Impacts of Drought
Droughts are natural events that occur when there are long periods of below average rainfall. Droughts lead to water shortages and also have serious consequences for the environment. This is why we need to conserve water, as it is difficult to know when a drought will occur and how long it will last for.
How severe the impacts are will depend on the amount of water in storage (from rainfall in previous years).
Drought and river health
Drought affects river health in a variety of ways. During drought, streams have less water flowing into them than they normally would, and this can lead to poor water quality. Some streams can stop flowing completely, leaving only a series of pools. These pools provide critical refuge for organisms such as fish, which allow them to recover once droughts break.
We plan for the effects of drought on river health through both short- and long-term management actions, such as ongoing monitoring of water levels and water quality in key refuge habitats, and in some cases, by implementing emergency response plans. Waterwatch volunteers play a key role in the ongoing monitoring of many of these drought refuges.
Drought and environmental flows
During drought, it is not just our water supplies that are affected. Environmental flows (the amount, timing and quality of water that flows in a river or creek) are also reduced, which in turn affects the health of our rivers and creeks.
Since different species rely on healthy rivers and creeks to survive, it is important that we plan for drought. One way we plan for drought is to examine the water requirements of different species. During a drought we must manage environmental flows downstream of a reservoir to ensure habitats are protected (as well as our water supplies).
We also need to set rules about pumping water from rivers to ensure environmental values are protected during drought. For example, there are legal limits around when Melbourne Water can pump from the Yarra into Sugarloaf Reservoir. Restrictions are also placed on businesses (waterway diverters) that draw water from the Yarra to make sure this important river stays healthy.
More information:
- Water for the environment
- Stream flow management
- Waterway diverters – Drought Response Plan
- eWater CRC – Drought Science website
Drought and bushfires
Extremely dry conditions are one of the key ingredients of bushfires. Dry grass, shrubs, leaves and twigs are a bushfire's basic fuel. During droughts even large logs and the green leaves on large trees can become highly flammable.
Australia’s worst bushfires (the Black Saturday bushfires in February 2009) happened during Victoria’s worst drought on record.
Negative impacts of bushfires on our water catchments include:
- loss of nearby vegetation
- fallen and burnt vegetation in the water
- increased sediment and erosion
- reduced water quality
- loss of habitat for birds, animals and fish.
After bushfires comes a period of regrowth in forests – and young trees are thirsty.
Much of Melbourne's water supply catchment area is covered in Mountain Ash, which are among the world's largest hardwood trees. These forests reach their maximum water yield after 120 years or more (following a minimum yield at about 30 years).
Given it takes such a long time for these forests to reach their maximum water yield, it is vital that we protect them from bushfires.
More information: