Hydrology. The river network is well developed in the preserve: there are 0.7–0.9 km of waterways per square kilometer of land. Almost all rivers are mountainous, with sources fed by snowfields, glaciers,and groundwater. Waterflow in upper reaches of rivers is significant (from 1.5 to 2.5 meters/second); the river beds are full of rapids and sometimes waterfalls. Downstream, rivers slow in the coastal lowlands and their velocity falls to 0.7 to 1.5 meters/second.  

The largest river of the preserve is the Ozernaya River, which flows out of Kuril Lake. Its main characteristics are: length — 62 km;width — up to 100 m; depth — up to 3 m (0.7 m on rapids); watershed area — 848 km2; mean altitude of watershed — 440m; maximum flooding — 163 cm; during flash floods — 149 cm;and the maximum rise in water level in 24 hours — 231 cm. Theriverfreezesoveronly in its lower reaches (completely in the first three kilometers from its mouth and in areas up to 10 km) from November to February. 

There are many lakes in the Preserve. The largest, Kuril Lake, lies in a caldera. 

Other lakes, compared to Kuril are modest in size and do not exceed 3 km in length. These are Kambalnoye (moraine origin), Etamynk (tectonic), Derzhavina, and Uliyanovskoye (lava dam-pond type). There are numerous shallow lakes in the tundra and marshy lowlands of Kambalny Bay and Lopatka Cape and the lower reaches of Tri Sestry River. Some of them (i.e. Kazachye, Kozakova) are probably marine in origin, and are separated from the sea by narrow sandy spits. The numerous lakes near the upper reaches of the Kambalnaya Rivera re evidently moraine in origin. 

Southern Kamchatka is not able for its high snow level. As a result, even small volcanoes have glaciers. The biggest glacier “Ararat” — 1.4 km2 in area — is on the top of Kambalny Volcano. There is also a glacier on Koshelev Volcano. There are several thermal formations here: two outcrops of thermal springs (on the northeastern side of KurilLake), Verkhne-Koshelevskiye Hot Springs (Gremuchiye springs) and Nizhne-Koshelevskiye Hot Springs, and also some springs at the foot o fKoshelev Volcano in theTretiya Rechka watershed.