If the water is lost to deep percolation and surface runoff, then crop production levels would reach 5 tonnes per hectare and perhaps up to 7.5 tonnes per hectare, assuming that plant nutrient availability is non-limiting. In reality, only a small fraction of rainfall is used by plants (through transpiration), and the rest is channelled into non-productive use or lost as evaporation. Water stress, particularly during critical growth stages, reduces crop yield and may even damage the entire crop.