California’s Records and Reserves
The 2012-2016 drought was arguably the worst in memory. In a quick turnaround, the state’s infrastructure is full and water managers are battling with the wettest winter, and possibly year, on record since 1985.
The 2016-2017 October-February statewide precipitation total was 28.5 inches, an extra foot of water covering the entire state. At 180% above average, this year ranked first of 122-year period of record. In the San Joaquin and Tulare Lake region, the amount of precipitation was greater than the statewide average, but not enough to break any records. For Tulare, the October-February precipitation total was 15.2 inches, 6.5 inches or 175% above average, and ranked 4th wettest winter in the 122-year period of record.
Just when spring is showing bluer skies, and we have a handle on local flooding, there’s more coming from the mountains. After five years of thin and non-existent snow cover, the CA DWR snow survey data suggests nearly 47 inches of snow water equivalent. That is, there’s nearly four feet of water sitting on top of the Sierras ready to melt and meet us in the valley! You can keep up to date with snow water equivalent on DWR’s website.
The extreme winter of 2017 also highlighted the key issues surrounding our surface and ground water storage infrastructure: We could have stored this abundant water in anticipation of another drought, not in new reservoirs, but right under our feet.
At the beginning of the year, reservoir managers started holding back and reserving water behind dams in anticipation of continuation of the current drought. But the heavy rain and snow was overwhelming, and reservoirs were near capacity by the mid-February, losing the capacity to further store runoff and mitigate for floods. In other words, irrespective of wet or dry year there is a limit to how much water we can store behind these dams.
On the other hand, the amount of groundwater storage (between 850-1300 million acre feet) in California dwarfs our surface water storage (42 million acre feet). Unfortunately, with some inspiring exceptions, California does not typically manage or store surface water and groundwater conjunctively. But with patterns like long drought-extreme winter, or like the years 2012-2017, becoming more normal, we have the opportunity to prepare groundwater storage infrastructure, take the excess surface water, and store it in aquifers. If 2017 was a missed opportunity, perhaps, especially for basins battling with overdraft issues, we’ll be ready for the next extremely wet winter when it comes.