Author(s): Marijus Pileckas,Gražina Žiliūtė / Language(s): Lithuanian
Issue: -/2022
Bathymetric surveys of Juodis and Lydekinis Lakes (located in outskirts of Vilnius city, Lithuania) were carried out on April 28 and May 1, 2020, from a boat with attached Lowrance HDI SKIMMER XDCR transducer (200 kHz), Simrad GO5 chartplotter and Lowrance Point-1 GPS/Glonass receiver. Average distance between profiles was ~10 m and depth measurement accuracy up to 2–5 cm. Accuracy of water surface elevation measurement using GNSS receiver Topcon Hiper SR up to 1–2 cm. Later, detailed (0.5x0.5 m) digital lake bottom models (DEM) were developed, bathymetric plans of the lakes were created, the main morphometric features were calculated, the boundaries and area of the lake catchments were defined, and the physical-geographical characteristics of the lakes were described based on field observations and various data. Juodis and Lydekinis are small shallow lakes of glaciokarst origin, located in Tapeliai glacial tunnel valley. Juodis Lake is considerably elongated while shape of Lydekinis Lake is close to the circle. According to survey data, the surface area of Juodis Lake is 9.2 ha, water surface elevation 135.8 m a.s.l., maximum depth 3.7 m, mean depth 1.2 m, volume 114.9 thousands m3, catchment area 344 ha. The surface area of Lydekinis Lake is 1.7 ha, water surface elevation 138.2 m a.s.l., maximum depth 4.9 m, mean depth 2.2 m, volume 36.3 thousands m3, catchment area 71 ha. During the observation period (from June of 2018 to April of 2022), the annual amplitude of water level fluctuations in Juodis Lake reached up to 0.16 m. Water level fluctuations in Lydekinis lake were very large due to the reconstruction of the dam and the installation of new culverts. Currently, the water level in Lydekinis Lake is significantly raised, most of the lake shore and the surrounding wetland are flooded.
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