The California Drought is Over. Definitively.

From the Cliff Mass Weather Blog

Cliff Mass

After over a month of torrential rain and massive mountain snow, the drought is over in California.

Yet with all the liquid bounty, some in the media and elsewhere don’t want to give up on it, as noted in the NY Times headline below.

And the U.S Drought Monitor has severe drought over much of the state.

I believe the evidence for the end of California drought is quite overwhelming. But consider the facts found below and decide for yourself.

Reservoirs and Snowpack

Let us start with the most critical measure of drought…the total water storage in the reservoirs plus the water that will be available from the snowpack (see below).

It is now WAY above normal.  

In fact, the total water available right now is greater than normally available in April after months of additional precipitation.

The previous deficit in California reservoir water storage is now gone.  For example, consider the huge Lake Orville Reservoir in northern CA” during the past month it went from roughly 60% of normal to 106%!  Wow.

Current snowpack, a critical water source for late spring, summer, and fall?

It is now over 200% of normal for all major Sierra regions…and nearly 300% for the south Sierra area.  Good skiing as well.

Soil Moisture and Rivers

The state has experienced flooding and highly saturated conditons from all the rain.   As you might expect, the soil moisture values arecurrently  very, very high (see below from NOAA National Integrated Drought Information System, NIDIS).  Green is above normal.  Dark green indicates the top 1% wettest period on record for the date.

Rivers around California are generally very high, with many running above the 90th percentile (top 10% flows for this period).

And the Palmer Drought Severity Index, which considers current and past precipitation plus temperatures, indicates wet conditions over the state.  No drought.


Making Up For Several Years of Precipitation Deficit

An important aspect of the massive amount of recent precipitation is that it has erased a multi-year deficit in precipitation.  Consider San Francisco, where the observed cumulative precipitation for the past two years is shown by green (and climatological variation indicated by the brown line)

For most of the past two years, San Fran has been behind normal precipitation, but the recent torrent has pushed it above normal!

A similar situation for Los Angeles.

But What About Lake Mead/Lake Powell and Ground Water?

The media has been fixated on Lake Mead/Lake Powell, whose water levels are both well below normal; both are fed by the Colorado River, not the Sierra Nevada reservoirs/snowpack  (see Colorado watershed below).   The water in these lakes supports water needs in southern CA and Arizona and provides electricity from Hoover Dam.

It is true that the water levels in the critical storage lakes/reservoirs (Mead and Powell) are dropping (see a plot for Lake Mead below).

But this decline is not from changes in meteorology/climate, but from increased usage to support a growing population and water-intensive agriculture.  You can see this by looking at the long-term trend in Colorado River Basin snowpack and water flow into Lake Mead (below).

Dropping groundwater levels in California are a similar story, with the largest drops during the past 20 years in agricultural areas of the southern Central Valley (see below).  We are mining too much sub-surface water to be sustainable.

The Bottom Line:   Much of California is a relatively arid, with little long-term trend in precipitation.  There is a reason that that Spanish did not move northward into California for two centuries:  the place was too dry for agriculture. Only a massive reservoir and water transportation system made a heavily populated state possible.

Much of California goes through natural periods of above and below normal precipitation, and we have just gone through such a cycle, moving from a few years of dry condition to a very wet winter.   

The recent meteorological drought is now over.  But California needs better long-term planning and infrastructure to sustainabley support the current and future pooulation and a huge agriculural industry.

 Blaming climate change as the primary cause for current problems and recent “drought” leads to not dealing with the real problems.

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January 22, 2023 at 08:49PM

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