Lake Level Watch
Mono Lake Surpasses 6380
Over the past two years, the word " rising" has been used numerous times to describe Mono Lake and its recent behavior. This summer has been no exception.
On August 15, 1996, Mono Lake stood at an elevation of 6,380.1 feet above sea level. This is 2.3 feet higher than it was last October 1, when the 1996 water year began. Combined with the previous year's rise, Mono Lake has risen 5.5 vertical feet since the Water Board decision-the result of two years in a row of above-normal runoff and limited diversions from the lake's tributary streams.
This year's runoff is officially classified as "wet-normal. " Snowmelt-fed streams peaked in June, but flows were only a little over half as high as last year's tremendous peak flows. Grant Lake Reservoir, on Rush Creek, spilled from May 6 until the end of June. This was roughly the same period during which Mono Lake was rising the fastest, about a tenth of a foot per week.
This runoff eventually reached Mono Lake, but two events adversely affected Lee Vining Creek. The first occurred on June 20 when Southern California Edison had a malfunction at its hydropower facilities upstream. The plant shut down automatically, reducing the flow in Lee Vining Creek by about 110 cubic feet per second (cfs). At the same time DWP was testing a scheme to augment Rush Creek flows with water diverted from Lee Vining Creek. As a result, Lee Vining Creek was running at only 68 cfs below the diversion dam at a time of year when flows typically exceed 150 cfs. This caused newly exposed algae to smell, the water to warm up, and some side channels to be dewatered.
The inflow drop, it seemed, was due to an unlikely combination of events-until it happened again seven days later. The second event had similar causes and worse effects. Streamflow below the diversion dam fell much lower, down to only 16 cfs, which violated the Water Board's 1994 Mono Lake decision. DWP reduced its diversions as soon as it became aware of the situation, and streamflow returned to normal levels within twenty four hours. The Mono Lake Committee documented both events extensively, and the information points out the need for an outlet in Grant Lake Dam which can reliably provide high flows in Rush Creek without drawing water away from Lee Vining Creek.
The last time Mono Lake was at 6,380.1 (not counting brief rises following the wet winters of 1984 and 1986) was in 1974. That was 22 years ago, even before the Mono Lake Committee formed. Today's elevation is only 8 feet above the lake's historic low, however, and the lake is still a whopping 37 feet below its prediversion level. Its surface area is 18 square miles smaller, its salinity is 75% higher, and it only contains 58% of its pre-diversion volume.
Mono Lake has 12 vertical feet to rise and 8.5 square miles of surface area to cover before it reaches the Water Board-ordered stabilization level, a rise expected to take 20 years or more.
Return to Fall 96 Newsletter
 |
 |
 |
 |
 |
 |
 |
 |
 |
|