The average surface area is 982 square kilometres (379 sq mi) (it may vary between 733 square kilometres (283 sq mi) and 2,090 square kilometres (810 sq mi) depending on water level). The lake is fed by 52 inflowing rivers, the four main ones being the Msta, the Pola, the Lovat, and the Shelon. It is drained through a single outlet, the Volkhov, into Lake Ladoga, and subsequently via the Neva into the Gulf of Finland.