Water Resources Overview - Sequoia & Kings Canyon National Parks (U.S. National Park Service) Winter snowpack in the Sierra Nevada is a natural storage system for the precipitation that accumulates during winter months. The amount of water stored as snowpack increases through mid-April at higher elevations. Meltoff typically begins in April and continues through May or June. October is the month in which the least water runoff occurs from park watersheds. Snowfields, forests, lakes and streams collect, store, and release the water supplied from winter storms so it is available throughout the dry summers for agriculture, recreation, electrical power generation and other uses. The amount of snowpack is also important to park vegetation and wildlife. In years of low snowpack accumulation, there is less water available for plant growth (for example, many trees will produce a small annual ring in years of drought). During these drought years, reduced plant growth and fruit and seed production result in altered food production for wildlife.