San Francisco, Dec 16 (IANS): Preparing for a fourth consecutive dry year amid extreme drought conditions, the largest supplier of treated water in the US has declared a regional drought emergency for all of Southern California.

The Metropolitan Water District of Southern California called upon water agencies in the region to immediately reduce their use of all imported supplies, reports Xinhua news agency.

The Metropolitan Water District of Southern California is a state-established cooperative that, along with its 26 cities and retail suppliers, provides water for 19 million people in six counties, including Los Angeles, the nation's most populous county.

"Over the last three years, communities across the West have experienced the devastating effects of an unprecedented drought. We must be prepared for these conditions to continue in 2023," the supplier saud.

The Metropolitan Water District of Southern California warned that the water-saving call could become mandatory if drought conditions persist in the coming months.

By April, the agency will consider allocating supplies to all its member agencies, requiring them to cut their use of imported water or face steep additional fees on water purchased from the agency.

It called on the entire region to further cutback water use as all imported water supplies are stressed by drought and climate change.

The agency on average imports about half of the water used in Southern California from the Colorado River and from the northern Sierra, via the State Water Project (SWP).

The past three water years were the driest in California's history, resulting in record-low SWP deliveries to Southern California, said the agency.

The long-term drought in the Colorado River Basin has left lakes Mead and Powell -- the nation's two largest reservoirs --dangerously close to levels that would no longer allow water to be released for use by cities and farms.

In response, the federal government has called on Colorado River water users to curtail their use in 2023 and 2024 by as much as 4 million acre-feet a year - the total amount used by California in a year, according to the news release.

Colorado River, one of the principal rivers in the southwestern US and northern Mexico, is facing alarming constraints as a result of a megadrought amid changing climate.

A study published in February in the journal Nature Climate Change suggests the megadrought that has ravaged the US West for the past 22 years is the worst in at least 1,200 years.

Authorities said that California had the driest January, February, and March in 2022 in over 100 years.

California ended Water Year 2022 on September 30 with total annual average statewide precipitation at 17.9 inches and 76 per cent of historical average.

Statewide reservoir storage ended the water year at 14.70 million acre feet and 69 per cent of historical average, according to the California Water Watch.