Hydro plants seek waivers amid California drought

California hydroelectric plants are trying to temporarily modify water release requirements in their licensing agreements as the severe drought across the western US enters another summer.

Plants with more than 300MW of generating capacity in the last three weeks have asked federal energy regulators to waive some of their licensing requirements amid a drought that one plant owner described as "unprecedented" and a water supply situation that is expected to be "dire."

California's snowpack at present is 3pc of typical conditions. The largest reservoirs in the state are at two-thirds of average storage levels, state data show.

Licenses for hydroelectric plants often set minimum stream flow and storage levels to protect wildlife and enable recreational uses such as rafting. But years of drought in the state and forecasts for more dry weather have prompted plant owners to ask the Federal Energy Regulatory Commission (FERC) to waive certain terms of their licenses until conditions improve. The plants do not explicitly say how they expect the drought conditions could affect hydroelectric output.

The Merced Irrigation District, which owns the 104MW Merced River hydroelectric project in northern California, last week asked FERC for a variance from its license because it does not expect the reservoir behind its dam will ever fill up this year to meet a minimum-required level of 115,000 acre-feet (142mn m3). The reservoir two weeks ago had 96,000 acre-feet of storage.

If that happens, it would be the first time it has not met that level since a dam on the river was constructed in 1967. The district also wants to cut downstream flow at one location by a third to 40 cf/s (1 m3/s).

Pacific Gas & Electric last week asked for a one-year variance of license requirements for the upper lakes of its 206MW Mokelumne river project, citing a snowpack as of 1 April that was the lowest since records began in 1918, at only 13pc of typical conditions. The utility wants to cut water flows in one area by 60pc to 2 cf/s and make other changes to its license.

The El Dorado Irrigation District on 10 April asked for a temporary amendment to the license for its 20MW El Dorado hydroelectric plant. The district wants to cut minimum stream flows below one of its dams by 67pc to 2 cf/s at one location to help conserve storage.

Hydropower output in California this year is ahead of the year-earlier level. Precipitation since 1 October 2014 has been at 76pc of average levels, according to the state Department of Water Resources. But an unusually warm winter that cut into the snowpack resulted in higher water runoff, which boosted hydropower output on the Independent System Operator grid by 14pc year over year.

Thermal plants' output — mostly natural gas — is 17pc lower year over year on the state's primary grid.

California wholesale power prices this year have averaged 40pc lower than a year earlier.

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