Saving the azure clarity of California's Lake Tahoe

World-renowned Lake Tahoe - the sky-blue, mountain-girt body of water that straddles the California-Nevada border - has been given a new lease on life.

So have efforts to mesh scientific research with the political process to preserve precious natural areas, say participants in a procedure that culminated in an agreement aimed at preserving Tahoe's famous clarity.

For Dr. Charles Goldman of the University of California at Davis, the Aug. 26 decision of the Tahoe Regional Planning Agency was the payoff on 23 years of devoted research. Limnologist Goldman, director of the Tahoe Research Group, says deterioration of the lake environment has become more rapid in recent years. Algal growth has become ''exponential,'' he explains, and the prized transparency of Tahoe's water is being lost at a rate of one-half meter a year.

Strong resistance - especially by Nevada members of the planning agency - to putting strictures on building and other environmentally risky activities finally gave way to Goldman's warning, based on scientific data, that Tahoe is fast becoming ''an ordinary lake.''

Huey Johnson, California secretary for natural resources, hailed the new environmental standards as ''a monumental victory'' because it requires that scientific evidence be used when determining how much development may take place in the basin. If the Tahoe agreement is successfully implemented, he asserted, it will ''be an environmental model for the rest of the world.''

Goldman termed the Lake Tahoe Basin ''a microcosm for pollution problems'' and a rare instance of successfully ''applying science to a political situation.''

Political realists predicted that the recent meeting of the Tahoe Regional Planning Agency - with seven representatives each from California and Nevada appointed by the state governors - would not even come near to agreeing on environmental ''thresholds'' (minimum standards). For many years, the membership from both states was heavily development-oriented. Recently, especially during the administration of Gov. Edmund G. Brown Jr., a majority of the California delegation has favored strong environmental protection. But within the past year Nevada Gov. Robert List appointed two members known to be linked to development forces.

With a majority vote of each state's members required to approve the proposed new standards, the expectation was that Nevada would block the plan. But the pressure of public opinion, manifested in such groups as the League to Save Lake Tahoe, and reportedly some urging from the White House, apparently brought around a Nevada majority.

Also, say Goldman and Johnson, even the most pro-development people have come to realize they could spoil a good thing commercially by despoiling the lake.

Among the more significant thresholds:

* Water clarity - 33.4 meters during the December-March period (when there is the least intrusion of pollutants, explains Goldman). This means that a white, plate-sized disk can be clearly seen at that depth. The limnologist points out that the lake has lost 25 percent of its relative transparency in the last 15 years.

* Introduction of nutrients into water - 52 grams per square inch per year. These nutrients, the result of clearing land for development, fertilizing plants and golf courses, and other activities, are chiefly responsible for algae growth. Goldman recalls: ''My most significant contribution up to now was convincing people not to put sewage into the basin. This (which happened in 1963 ) gave the lake a breathing spell.'' Most waste now goes into sewers that take it out of the Tahoe Basin.

* Air quality - carbon dioxide is to be limited to 9 parts per million in an eight-hour period. A visibility standard has been set - 103 miles at least 50 percent of the time. The once-pristine air now is affected by the exhausts of autos driven by the 50,000 year-round residents and the 300,000 visitors that come into the area on peak days in both summer and winter.

* Development - each proposal will be reviewed for conformity to the threshold standards. In effect at present is a five-year state compact under which each proposal will be reviewed for compliance with the new standards. The compact expires in August 1983.

Other factors covered by the agreement include: fisheries and wildlife, noise , recreation, scenic resources, soil conservation, water quality, and vegetation.

Goldman says a good deal of the damage to the lake can be undone, but it will take many years. Lake Tahoe naturally drains slowly (its ''retention time'' is 700 years), and a flow-control dam now keeps its level from dropping below a minimum. ''Most important,'' he emphasizes, ''is to stop progressive deterioration.''

Helping guarantee that the agreement will be carried out, he explains, is an interagency monitoring program developed within the last two years. The data produced by the Goldman team will thus be made available to local, state, and federal agencies with ''enforcement authority.''

The most important effect of the new agreement, in Goldman's view, is that it ''provides the political muscle to begin corrective action and phase out construction on the steep slopes'' around Lake Tahoe.

Aiding this new initiative to protect Lake Tahoe is a land-acquisition plan announced earlier this year by the US Forest Service. Possibly by the end of this year, the Forest Service will begin buying some 21,000 acres of ''enviromentally sensitive'' land in the basin.

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