An Introduction Lake Tahoe is the pristine jewel of the West Coast, known around
the world for its beauty. The Lake Tahoe area was even in the spotlight for the
winter Olympic Games at Squaw Valley in 60's. Over the decades we have learned,
by mistake, what needs to be done to protect the lakes' beauty and character.
The lake is foremost known for its color and clarity, and has been capitalized
on for these qualities. However, upon enjoying the lake and creating a tourist
and recreational draw we have jeopardized the lake for all the features that we
most enjoy and treasure. Simply put the clarity, color and beauty of the lake
are in trouble, and the transparency is decreasing at a frightening rate. The
build up of phosphorous and nitrates in the lake has promoted the growth of
algae that clouds the water, changing the famous aqua, sapphire blue color to a
murky, cloudy green. Let's take a look at why we should be concerned with the
declining clarity of a lake, and why this lake is so special and unique, and why
the surrounding environment is so important. There are many factors involved in
causing the decline briefly discussed in this paper; including soil erosion, air
quality/pollution, stream conditions which are water flow, and algae growth.
Concluding with some positive measures that will help the lake over the long
term. Lake Tahoe -- History In exploring what makes this lake unique and special
we must first explore where it is, how it got there, and it's aquatic makeup.
Lake Tahoe known only to the Paiute Indians until it was "discovered"
by General Fremont in 1844. The Lake's exceptional transparency was described by
Mark Twain as "the finest picture earth affords." The lake is over a
mile high and is nestled amongst the Sierra Nevada, snowcapped, mountain range.
Lake Tahoe is uniquely divided between two states, Nevada and California, which
presents difficulties in long-term studies, developmental controls, and
protection goals.(See figure one) The Tahoe Basin has many political arms
wrapped around it , often with overlapping jurisdiction, including the Federal
Government, two States, five Counties, and a City. One example of this problem
is the fact that: "Lake Tahoe is designated as an Outstanding National
Resource Water (ONRW) under U.S. Environmental Protection Agency Water Quality
Standards Program and the Clean Water Act. With this designation, Lake Tahoe is
provided the highest level of protection under the antidegradation policy and no
further degradation should be permitted. The state of California recognizes this
designation, while Nevada does not."(1:1) The one fact that everyone seems
to agree on is Lake Tahoe needs its purity protected and preserved. Contrary to
the belief that the lake was formed by a volcanic crater collapse; the lake
actually, was formed by the rise and fall of the landscape due to faulting. The
Sierra Nevada is a batholith, "an enormous, complex masses of solidified
magma, usually granite .... composed of many individual plutons that push aside
some of the rocks of the crust while melting and digesting others" (2:403).
This pushing aside and uplifting formed a "deep graben fault basin"
(3:42). The lake has a surface area of 193 square miles (122,200 acres); a depth
of 1,645 feet at maximum and 989 feet at average; a surface temperature of 68°F
maximum and 41°F minimum; a capacity of 122,160,280 acre-feet of water; a
length of 22 miles and width of 12 miles; a surface elevation of 6,229 feet
above sea level; and a shoreline of 71 miles, divided into 42 miles in
California and 29 miles in Nevada. Lake Tahoe's great depth makes it the third
largest in North America and the tenth deepest in the World, rivaled by such
lakes as Oregon's Crater Lake and Russia's Lake Baikal(3:42,4:1,5:2,6:87).
"Lake Tahoe is as long as the English Channel is wide. The Panama Canal,
700 ft wide and 50 ft Deep, could be filled with Lake Tahoe's water even if it
circled the globe, at the equator, and there would still be enough water left to
fill a canal of the same size running from San Francisco to New York."
(3:1) The altitude of the area and freezing mountains would cause one to think
the lake would freeze over, however, the tremendous depth prevents the lake from
freezing. The theory of convection is proven here; the volume is always in
motion, as the surface cools it gets heavier and sinks, and the warmer, deeper,
water is lighter and rises, mixing with the cool water and thus the lake does
not freeze over. Some inlets, however, being shallower, have been covered with a
thin layer of ice. The lack of ice on the top of the lake does not affect the
quality, in any way, other than to demonstrate its depth that does contribute to
its clarity and color. The lake basin is affected by its surrounding composition
and rock content, which are mostly glacial till and sediment. Another
contributing factor to the lakes' environmental delicacy is that the lake has an
extraordinarily long retention time. In other words, if completely drained it
would take over 700 years to refill to its existing level. There is some water
loss due to evaporation but only one river flows out of Lake Tahoe, the Truckee
River (63 streams flow into the Lake). Little turn-over action occurs to the
nutrients that flow into the lake, because of this limited drainage and
capacity. Lake Clarity -- Introduction to Causes One issue that was addressed in
the late 1950's and 1960's was sewage. The flow of sewage has been diverted away
from the lake since the 1960's. First with the costly and controversial Culp's
advanced five-step treatment wastewater system and now a simpler, at least more
effective, waste management system. Even with sewage being exported the
development to the Tahoe Basin over the last few decades has brought increased
pollution, both to the streams, the atmosphere, and the groundwater. The
increased nutrients from all of this pollution have brought steady algae growth
and increased loss of clarity. According to, Mr. Bob Richards, of the Tahoe
Research Group, in Tahoe City, the lake is loosing one foot per year of
transparency (1). Another expert and researcher on the conditions of Lake Tahoe
for the past thirty years, Mr. Charles R. Goldman states that, "lake
chemistry and biology since the early 1960's has shown that algal production is
increasing at a rate greater than 5 percent per year with concomitant decline of
clarity at the alarming rate of 0.5M per year" (7:140). How do they find
these ratings? The process is simple but very accurate. A 10 inch diameter,
white plate, a secchi disc, is lowered, on a meter line, the team of researchers
records the point that the disc disappears from view, then raises it back up and
records the point at which they can just see it. This process is repeated till
30-35 measurements are recorded, per session, several times a year, and the
average of those readings is the annual for the year.(See figure 2) As evident,
by the secchi disc ratings, the clarity has been dramatically affected; now
let's look at how the lake got this way. Many contributing factors are at work
on the lake soil erosion, atmospheric pollution, water inflow, and algal growth.
Below I'll discuss briefly each factor. Soil Erosion Examining soil erosion has
brought some great public debates to bear. These debates have resulted because
this issue affects the money and power that be, and others: developers, casinos,
hotels, and homeowners. Lake Tahoe's population has increased dramatically over
the past few decades and can inflate to over a quarter of a million people on
peak holiday weekends.(See figure 3) One debate involving soil erosion is
whether the logging activities of the 1800's are what has caused the lake
clarity reduction we're combating today. However, extensive studies and
reconstruction of the effects that the logging might have caused have concluded
that the lumbering activities were undetectable and little impact on the
clarity. "The major changes in the lake documented in recent years are much
greater and longer lasting than those, if any, resulting from the 1800's logging
of the basin."(5:4) Disrupted soil and enhanced run-off, vegetation
removal, fire, and the loss of wetlands, over the last thirty years, are all
nutrient providing elements that have accelerated the growth of plankton and
attached algae. The building boom of the 1960's and 1970's paid little concern
to the environmental impacts they were causing, by paving roads, cutting into
the slopes, destroying wetlands, and more. The area where there was earth is now
paved, which in turn causes more phosphorus-rich sediment to run into the lake.
The surface water runoff and eroded soil carry the pollutants to the stream that
feed into the Lake, and are directly attributed to the increase in algae
population. The wetland areas are proven to buffer the land from receiving
waters, like an antacid buffers from the foods eaten and your stomach lining.
The wetland stabilizes nitrogen, the compounds causing algae growth, into
unusable nitrogen gas, thus limiting the growth population of algae. The
destruction of the wetlands has removed a vital link in the ecosystem. Air
Quality Not only concrete paving is the problem but with every expansion, or
some might call improvement, population has increased and thus more automobiles,
which means more atmospheric pollution. To comprehend why air pollution is
detrimental to the lake conditions lets review the water cycle; the "three
main sources of new nutrients entering the lake are streams, groundwater, and
direct atmospheric deposition (rain, snow, ice, dust particles) onto the land
surface" (5:9). Research has demonstrated that air quality, in the form of
pollution, is a problem, especially where there are increased vehicles. These
pollutants are trapped in the air above the lake by an inversion layer during
the winter and when it snows or rains the pollutants are delivered into the lake
directly or via streams and runoff. In addition winds carry sulfur contaminants
into the air over the basin adding to the pollutant deposits. Most of the
pollutants are already in the area in the forms of automobile emissions, road
dust from construction, wood fires, and combustion of diesel fuel and heating
oils (3:45). Also, acid rains do fall, noticeably, in the Tahoe area carrying
and depositing considerable amounts of nitrogen, which stimulates aquatic plant
and algae growth. Compound these pollutants with the destruction of the wetland
communities, of the ecosystem in the basin, and the capacity to filter-out
nitrogen and other pollutants is inhibited. Wetland vegetation, as mentioned
previously, takes up the nitrogen and buffers it, keeping it from fueling the
algae growth. The precipitation deposition into the lake adversely reacts with
these destruction's; wetland reduction, and the slick-impervious rooftops,
roads, and parking lots' run-off, and soil erosion, all combining to accelerate
release of nutrients into the lake. The adversity varies with the varying land
disturbances. Air quality controls obviously aid in the fight to protect the
lake, but more emphasis is needs to be geared towards wetland preservation and
land controls and watershed management. Water Inflow and Algae Growth Waterflow
into lake Tahoe is the number one contributor to the decline in clarity because
of all the elements combining to impact the quality of input into the lake. Lake
Tahoe is filled by 63 streams and thus creating a web linking the wetlands,
groundwater, streams and lake ecosystems. Displayed earlier is the importance of
each ecosystem to each other in creating a balance in the lake. The uniqueness
of Lake Tahoe is its color and clarity, but, also in its phosphorous quality,
nitrogen limited system. "In most productive lakes the levels of nitrogen
and phosphorous are in the low parts per million range. In Lake Tahoe there are
only a few parts per billion of these same elements, and the ratio of nitrogen
to phosphorous has been well below the 10 to 1 ratio required by most
plants." (3:50, 8:1322) However, over the last decade the ratio is
beginning to change causing changes defined as early "eutrophication".
Research has shown that streams do carry stimulating nutrients into the lake
enhancing algae growth. The streams thus cause nutrient loading of the lake and
the wetlands are what helps reduce this process. Land use is strongly tied to
the watershed characteristics and whether the watershed will be nutrient high.
In watershed analysis of Trout Creek and Blackwood Creek nitrite and nitrate
concentrations have been declining over the last 10 years, or more, where the
increases were caused from sewage and logging consecutively, up to 20 years ago.
This decline and hence recovery may be partly due to the rapid vegetation
re-growth after the logging activities. But today's destruction of land is
extensive with the road cuts and developments. "Watershed recovery times at
Tahoe may take at least 10-20 years, whereas disturbances such as run-off
enhancement from increased impervious surface area may be permanently enhance
the nutrient loading of the streams and in turn the lake.(10:87)" The
cycling of nutrients, as seen in figure four, show the delicate balance and the
nutrient capacity will depend upon streams inflow, air quality sources, and
sedimentary soil controls. The nutrient inflow or loading of the lake water
directly results in creased algae or Planktonic algae, which there are two
kinds: free-floating algae, and attached. Worse case scenario of high nutrient
loading would be "the suspended algae cloud the lake water and when algal
cells die and decay, they often reduce the dissolved oxygen levels to the point
where aquatic organisms can no longer survive in the deep waters(5:6)."
Now, Tahoe is not there, yet, but there is evidence of decreasing clarity,
increasing planktonic, attached and free-floating algae. Algae has been found to
be greatest where there is greater development, logically the run-off. of
fertilizers from lawns and golf courses, and other land disruptions discussed
prior. In addition the highest production of algae occurs when Tahoe has had an
extremely high precipitation season. "The El Niño event of 1983 modified
weather to produce heavy precipitation resulting in high levels of surface
runoff from the disturbed watershed as well as wind-mixing of stored nutrients
(5:7)." These conditions tend to provide the nitrogen needed for the
"lighted zone," of the lake water, to produce record crops of algae.
Lake Tahoe has been studied and compared to other Western Lakes, such as, Castle
Lake and Pyramid Lake, and arguments have been made that the climatic variations
affect all the lakes of the west equally, increasing fertility to the same
degree. However, Castle Lake has not shown the same fertility, despite same data
collection methods.(3) Which demonstrates Lake Tahoe's problems are
self-inflicted. Steps Towards Protection The construction and building boom has
monopolized the Tahoe basin and has helped to wreak havoc on the precious
balance in the lake. Today environmentalist, scientists, and concerned citizens
have begun to understand and change the way we treat the environment and the
lake, thus protecting the lake quality. Gone unchecked the lake conditions will
worsen. Even in the 1960's, in May and June, large crops of attached algae died
and released from their sites (along piers and shore rocks), coating the beaches
and marinas with a brown, slimy, smelly material that decays and eventually
returns as bacteria and nutrients to the lake through wave action (3:47). This
picture is not what most people envision when picturing the sapphire blue waters
of the lake. Obvious changes and the educated observations have led to great
concerns over the quality of the lake. Many changes are not as visible but if
left alone will quickly become visible, thus destroying the ecosystem of the
basin. As mentioned, the lake is the center of many factions of political
control. The Tahoe Regional Planning Agency (TRPA) has been a strong facilitator
of the needs for controls, there is little evidence to show they have made any
tremendous impact needed to reverse the trends of fertility in the Lake. TRPA
has put forth pollution control measures called "Best Management Practices
or BMP's." The program requires new projects to implement the BMP's
required paved driveways, which at first seems like a contradiction to the
research, however, if we compare a graded, disturbed, un-paved surface with a
properly paved surface, the un-paved has nothing to hold the soil in place,
washing the unnecessary sediment into the lake. Other BMPs, include but are not
limited to, revegetation programs, retaining structures, and slope
stabilization. To protect the lake all parties involved need to unify the
conservation efforts and develop an organized protection and planning bureau or
assembly, sponsored with governmental support, above and beyond the Tahoe
Regional Planning Agency and Lake Tahoe Interagency Monitoring Program. The
current agencies, and committees have taken positive steps to protect the area
which includes: * slow releasing or no chemical fertilizers on lawns and golf
courses. * ski slopes are no longer allowed to use ammonium nitrate to help make
snow. * California passed a 85 million dollar bond in 1982 to buy-up sensitive
lands, potentially endangering the lake, now are protected. * Nevada passed a
similar 30 million dollar buy-up bond in 1986. * The afore-mentioned mentioned
BMP's. Without these positive approaches, the dedication of the University of
Davis, Researchers and Scientists, Tahoe Regional Planning Agency, and other
groups of concerned organizations, Tahoe would be unclear and green today. The
general public can take measures by treating our delicate ecosystems with
respect and becoming educated on our delicate balances. Steps could include: *
Bike more or walk- save our air quality. * Maintain cars properly and up to
codes. * Don't Drip. Leaky facets waste 9 liters of water per minute. * Don't
pour toxins into the drainage system (paint, gases, fertilizers, etc.) * Recycle
* Influence your work place to take steps in being Earth conscious. For heavens'
sake even the cartoons are teaching our children to be earth aware with
"Captain Planet, he's our hero, taking pollution down to zero...,"
teaching children to reduce, reuse, and recycle, and to fight the bad-guys who
pollute our earth's ecosystems. All adults can be Captain Planets and protect
our world.

Bibliography
1) Richards, Bob. Personal Phone Interviews, FAX. 24 Feb. 1997, 16 Mar 1997.
2) Gabler, Robert, Sager,Robert, and Wise, Daniel Essentials of Physical
Geography. 5th ed. Orlando:Saunders College Publishing,1997. 3) Goldman, Charles
R., Richards, Robert. The Urbanization of the Lake Tahoe Basin: A Microcosm for
the Study of Environmental Change with Continuing Development. Proceedings,
State of the Sierra Symposium 1985-86, Pub. #177. California:University of
Davis, 1986 4) Tahoe Research Group, State Natural Resources. Lake Tahoe
Facts", "Ten Most Frequently Asked Questions. Internet
address:WWW.Ceres, 15 April 1997. 5) Goldman, Charles R., Byron, Earl R.
Changing Water Quality at Lake Tahoe: the First Five Years of the Lake Tahoe
Interagency Monitoring Program. The California State Water Resources Control
Board. California:University of Davis, Institute of Ecology, Tahoe Research
Group, 1987. 6) Sheaffer, John R., Stevens, Leonard A., Future Water, An
Exciting Solution to America's Most Serious Resource Crisis. New York: William
Morrow and Company, Inc., 1983. 7) Reuter, J.E., et al. University Contribution
to Lake and Watershed Management: Case Studies From the Western United
States--Lake Tahoe and Pyramid Lake. Watershed '96 A National Conference on
Watershed Management. Maryland:Baltimore, Water Environment Federation, 12 June
1996. ISBN: 1-57278-028-2. 8) Goldman, Charles R. Primary Productivity,
Nutrients, and Transparency During the Early Onset of Eutrophication. American
Society of Limnology and Oceanography, Inc.. 33(6, part1),1321-1333. 1988. 9)
Goldman, Charles R., Jassby Alan D., de Amezaga, Evelyne. Forest Fires,
Atmospheric Deposition and Primary Productivity at Lake Tahoe,
California-Nevada. Verhandlungen-Proceedings-Travaux of the International
Association for Theoretical and Applied Limnology, Congress in Munich. Iss 24,
499-503. Stuttgart, Germany, 1990. 10) Byron, Earl r., Goldman, Charles R.,
"Land-Use and Water Quality in Tributary Streams of Lake Tahoe,
California-Nevada". Journal of Environmental Quality Vol. 18,no.1, (Jan-Mar
1989):84-88. 11) Bowman, Chris. "Clinton Seeks Summit on Lake Tahoe
Pollution" The Sacramento Bee 26 October 1996:B1 12) Bowman, Chris, Hoge,
Patrick. "Runoff, Air Pollution Cloud Waters of Crystal-Clear Lake"
The Sacramento Bee 8 December 1996:A28 13) Associated Press. "Team Seeks
Clues to Cloudy Lake Tahoe Water" The Sacramento Bee 16 October
1995:SUPCAL. 14) Malley, George. Personal Interview. 15 April, 5 May 1997 MAPS
AND GRAPHS -- REFERENCES Figure One, Tahoe Region Map: AAA Travel Book. 1997 ed.
Figure Two, Secchi Depth Chart: Goldman, Charles R. Primary Productivity,
Nutrients, and Transparency During the Early Onset of Eutrophication. American
Society of Limnology and Oceanography, Inc.. 33(6, part1),Pg. 1329. 1988. Figure
Three, Population Growth Chart: Goldman, Charles R., Richards, Robert. The
Urbanization of the Lake Tahoe Basin: A Microcosm for the Study of Environmental
Change with Continuing Development. Proceedings, State of the Sierra Symposium
1985-86, Pub. #177. California:University of Davis, Pg. 43. 1986. Figure Four,
Water Cycle Chart: Goldman, Charles R., Richards, Robert. The Urbanization of
the Lake Tahoe Basin: A Microcosm for the Study of Environmental Change with
Continuing Development. Proceedings, State of the Sierra Symposium 1985-86, Pub.
#177. California:University of Davis, Pg. 43. 1986.