What do the chalk layers form beneath the London area with the uplands of the Chilterns and North Downs?
Is chalk porous?
How is water in London normally extracted?
Though boreholes and Wells
What became exploited and when?
During the 19th and the first part of the 20th century, the chalk-basal sands aquifer had been increasingly exploited.
Why was the chalk-basal sands aquifer becoming increasingly exploited?
Due to increased industrialisation and the associated development of groundwater sources.
When was the peak of abstraction?
How far did the groundwater levels in central London drop in the 1960s?
Groundwater levels beneath central London had dropped to 88m below sea level
What did the 1960s drop in water lead to?
A large depression in the water table and a small cone of depression to the east below the River Roding in Essex
What has happened since the mid-1960s?
Industries such as brewing in central London relocated or were closed down
What replaced the industries that closed down?
Economic activity turned to service industries and commerce rather than heavy industry.
Why did groundwater levels start to recover?
There was no more heavy industry to abstract the water
By how much each year were groundwater levels increasing by the early 1990s?
By the early 1990s, groundwater levels were recovering by as much as 3m/year
What is a threat concerning rising groundwater levels?
The London Underground and building foundations could be affected by flooding.
What does GARDIT stand for?
General Aquifer Research, Development and Investigation Team
What has led to the implementation of GARDIT?
The threat of rising groundwater levels
What is the aim of GARDIT?
To control water levels
What does GARDIT do?
Carefully manage abstraction and artificial recharge which it had largely achieved by 2000
Why is there a risk of saline intrusion around the River Thames?
The chalk outcrops around the River Thames run from Greenwich to Woolwich and when groundwater levels are lower than the water level in the River Thames, saline water can enter the chalk aquifer.
What has happened to groundwater levels between 2000-2014 in west London?
Groundwater levels have risen by 4-8m however they are now levelling off.
Why have groundwater levels risen between 2000-2014 in west London?
This has been due to limited abstraction in the area
What has happened to the groundwater levels between 2000 and 2014 in central and east London?
They have fallen in the order of 5-7m since 2000
Why did groundwater levels in London decrease between 2000 and 2014?
Due to increased abstraction
What has happened to groundwater levels in south London?
They have fallen more than 2m, with falls of up to 12m concentrated around the many large public water supply abstractions