Why Recent Rain Doesn’t Mean an End to Drought
After a long, hot and exceptionally dry summer, recent rainfall has been a very welcome relief. But for our rivers, a few wet days aren’t enough to undo the effects of a prolonged drought.
The East Anglian region continues to experience the effects of an exceptionally dry period. Rainfall in July was just 3% of the long-term average, while August saw only 34% of normal rainfall. The Environment Agency is also reporting soil moisture levels around 30% below average.
Our landscapes are thirsty
After such a prolonged dry spell, our soils are exceptionally dry and, in many places, hard and compacted. The ground has lost a huge amount of moisture over the summer, so when rain finally arrives, the first job is to replenish the soil itself.
Dry, compacted soil can also make it much harder for rain to soak in. Instead, water can run off this impacted surface, particularly when rainfall is heavy, increasing the risk of localised and flash flooding rather than immediately benefiting our rivers and groundwater.
This video from the University of Reading shows an experiment by Dr Rob Thompson demonstrating how much more difficult it is for water to soak into dry, hard earth after a heatwave.
Once the soil has had a chance to recover, rainfall can begin to infiltrate deeper into the ground. From there, water can slowly make its way into groundwater stores, streams and rivers, and eventually help replenish reservoirs.
Drought has a direct impact on our rivers
Prolonged dry weather means less water is entering rivers from rainfall, groundwater and smaller tributaries. As river levels and flows fall, rivers become shallower and warmer, while habitats can shrink and water quality can deteriorate. Low flows also put additional pressure on fish, aquatic plants and invertebrates, which depend on sufficient clean, cool, flowing water to survive.
This is why a few days of heavy rain don’t necessarily mean that river levels will suddenly rise. After an extended drought, it can take sustained rainfall over a much longer period for water to move through the landscape and start restoring the water that has been lost.
Drought recovery takes time
There is also no single amount of rainfall that signals the end of a drought or that will bring an end to water restrictions and Temporary Use Bans (TUBs). Water companies and the Environment Agency look at a range of factors, including river flows, groundwater levels, reservoir levels, soil moisture and the wider impacts on nature.
The recent rain is certainly encouraging, but nature needs sustained wetter weather over the coming months to recover from the prolonged dry conditions. In the meantime, using water wisely remains important. Every drop we save helps to reduce pressure on our precious water resources and the rivers and wildlife that depend on them.
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