Drought is inherent to California’s climate. Throughout recent history, the state has experienced periodic droughts.
Its most recent one was in 2020-2022. However, dramatic fluctuations in its climate have been observed in the 21st century.
In 2015, California experienced its lowest snowpack in at least 500 years, and 2012 to 2015 was the driest period in at least 1200 years. However, the winter of 2016–17 was the wettest ever recorded in Northern California.
The winter of 2022 to 2023 also brought a series of intense, back-to-back atmospheric rivers to the West from December 2022 to March 2023, causing extreme rainfall and flooding.
As a state experiencing floods in winter and droughts in summer, can they store the influx of water to ease future droughts and water shortages?
According to Vox, most of the water delivered to the state this year flows back into the ocean rather than being saved for the rest of the year.
There are three reasons for this. First, the state needs more water storage infrastructure. Second, it is about water management decisions. Third, prolonged droughts have diminished the capacity of groundwater to recharge, and even streambeds and creeks to slow down water flows.
California has big dams and reservoirs, but they are in the mountains, away from areas like central and south California that need water the most. The state has approved seven water storage projects, but so far, nothing has been done about them. The article also notes that most ideal sites are no longer available, plus land and construction costs have become expensive.
Existing reservoirs have two functions – to store water and to control floods. So once these reservoirs are near capacity, water managers release this water to have more space from incoming rains.
California’s combined reservoirs store 45 million acre-feet of water. An acre-foot could provide water for two households in a year. Most of these reservoirs hold water below their total capacity.
Still, with improved weather forecasting, water managers could anticipate major storms weeks ahead, which could help them decide whether to keep or release the water.
This leaves groundwater to store much of this rainwater. Groundwater can hold up more than 1,300 million acre-feet of water, but California faces some obstacles to maximizing its groundwater storage.
First, paved surfaces and farmlands prevent water from percolating underground. Second, unchecked groundwater pumping has removed water faster than it could recharge. It has also depleted resources and made water levels deeper – in some areas, farms and cities have to dig thousands of feet deep to reach the water.
One solution to recharge groundwater, which provides around 40% of the state’s water supply, is to restore flood plains. This strategy requires an area of land or farm to flood or accumulate flood waters to recharge aquifers. Managed recharge has been used for decades to replenish water supplies but is now gaining traction due to droughts that are becoming severe and longer.
The Conversation notes that local agencies have proposed more than 340 recharge projects in California, which they expect to store 500,000 acre-feet of water on average every year. The idea is to flood the land in winter and then farm in the summer.
One program in the Pajaro Valley offers a rebate on their water use fee to encourage landowners’ participation. According to the article, the cost-benefit analysis of this strategy is cheaper than finding alternative water sources or using desalination or water recycling.
Climate change is predicted to bring more extreme weather events to the state.
For instance, severe rainfall could become more common as temperatures rise; dry spells could follow this.
Flooding and drought will remain urgent concerns for the state, and will have to prepare for both extremes.
Atmospheric Rivers. (2023, March 29). Climate Central. Retrieved from https://www.climatecentral.org/climate-matters/atmospheric-rivers-2023
Irfan, U. (2023, March 10). Why all that rain in California won’t solve its drought. Vox. Retrieved from https://www.vox.com/science-and-health/23553924/california-rain-atmospheric-river-drought-aquifer-reservoir
Fisher, A. (2023, January 7). How California could save up its rain to ease future droughts — instead of watching epic atmospheric river rainfall drain into the Pacific. The Conversation. Retrieved from https://theconversation.com/how-california-could-save-up-its-rain-to-ease-future-droughts-instead-of-watching-epic-atmospheric-river-rainfall-drain-into-the-pacific-197168