by Jay Lund

October 1 marked the beginning of the new Water Year in California. Water years here run from October 1 until September 30 of the next calendar year, and are named for the calendar year of the bulk of the water year (January-October).  It is a good time to reflect on the last year and make largely futile predictions of precipitation for the coming 12 months.

Reflections

The main lesson from the wild 2023 water year in California was the reminder that California’s hydrology is highly variable and rarely knows its average.  Following 2021, one of the driest years of record and another dry year in 2022, 2023 was one of the wettest years of record.  An earlier reminder of this occurred from 2014-2015 (two of California’s driest years) to 2017 (the wettest year in California’s official records).  Figure 1 shows a histogram of the Sacramento Valley’s annual water year runoff over 116 years. It is not a normal distribution.

What will happen in 2024?

Nobody really knows, but you can expect endless speculation from now until March.  Only by March (and sometimes late March) is it late enough in California’s mercurial wet season that we have seen most of the water year’s precipitation. 

Statistically, there is almost no correlation of unimpaired runoff in northern California from one year to the next, as seen in Figure 2.

Similarly, there is almost no correlation between El Niño conditions and runoff from northern California, as seen in Figure 2. However, these correlations are a bit stronger in southern California.

Sometimes in life, and always with California water, all we can do is to prudently prepare for contingencies and surprises, while we wait for the future.

California’s current water storage – Good short-term news

Current surface storage in California is generally in very fine shape.  Most reservoirs are well above average storage for this time of year.  Interesting exceptions are the large Trinity Reservoir in far northern California at 85% of average and Millerton Reservoir on the San Joaquin River at 80%.  This great surface water storage insulates the state somewhat if this year is dry, but could become a liability if this coming year has early floods.

Most water storage in California is underground and 2023 brought a lot of water for managed and incidental groundwater recharge.  For the Tulare basin, which averages about 2 million acre-ft (maf) of groundwater overdraft (with as much as 6 maf of additional overdraft in past drought years), the immense water availability in 2023 brought in only enough additional water for about two years of average groundwater overdraft, and not even one year of severe drought.  Even with major (even excessive) investments, wet year groundwater recharge will be far from sufficient to solve the southern San Joaquin Valley’s groundwater overdraft problems (but it will help some).

On the whole, we enter 2024 with less worry about drought and more worry for floods.  But we should worry about both, reasonably.

Strategic changes and climate handwringing

Many aspects of California water are eternal from our human perspective – a Mediterranean climate with large seasonal and interannual variability, a tendency to be dry, great internal geographic variability in hydrology and water demands, large structural changes in water uses and demands driven by technological changes and global markets, and recurrent introductions of non-native species.  California water management has always had to deal with large changes (both variability and structural changes).

Today’s climate (and more) is changing.  It is important to prepare for multiple interacting changes altogether. 

Fortunately, California’s ever-restructuring economy continues to become less dependent on abundant supplies of water.  This is especially true for cities, where more than 90% of the state’s population and economy are now largely (but not entirely) decoupled from water issues.  Even in irrigation-dependent agriculture, shifts to more profitable permanent crops (when accompanied by groundwater management) make rural economies less vulnerable to climate. 

California’s native ecosystems are becoming more vulnerable to changes in climate, the stresses of water and habitat reduction, fragmentation, and disruption combined with invasive species introductions promise continued declines.  There seems to be no plausible scenario where California’s future ecosystems will be like its past ecosystems.  Yet we have barely begun discussing realistic futures for managing California’s forest and aquatic ecosystems.

We need to think about and discuss how to adapt to these changes more strategically.  These discussions will be hard, but should be exciting if they open broad opportunities for more sustainably and resiliently achieving human and ecosystem objectives.

What to do?

Every year, water managers and users must be prepared for both flood and drought.  It has always been thus, and it is becoming more like this with a warmer climate. These trends indicate that water managers need to be serious about planning.

Californians should pay serious attention to water and its likely changes from climate change. But without complacency or panic over our remarkably effective yet substantially flawed water management system and institutions.  Complacency and panic are rhetorically convenient, but expensive and potentially life-threatening reactions to situations that deserve serious thought, analysis, and deliberations.

Our deliberations and analyses remain relics of the history of water infrastructure and allocation for agricultural and urban growth.  They are not without value, but need improvements to help us adapt to a changing climate, ecosystems, economy, and social concerns.  This requires more serious and difficult discussions than our distracting fixations on the state of El Niño and the latest now-banal climate projections.

Think hard and discuss these challenges soberly with others, especially those outside your current advocacy identity.  These are not conversations we should seek to control from a short-term perspective.

Now, go have a drink (of water) to celebrate surviving another surprising and enlightening water year that should help us prepare for future surprising water years.

Further reading

Sacramento Valley historical unimpaired runoff data. http://cdec.water.ca.gov/cgi-progs/iodir/WSIHIST

Moyle, P. (2023), “Future Ancestors of Freshwater Fishes in California,” CaliforniaWaterBlog.com, September 17.

Lund, J. “Happy New Water Year 2023!“ October 2, 2022.