That question was just fielded by the Sacramento Bee in a recent question and answer column.  And it’s not for the first time either.  Lake Tahoe, because of its immense size and depth, has been a target of water interests in California since the 19th century when tunnels through the Sierra were considered to tap the Lake and its water.  The Sacramento Bee does a credible job of answering the question (forget it, basically), but the large population in California (38 million people and rising) is a constant threat to water resources statewide.  Today, waters of the Truckee River (which includes all of the Lake Tahoe basin), are used in both California and Nevada.

Lake Tahoe is over 1,600 feet deep and contains a vast amount of fresh water, but has a very small watershed.

Most folks don’t realize that water from the Lake Tahoe basin already goes into a river that flows west to the Sacramento and eventually to the Pacific Ocean.  Late in the 19th and early 20th century, diversions of streams flowing to Lake Tahoe or to the Truckee River directly were constructed and still operate today.

Echo Lake Water is diverted to the American River by PG&E.

One of the diversions most everyone eventually drives past if they live anywhere in northern Nevada or California is at Echo Lakes at Echo Pass on US Highway 50. (Click on the map to see a larger version).  A dam on the lake provides 12 feet of storage that PG&E sends through a tunnel and pipeline to the American River to the west.  If the water followed its natural course it would flow to the Upper Truckee River, Lake Tahoe, and to the Truckee River.

The other diversion sends water from Independence Creek to irrigators in Sierra Valley.  The Sierra Valley Water Company owns the water.  Once the water is diverted it flows away from its natural course down the Little Truckee River (a major tributary to the Truckee River) and instead heads to Sierra Valley to the north.  There the water irrigates ranches and continues on to the west flowing Feather River.  A fly fishing website (http://www.flyline.com/places/little_truckee/) writes on its page:

“Much of the Little Truckee is diverted to Sierra Valley farmers at Hennese Pass and between the diversion and Stampede Reservoir the river is unable to support much trout life during the hot summer months.”

Independence Lake itself is a natural lake, but has a small dam.  Some of the water stored by the dam is owned by the Truckee Meadows Water Authority to supply the Reno-Sparks area during long-term drought.  So, in most conditions less water flows into the Truckee River because of the diversion to the Feather River and the storage of water in Independence Lake.

Map of Independence Lake in the Sierra showing Land Ownership (click for larger version)

The Nature Conservancy manages the private land surrounding Independence Lake.  (Click the link to see how the Nature Conservancy is protecting native Lahontan Cutthroat Trout at Independence Lake.)

These two diversions to California have operated for so long that most people don’t realize that water from both Lake Tahoe and the Truckee River already flows into west flowing American and Feather Rivers, through Sacramento and on to the Pacific Ocean.  Each takes water permanently away from the much smaller Truckee River.