What Does All This Rain Mean for California’s Drought?

First, even though storms may temporarily ease the dry conditions, drought is likely to return relatively soon. California has long cycled through spells of deluge and drought, in part because of natural climate variability. But research suggests that a warmer climate has supercharged the “whiplash” between these extremes.

Second, even an extremely wet winter isn’t a magic bullet for the long-term water concerns in the state, which have been exacerbated by years of extreme aridity, rising temperatures and unsustainable water use.

California’s groundwater aquifers have huge potential for storing water; they can hold eight to 12 times as much as all of the state’s major reservoirs combined. But, they have been badly depleted by decades of heavy pumping, especially in the agriculture-heavy Central Valley. Data suggests that groundwater supplies in the region decline precipitously during dry periods, recovering only modestly during wet ones.

When it comes to replenishing those aquifers, the state has had trouble capturing water from downpours and redirecting it to fields and sandy basins where it can seep underground, experts say. That means we still have a long way to go in restoring our groundwater supplies.

Heavy influxes of rain and snow during the winter can also have destructive repercussions later in the year. The state’s record-level snowpack could mean more flooding in the spring as the snow melts, especially if much of the soil is already saturated with water and can’t absorb much more of it.

And, as Alex Hall, the director of the Center for Climate Science at the University of California, Los Angeles, pointed out to me, disputes over the dwindling Colorado River still loom. Seven western states, including California, depend on the river for water, but those states have struggled to reduce their water use even as the river’s flow has plummeted because of climate change, drought and population growth.

Recent rains are not nearly enough to alleviate a crisis that has been decades in the making, Hall said. “We would need multiple years of good and healthy water inputs to recover.”