DIFFERENTIATION OF DELTA SEDIMENTS OF SIELPIA WATER RESERVOIR (ŚWIĘTOKRZYSKIE VOIVODESHIP, POLAND) PRELIMINARY RESULTS

Abstract

The Sielpia Reservoir is located on Czarna Konecka river in the northern part of Świętokrzyskie Voivodeship (central Poland), about 30 km NW from Kielce. This area is part of the Old Polish Industrial District, which was developed from the Middle Ages. The river was used to power up many ironworks, forges and water mills. This lead to appear many industrial ponds in the river. The Sielpia Reservoir is located in one of this kind of industrial ponds place. It was built in 1821 and use as industrial pond to 1921 and next it was drainage as result of dam failure in 1930s. The modern reservoir was built in the 1960s and currently has a retention and tourist function. The hydrotechnical works began in 2018 during which the reservoir was drained in order to deepen it. During this work, numerous subfossil trunks found in the alluvial bed of the reservoir underlying limnic deposits were dated using the radiocarbon and dendrochronological methods to La Tène–Middle Age period. Stratigraphic position, as well age of the oaks that were fallen during the phases of increased fluvial activity even before the development of the metallurgical industry and deforestation, they indicate that both historical and modern reservoir in Sielpia were very shallow, and its sediments were underlain with the Subatlantic alluvial floodplain. In the Czarna Konecka estuary into the reservoir a delta was formed. A geological cross-section was made here, and samples were taken from the profiles for grain size analysis. The sediments are bipartite here. The lower lake link is made of sands with organic matter, while the upper, sandy, builds a delta. This form was created, among others due to many flash floods caused by failures of the dams of former industrial ponds located upstream of the Sielpia Reservoir.