Assessment of hydrokinetic resources of small and medium-size rivers: the Lithuanian case

The aim of the study is to assess hydrokinetic energy resources of small and medium-size rivers in Lithuania. The estimation of technical resources was carried out for river segments, where for average longterm runoff the flow velocity exceeded 0.4 m/s, and the average depth was more than 0.5 m. The results of hydrological studies were used to calculate the average flow rate and the relationship between flow velocity and river depth. The width and depth of the river channel was estimated in accordance with physical and geographical factors. Part of the favourable for use sites of rivers located within protected areas cannot be used for energy production because of the priority of environmental protection. Navigation, recreation and other factors also limit the use of streams for energy production. In addition, in winter due to ice phenomena, hydrokinetic devices in small and medium rivers should be protected from mechanical obstacles. Moreover, Lithuania is a flat country and available hydrokinetic resources of such plain rivers are very small. Their estimated capacity comprises 13.6 MW, and they can generate 79.4 GWh of electric energy per year.