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California Precipitation: From Famine to Feast

By: Christopher C. Burt, 8:09 AM GMT on February 25, 2017

It’s amazing what a difference one year can make. California’s five-year long drought has come to a dramatic halt (or at least interruption) this winter season. The latest California Drought Monitor report, released on February 23rd, has no portion of the state under ‘Extreme Drought’ conditions for the first time in four years. Last year on this date 61% of state was enduring such. Here are some details about the rain and snowfall so far this season.

No pair of graphics can illustrate so clearly how the California drought has virtually come to end as these state drought monitor maps for Feb. 23, 2016 and Feb. 23, 2017 below:

The rainy season (July 1-June 30) for California has already exceeded the normal seasonal totals as of February 23rd with at least two normally wet months still to come. Below is a table listing a select group of California sites and where they stand precipitation-wise as of the end of the latest big storm on February 20th:

Note that most sites in California have already surpassed their average precipitation totals expected for an entire season. The above table and data courtesy of Jan Null, Golden Gate Weather Services.

Santa Rosa has already almost achieved its wettest season on record with a 51.60” sum (actually now up to 51.85” with post storm showers on Feb. 21-22). Their wettest season on record (with a POR beginning in 1902) was that of 1982-1983 with a 55.66” seasonal precipitation total. The additional 3.81” needed prior to July 1st to break the record is a virtual certainty (normal rainfall for March-June is 8.31”). Blue Canyon, at a 5,000’ elevation in the northern Sierra, also has a shot at their wettest season on record with 94.90” observed so far (an additional .37” accumulated in the days following the table’s creation). The site’s wettest season on record was that of 1994-1995 when 122.35” was measured. Normal March-June precipitation for Blue Canyon is 19.07”. Several rain gauges in the northern Sierra have already measured over 100” of precipitation this season, with Four Trees in Plumas National Forest in the Feather River Watershed now up to 124.85”. This site is located in the mountains above the nearly stricken Lake Oroville Reservoir. Closer to the San Francisco Bay Area, the perennial wet spot, Venado in Sonoma County north of the city, has picked up 120” of rainfall so far this season. The California state record for seasonal rainfall is more than likely safe: 257.90” at Camp Six in Del Norte County (in extreme northwestern California) during the 1981-1982 season. The state record for one month of precipitation also was measured at Camp Six with 81.90” in December 1981.

Many of the state’s reservoirs are now at or close to full capacity for the first time in five years. As you may have heard, Lake Oroville faced a crisis last week when the lake overflowed and one of the reservoir’s emergency spillways almost collapsed. Since then the water district authorities have released a huge amount of water from the dam lowering its current level down to just 80% of capacity (see map below). The state’s largest reservoir, Lake Shasta, is now at 93% capacity. Last year at this time it was at 83% and at one point, during the peak of the drought in 2015 it was as low as 37% of capacity.

Much of Blue Canyon’s precipitation has fallen as snow although most of the wettest storms so far this season have been warm atmospheric-river events with high altitude snowlines (generally above 7000’). At the highest altitudes truly phenomenal snowfalls have occurred, although we must rely on the ski resorts for most of the figures at this point. At the top of the list for seasonal accumulation is Sugar Bowl Ski Resort, near Donner Summit, which has reported 585” of snowfall so far at its base. Nearby Boreal Ski Resort has reported 557” and Mammoth Ski Resort 515”. The greatest snow depth so far reported is an amazing 350” (almost 30 feet!) at the 11,000’-level of Mammoth Mountain in the central Sierra. Note that the California state record for seasonal snowfall is 884” at Tamarack (near where Kirkwood Ski Resort is today) and the greatest snow depth ever measured was 451” (37.6’), also at Tamarack, in March 1911.

Snow depths and conditions for some of the Sierra’s ski resorts as of February 23rd.

Overall, the snow-water content in the Sierra is on track to be the greatest such on record in the central and southern Sierra districts, and close to such in the northern district. The season to match or beat was that of 1982-1983 that saw a very wet March, so the same would have to occur this March for any records to be set. At this time, February 24th, the forecast is for a long spell of dry weather for most of California until at least March 10th. Of course, this forecast could change at any time.

California snow-water content as a percentage of normal for this season (as of Feb. 23rd) compared to normal (the blue area) and the wettest, driest, and last season. Note how the driest season on record for all three Sierra districts was that of 2014-2015, just two years ago! Graphs courtesy of the California Department of Water Resources.

Is the Precipitation Regime becoming more Extreme in California?

As the graphs above illustrate, the Sierra went from one of its driest (if not driest) precipitation seasons on record (that of 2014-2015) to possibly one of its wettest this season of 2016-2017. Although this might seem extreme, the record shows that these feast and famine episodes are a fairly common trait of the climate of California. See below:

Chart of annual precipitation season (July-June) totals for the entire state of California 1895-2016. From NOAA’s NCEI Climate at a Glance archive.

Precedent for the wild swing from drought to flood (and visa versa) has been seen in the past: out of 121 seasons 1976-1977 was ranked the 2nd driest whereas 1977-1978 was ranked as the 4th wettest statewide. 1993-1994 was the 8th driest, 1994-1995 was the 3rd wettest, etc. Curiously, if one displays a trend line for the entire POR (1895-2016) there is virtually no change (well, virtually none: drier by .03” per decade statewide). Of course, California is a huge state ranging north to south some 800 miles, but the difference in the seasonal precipitation is only minor from north to south. In the southern drainage district the change is more pronounced: .12” drier per decade and for the northern district just .01” drier per decade, but for the central district .02” wetter per decade. So statistically for the state overall, it is not getting much drier or wetter over the past 121 seasons. Even if this season (2016-2017) ends up as one of the top 10 wettest on record this would not be at variance in terms of extreme variability from episodes in the past that went from extremely dry to extremely wet and visa versa.

So is this season a drought-buster? In most ways, yes. However, whether the crucial aquifers are replenished remains to be seen. California’s ‘water problems’ are likely going to be a permanent feature of life as the state’s population continues to grow out pacing the means to provide it with reliable water sources.

Christopher C. Burt
Weather Historian


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

wall of water in the snow pack when it melts out as well

nice entry good info thanks
Your 121 year graph and the analysis that essentially normalizes it to a trend line that indicates the long term precipitation totals haven't changed much during that period is most telling. The state's population was near 1.5 million in 1900, 10 million in 1950, 30 million in 1990 and now pushing 40 million. This doesn't include agricultural/industrial demand which is huge. Watching the overflow from the Oroville reservoir I could only speculate on whether some of that excess water feast could realistically be piped and injected into needy aquifers down state.

In any event, your presentation struck me as analogous to a single wage earner, with an up and down income, supporting an increasingly large family, needing his/her income trend line to increase (unlikely), the family to reduce its expenditures or to find someplace else to live.
Just North of Riverside Calif and I have 16.72 from 2/23/2016-2/21/2017 CoCoRahs (ca-rv-019)
Most of this came after 10/17/2017

Did you mean July-June? That is what the chart read, but the comment below is backwards.
I thought climate change has exacerbated California's drought problem, and perhaps even been a contributor to some of the flooding so far this year, but according to the graph, it looks like precip patterns haven't really changed since 1900.

I assume the greatest contributors to the drought have been California's exploding population, hence more water consumption, and rising temps leading to more water evaporation, more than any kind of shift in precipitation patterns themselves.
Interesting information, thanks for putting it all together! There does not seem to be a direct correlation with the steadily increasing temperature over the same time period. This shows there are still complicating factors we don't understand regarding long term predictions for precipitation as the planet warms.
Great article, Christopher! You covered it all with great info and graphics. Thanks for your work.

Regarding some questions and concerns raised in the comments:

How Water Use Has Declined With Population Growth - Water Deeply

Several different perspectives on percentages of how Calfornia's water is used and other things to know in this article.
Slideshow: Drought: 10 things to know about California water use | 89.3 KPCC

California already has multiple sophisticated systems for delivery of water from north to south. Events like February's deluge can overwhelm the systems and much water goes out to sea. However research is being done with flooding Central Valley fields for the purpose of recharging the underground aquifers.
As Rains Soak California, Farmers Test How To Store Water Underground : The Salt : NPR

Warmer temperatures cause more rain and less snow in the winter. More rain than the water control systems were designed for goes out to sea. Snowpack is the natural reservoir that supplies the man made reservoirs in the summer. Less snow means less water is available in the summer. Warmer temperatures in the summer cause more evaporation which leads to quicker drought onset and deeper drought.

I don't recall any predictions of more precipitation with increasing temperatures per se. What I do recall is more frequent drought and flood and more and greater extremes. That would be tough to eyeball from the California precipitation graphic. Those sort of changes would be easier to spot for some other geographic areas.
You know what is also kinda interesting? My brother and six of his churches in Western Kern County prayed hard for rain-had daily gatherings for months last year. When the first storm came, they all had a joint celebration.

Now, there are grumblings for a reversal prayer gathering for dry.

As the headline would read: "Be Careful What You Pray For." LOL

But what is also kind of nice to reflect on--we used to call this stuff "An embarrassment of riches." At least according to some older folks I know. :-)
I am in San Carlos , California and we have 175 percent of normal rainfall, 20 inches season average, current 35.01 inches
And of course now everything is all good and the state can go back to their normal wasteful water practices because there will never be another drought like they just experienced. /snark
In reading the comments I need to point out being a Hydro-geologist working in California that the moisture cycle follows a pretty predictable pattern of one heavy year of precipitation followed by 9 to 10 years of below normal rainfall. Every so often the drought years extend resulting in the drought condition we are now coming out of or we will get a couple heavy moisture years. The biggest problem with this weather cycle is that during the years that moisture levels are around normal or heavy no one has really been preparing for the pending drought years that inevitably come. The other problem is California's agriculture and population keep on growing exponentially. This last drought is no worse than the previous ones but water usage gained by 40%. Unless planning is put in place for the next drought we will be bound to repeat our mistakes and have a water shortage again at the end of the next moisture cycle.
Impressed am I by the talent at writing by Mr. Christopher C. Burt.

[My admiration is Serious: years-ago I was a Proficient Writer: in 1990 after more than 5-years of Toil, I earned a PhD in Chemical Engineering from the University of Minnesota. This degree hangs above my desk: where I typed this! :-) ]
Moving back into an El Nino, plus every 1 C increase implies 7% more water vapour, plus 15% faster evaporation. Kinda tough being a farmer these days. Drought and flood same year.
weatherhistorian has created a new entry.