Serga is the right tributary of the river Ufa.
The total length of the Sergi is 113 kilometers, flows through the territory of the Sverdlovsk region through the territory of the Nizhneserginsky district,
The area of ​​the basin is 2170 km ².
The source originates on the western slopes of Shunut - Kamen, flows into the Ufa river.
The largest tributaries: Kozia, Teague, Bardum, Demid, Cuba. There are 6 reservoirs on the river and tributaries. In the lower part of its current, Serga flows along the western slopes of the Bardym mountain range, cutting into the limestone layer.
The valley of Sergi is characterized by karst relief: an abundance of caves and other karst formations. Only in the territory of the "Deer Stream" park there are several of them: Druzhba cave, one of the largest in the region; cave Arakaevskaya, where the largest in the Middle Urals colony of bats every winter; a karst dip of 40 meters deep, at the bottom of which snow remains until the end of summer; Rock Karst Bridge is the most interesting form of education on the left bank of the Sergi.A typical mountain, shallow river, the depth is from 0.5 to 2 m, under rocks 10-15 m there are outcrops of underground ascending sources. The current velocity is 0, 3- 0, 5m. The bottom is on pebble beds (porphyrite, limestone, siliceous pebbles)
On the slow sections the bottom is loamy, sandy, solid. Many fords.
The banks are often steep, rocky with limestone outcrops, up to 30 m high.
The floodplains are forested, sometimes meadow. Characteristic of the presence of endangered streams (Fedotov, Gromotucha, Dry Creek Stream), cat. in consequence of the karst of the channels repeatedly go to the ponors under the ground.
The valley is narrow 0.5 - 0.8 km, has 3 terraces above the floodplain, the first is 3-5 m (compare Pleistocene), the second - 12-14 m (Alpine mountain building), the third - 25 m (Neogene) above the water level.
The width of the river is 20-30 meters. almost no wetlands due to good drainage of fractured limestones. There are heavily overgrown lakes of the old man, the kingdom of beavers and ducks.
Behind the river is the ridges of the Bardym mountain range.