The Prut river is one of main tributaries of the Danube. Being a transboundary river (length - 967 km, basin - 27540 km2), it begins from the Ukrainian Carpathians and flows through Romania and the Republic of Moldova forming a natural border between these two countries. Present research is dedicated to assessment of general dynamics of the Prut river flow in the Moldova limits. The Prut river flow is regulated by the Costesti-Stanca reservoir, built in the beginning of ’80 of the last century (length – 70 km, total volume 1,400 mil. m3), its hydropower plant is jointly operated by Romania and Moldova. The Prut river flow measurements are performed at Sirauti (1990-present, basin area - 9230 km2) situated upstream reservoir and at Ungheni (1956-present, basin area -15200 km2) positioned in the downstream. At Sirauti station the following hydrological characteristics are calculated: average flow 72.2 m3/s, runoff - 247 mm, volume 2.26 km3. Seasonal flow distribution is: winter - 13%, spring -35%, summer - 35%, autumn -17%. At CostestiStanca station (measuring the outflow from reservoir) the hydrological characteristics are: average flow - 76 m3/s, runoff - 203 mm, volume 2.4 km3. Seasonal flow distribution is: winter - 15%, spring -30%, summer - 36%, autumn -20%. At Ungheni station, before the Costesti-Stanca reservoir construction, the hydrological characteristics were: average flow - 86.6 m3/s, runoff - 180 mm, volume 2.73 km3. Seasonal flow distribution is: winter - 12%, spring -38%, summer - 33%, autumn -17%. After hydrotechnical structure construction the flow is as follows: average flow - 80.4 m3/s, runoff - 167 mm, volume 2.54 km3. Seasonal flow distribution is: winter - 17%, spring -29%, summer - 35%, autumn 19%. Thus, the average flow and volume increase with the basin area, main water resources are formed during spring and summer (70%), however, the reservoir contributes to a distribution of flow from spring months to summer - winter months.