Irrigating near Luggate, Central Otago.
Potential evapotranspiration deficit (mm) that is likely to be equalled or exceeded once every 20 years.
Drought is often hard to quantify, and its severity and duration affect different enterprises in different ways.
One way of measuring drought is to calculate the amount of water typically available for a particular purpose, and then estimate the reduction in water available for that purpose during low rainfall seasons.
For example, we can estimate the amount of water that is 'consumed' during normal pasture growth