A methodology for the evaluation of the energy potential of a river for the development of hydroelectric power plants based on hydrokinetic turbines has been developed during this work. The methodology can be used for evaluation of any river or a span of a river where it is possible to move using boat or any simi lar floating device and keep this floating device motionless against the banks of the river. The methodology simplifies further research of rivers for this kind of evaluation and reduces the cost of research. The descriptions of both the methodology and its case study are presented in the work. Statistical data regarding flow rates of the rivers of interest is very valuable for validation of the data from measurements of the flow speeds and additional information for the evaluation. This data regarding al l rivers in Latvia that could be of any interest is readily available from the internet site www.meteo.lv. In Latvia the data is col lected by state financed observation station network. Likewise this information must be obtainable in many other countries. Usage of such data is descri bed in the methodology and its case study. Based on the analysis of the measurements in the river Daugava (e.g. data obtained using the methodology) it has been found, that changes in the flow rate have small impact to the flow speed in a particular place. This confirms hydrokinetic turbines as stable and predictable sources of electrical energy both in long the term and, especially, in the short term. A review of the data and findings are presented in the work.