Sustainability & Energy Efficiency

California Drought Status

4 min read

Although California remains in a severe drought, we’ve seen some “April showers” come a month early, bringing some relief to the state due to the current El Nino pattern.

As of March 1, 35% of California remained in a state of “exceptional drought,” down from 45% on December 31, 2015. Fifty-five percent of California remains in a state of “extreme drought,” down from 69% at the beginning of 2016. As the map below illustrates, the drought will still be a factor this summer, but the state’s reservoirs have received a much needed boost.

U.S. Drought Monitor

California (as of March 15)


Source: National Oceanic and Atmospheric Administration (NOAA)

Current El Nino Pattern

Additional help has come from the current El Nino, which refers to warmer than normal water temperatures off the equatorial Pacific. Its influence on a very strong jet stream created a trough over the eastern Pacific and sent a series of storms into the West. This trough, or “atmospheric river” as described by the National Oceanic and Atmospheric Administration (NOAA), brought both heavy rain and snow to California and the Pacific Northwest in the first half of March. As a result, the two largest reservoirs in California, Lake Shasta and Lake Oroville, each received enough rain to return to historical average levels for the first time in over three years.

Lake Oroville saw its biggest, single-day rise in capacity level in 12 years on March 6, while Lake Shasta has received 16 inches of rain since March 1.

While reservoirs in northern California have been boosted back to historical average levels, the southern part of the state remains a mixed picture. The strong El Nino pattern we’ve seen this winter brought much needed rain to California, but it has been weakening. It is currently at 1.8 C, down from 3.0 C in December 2015. If it slowly weakens this spring into summer, that could likely bring further rain. However, if it weakens rapidly and becomes a La Nina (cooler than normal waters off the central equatorial Pacific), it could lead to drier conditions this summer.

Water Content Levels

While current reservoir levels are important, they may very well continue to improve because the storms in March also improved snowpack in the Sierra Nevada Mountains from 25% of normal in 2015 back up to 100% this year. As the snowpack melts this spring, this runoff will further refill reservoirs and potentially help power hydroelectric generation levels.

In addition, the graphs below illustrate the water content in northern and central California rivers this year versus last year against average flow levels and against flow levels in past wet and dry years.  In both regions, current water content levels are 100% of normal (pink line) compared to 25% for 2014 and 2015 (green line).

Normal water content levels will help hydro generation levels recover from their low levels in 2014 and 2015—when they provided only 10 percent of California’s in-state generation—to more average levels of 20%.

However, this must be balanced against the need to refill the state’s reservoirs. Given the potential impacts on the use of natural gas this summer for electricity production due to the issues at the Aliso Canyon natural gas storage field, increased hydro production may have increased importance.

California Hydro Flows as a Percent of Normal


Source: CA Dept. of Water Resources

Northwest Rivers Percent of Snow Water Equivalent

Snowpack is higher in the Pacific Northwest for 2016 than in 2015. California relies on imports of hydro-electric from dams in the Northwest. Specifically, in March 2015, hydro levels in the Pacific Northwest were 75% of normal with many regions along the coast at 50% or less; comparatively, the Pacific Northwest “snow water equivalent” stands at 105% of normal for 2016.

SW_rainfall  Snow_water_equivalent

While the much needed rain has helped improve the state’s reservoir levels, there is still more to be done. Hydroelectric generation may be impacted this spring by the need to further refill California’s reservoir system. A hot summer developing as a result of a rapidly declining El Nino could further strain both water resources as well as gas storage inventories, especially in southern California.

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