She said a goal is to restore Tahoe's clarity to 78 feet over the next 15 years.
Lake Tahoe Restoration Act of 2000, committed 4 million to environmental projects designed to protect the lake's famed clarity and its surrounding forests from catastrophic wildfire.
Many streams flow into Lake Tahoe, but the lake is drained only by the Truckee River, which flows northeast through Reno and into Pyramid Lake in Nevada.
Lake Tahoe Facts: * Lake Tahoe is the highest lake of its size in the United States and the largest alpine lake in North America.
The Lake Tahoe Basin was formed by geologic block (normal) faulting about 2 to 3 million years ago.
A geologic block fault is a fracture in the Earth's crust causing blocks of land to move up or down.
Uplifted blocks created the Carson Range on the east and the Sierra Nevada on the west.
Down-dropped blocks created the Lake Tahoe Basin in between.
The report from UC Davis researchers said the lake's waters were clear to an average depth of 68.1 feet in 2009, down from 102.4 feet in 1968, when the school began measurements.
An eight-year extension of the act, which would authorize another 5 million, is pending in Congress.
The federal money, much of which came from the sale of federal lands in southern Nevada, was used to generate a total .5 billion from state, local and private sources.
Some of the highest peaks of the Lake Tahoe Basin that formed during this process were Freel Peak at 10,891 ft (3,320 m), Monument Peak at 10,067 ft (3,068 m) (the present Heavenly Valley Ski Area), Pyramid Peak at 9,983 ft (3,043 m) (in the Desolation Wilderness), and Mt. Snow, rain, and streams filled the southern and lowest part of the basin, forming the ancestral Lake Tahoe.
Modern Lake Tahoe was shaped and landscaped by the scouring glaciers during the Ice Age (the Great Ice Age began a million or more years ago).
* Lake Tahoe is as long as the English Channel is wide with the width of Tahoe being half again as wide as San Francisco Bay.