For the first time since 2011, California’s drought is significantly weakening—a result of one of the wettest winters on record. California has experienced record levels of precipitation this winter, and unlike last winter, cooler temperatures over the 2016–2017 winter season have enabled the precipitation to build up snowpack (the total accumulated snow and ice on the ground). High precipitation and snowpack levels, both of which supply hydroelectric generators throughout the year, suggest that hydroelectric generation in California in 2017 will significantly exceed 2016 levels.
Although the drought state of emergency declared by California authorities in January 2014 is still in place, drought conditions have noticeably improved, and the northern half of the state is no longer classified in any stage of drought severity. The area of the state classified as being in exceptional drought (D4), the most extreme category, has dropped to zero, a significant improvement over the 40% and 35% of the state’s land area classified as being in exceptional drought in March 2015 and 2016, respectively. However, 8% of the state—mostly regions in the south—is still in a moderate drought (category D1) status or worse. Mandatory water restrictions, enacted for the first time in the state’s history in April 2015, remain in effect in California. State officials are expected to wait until the full winter season ends in April to amend or rescind the state’s emergency drought declaration.
Snowpack levels have increased significantly from the near-zero levels measured in the Sierra Nevada Mountains in April 2015. As of March 21, 2017, the California Department of Water Resources reported that statewide snowpack was 158% of normal for that date. A more important metric when considering snowpack is the snow water equivalent (SWE)—the total amount of water contained within the snowpack. California’s SWE levels have noticeably increased this year, and as of March 21, the California Department of Water Resources reported that the statewide snow water equivalent was also 158% of average for that date.
Snowpack and SWE are strong drivers of hydroelectric generation because runoff from melting snowpack feeds hydroelectric plants in the spring and summer months. California’s hydroelectric generation increased through most of 2016, especially toward the end of the year. Total 2016 hydroelectric generation in California was well above the 2013–2015 range and was nearly as high as the longer-term, pre-drought generation average over 2001–2010. High levels of SWE from the 2016–2017 winter suggest increases in hydroelectric generation in California later in 2017.
Decreasing hydroelectric generation in California in recent years has been offset by increasing natural gas, wind, and solar generation. An increase in hydroelectric generation could decrease reliance on generation from other sources, particularly natural gas-fired generation, potentially helping to mitigate the ongoing limitations at the Aliso Canyon natural gas storage facility in Southern California. According to data from the California Independent System Operator (CAISO), the grid operator for much of the state, hydro generation in the CAISO service area so far in 2017 has been double that over the same period of 2016. Over the same time, natural gas generation has been down nearly 20%.
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