Long droughts can be disruptive and dangerous for many sectors including agriculture, water supplies, fisheries, health, and infrastructure. They cause river and reservoir levels to drop, making them particularly straining for farmers. The 1976 drought in the UK made an estimated £3,500 million worth of crops fail. They can also be extremely dangerous – it was drought conditions that allowed the so-called ‘King fire’ of California to spread so quickly in 2014.
One of the challenges of managing droughts is that they are hard to predict. Their long, extended nature means current technology can't give more than one month’s warning.
Their drawn-out nature also means that the term ‘drought’ has no exact definition. The common understanding that droughts are a space of abnormally dry weather isn't very useful as what's ‘abnormal’ changes from one region to the next. Bali is so wet that six days without rain is enough to create a drought, while in Libya it is pretty normal for nearly two years to go by without any rain at all.
CEH Fellow Terry Marsh has written this short blog post which examines "What is a drought?"
A drought’s slippery definition means it is sometimes easier to refer to them by their causes or impacts:
- hydrological drought - refers to a lack of water in all parts of the water cycle
- meteorological drought - determined by the number of days without rain
- agricultural drought -focuses on the amount of water in the soil
- socioeconomic drought - a lack of water means that demand for an economic good exceeds the supply