Modelling the impact of small hydropower dam on sediment retention in the river Virvyte

Abstract

The hydroelectric power plants (HPP) are a valuable source of renewable energy; however they negatively impact the environmental conditions in the river. The paper presents investigation of the ways to coordinate these problems. The mathematical-hydraulic modeling is used to investigate sedimentation process in the riverbed and in the flooded valley. The sedimentation and sediment retention in the valleys is more intensive, when the HPP dams are not high (H≤4 m) and their ponds do not overflow into floodplains. The great sediment retention was estimated during the 1 % probability flood of 1958 (8000t/year) in the investigated interval of the river Virvyte. Having arranged 3 ponds in this reach, sediment retention decreased by about 50 %, as the height of Kapėnai HPP dam was too big. The sedimentation during the years of various water heights in this river interval has been 500-2000 t/year, i.e. quite heavy. Grass in the flooded meadows entrap the sediments and decrease the water contamination below dam.