The onset of meromixis during restoration of Mono Lake, California: Unintended consequences of reducing water diversions

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Abstract
Diversions of freshwater streams out of the Mono Lake basin since 1941 have led to a gradual decrease in size, an approximate doubling of lake‐water salinity, and associated environmental impacts. To restore Mono Lake, the state of California amended Los Angeles' water rights by restricting diversions until the surface elevation rises 6 m above its 1982 low stand. Given the reduced volume of the lake, the cessation of diversions and an above average snowmelt runoff in 1995 led to an abrupt l‐m rise in surface elevation and the onset of persistent chemical stratification (meromixis). Long‐term simulations using a one‐dimensional vertical mixing model modified for application to hypersaline Mono Lake predict the current episode of meromixis is likely to persist for several decades, given the management policy of the state. A similar episode of meromixis in the mid‐1980s following record snowmelt runoff in 1982–1983 and reduced diversions led to reductions in vertical mixing, recycling of nutrients, and primary productivity. That episode ended following an extended period of drought and the resumption of diversions. The ecological consequences of the predicted multidecade period of meromixis are largely unknown.

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