Hawaii's hydrology is characterized by limited surface water due to high evapotranspiration rates and steep topography. Major surface flows include the Wailuku, Wailoa, and Kailua streams on the island of Hawaii, and the Hanalei and Wailua rivers on Kauai. The state has several reservoirs and dams, with the largest being the Kaloko Reservoir on Kauai. Hawaii's climate is tropical, with rainfall varying greatly across the islands and between seasons. The leeward sides of the islands are generally dry, while the windward sides receive more moisture. Watershed health is crucial to maintain water quality and quantity, with some watersheds experiencing degradation due to land use changes and invasive species. Snowpack is not relevant to hydrology in Hawaii due to its location in the tropics.