However, upon enjoying the lake and creating a touristand recreational draw we have jeopardized the lake for all the features that wemost enjoy and treasure. Simply put the clarity, color and beauty of the lakeare in trouble, and the transparency is decreasing at a frightening rate. Thebuild up of phosphorous and nitrates in the lake has promoted the growth ofalgae that clouds the water, changing the famous aqua, sapphire blue color to amurky, cloudy green. Let’s take a look at why we should be concerned with thedeclining clarity of a lake, and why this lake is so special and unique, and whythe surrounding environment is so important.
There are many factors involved incausing the decline briefly discussed in this paper; including soil erosion, airquality/pollution, stream conditions which are water flow, and algae growth. Concluding with some positive measures that will help the lake over the longterm. Lake Tahoe — History In exploring what makes this lake unique and specialwe 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 byMark Twain as “the finest picture earth affords. ” The lake is over amile high and is nestled amongst the Sierra Nevada, snowcapped, mountain range. Lake Tahoe is uniquely divided between two states, Nevada and California, whichpresents difficulties in long-term studies, developmental controls, andprotection goals. (See figure one) The Tahoe Basin has many political armswrapped around it , often with overlapping jurisdiction, including the FederalGovernment, two States, five Counties, and a City. One example of this problemis the fact that: “Lake Tahoe is designated as an Outstanding NationalResource Water (ONRW) under U.
S. Environmental Protection Agency Water QualityStandards Program and the Clean Water Act. With this designation, Lake Tahoe isprovided the highest level of protection under the antidegradation policy and nofurther degradation should be permitted. The state of California recognizes thisdesignation, while Nevada does not. “(1:1) The one fact that everyone seemsto agree on is Lake Tahoe needs its purity protected and preserved.
Contrary tothe belief that the lake was formed by a volcanic crater collapse; the lakeactually, was formed by the rise and fall of the landscape due to faulting. TheSierra Nevada is a batholith, “an enormous, complex masses of solidifiedmagma, usually granite . . .
. composed of many individual plutons that push asidesome 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 depthof 1,645 feet at maximum and 989 feet at average; a surface temperature of 68Fmaximum and 41F minimum; a capacity of 122,160,280 acre-feet of water; alength of 22 miles and width of 12 miles; a surface elevation of 6,229 feetabove sea level; and a shoreline of 71 miles, divided into 42 miles inCalifornia and 29 miles in Nevada. Lake Tahoe’s great depth makes it the thirdlargest in North America and the tenth deepest in the World, rivaled by suchlakes 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 itcircled the globe, at the equator, and there would still be enough water left tofill 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 thinkthe lake would freeze over, however, the tremendous depth prevents the lake fromfreezing. The theory of convection is proven here; the volume is always inmotion, 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 doesnot freeze over. Some inlets, however, being shallower, have been covered with athin layer of ice. The lack of ice on the top of the lake does not affect thequality, in any way, other than to demonstrate its depth that does contribute toits clarity and color.
The lake basin is affected by its surrounding compositionand rock content, which are mostly glacial till and sediment. Anothercontributing factor to the lakes’ environmental delicacy is that the lake has anextraordinarily long retention time. In other words, if completely drained itwould take over 700 years to refill to its existing level. There is some waterloss due to evaporation but only one river flows out of Lake Tahoe, the TruckeeRiver (63 streams flow into the Lake). Little turn-over action occurs to thenutrients that flow into the lake, because of this limited drainage andcapacity.
Lake Clarity — Introduction to Causes One issue that was addressed inthe late 1950’s and 1960’s was sewage. The flow of sewage has been diverted awayfrom the lake since the 1960’s. First with the costly and controversial Culp’sadvanced five-step treatment wastewater system and now a simpler, at least moreeffective, waste management system. Even with sewage being exported thedevelopment to the Tahoe Basin over the last few decades has brought increasedpollution, both to the streams, the atmosphere, and the groundwater.
Theincreased nutrients from all of this pollution have brought steady algae growthand increased loss of clarity. According to, Mr. Bob Richards, of the TahoeResearch Group, in Tahoe City, the lake is loosing one foot per year oftransparency (1). Another expert and researcher on the conditions of Lake Tahoefor the past thirty years, Mr.
Charles R. Goldman states that, “lakechemistry and biology since the early 1960’s has shown that algal production isincreasing at a rate greater than 5 percent per year with concomitant decline ofclarity at the alarming rate of 0. 5M per year” (7:140). How do they findthese 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 researchersrecords the point that the disc disappears from view, then raises it back up andrecords the point at which they can just see it.
This process is repeated till30-35 measurements are recorded, per session, several times a year, and theaverage 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; nowlet’s look at how the lake got this way. Many contributing factors are at workon the lake soil erosion, atmospheric pollution, water inflow, and algal growth. Below I’ll discuss briefly each factor.
Soil Erosion Examining soil erosion hasbrought some great public debates to bear. These debates have resulted becausethis issue affects the money and power that be, and others: developers, casinos,hotels, and homeowners. Lake Tahoe’s population has increased dramatically overthe past few decades and can inflate to over a quarter of a million people onpeak holiday weekends. (See figure 3) One debate involving soil erosion iswhether the logging activities of the 1800’s are what has caused the lakeclarity reduction we’re combating today. However, extensive studies andreconstruction of the effects that the logging might have caused have concludedthat the lumbering activities were undetectable and little impact on theclarity. “The major changes in the lake documented in recent years are muchgreater and longer lasting than those, if any, resulting from the 1800’s loggingof the basin.
“(5:4) Disrupted soil and enhanced run-off, vegetationremoval, fire, and the loss of wetlands, over the last thirty years, are allnutrient providing elements that have accelerated the growth of plankton andattached algae. The building boom of the 1960’s and 1970’s paid little concernto the environmental impacts they were causing, by paving roads, cutting intothe slopes, destroying wetlands, and more. The area where there was earth is nowpaved, 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 thatfeed into the Lake, and are directly attributed to the increase in algaepopulation.
The wetland areas are proven to buffer the land from receivingwaters, like an antacid buffers from the foods eaten and your stomach lining. The wetland stabilizes nitrogen, the compounds causing algae growth, intounusable nitrogen gas, thus limiting the growth population of algae. Thedestruction of the wetlands has removed a vital link in the ecosystem. AirQuality Not only concrete paving is the problem but with every expansion, orsome might call improvement, population has increased and thus more automobiles,which means more atmospheric pollution. To comprehend why air pollution isdetrimental to the lake conditions lets review the water cycle; the “threemain sources of new nutrients entering the lake are streams, groundwater, anddirect atmospheric deposition (rain, snow, ice, dust particles) onto the landsurface” (5:9).
Research has demonstrated that air quality, in the form ofpollution, is a problem, especially where there are increased vehicles. Thesepollutants are trapped in the air above the lake by an inversion layer duringthe winter and when it snows or rains the pollutants are delivered into the lakedirectly or via streams and runoff. In addition winds carry sulfur contaminantsinto the air over the basin adding to the pollutant deposits. Most of thepollutants are already in the area in the forms of automobile emissions, roaddust from construction, wood fires, and combustion of diesel fuel and heatingoils (3:45). Also, acid rains do fall, noticeably, in the Tahoe area carryingand depositing considerable amounts of nitrogen, which stimulates aquatic plantand algae growth. Compound these pollutants with the destruction of the wetlandcommunities, of the ecosystem in the basin, and the capacity to filter-outnitrogen and other pollutants is inhibited.
Wetland vegetation, as mentionedpreviously, takes up the nitrogen and buffers it, keeping it from fueling thealgae growth. The precipitation deposition into the lake adversely reacts withthese destruction’s; wetland reduction, and the slick-impervious rooftops,roads, and parking lots’ run-off, and soil erosion, all combining to acceleraterelease of nutrients into the lake. The adversity varies with the varying landdisturbances. Air quality controls obviously aid in the fight to protect thelake, but more emphasis is needs to be geared towards wetland preservation andland controls and watershed management. Water Inflow and Algae Growth Waterflowinto lake Tahoe is the number one contributor to the decline in clarity becauseof all the elements combining to impact the quality of input into the lake.
LakeTahoe is filled by 63 streams and thus creating a web linking the wetlands,groundwater, streams and lake ecosystems. Displayed earlier is the importance ofeach ecosystem to each other in creating a balance in the lake. The uniquenessof Lake Tahoe is its color and clarity, but, also in its phosphorous quality,nitrogen limited system. “In most productive lakes the levels of nitrogenand phosphorous are in the low parts per million range. In Lake Tahoe there areonly a few parts per billion of these same elements, and the ratio of nitrogento phosphorous has been well below the 10 to 1 ratio required by mostplants.
” (3:50, 8:1322) However, over the last decade the ratio isbeginning to change causing changes defined as early “eutrophication”. Research has shown that streams do carry stimulating nutrients into the lakeenhancing algae growth. The streams thus cause nutrient loading of the lake andthe wetlands are what helps reduce this process. Land use is strongly tied tothe watershed characteristics and whether the watershed will be nutrient high.
In watershed analysis of Trout Creek and Blackwood Creek nitrite and nitrateconcentrations have been declining over the last 10 years, or more, where theincreases were caused from sewage and logging consecutively, up to 20 years ago. This decline and hence recovery may be partly due to the rapid vegetationre-growth after the logging activities. But today’s destruction of land isextensive with the road cuts and developments. “Watershed recovery times atTahoe may take at least 10-20 years, whereas disturbances such as run-offenhancement from increased impervious surface area may be permanently enhancethe nutrient loading of the streams and in turn the lake.
(10:87)” Thecycling of nutrients, as seen in figure four, show the delicate balance and thenutrient capacity will depend upon streams inflow, air quality sources, andsedimentary soil controls. The nutrient inflow or loading of the lake waterdirectly results in creased algae or Planktonic algae, which there are twokinds: free-floating algae, and attached. Worse case scenario of high nutrientloading would be “the suspended algae cloud the lake water and when algalcells die and decay, they often reduce the dissolved oxygen levels to the pointwhere 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 tobe greatest where there is greater development, logically the run-off.
offertilizers from lawns and golf courses, and other land disruptions discussedprior. In addition the highest production of algae occurs when Tahoe has had anextremely high precipitation season. “The El Nio event of 1983 modifiedweather to produce heavy precipitation resulting in high levels of surfacerunoff 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, CastleLake and Pyramid Lake, and arguments have been made that the climatic variationsaffect all the lakes of the west equally, increasing fertility to the samedegree. However, Castle Lake has not shown the same fertility, despite same datacollection methods.
(3) Which demonstrates Lake Tahoe’s problems areself-inflicted. Steps Towards Protection The construction and building boom hasmonopolized the Tahoe basin and has helped to wreak havoc on the preciousbalance in the lake. Today environmentalist, scientists, and concerned citizenshave begun to understand and change the way we treat the environment and thelake, thus protecting the lake quality. Gone unchecked the lake conditions willworsen. Even in the 1960’s, in May and June, large crops of attached algae diedand released from their sites (along piers and shore rocks), coating the beachesand marinas with a brown, slimy, smelly material that decays and eventuallyreturns as bacteria and nutrients to the lake through wave action (3:47). Thispicture is not what most people envision when picturing the sapphire blue watersof the lake.
Obvious changes and the educated observations have led to greatconcerns over the quality of the lake. Many changes are not as visible but ifleft alone will quickly become visible, thus destroying the ecosystem of thebasin. As mentioned, the lake is the center of many factions of politicalcontrol. The Tahoe Regional Planning Agency (TRPA) has been a strong facilitatorof the needs for controls, there is little evidence to show they have made anytremendous impact needed to reverse the trends of fertility in the Lake. TRPAhas put forth pollution control measures called “Best Management Practicesor BMP’s.
” The program requires new projects to implement the BMP’srequired paved driveways, which at first seems like a contradiction to theresearch, however, if we compare a graded, disturbed, un-paved surface with aproperly 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 notlimited to, revegetation programs, retaining structures, and slopestabilization. To protect the lake all parties involved need to unify theconservation efforts and develop an organized protection and planning bureau orassembly, sponsored with governmental support, above and beyond the TahoeRegional Planning Agency and Lake Tahoe Interagency Monitoring Program. Thecurrent agencies, and committees have taken positive steps to protect the areawhich includes: * slow releasing or no chemical fertilizers on lawns and golfcourses. * ski slopes are no longer allowed to use ammonium nitrate to help makesnow.
* California passed a 85 million dollar bond in 1982 to buy-up sensitivelands, potentially endangering the lake, now are protected. * Nevada passed asimilar 30 million dollar buy-up bond in 1986. * The afore-mentioned mentionedBMP’s. Without these positive approaches, the dedication of the University ofDavis, Researchers and Scientists, Tahoe Regional Planning Agency, and othergroups of concerned organizations, Tahoe would be unclear and green today. Thegeneral public can take measures by treating our delicate ecosystems withrespect and becoming educated on our delicate balances.
Steps could include: *Bike more or walk- save our air quality. * Maintain cars properly and up tocodes. * Don’t Drip. Leaky facets waste 9 liters of water per minute. * Don’tpour 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 whopollute our earth’s ecosystems. All adults can be Captain Planets and protectour world. Bibliography1) Richards, Bob. Personal Phone Interviews, FAX. 24 Feb.
1997, 16 Mar 1997. 2) Gabler, Robert, Sager,Robert, and Wise, Daniel Essentials of PhysicalGeography. 5th ed. Orlando:Saunders College Publishing,1997.
3) Goldman, CharlesR. , Richards, Robert. The Urbanization of the Lake Tahoe Basin: A Microcosm forthe Study of Environmental Change with Continuing Development. Proceedings,State of the Sierra Symposium 1985-86, Pub. #177. California:University ofDavis, 1986 4) Tahoe Research Group, State Natural Resources.
Lake TahoeFacts”, “Ten Most Frequently Asked Questions. Internetaddress: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 TahoeInteragency Monitoring Program. The California State Water Resources ControlBoard. California:University of Davis, Institute of Ecology, Tahoe ResearchGroup, 1987.
6) Sheaffer, John R. , Stevens, Leonard A. , Future Water, AnExciting Solution to America’s Most Serious Resource Crisis. New York: WilliamMorrow and Company, Inc. , 1983.
7) Reuter, J. E. , et al. University Contributionto Lake and Watershed Management: Case Studies From the Western UnitedStates–Lake Tahoe and Pyramid Lake. Watershed ’96 A National Conference onWatershed Management.
Maryland:Baltimore, Water Environment Federation, 12 June1996. ISBN: 1-57278-028-2. 8) Goldman, Charles R. Primary Productivity,Nutrients, and Transparency During the Early Onset of Eutrophication. AmericanSociety 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 InternationalAssociation 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-Mar1989):84-88. 11) Bowman, Chris. “Clinton Seeks Summit on Lake TahoePollution” 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 SeeksClues to Cloudy Lake Tahoe Water” The Sacramento Bee 16 October1995:SUPCAL. 14) Malley, George. Personal Interview. 15 April, 5 May 1997 MAPSAND 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. AmericanSociety of Limnology and Oceanography, Inc. . 33(6, part1),Pg.
1329. 1988. FigureThree, Population Growth Chart: Goldman, Charles R. , Richards, Robert.
TheUrbanization of the Lake Tahoe Basin: A Microcosm for the Study of EnvironmentalChange with Continuing Development. Proceedings, State of the Sierra Symposium1985-86, Pub. #177. California:University of Davis, Pg. 43. 1986.
Figure Four,Water Cycle Chart: Goldman, Charles R. , Richards, Robert. The Urbanization ofthe Lake Tahoe Basin: A Microcosm for the Study of Environmental Change withContinuing Development. Proceedings, State of the Sierra Symposium 1985-86, Pub. #177.
California:University of Davis, Pg. 43. 1986.Geography