estuary basin during the 19th‑20th centuries was carried out disregarding the natural territorial regularities and led to a critical condition of the geosystem of the reservoir. Hydrotechnical engineering on the banks and waters of the Kuyalnitsky Estuary was aimed at regulating the hydrological regime in order to create favorable conditions for salt precipitation. One of these structures is an unexplored Novoselsky-Rozhkov dam. Data & Methods Measurements were carried out using geodetic rail 3 m long, being on the rubber boat. Determination of depths and coordinates was carried out after the boat stopped at the measurement point. Аlong with measurements were determined the depths above the flooded crest of the hydrotechnical structure. The surface of the dam was explored by walking routes. The position of the boat and points on the dam was determined by Garmin GPS72H navigator. Depths were determined with an accuracy of 0.01 m. The studies were carried out under conditions of complete calm; during measurements at a temporary water measuring post no level fluctuations were recorded. Results. One of the hydrotechnical objects that exist in the water area of the estuary is the Novoselsky -Rozhkov dam. Dam was built in 1858–1859. to transform the Kuyalnitsky estuary into salt-forming self-sedimentary lake. Initial parameters of the dam: length – 2929 m, width along the top – 6.4 m, width in the lower part – 17.1 m. The height of the structure did not exceed 1 m above the water level due to constant subsidence on soft soils in the estuary. During the 165 years of its existence, the above-water part of the dam was destroyed by floods. The parameters of the underwater part and the axis of the structure remained close to the initial ones: length – 2900 m, average top width –14.2 m. The modern surface profile of the dam has a concave shape and is the same as the bottom profile. The dam affects the natural system of the Kuyalnitsky estuary as an artificial relief form: it causes the accumulation of material at the bottom and near the shore in the southern corners of the structure; water temperature rise in coastal shallow waters and above the surface of the dam by 2–3 0 С was noted in comparison with the water masses of the nearby water area.