Hydraulic geometry of the river Neris for the assessment of hydrokinetic resources

Abstract

Stage, discharge, flow velocity, and flow cross-section area data of the Lithuanian Hydrometeorological Service gauging (hydrometric) stations (GS) was used for the assessment of hydrokinetic energy resources (on the basis of the Neris river case). Close correlation of water level, discharge, velocity, and cross-section relations was identified during the investigations whereas GS water flow velocity histograms were compiled according to multi annual daily discharge curves and mean cross-sectional velocities as well as discharge relationship. The histograms are based on theoretic probability distributions and data validation tests. The best compliance is that of extreme value distribution. Hydraulic and geometric characteristics of the river flow, defined by the hydrological method, were compared with the results obtained by the hydraulic model (HEC-RAS). The compliance determined was valid. Transposition of the relation among flow velocity, bed cross-section area, depth of the river and the discharge over the length of the river is not possible for the assessment of hydropower resources due to the poor correlation of the data. Hydraulic simulation, using the digital terrain model (DTM) of the river bathymetry, is the main and the most precise method to assess the resources of hydrokinetic energy and select the most efficient location for the generation of hydropower whereas field measurements bear significance only for validation of the data.