Watershed Restoration at Lake Tahoe
USDA-Forest Service, Lake Tahoe Basin Management Unit
Lake Tahoe is renowned for its remarkable clarity and deep, blue waters. Extensive urban development during the past 30 years has had direct negative effects on the water quality of Lake Tahoe. Since the early 1960s, the lake has lost about 23 feet of clarity.
Increased nutrient loading from the streams, atmosphere, and groundwater has resulted in increased algal growth and a progressive loss of clarity. Studies have shown that stream flow from disturbed Lake Tahoe watersheds stimulates the growth of algae, and is the most important single source of nutrients responsible for this enhanced algal growth.
As the largest land owner in the Basin, the U.S. Forest Service plays a critical role in the protection of Lake Tahoe's water quality. To live up to this role the Lake Tahoe Basin Management Unit (LTBMU) has developed an aggressive watershed restoration program. Restoration projects have ranged in size from watershed-wide undertakings, such as Blackwood Canyon, to revegetation of 1/4-acre city lots purchased through the Santini-Burton Land Acquisition Act. Since 1977 the LTBMU has restored over 2,000 acres of disturbed lands.
Several criteria are used to prioritize and select projects, including: sites known to be heavy sediment or nutrient producers, disturbed or unstable stream environments, disturbed highly erodible lands, and projects which are controversial, highly visible, or politically sensitive.
Over the past 2 years we have stressed the coordination of watershed restoration with fisheries habitat improvement projects. Although we do our share of structural work, the emphasis is on long-term stabilization through revegetation - an effort that has met with mixed success.
A short, dry growing season, low fertility soils, and high elevations with very cold winter temperatures present challenging revegetation conditions. We have learned through our failures that in many cases grass seed, fertilizer and straw mulch just won't do the trick. We now rely more heavily on native shrubs and trees, and irrigate whenever possible. At some particularly harsh sites we use topsoil and organic amendments to rebuild a soil profile before planting.
Some of our most interesting and fun projects involve streambank stabilization. We have had good success using bio-technical methods such as willow-wattling and layering.
The Forest Service is not the only agency in the Basin doing watershed restoration. All five counties and the City of South Lake Tahoe are also involved in restoration, with the focus being on urban areas. Typical measures include biological and structural roadside slope stabilization, road and storm drainage improvements, and some streamzone stabilization.
The Forest Service, through the Erosion Control Grants Program, has contributed $12 million to these agencies since 1984. Watershed restoration at Lake Tahoe is exciting, challenging and evolving - we've learned a lot in the past 10 years. Hopefully the big payoff will be 20 years from now when Lake Tahoe is as clear, or clearer, than it is today.
Sally can be reached at (916) 573-2600