Esidronio Arreola never gave much thought to the well that so reliably pumped water to his traditional clapboard house in the foothills of the Sierra Nevadas. But one day in March, he opened the tap and all he got was air.

Through the searing summer heat, the Mexican immigrant to California’s Central Valley and his family endured a daily routine of collecting water in his pickup truck from an emergency communal tank, washing from buckets and struggling to keep their withering orchard alive while they waited for snow to return to the mountains and begin the cycle of replenishing the aquifer that provides water to almost all the homes in the region.

But as more of Arreola’s neighbours in East Porterville, a ramshackle, low-income town in sprawling Tulare County, reported their wells running dry, and state officials warned that the most severe drought in living memory may well extend into 2015 and beyond, he realised he might not have water for years to come.

So Arreola, who makes his living dealing in old fridges and washing machines from his garage, bit the bullet and borrowed the lion’s share of the $11,000 it cost to drill a new well four times as deep as his old one. In mid-November, seven months after the pipes went dry, water began flowing to his taps again. Arreola just doesn’t know for how long.

Yet for all the difficulties, he considers himself fortunate. “We’re among the lucky ones. It’s weird to say that, but our old well was shallow and ran dry early – so, once we decided, we only had to wait a month for them to start drilling a new one. Now the waiting list is a year and I hear the price has gone to $17,000,” he says.“There are a lot of people who cannot afford a new well. Even if you drill one, you don’t know how long it will last.”

Spray fan: Daniel Arreola and his father Esidronio use their new well after not having running water for over six months. Photograph: Barry J Holmes for the Observer

At the other end of Tulare County’s 4,800 square miles, Chris Kemper is the principal of the poorest school in California: Stone Corral Elementary. The water supply to his entire small town of about 500 people, Seville, stopped in April when its collective well ran dry.

“We had sponge baths, like in the army. Doing that for a week or two isn’t bad but for months – it’s difficult. Well, it’s awful. The school found it harder and harder to function. When the kids would flush the toilet nothing would happen,” says Kemper. “If you can imagine going to an underdeveloped country, it was worse. No potable water. It was a humbling experience. You figure you’re here in California, which is a rich state in a developed country, but you turn on the water and it comes out in drips.”

The only supply for Kemper and his eight children through a scorching summer was bottled water delivered by the county’s emergency office.

“We used that for bathing. We used it for washing our clothes,” he said. “It really made you manage your life differently. It changed how we think about water. You appreciate just how precious water is in our lives.”

Eight decades ago, the worst drought in living memory helped drive hundreds of thousands of people from Oklahoma’s Dust Bowl to central California in search of work and a future toiling on the fruit farms that fill the San valley. It’s a part of the American epic immortalised in John Steinbeck’s bitter novel, The Grapes of Wrath.

In time, many of the “Okies” were replaced by Mexican migrant workers as the Central Valley farms grew to produce up to half of the US’s fruit, nuts and vegetables. But now the 400-mile long agricultural basin of four million people is facing its own life-changing drought that, like the Dust Bowl of the 1930s, is hitting hardest those with the least.

California’s governor, Jerry Brown, declared an emergency in January as 2013 was the driest on record in the state, and this year is little better. The federal authorities say more than half of California is enduring “exceptional drought” – the highest category. The state’s main reservoirs are at an average of only 40% of capacity.

A lot of bottle: Chris Kemper, principal of the school in Seville, which has had to rely on delivered water. Photograph: Barry J Holmes for the Observer

At the beginning of the year, John Laird, the state’s secretary for natural resources, told the US Congress in a letter that “California is experiencing the worst water crisis in our modern history. We are in our third consecutive year of below-normal precipitation and this year’s snowpack – on which 25 million Californians depend as the source of their water supply – currently is only 10% of what it should be.

“As you know, California’s climate is such that it is generally dry for almost half the year – and we rely on rain and snow during the winter season to carry us through the year,” he wrote. “Conditions – in terms of both supply and quality – are unprecedented and serious.”

A recent study for the National Science Foundation, a US government agency, found that the drought is “very likely” linked to climate change. The immediate cause is a region of high atmospheric pressure over the Pacific, diverting storms away from California. Known to scientists as the “Ridiculously Resilient Ridge”, it is blamed on rising greenhouse gases and the study described its persistence and intensity as “unrivalled”. Other studies say California is part of a “mega-drought” in the western US that could stretch for decades, even if the rains return periodically.

The sharp drop in water levels in rivers, canals and dams is responsible for what a University of California report called “the greatest absolute reduction in water availability for California agriculture ever seen”.

That has prompted farmers to seek alternative sources of irrigation for ever-more-demanding crops. Drought-resistant cotton has given way to more profitable but thirsty plants such as the massive almond farms which now grow 80% of the world’s supply – farmers are now drilling under their fields to tap into aquifers. But that has only added to the pressure on groundwater already depleted by lack of snow on the mountains. As agriculture drew heavily, wells serving individual houses and small communities began to suck air.

The impact in Tulare County, where some of the richest agricultural areas in the US sit alongside people with the lowest incomes, is starkly on display. There are queues at communal water tanks and the irrigated fields plump with crops abruptly give way to hard-baked soil forced to sit fallow.

‘We bought in three truckloads of water and got rid of it in eight hours’: Andrew Lockman, manager of the Office of Emergency Services for Tulare County, being interviewed. Photograph: Barry J Holmes for the Observer

Within Tulare County, where one-third of the population lives below the poverty line, nowhere is harder hit than East Porterville – a community of about 7,400 people. More than half of homes are now without running water and many of the remainder wonder how long their wells will last. “Back in January, the county was getting these sporadic calls: ‘Hey, my well’s gone dry,’” says Andrew Lockman, head of Tulare County’s Office of Emergency Services, who is in charge of relief efforts. “By June, there were over 800 households with dry wells. In East Porterville, we brought in three full truckloads of bottled water – 15,552 gallons of drinking water – and we got rid of all of it in about eight hours.”

Lockman installed a 5,000-gallon tank in front of the fire station with a motorised pump. A steady stream of residents make the daily journey to fill buckets and drums.

Houses without running water – mostly small, low-slung bungalows on plots marked out by wire fences – are often signalled by large blue storage barrels. Many of the houses are wood with corrugated iron roofs that drive people outdoors in the scorching midday heat. The sun has drained colour from their walls and paint is luxury for families struggling to pay for utilities. If there are gardens at all, and mostly there is only bone-dry dirt, they have withered for want of water. No one is going to waste it on grass, although some, like Arreola, are trying to save sources of food. He’s been using waste water to keep alive a small orchard of kiwi fruits, and lemon, apple and cherry trees. There has been no fruit this year but the vines have survived.

If the drought has taken a physical toll it doesn’t seem to show on faces already weathered by years in the fields. Some seem to shrug off the added hardship as just another price of poverty. Lockman has been struck by the stoicism of people. “We’re seeing a lot of neighbour helping neighbour,” he says. “We see a lot of folks in East Porterville who say, ‘You’re out of water, hook up to mine,’ knowing full well that theirs is low and then theirs goes out. Choosing to help their neighbours to their own detriment over time is pretty refreshing to see.”

For all that, some residents in low-income communities feel shunned by more affluent towns close by. The city of Porterville has for years resisted incorporating East Porterville into its municipality, and hooking it up to a reliable water system, out of a suspicion that it would drag down property values.

And as grateful as residents are for the assistance they receive, there is worried talk in some low-income communities that people could lose their homes because of regulations requiring houses to have running water. Steve Worthley, a member of Tulare County’s council, the Board of Supervisors, is aware of the concern but does not entirely allay fears. “We’re not doing that and we have no desire to, but as a long-term situation, people cannot live in a home without water,” he says.

With winter setting in, Lockman decided it was too much to ask people to wash in buckets, so in mid-November he moved in two articulated lorries with shower stalls. Some residents had already taken to using the showers at a camp site at a neighbouring artificial lake.

Success Lake: fishing well below the usual shoreline. Photograph: Barry J Holmes for the Observer

Water levels have fallen so far that much of Success Lake’s 150ft-high dam is visible. A road that served as a boat ramp now ends abruptly 35ft above the water. “Have you seen the lake?” says Katherine Hampton, sitting on the doorstep of her wood cabin home on the edge of East Porterville. A large broken window is roughly patched up with a piece of board. “It’s normally so full. It’s so down right now you can walk across it.”

Hampton, 32, has five children and is pregnant with her sixth. The drought has cost her husband, Johnathan, his job. “I haven’t worked in eight months,” he says. “I work in agriculture doing anything: transplanting trees, yard work, tilling ground. I was going around all the farms asking, and everyone was saying ‘no’. I thought maybe they had a problem with me. I went to four or five different farms in Tulare. Then I came across a big old sign: ‘Water shortage. No jobs for farm hands.’ So I came home.”

Hampton gets no unemployment benefit because he didn’t hold a permanent job. He takes the hardships in his stride. “I do anything I can do. Cleaning people’s houses when they move out. There’s not much work. We get by because we don’t spend much,” he says. He’s a man of God and says the drought is part of the Lord’s plan. “People are small in their faith and bring this on themselves,” he said. “I’m hoping people start praying there’ll be some water.”

The University of California report estimates that the drought has already cost the state’s agricultural industry $1.5bn and 17,000 jobs. But the dependence of so many people in Tulare County on agriculture for a living has largely muted any criticism of farmers for drilling deeper and pumping more. “People see farms getting water as a necessity,” said Kemper. “They’re more resentful of the water going to the cities than to the farmers.”

The drought has exacerbated a less visible but widespread issue: pollutants contaminating the underground water. Nitrates from fertilisers and septic tanks have been feeding into the groundwater for decades. A University of California study found that one in 10 people in the Central Valley are exposed to unsafe drinking water. But as water levels have fallen, the nitrates – which are dangerous to young children, nursing mothers and the elderly – have become more concentrated and the drinking water even less safe.

Susana de Anda, director of the Community Water Centre in Tulare County, which campaigns for access to clean water, said more than one million people in California are drinking from contaminated supplies. “More residents are getting notifications not to drink the water because they are over the legal limit of the contaminant,” she says.

Tulare’s health department has issued thousands of letters to users of municipal systems warning against drinking the water, but no one knows how many individual wells are also affected because they are not tested.

The situation in Seville was so bad that in 2011 it attracted the attention of a United Nations investigation into lack of access to clean water. Its report warned that what amounts to discrimination in the provision of water and sanitation in parts of the US “may intensify in the coming years with climate change and competing demands for ever scarce water resources”.

Earlier this year, Seville’s school board became so alarmed at tests showing high levels of contamination that it decided to start buying bottled drinking water for students at a cost of $700 a month from Kemper’s budget. “That’s money we’re spending that could buy a laptop a month for the school,” he says.

But the drought has, to some extent, proved fortuitous for Seville because one crisis has drawn action on another. The state and federal authorities did little over the polluted water, but once there was none at all, funds were rapidly found to drill a new well. It was built and on line within a week in August – a speed Lockman describes as unprecedented – at a cost of more than $250,000. “Frankly, we kind of look at that as a silver lining of the story,” says Lockman. “If we didn’t have all the other drought issues going on, we probably wouldn’t have been able to make that happen.”

But Lockman says that Seville is probably not an example for a lot of other towns. For a start, it already had an established municipal water system. “There’s going to be a lot of places where there’s nothing around,” he says. “East Porterville is probably our biggest challenge. We’ve looked at putting in a new water system. It’s really not viable to do, largely because that area has nitrate contamination.”

The crisis has forced California to think about long-term management of the ever-increasing demand for its limited water supplies. A state-wide conservation campaign has reduced water consumption in urban areas by about 10% over the past year, even if some of southern California’s wealthiest residents have come under fire for continuing to water the vast lawns of their sprawling mansions as if there was no crisis. Individual cities have introduced a slew of initiatives, such as San Diego’s recycling of wastewater for drinking.

In October, the governor approved new laws to regulate the use of underground water supplies for the first time in the state’s history. Worthley says that should include rationing in agriculture.

“There are going to be some very serious issues in agriculture about what is going to be a sustainable yield of water,” he points out. “My guess is that there’s going to be a monitoring of the wells to see how much they’ve been taking out and a limit on how much they can remove. You’re going to have to decide: how much of my land do I allow to go fallow? Do I grow a different kind of crop?”

Farmers are not likely to accept further restrictions without a fight. Relief programmes are in part funded by federal money and Congress in Washington is considering its own legislation to address the crisis. But California’s leaders fear federal laws being used for political ends – particularly to weaken environmental standards at the behest of large agricultural corporations and some cities, which object to water being shifted from farms to fish conservation.

While the severity of the drought in some ways matches that which created the Dust Bowl of the 1930s, the consequences so far are very different. For a start, it has not prompted a mass migration. Kemper came to Seville from LA because he was weary of the problems and violence of an inner-city school. Back then he wondered why modern day agricultural workers didn’t follow the example of the Okies in the 1930s and go somewhere else.

“When I lived in Los Angeles and I’d hear about drought I used to think, ‘Why don’t those people just move?’ But living here, you see why. Where do you go? When you’re a poor family, to move is very expensive. You have to have a job and most people here work in agriculture and those jobs are hard to find elsewhere,” he said. In any case, a house without water is almost impossible to sell.

But even in Seville, with its new well, there is a recognition that, with warnings of waves of drought to come, it is only a solution for so long as there is water under the town. “It’s the future we’re afraid of,” says Kemper. “What happens if this isn’t the end? Life is going to change totally in our society. When water ceases, what do you do? If we don’t have agriculture, we don’t have anything here. If water goes, it’ll turn into another wasteland.”