Why can’t California just provide all the rain water?


Caught between deluge and drought, most of California’s recent rain is evaporation. But more of this water can be saved for a sunny day.

The western United States is still experiencing a massive drought The worst in more than 1,200 years. Several driven atmospheric riversThe heavy rains over California in recent weeks have quenched some of that thirst. More rain and snow It is expected this week. But on its own, this is an epic downpour It cannot last for decades of hot, dry weather.

Across the West, precipitation is measured across “water yearFrom October 1 through September 30 of the following year. Cities like Sacramento It has already received more than twice as much rain this winter as it did in the entire water year. The rain filled reservoirs and waterways that were only in a small part capacity last year. Reservoirs usually help drain water throughout the year. However, relentless storms have overwhelmed the drainage, creating dangerous and fatal floods.

A boy and girl ride their feet through the deep waters that flood the street, encroaching on porches and garages.

Most of California’s heavy rain in recent weeks flows into the ocean and does little to alleviate the massive drought.
Bronte Whitpen/San Francisco Chronicle via Getty Images

Much of the water that was delivered to the Golden State in this month’s storms now flows into the ocean instead of being supplied for the rest of the year. This is due in part to inadequate infrastructure and restrictions on how quickly the landscape can absorb water. But it is also due to water management decisions, including deliberately limiting water storage in reservoirs below capacity due to flood control requirements.

The combined stress of massive droughts and the urgency of massive rainstorms “puts an exclamation mark on the need for creativity in finding ways to get rid of some of this water that’s coming fast and furious at us,” he said. Thomas HarterProfessor of Earth, Air and Water Resources at the University of California, Davis.

Several efforts are already underway to increase storage capacity in the state, from improved forecasting to building new storage facilities to intentional flooding to allow underground layers of water-permeable rock known as aquifers to refill. But as average temperatures rise, the West Coast faces the possibility of more frequent and extreme weather weather injury between wet and dry, which further stresses the water infrastructure.

Drought and heavy rains are putting pressure on California’s water storage

There are four main places California can store water: in soil and vegetation, in mountain snows, in surface reservoirs, and in aquifers. According to Harter, the ongoing massive drought and recent atmospheric rivers have stressed it all out.

Years of drought have dried out and compressed soil sediments, making it paradoxically difficult for them to absorb water. Then, during heavy rains, dry riverbeds and streams turn into sleighs that quickly carry water downstream. This, in turn, leads to flooding. Meanwhile, the grasses and woodland that used to anchor the soil are also dead in many areas of the state, and since massive wildfires in recent years have left burn scars through the pine and chaparral forests, this heavy rain plus rough, bare soil is a way to go. prepare the Mudslides.

Snowpack, on the other hand, stores huge amounts of water during the winter and slowly dumps it throughout the warmer seasons as it melts. Until recently, it was the Sierra Nevada snowpack – which usually meets 30 percent of California’s water needs – They experienced winters with warmer temperatures that resulted in more precipitation falling as rain rather than snow. Last year, the Sierra Nevada was at 38 percent of its capacitythe lowest levels in seven years.

This winter, parts of the Sierra Nevada mountains are snowing more than 260 percent From average levels for this time of year. This bodes well for the water supply in the West. But snow is not immediately accessible for drinking, and changes in weather such as an early season heat wave can begin to deplete these reserves before they can be used. “While some places are setting records for snow on the ground in mid-January, there is still a long winter ahead and weather patterns can change,” Keith Musselmansaid a scientist at the University of Colorado Boulder’s Arctic and Alpine Research Institute in an email.

Drought and hot weather have reduced water levels in reservoirs as well. California master tanks can stock en masse 45 million acres of water. An acre foot of water is enough to cover an acre of land one foot deep, about 326,000 gallons. This adds to the annual water needs of two households.

Currently, the main reservoirs of water levels such as Shasta and Oroville remain below the historical average half of its total capacity. That’s because cabinets have two functions that can clash. The first is to store and provide water for drinking and farms, and the other is to help prevent floods. Water managers deliberately leave some overhead space in reservoirs, sometimes up to half their capacity, to retain runoff from potential storms later in the season.

Water flows through a spillway at Nicasio Reservoir in California after heavy rain. Many reservoirs release water rather than supply it in order to leave room for runoff from future storms to collect.
Justin Sullivan/Getty Images

This leaves the groundwater, which acts like a savings account for water. In a normal year, groundwater provides about 40 percent of the state’s water supply. During droughts, this share can rise to 60 percent. Groundwater holds out 1300 million acres of water. “This is where we have a lot of room to store that water,” Harter said.

The problem is that it takes time for water on the surface to seep into aquifers underground. And with more rooftops and farmland, there are fewer rooftops in California to recharge their reserves. With a massive drought, Californians were increasingly relying on groundwater faster than it could be refilled, and even two years ago, that process was He went unchecked.

The overdraft of groundwater reserves also brings with it a set of its own environmental problems. Streams and other water flows fed from groundwater can dry up. Salt water can intrude and contaminate stores. The water table is dropping, requiring access to deeper wells. In some parts of the state, towns and farms are digging more than a thousand feet deep to get to the water. Currently, 64 percent Of the groundwater monitoring wells are below normal level, while 10 percent are above normal.

It all adds up to a situation where despite the rain, the West Coast is still struggling to save it. “What we’ve been doing this year so far is putting a lot of money into our wallet,” he said. Benjamin Hatchet, assistant research professor of atmospheric sciences at the Desert Research Institute in Reno, Nevada. “We hope to put some of that back into our savings account.”

California could store more water, but it’s getting tougher

Improving water infrastructure is a slow and expensive process, but efforts are underway. Many reservoirs operate under guidelines from the US Army Corps of Engineers that limit the amount of water they can hold at a given time in the season. This means that some reservoirs allow water to be released preemptively to leave room for runoff from storm surges that never arrive.

Now there is a drive to make these stores adaptable. In reservoirs like Lake Mendocino, water managers take advantage of Weather forecast improvements. If they don’t expect big storms in the coming weeks, they allow the reservoir to store more water for the winter. If there is rain on the horizon, they can pre-free some of their belongings.

“This is state of the art, and it’s being tested in several ponds in California,” Hatchett said. “We view it as one of the most promising potential adaptation strategies for increasing climate variability.”

Another strategy for Floodplain restoration So that the accumulated surface water can replenish groundwater. For decades, the state has tried to limit flooding in areas like the Central Valley to protect farmland and development. Now, the California Department of Water Resources is devising strategies to allow floodwaters to build up, sometimes Managed recharge of the aquifer. Farmers can, for example, allow fallow fields to flood. There is, too New laws Controls the amount of groundwater that water communities can extract.

In an aerial view, a car drives through flood waters on January 11, 2023 in Planada, California.

Many parts of California have already received twice as much rain as is typical by this time of year.
Justin Sullivan/Getty Images

The state is pursuing new reservoirs as well, but most of the ideal sites have already been taken, land values ​​have increased, and construction costs have gone up, so it is becoming more and more expensive. “We’ve gone too far in terms of expanding our surface water reservoirs,” Harter said. California agreed Seven water storage projectsbut they had been languishing in the planning stages for nearly a decade and none of them were ever built.

All of these measures—increasing reservoir storage, building new infrastructure, restoring floodplains—will still retain only a fraction of the recent rains and will mitigate a fraction of the mega-drought.

California also has to consider how water levels might affect concerns like wildfires. Heavy rains early in the year can fuel a bumper crop of fast-growing plants. “If that plant grows and then dries up soon, early in the spring, then we have a big, prolonged bushfire problem,” Hatchett said. “That’s why we want to keep the rain coming into the spring to keep those plants and grasses happy.”

The climate is also changing. Heavy precipitation events It is poised to become more common as average temperatures rise. This means that California could experience periods of more intense rainfall in the coming years, in many cases followed by dry spells.

So, as Californians may be tired of the wet weather, the state will still need more rain throughout the year to meet its water needs and stop other problems. Floods and droughts remain pressing concerns and the country will have to prepare for both extremes.



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