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Water quantity

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water quantity
Changing land management can significantly increase the amount of water stored in the landscape.

Whether it's alleviating soil compaction, restoring wetlands or encouraging water-storing sphagnum mosses, Upstream Thinking approaches can significantly increase water storage and reduce run-off.

Here's why:

Case study - Working Wetlands

Culm grassland ragged robin
 In the Working Wetlands project in central Devon researchers showed that 11 times more water leaves intensively managed grasslands than Culm grasslands during storms.

At Meshaw in the Taw catchment, an area of pristine Culm grassland is situated adjacent to an intensively managed grassland (used for silage cropping) with only a Devon hedge-bank separating them.

Detailed analysis of the soils were undertaken and dipwells installed in both of these fields to monitor soil water levels. The differences were staggering, with the Culm soils storing a massive 277 litres of water per m² compared with only 61 litres /m² being stored in the soils of the adjacent silage field. The main reason for this is the depth of soil, with the Culm soils being 47cm deep, compared with just 27cms for the heavily compacted silage field.

Not surprisingly then, the research suggests that 11 times more water leaves intensively managed grasslands than Culm grasslands during storms, increasing the risk of flooding downstream.

Case Study 2 - Exmoor Mires

sphagnum moss
Restoration of peat bogs on Exmoor has resulted in a third less water leaving the moorland during heavy rainfall compared with three years ago.

By blocking up drainage ditches, the moorland can now hold more water and release it more slowly, reducing potential flooding elsewhere.

In order to evaluate whether the restoration program has been successful so far, Professor Richard Brazier and his team of researchers at the University of Exeter were tasked with monitoring the hydrology, water quality and carbon storage within two experimental sites located on Exmoor. 

Extrapolated across the whole 2000 hectares of restored moorland - which was the 2015 target for the Exmoor Mires Project - the results  indicated that the amount of storm water running off the moorland has reduced by a third, the equivalent of more than 6,630 Olympic-size swimming pools less water entering downstream rivers.

It also indicates increased water storage in the peat of 260,000 cubic metres. Put another way, that's 104 Olympic-sized swimming pools of water removed from the river system flowing down to major population centres like Exeter.

Prof Brazier said: "Across the experimental site we are seeing a rise in water table levels of up to 2.65cm that can be attributed to the ditch blocking and moorland restoration.

"This enhanced water storage could, when replicated across the whole of Exmoor, provide a significant buffer against downstream flooding in rivers like the Exe."

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