DAVIS California (Reuters) - At the University of California's prized winemaking institute near Sacramento, a sleek metal wine crusher on Thursday morning let out a deep rumble and began to shake, jostling grapes made sweeter by the state's ongoing drought into sticky juice.
Dry conditions have made this year's crop ripen early, and winemakers across the state are picking and crushing their grapes weeks ahead of the usual harvest time as the lack of water has caused them to ripen faster than usual.
"All right, let's go!" hollered Chik Brenneman, resident winemaker at U.C. Davis, to his team of four student workers.
A teal-colored tractor dumped a square plastic drum of freshly harvested Chardonnay grapes into the mouth of the roaring machine and an earthy, tangy smell like fall leaves and sour fruit filled the air.
The early harvest has stoked winemakers' concerns that ongoing drought conditions could pose a serious threat to wine quality next year, since grapes that ripen too fast can become too sweet for winemaking.
California is in its third year of a catastrophic drought that has threatened a half-billion acres of farmland and strained water supplies for 40 million people.
The grape crop has mostly been protected, as many growers have managed to spend extra cash on underground well water to protect the quality of their vines.
But well water is an expensive and limited resource, and underground wells throughout the state are becoming drier.
Already, this year's grapes have reached their peak sweetness faster than last year's, Brenneman said, and if the trend continues, it could be difficult to make good wine with the 2015 crop.
"This has been a tough year," said Brenneman, whose students made 300 gallons of juice on Thursday. "Sugar (levels) are rising very rapidly."
California is the fourth-largest wine producer in the world and brings in more than $60 billion in state revenues each year.
But while grapes are not the most water-dependent crop in California, winemaking can use more than six gallons of water for every gallon of grape juice it processes.
"Most people spent extra money to get water to their vines this year," said winemaking scientist Anita Oberholster. "Others had to be more creative to get water."
Oberholster and Brenneman are part of a team of Davis scientists who are working to invent new ways of capturing rain water and re-using water that has been discarded during the winemaking process to irrigate crops.
Among their areas of study is the question of whether using recycled water, as the wine industry giant and filmmaker Francis Ford Coppola and others have done, hurts the quality of the grapes or the wine that is produced from them.
So far, Oberholster said, the results have been positive, although the group is still studying the impact on grapes used for red wines such as Cabernet Sauvignon.
"People are getting really excited," said Oberholster. "Because if we can re-use our waste we can save tons of water."
Editing by Sharon Bernstein, Bernard Orr