Overview of Lake Tahoe

Lake Tahoe is located in the Sierra Nevada mountain range along the border between Northern California and Nevada. Two-thirds of Tahoe’s shoreline lies in California with the remainder lying in Nevada, and many parts of the shoreline lie in protected areas. Mountain peaks of the Sierra Nevada border the west of the lake and the Carson Range borders the east. Average temperature around Lake Tahoe ranges from high 20s in the winter to high 60s in the summer. 

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Over 60 tributaries in the surrounding watershed provide the lake with 65% of its water, with the remaining 35% being provided by precipitation. Approximately one-third of the water leaving the lake flows into the Truckee River through the Lake Tahoe Dam for human use. The remaining two-thirds of the water leaving the lake leaves through evaporation from the lake surface.

The table below summarizes the various 
measurements of the lake:

Surface Elevation	6,225 ft.
Average Depth	1,000 ft.
Maximum Depth	1,645 ft.
Total Volume	40 trillion gal.
Maximum Length	22 mi.
Maximum Width	12 mi.
Surface Area	192 mi.2
Total Shore Length	71 mi.

Thousands of people visit Lake Tahoe each year to enjoy the variety of recreational activities available around the lake. Whether it be skiing or snowboarding in the winter, hiking or boating in the summer, or vacationing year-round, the natural beauty of Lake Tahoe always has something to offer.

http://www.laketahoetours.net/

Historical State of Lake Tahoe

http://evergreenmagazine.com/magazine/

article/Western_National_Forests_.html

 The Washoe Indians are the original inhabitants of the Lake Tahoe basin. However, the discovery of silver around the Tahoe Basin in the 1850s would spark a massive influx of Euro-American settlers to travel to the area and create permanent establishments on Washoe territory.

Whereas the Washoe had historically respected the land and used only what resources they needed, the new Euro-American settlers viewed the land as an object to exploit for wealth. The new settlers took advantage of the abundance of lumber and cut down all but the largest fir trees. Consequently, these fir trees provided the seeds for Tahoe’s next forest. The result today is that pine trees, which are better adapted to the drought conditions that Tahoe periodically experiences, have had a hard time competing with the numerous fir trees in the basin, effectively creating an overly dense, fir-dominated forest that is vulnerable to the effects of drought.

http://www.news.ucdavis.edu/tahoetv/forests.html

Current Human Impacts on Lake Tahoe

One major way that humans have impacted Lake Tahoe is the increased eutrophication of the lake. Eutrophication refers to an overabundance of nutrients, which leads to increased algae growth and ultimately contributes to decreased clarity of the lake. Normally eutrophication is a natural process that occurs as a lake ages, eventually forming a marsh and then a meadow. However, while this process would naturally take place over millions of years, pollution from the urbanization of areas surrounding the lake has increased nutrient runoff into the lake and accelerated the eutrophication process. When combined with the equally damaging effects of fine-particle pollution from human-caused erosion, also attributable to urban development in the Tahoe Basin, the result is current water clarity of 70 ft, a 30ft decrease from 1960s levels when readings began.

http://terc.ucdavis.edu/stateofthelake/StateOfTheLake2012.pdf

Potential Ways to Improve Human Impact on Lake Tahoe

One way to decrease human contribution to the eutrophication and pollution of Lake Tahoe is to have developed properties function more like a natural watershed. One of the primary ways that humans deliver nutrients and particles to the lake is through sewer water runoff from their properties.  The Tahoe Regional Planning Agency (TRPA) has implemented a program that aims to install Best Management Practices (BMPs) in all private and public properties in the Tahoe Basin. These BMPs include methods that filter water runoff through soil or vegetation to remove pollutants and nutrients before they enter the lake.  BMPs have the benefit of targeting reductions in urban watershed runoff and atmospheric deposition of fine particles, which are two major sources of pollutants as shown in the table below:

  

Sources of Various Pollutants in 2011

	Urban Watershed	Non-Urban Watershed	Atmospheric Deposition	Stream Erosion	Shoreline Erosion	Groundwater
Nitrogen	16.0%	15.5%	55.0%	0.5%	0.5%	12.5%
Phosphorus	39.0%	26.0%	15.0%	1.0%	4.0%	15.0%
Sediment Particles	72.0%	9.0%	15.0%	4.0%	<1%	0.0%
Average	42.3%	16.8%	28.3%	1.8%	2.3%	9.2%

Although BMPs have high potential to reduce the rate at which Lake Tahoe’s water clarity declines, they will need to be implemented on a large scale in order for the effects to be significant. The main issue that the TRPA is struggling with at the moment is the compliance rate of property owners, and until there is widespread acceptance of the effectiveness and importance of installing BMPs, their effectiveness in the Tahoe Basin will be minimal at best. The TRPA will need to focus on their marketing and publicity efforts to make sure that their message reaches as many property owners as possible. Efforts should also be made to collaborate with designers and construction companies to find ways to implement BMPs that are both effective and aesthetically pleasing. Focusing on large scale reduction of sewer water runoff can deal a major blow to increasing nutrient and particle levels in Lake Tahoe.

http://www.tahoebmp.org/BMPs.aspx

Future Prospects

Because of Lake Tahoe’s exceptional natural beauty, there are many organizations that are working to maintain the lake’s condition. Researchers are actively searching for ways to combat the issues facing the lake, including pollution and invasive species, and some results have been promising. For example, a recent attempt to exterminate part of an invasion of Asian Clam in the lake through suffocation has been successful in wiping out a majority of the invasion, and growth after the extermination has been very gradual. Pollution rates have at least been stable in recent years, and efforts such as the BMPs discussed previously show potential to start decreasing the amount of pollutants entering the lake.

However, a challenge in Tahoe’s future will be to raise awareness and support for reducing pollution in the lake because much of its population is seasonal. It will be hard to convince people to implement BMPs on their property when they only visit Tahoe during ski season. Furthermore, the use of financial incentives may be necessary to convince the numerous casinos, ski resorts and other businesses in the area to adopt pollution-preventing measures.    

http://www.laketahoetours.net/

References


1.Cobourn, John and Kocher, Susie."Natural Resource Issues in the Lake Tahoe Basin: An Extension Needs Assessment." Web. 2007. <http://www.unce.unr.edu/publications/files/nr/2007/sp0720.pdf>

2. Dolislager, L., Lashgari, A., McCauley, E., Pederson, J., and VanCuren, R. "Road Dust and Urban Aerosols at Lake Tahoe, California – Nevada." Web. 2012. <http://www.sciencedirect.com/science/article/pii/S1352231009010103#>

3. UC Davis Tahoe Environmental Research Center. "Environmental Problems Facing Tahoe." Web. 2006. <http://terc.ucdavis.edu/documents/DocentManual_Chap4_ScienceAndResearch.pdf>

4. UC Davis Tahoe Environmental Research Center. "Tahoe: State of the Lake Report 2012." Web. 2012. <http://terc.ucdavis.edu/stateofthelake/StateOfTheLake2012.pdf>

5. United States Department of Agriculture Forest Service. "Environmental Impact Statement." Web. 2012. <http://www.fs.usda.gov/wps/portal/fsinternet/!ut/p/c4/04_SB8K8xLLM9MSSzPy8xBz9CP0os3gjAwhwtDDw9_AI8zPwhQoY6BdkOyoCAPkATlA!/?ss=110519&navtype=BROWSEBYSUBJECT&cid=FSE_003756&navid=130100000000000&pnavid=130000000000000&position=BROWSEBYSUBJECT&ttype=main&pname=Lake%20Tahoe%20Basin%20Mgt%20Unit-%20Planning>