The new rules will limit watering on public property and impose cuts of up to 36% on water usage from 2013 levels.
The state board drew up the rules in response to Governor Jerry Brown's earlier order to cut water use state-wide.
California is in its fourth year of severe drought, believed to be the worst there in 1,200 years.
The board voted after five hours of public testimony on Tuesday.
Chairwoman Felicia Marcus said it was better "to prepare now than face much more painful cuts should it not rain in the fall".
Governor Jerry Brown has called for "unprecedented action" in response to the historic drought, but a previous voluntary cutback in 2014 did not result in significant usages.
A new survey of water agencies found only 9% savings in water usage since last summer and only several hundred notices sent to water wasters out of tens of thousands of complaints.
Experts say Brown's tough love approach is necessary because so many people are apathetic towards water conservation. About 50% of water used in residential areas is outside the home.
Getting rid of grass will be a huge lifestyle shift for many, but it is the biggest single measure that individual Californians could take to ease the crisis, according to Jay Famiglietti, a senior water scientist with Nasa.
"Drought tolerant native landscape is beautiful - we just have to get over this grass thing," he explains.
"We live in an arid and semi-arid state and we need to start acting that way."
Peter Bowes: Will the Golden State turn brown?
The restrictions cover hundreds of local agencies of very different sizes, with water restrictions from 8% to 36% depending on the city.
It is unclear how the board will enforce penalties as many local agencies have declined to serve notices to those wasting water.
But board officials said they expected dramatic water reductions by June and were willing to add penalties for those lagging behind.
Mr Brown said he would push for fines of up to $10,000 (Â£6,545) for extreme wasters, but he needs approval from the California legislature.
While the vote was unanimous, some cities criticised the targets. San Diego water agencies said they have significantly cut consumption and spent $3.5bn to prepare for dry periods.
"San Diego has lived the horror of what the state is going through right now," Mark Weston, chairman of the San Diego County Water Authority, told regulators.
About 80% of California's water usage is through agriculture. The new restrictions do not cover farms but water deliveries from government reservoir systems have been slashed.

Sum: California's water board has unanimously passed sweeping mandatory drought restrictions for the summer.


They say that so far in 2015 there have been about 25 cases.
In October officials said that Pakistan had its highest number of cases for 15 years, mostly due to militant attacks.
At that time they said there were more than 200 cases across the country.
The number in October exceeded the 199 cases in 2001 but was short of the 558 cases in 1999.
Most polio infections are in the north-western tribal region where militants have targeted health teams.
They accuse doctors of being spies and say the vaccinations are part of a Western plot to sterilise Muslims.
Prime ministerial polio adviser Ayesha Raza said on Wednesday that while it had taken time to eradicate militancy in North Waziristan, the rewards from doing so were "already visible in the polio programme".
Ms Raza told the BBC that polio samples from high-incidence zones - which used to be positive for months on end - were now testing negative again.
The Federally Administered Tribal Areas (Fata) had only reported seven cases so far this year, she said, while Karachi had reported none.
"The army has been a great help in both these areas," Ms Raza said.
"With their help, and with the help of funding from the United Arab Emirates, we have been able to extend immunisation drives to high-risk areas.
"We got access to populations in Waziristan after more than two years. We have also now penetrated some formerly no-go zones in Karachi."
Officials say that in recent months there has also been a clear decline in the number of attacks on polio teams. A number of men involved in such attacks have been arrested.
The BBC's M Ilyas Khan in Islamabad says that while Pakistan is celebrating the latest figures, the two other countries in the world where polio is endemic have done equally well if not better.
Nigeria has reported no new cases this year, and Afghanistan has only reported one.
Our correspondent says that a major chunk of the North Waziristan population who lived under a militant-imposed vaccination ban for several years have now been vaccinated several times over along with their children.

Sum: Polio cases in Pakistan have dropped by 70% this year as troops make territorial advances in the north against militants opposed to vaccination programmes, government officials have told the BBC.


About 30 people were removed from the seven-storey building on Buckingham Gate at around 04:00 GMT.
Bailiffs were called to the property after an application for eviction was made to the High Court on Friday.
The Met said it was concerned the occupiers could see into the royal grounds if they accessed the roof of an adjoining building.
Court documents seen by the Press Association showed a Metropolitan Police royal specialist protection officer raised the "potential security risk" posed by the group.
Snipers stationed on the roof of Wellington Barracks were also in "regular contact" with the owner of the building next-door to raise concerns about the view into the palace gardens from the roof, the document said.
But one of the protesters insisted they were not "going to do anything".
Daniel, one of the 30 people who had been 19 Buckingham Gate, which is believed to be owned by a Bahraini national, said: "It was pretty unprecedented. To just wake up and you are surrounded by bailiffs, they came in stealth mode.
"I opened my eyes to bailiffs on the staircase."
He described the operation as a "swift and silent eviction", adding: "I didn't see them (the bailiffs) turn on the lights until I was outside at the door."
He added he had never experienced an eviction executed so quietly and with such a number of bailiffs.
Asked whether they would move into another property in the Buckingham Palace area, Daniel said: "We have to stay in the area... it would be nice to continue with it."
The squatters, who call themselves the Autonomous Nation of Anarchist Libertarians, have occupied a series of properties in Belgravia, west London, since the start of the year, having been evicted from an empty mansion in Eaton Square believed to have be owned by Russian oligarch Andrey Goncharenko on 1 February.
The group say one of their aims is to highlight the number of empty properties in that part of London, which it believes could be used to accommodate the homeless.
Video footage posted on Twitter by Occupy London shows the protesters leaving the building, which they had re-branded the Rogue Embassy.
Within some of the footage, a man can be heard describing how squatting 100 metres from Buckingham Palace was the "basic aim" of the protest.
Signs stapled to the door of the property, state it is now being protected by a private security firm.

Sum:
Squatters branded a "security risk" to the Queen have been evicted from a mansion close to Buckingham Palace.