On 2nd October Tasmania and Victoria were experiencing bushfires in Spring. On the 7th of October the Bureau of Meteorology (BOM) started issuing multiple media alerts. The Indian Ocean had cooled down creating dryer conditions, September was the third driest on record and October is likely to be one of the warmest on record. On 8th October the BOM issued special climate statement 52 for unusual early season heat for southern Australia. Inland Queensland and Western Victoria have been dry for three years. While the big dry has generally stayed away from Coastal cities Townsville water storages have reached 30%, triggering Stage 2 water restrictions.
El Nino is a complex, global weather pattern that usually results in below average winter spring rainfall over eastern Australia. The actual relationship between an El Nino event and a drought is quite indirect and the El Nino events in the Millenium drought were much less severe than those in 1997. This El Nino has been hovering in the wings for a couple of years, but it has swung in with a vengeance now and is predicted to be a record breaking event.
So what can we expect? According to Michael Roderick from ANU there are different kinds of drought. Increased temperatures and decreased rainfall in wetter areas leads to more evaporation, less runoff and decreased streamflow which affects our dams. However in dryer areas higher temperatures and decreased rainfall means less water in the soil and plants. This leads to LESS evaporation, and therefore less cooling effect. Higher temperatures lead to less clouds, more blue sky, and even less rain. This kind of drought is slow and merciless across large parts of inland Australia. The impact is well established, stock losses, bushfires, dust storms and long term declines in ground water. The November-January BOM outlook is for southern heatwaves and bushfires.
Dry conditions affect another environment, the cities that most of us live in. An increasing number of BOM Special Climate Statements are about unusual heatwaves. There is not much green space in our cities and when it dries out it is like someone has switched off the air conditioner, the cooling effect dries out too. Research by Nigel Tapper at Monash University shows a 20 degree difference in air temperatures above road pavement and a shady park. On a hot summer day the centre of our cities could be as much as 4-6 degrees warmer than the surrounding rural areas. This might not sound like much but heat stress is a silent killer and every degree matters. Based on research on the 2009 Victorian heatwave there seems to be a temperature tipping point above which there is jump in mortality.
The excellent work done by 202020 Vision to increase green space in our cities is very important in this context. This is another role for water in this urban scenario. Irrigating urban forests and green spaces will reduce temperatures, improve air quality and could save lives. Even in a drought there are rain events, capturing rain water and storm water and retaining it to keep plants alive could be an important drought response.