Mono Lake forecast to drop due to dry winter

The Mono Lake Committee recently received the Los Angeles Department of Water & Power’s (DWP) forecast for Mono Lake levels for the 2013 runoff year (April 1, 2013–March 31, 2014). The lake level forecast is primarily based on the preliminary April 1 runoff forecast of 66%, which makes this year officially “dry.”

Median levels of precipitation and evaporation are assumed, so after September the accuracy depends on how wet next fall and winter will be. The elevations in the table below are in feet above mean sea level.

The predicted lake levels for this summer around 6,381 feet are similar to what was observed in summer 2004 and winter 2009–10 (2004 and 2009 are shown above for comparison, but both were wetter years than this year). If the lake does drop to a fall low point of 6,380.4 feet, it would be the lowest Mono Lake has been since 1996.

This is the second dry year in a row. It follows a very warm year last year when Mono Lake dropped 1.8 feet, entirely erasing the rise in lake level from the previous wet year, and an extraordinary drop for recent decades (see more on this in the Spring & Summer Newsletter Lakewatch article—coming soon).

As long as Mono Lake remains above 6,380.0 feet on April 1 each year, DWP is permitted to export 16,000 acre-feet of water during the runoff year. Exports are cut back to 4,500 acre-feet when Mono Lake is below 6,380.0 feet, and zero export is allowed any time the lake falls below 6,377 feet. Over the long term, the lake is currently rising to a target level of 6,392 feet above sea level, when export restrictions will change. It rises in wet years and falls in dry years, so the transition to the future management level is expected to take decades. After September 28, 2014 (20 years after the State Water Board’s Decision 1631 ordering the lake to rise) the State Water Board will hold a hearing on the lake’s condition.