Potatoes require 500-700 mm of water over a typical 120-150 day growing season, according to FAO Irrigation and Drainage Paper 56. For shorter-season crops (~90 days), the requirement is 350-500 mm, while hot/dry irrigated systems like California's Central Valley or Egypt may need up to 800 mm.
The daily water demand varies significantly by growth stage. During peak tuber bulking, potatoes use 5-8 mm per day (FAO), with some sources citing 4-7 mm/day during this critical period. The crop coefficient (Kc) ranges from 0.45-0.50 at emergence to 1.05-1.15 during full canopy coverage, then drops to 0.70-0.75 at maturation.
Water Use Efficiency: Potatoes are exceptionally water-efficient, producing 4-7 kg of fresh tubers per cubic meter of water used (FAO). This translates to approximately 200-250 liters of water per kg of tubers. The CIP notes that potatoes produce up to seven times more food per unit of water than cereals — wheat requires 0.6-1.0 kg/m³, maize 1.2-2.0 kg/m³, and rice only 0.4-1.1 kg/m³.
The most critical period for water supply is during tuber initiation and early bulking (30-60 days after planting), when even brief drought can reduce yields by 20-30% according to research published in Potato Research. Water stress during the bulking phase reduces yield by 10-30% per week of stress (Shock et al., 1998, American Potato Journal).