Hydraulic Properties of Sulejów Reservoir in Poland as a Driving Factor of Sedimentation Processes

In the 1970s, a large artificial lake—the Sulejow Reservoir—was installed in the middle course of the Pilica River in Poland. The reservoir has a length of 15.5 km, a maximum width of 2.1 km, a surface area of 22 km2, and a total storage capacity of 77.6 m3 × 106 m3. It has a very long water retention time of more than 30 days. The Sulejow Reservoir suffers from significant eutrophication due to the supply of nutrient compounds from both point and nonpoint (diffuse) sources. In understanding the role of the reservoir as a storage or source of nutrients it is very important to have a good description of the abiotic properties of the reservoir in the longitudinal profile. With the improvement of hydrodynamic models, it is possible to approach that problem using Computational River Dynamics (CRD) methods. In this study, 1D hydrodynamic model (HEC-RAS) was used to study the distribution of hydraulic parameters in the longitudinal profile of the reservoir. The very accurate DTM of the reservoir was calculated from the newest echo-sounding data obtained in the year 2016. The new value of the reservoir volume was calculated. In the longitudinal profile of the reservoir, zones of the riverine, transitional, and lacustrine conditions were delineated. The distribution of velocities in the longitudinal profile shows the different roles of reservoir sub-basins as sediment traps.