Although wine grapes don’t need much water during the season, they need to drink frequently and at key times, says Dr. Markus Keller, viticulturist for Washington State ­University. The following are average amounts of water that grapevines use during growth stages. • Bud break to bloom—uses less than 5% of its total requirement, equivalent to less than 1 inch of water. • Bloom to fruit set—uses 15% or 2 to 4 inches • Fruit set to veraison—uses 60% or 6 to 12 inches • Veraison to harvest—uses 20% or 2 to 5 inches