The water bodies within Sierra County may be adversely affected by the introduction of certain nonnative species which have the potential to rapidly proliferate, harm and/or consume native species and food resources, and drastically alter the ecosystem of those water bodies. This can adversely impact to the ecology, recreation, water supply, water quality, and economy of the region.

In particular, species of Dreissenid mussels such as quagga and zebra mussels pose a significant and imminent threat to the water bodies within Sierra County. Dreissenid mussels have already created serious and irreparable harm to bodies of water located in other locations in the United States and California.

Presently, it does not appear that any water body in Sierra County has been infested with Dreissenid mussels. However, water vessels entering Sierra County from other areas may have recently been launched in infested waters, making those vessels at high risk to carry mussels, both adults and larvae, into Sierra County waters.

A screening and inspection program is integral to the preservation of the water bodies and water distribution systems with Sierra County and to the drainages from Sierra County.