Yield = 6 tons = 6000 kg per hectare.
Water use = 2000 mm.
Water Use Efficiency (WUE) = \( \frac{6000 \, \text{kg}}{2000 \, \text{mm}} = 3 \, \text{kg/mm} \)
Expressed per hectare per mm: \({0.3 \, \text{kg/he-mm}} \)