Lake Tahoe On West Coast 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 68F maximum and 41F 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 nut …