Hydrology. Rivers run from the slopes of mountain ridges, and only some of them form straight valleys (such as the Kronotskaya River). Rivers here are fast and not navigable; there are some waterfalls and rapids. The density of the river network is high with 650 m of different watersheds per 1,000 square meters of land. The maximum flow is usually in June-July, the minimum is in February-March. In summer discharge is often 5–7 times more intensive than in winter. Flood waters reach 1–1.5 m above low water levels. 

Waters freeze over in late October to mid-November. The ice depth is about 50 cm. Some rivers freeze through. The breakup of ice and opening of rivers occurs in April-May. 

There are many lakes, but most of them are small in size. The biggest is Kronotskoye Lake, with a surface area of 242 square meters. There are also lagoons, formed as result of river estuaries being influenced by the sea. Such lakes have brackish water (Semyachinsky Lagoon). Less common are caldera lakes (Tsentralnoye), maar lakes (Dalneye, Krokur), or lakes formed by the damming of rivers during lava flows (Kronotskoye). Another example of a type of a lava lake is a lake in the lower reaches of the Geyser River, formed after the mudslide of 2007. In the tundra of the Siniy Dol (Blue Dale) and near to Kropotkin Glacier, there are some shallow and partially dried moraine lakes. 

Bogs are mainly are oligotrophic (poor in nutrients), nourished by the atmosphere, and peat bogs occupy a significant portion of wetlands. The swampiest parcels are near Semyachensky Lagoon, in the floodplains of the Tikhaya, Mutnaya, and Komarov Rivers, between the lower reaches of the Kronotskaya and Bogachyovka rivers and between the Bolshaya Chazhma and Malaya Chazhma rivers. 

Glaciers cover a significant part of the Kronotsky Peninsula mountains. Some of the ice tongues descend to 345–600 m above sea level. In addition, there are glaciers on the tops of Valaginsky Ridge and on some volcanoes (Kronotsky, Gamchen, Kikhpinych, Zubchatka). They fill caldera and crater hollows, and form glacial valleys, cirques, and corries.