Tundja river takes its source from the influx of the Selskata river (originating from the Pileshki Polog saddle) and Kapaklyska river. It is the biggest tributary of Maritsa river, and its total water area is 7880 sq. km. The upper stream of Tundja river is included within the boundaries of Djendema reserve and bears all its characteristic features – impressive rocky landscape and mixed beech forests and sheltering exclusive wildlife diversity.
Its waters are used usually for irrigation, and therefore there are a lot of built of pumping stations and water – retention. Accept Tundja river there are two more rivers on the Nova Zagora territory – Sazliika and Blatnitsa rivers. At Tudja river was built Jrebchevo dam, which total area is 400 million cubic meters and also is used mainly for irrigation.
The river is high – water in the spring, when the snow is melting and is shallow in the summer when the water is used for irrigation. The crops in the valley of Tundja river is always opulent – juicy peaches, aromatic grapes, vegetables.
At the distance of 5 km. to the east of Kazanlak, in the immediately proximity of Tundja river are located the Kazanlak spa.