Monday's session was attended by Israeli Justice Minister Tzipi Livni and Palestinian negotiators Mohammed Shtayeh and Saeb Erakat, the official said.
The official did not elaborate, but the question of water rights is one of the core issues that must be settled in any peace deal.
Israel controls most of the underground water resources in the West Bank, and the Palestinians want a more equitable share of them.
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US Secretary of State John Kerry said on Monday that negotiations, which take place under an American-imposed media blackout, have "intensified."
Speaking in Paris, Kerry said that, since the end of July, 13 direct meetings have taken place, including three in the past four days.
"The pace has intensified, all the core issues are on the table and they have been meeting with increased intensity," Kerry said.
"It is no secret to anybody that this is and remains a difficult process, there is no shortage of passionate sceptics," he added.
Kerry will be meeting Israeli Prime Minister Benjamin Netanyahu in Rome on Wednesday.