How serious is this drought and what does it mean for fire season?
Rainfall and fire fuel moisture levels are significantly below historical averages this year. So how concerned should Santa Cruz County residents be?
The U.S. Department of Agriculture is classifying Santa Cruz County as being in “severe drought” conditions, rainfall is at about half the average for this time of year and the smattering of rainfall last weekend didn’t help much.
But as drought grips California and other parts of the West — and the Santa Cruz Mountains and elsewhere are still recovering from last year’s historic wildfires — two related questions are top of mind: Should Santa Cruzans be worried about severe water shortages, as well as a repeat of last year’s fires?
Here are the short answers: Scientists and local officials say that some dry years are normal, and there is enough water in reserves for now, but the fact that last year was also dry makes the situation more serious. Parched vegetation also sets the stage for another big fire year — but that will depend largely on human behavior.
There’s a lot more to unpack on both subjects, so Lookout dives into the details here:
How bad is the water situation?
Rainfall in the Santa Cruz Mountains stands at about 50% of normal, and as April rolls into May the chance for more rain is pretty much over. The rainfall last weekend was “our last gasp hope of getting any sort of notable rainfall this year,” said interim Santa Cruz County water resources manager Sierra Ryan, and that ended up being so minimal it was “not even a drop in the bucket.”
Ryan said there is one silver lining to this year’s lack of rain — less risk of debris flow in the CZU burn scar. “[A wet winter] could have led to extensive damage due to landslides, and possible loss of life,” Ryan said. “So, in some ways this dry year, while definitely very troubling from a water supply and from a future fire safety standpoint, at least what it did do was prevent any sort of negative impacts in the burn scar area.”
The other good news is that because Santa Cruz County residents already practice so much water conservation, “we are in a much better position for this kind of weather right now than we were during the beginning of the last drought,” Ryan said. “People are using on average, 20-to-30%, less water than they were in 2012 at the beginning of the last drought phase.”
The high level of conservation in place already means this year’s drought likely won’t prompt water districts to enact severe restrictions. But Ryan said it is still essential that people continue good water saving habits, and do whatever they can to conserve even more, because no one knows whether next winter will bring more rain or another dry spell.
Brian Garcia, a meteorologist with the National Weather Service Bay Area, said the winter of 2021-22 will be a defining moment.
“California is a heavily managed water state, meaning that we capture all this water in reservoirs all over the place and we try to sequester all this water for future use,” Garcia said. “This winter, we have a little bit in the bank, and we didn’t get any rain, and so we’ll have to use that this summer. Now, if we hit next winter — and we do a winter like this again, or even a winter like the previous winter — that’s when we’re in an absolute world of hurt.”
Santa Cruz County relies mostly on groundwater, and groundwater reserves can be hard to measure, but the city of Santa Cruz uses the reservoir of Loch Lomond to sequester water for dry years, and when the level on the reservoir drops it’s plainly obvious. Currently, it’s at 71%. If the city were relying solely on Loch Lomond, the water would last for about a year.
“Everybody this summer is going to be using reserve supplies, the groundwater basins are our reserve supplies, the Loch is our reserve supply, so everybody is basically using that this year,” Ryan said. “That means that every drop of water you use this summer is a drop of water that’s not available next summer.”
Every drop of water you use this summer is a drop of water that’s not available next summer.
— Sierra Ryan, interim Santa Cruz County water resources manager
What does the drought mean for fire season?
Warm, dry summers are nothing new for Santa Cruz, and this has always been a risky time for fires. But the size and ferocity of the CZU Lightning Complex fire was unprecedented. This year, the mountains are dried out and the stage seems to be set for another bad fire season.
Vegetation in the Santa Cruz Mountains is as dry as it’s ever been. The fuel moisture content — a way to measure how much water is stored in plants and trees — “eclipsed” previous records for dry fuels when it was measured before the April rains, said Garcia.
Craig Clements, a professor and director of the Fire Weather Research Laboratory at San Jose State University, has been measuring fuel moisture content and looking at the amount of new growth in the Santa Cruz Mountains every year since 2009 and he’s found that “everything’s below normal.”
“April’s not looking good, which is when we’re supposed to kind of have the highest fuel moistures,” he said. “It’s similar to our drier years, but I think because this drought is so severe, we can expect extremely dry fuels and probably a lot of dead fuel accumulating, because a lot of these shrubs are going to die.”
But the most important factor in this year’s fire season may not be the state of the fuels.
“Very few fires, in the larger scheme, are naturally caused,” said Cal Fire CZU unit chief Ian Larkin. Most frequently, humans throw the spark that sets fires off. The most unique aspect of the CZU complex fires, and a huge factor in the massive destruction they caused, was probably the clustered dry lightning that set them off, and it’s unlikely that will happen again this year.
Said Clements: “The fact that we had this lightning event in August, a day after we came out of an epic weeklong heat wave really set the stage.”
So far, scientists don’t know whether the frequency of dry lightning storms in California is shifting as a result of climate change.
“We have no evidence either way, really,” Daniel Swain, a climate scientist at the UCLA Institute of the Environment and Sustainability, told Lookout in an interview in the fall. Part of what makes it hard to detect any patterns is that lightning events like what happened last year are so “vanishingly rare,” he said.
Lightning typically is not the ignition source for wildfires in California. That means the severity of the fire season is, to some extent, in human hands.
Common ways in which people can inadvertently start fires are if burn piles get out of control or aren’t properly extinguished, or if cars aren’t maintained well and lose a piece of hot metal from the catalytic converter. Mowing the lawn in the middle of a hot day can also be dangerous.
Most importantly, Larkin said, people should be vigilant and call 911 if they see smoke.
During warm weather, especially if the winds are coming up, Santa Cruz residents shouldn’t just think about it being a beautiful day, Larkin said. “They need to be thinking fire.”
10:56 AM, May. 02, 2021: This story was updated to reflect that scientists don’t know yet whether climate change is impacting dry lightning storms.