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Lake Level WatchRecord Snowpack, Highest Lake Level Since 1974...by Greg Reis What a winter! Until mid-February it was wetter than the winter of 1982-83. Storm after storm brought heavy snow to the Mono Basin. The Gem Pass snowpack, which is representative of the Mono Basin snowpack overall, was at record levels on February 1. There were 47.7 inches of water content, which was 150% of normal for that date. The previous record-holder, the winter of 1956, had a similar wet weather pattern, but turned dry after February--the April 1, 1956 snowpack was equal to the February 1 snowpack. Coincidentally, this year looks similar, with no significant precipitation in February or March. Some of this year's storms brought rain, raising Mono Lake and filling reservoirs (see New Year's rainstorm article). Grant Lake Reservoir, on Rush Creek, spilled for a week or so, starting on January 25! This is the third year in a row it has spilled, but it has only spilled during January twice: in 1943 and 1983. According to Dave Allen of LADWP, Rush Creek will probably be flow-through this year. This means that the flows released from Edison's upstream reservoirs will make it past Grant Dam, resulting in a more natural hydrograph for lower Rush Creek. And what will those flows be? The March 1 runoff forecast for April-September 1997 is 153% of the fifty year average for the Mono Basin! This is categorized as a "wet" year--near the high end of this year type--and the peak flows in the streams can be expected to be close to the ones we witnessed in 1995. Of course, this forecast assumes average precipitation for the rest of the season. Even if spring is quite dry, however, we are assured of an above average year. The current snowpack is greater than the April 1 snowpack was in 1996, which ended up being a "wet-normal" runoff year. So what does all this mean for Mono Lake? Mono Lake, as of March 6, is already at 6381.4 feet above sea level, the highest level since 1974! It has come up 6.7 feet since the Water Board decision, and 1.7 feet from last year's low point in early November--an average rise of 0.5 feet per month between November and February! Based on this lake level, the Water Board decision will allow DWP to export 16,000 acre-feet of water this year. Nonetheless, by late summer the lake should rise to at least 6383 feet--maybe closer to 6384 if we get significantly more precipitation! This would be a dramatic rise in a short period of time, comparable to the 8.5 foot rise between 1982 and 1984. Just as in 1982-84, the rapid rise beginning in 1995 has set up meromixis, and, due to the large amount of fresh water expected to enter the lake this year, this meromictic condition will likely persist (see winter 1997 Newsletter for more on meromixis). Another exciting development at the lake was the presence of a significant amount of ice on the western portion of the lake in January. It wasn't thick enough to support a person's weight, but it sure looked pretty. It broke up during storms, only to return soon after because of the calm winds, freshwater inflow, and cold temperatures. Between the ice and the rising lake level, excursions to the lakeshore recently have been filled with new discoveries. And they will continue to be.
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