The whole territory of the Protected Area National Park Mavrovo basically is included in the watershed of the Radika River. The mean annual flow of the Radika River for a period of 50 years (1961-2010), at the measurement point Boshkov Most is 19.63 m3/s. The headwaters of the Radika River are not composed of a single spring, but of large number of small mountain streams that spring up at the slopes and the bottom of the cirque Gorni Def-Velin Beg. Officially the headwaters of the Radika River are represented by a small mountain stream that is forming North-eastwardly of the mountain peak Golema Vratsa, at an elevation of 2,260 m. The total length of the Radika River course is 64.7 km, while the total length of all water flows (Radika River and its tributaries) in the Radika River watershed is 763.4 km.
The Radika River Watershed encompasses an area of 879.8 km2. Larger portion of the watershed surface is on the left side of the river (575.3 km2); while significantly smaller portion is on the right side (304.5 km2).
From hydrological point of view, besides the rivers, on the territory of the Park, other hydrological forms are also present, of which as important natural habitat types we shall mention the springs, glacial lakes, temporary pools, as well as the reservoir Mavrovsko Ezero Lake.
One of the most complex hydropower systems (HPS Mavrovo) is located in the Municipality of MavrovoRostushe. The Mavrovo Hydropower System with its three hydropower plants: HPP Vrutok, HPP Raven and HPP Vrben, and with a total capacity of the reservoirs of 277 million m3 is one of the largest and most complex system in the Macedonian Hydropower systems. It accounts for 42% of the total installed hydropower capacity in Macedonia. The Mavrovo Hydropower system is the largest and the most complex system of hydropower plants in the Republic of Macedonia comprising three hydropower plants with 9 turbines in total, the Reservoir Mavrovsko Ezero Lake, 133.3 km of intake tunnels, pipelines and channels, 91 km of which being closed headrace channels, 36 km of tunnels and 6.4 km of high pressure steel siphons and pipelines, as well as 167 km of access roads for maintenance and facility surveillance.