Water Extraction Flashcards
How is water extracted to meet public industrial and agricultural demand?
Water is extracted from surface and groundwater.
What happens when there is direct human intervention in the water cycle?
Direct human intervention in the water cycle changes the dynamics of river flow and groundwater storage.
Which area does the River Kennet in southern England drain?
The River Kennet in southern England drains an area of around 1200 km² in Wiltshire and Berkshire.
What type of rock is predominant in the upper catchment of the River Kennet?
The upper catchment of the River Kennet mainly comprises chalk, which is highly permeable.
What contributes most to the flow of the River Kennet?
Groundwater contributes most of the Kennet’s flow.
What are some characteristics of the water in the River Kennet?
The water in the River Kennet, filtered through the chalk, has exceptional clarity, high oxygen levels, and is fast-flowing.
Which urban areas rely on water from the Kennet basin for public supply?
Several urban areas within and close to the catchment rely on water from the Kennet basin for public supply.
What is the population of Swindon, the largest urban area relying on water from the Kennet basin?
Swindon, the largest urban area relying on water from the Kennet basin, has a population of over 200,000.
How does Thames Water extract groundwater from the upper catchment?
Thames Water abstracts groundwater from the upper catchment of the Kennet through boreholes.
What has been the impact of water extraction from the Kennet and its catchment?
Water extraction from the Kennet and its catchment has led to a reduction in flows in the River Kennet by 10-14%, and even up to 40% during dry conditions in the early 1990s. It has also reduced flooding, standing water, wetlands on the floodplain, and the occurrence of springs and seepages.
What are aquifers?
Aquifers are permeable or porous water-bearing rocks such as chalk and New Red Sandstone.
How is groundwater abstracted for public supply from aquifers?
Groundwater is abstracted for public supply from aquifers through wells and boreholes.
What is the upper surface of saturation in an aquifer called?
The upper surface of saturation in an aquifer is known as the water table.
What factors affect the fluctuation of the water table?
The water table fluctuates seasonally and is affected by periods of exceptional rainfall, drought, and abstraction.
When does the water table typically fall and rise in southern England?
In normal years in southern England, the water table falls between March and September due to rising temperatures and increased evapotranspiration losses. Recharge typically resumes in the late autumn.
What is an artesian aquifer?
An artesian aquifer is an aquifer confined between impermeable rock layers that contains groundwater under artesian pressure.
What happens when groundwater in an artesian aquifer is tapped by a well or borehole?
When groundwater in an artesian aquifer is tapped by a well or borehole, water will flow to the surface under its own pressure.
What determines the level to which water will rise in an artesian aquifer?
The level to which water will rise in an artesian aquifer, known as the potentiometric surface, is determined by the height of the water table in areas of recharge on the edges of the basin.
Where is London located in relation to a synclinal structure forming an artesian basin?
London is located at the centre of a synclinal structure that forms an artesian basin.
What rock layers trap the groundwater in the chalk aquifer beneath London?
Groundwater in the chalk aquifer beneath London is trapped between impermeable London Clay and Gault Clay.
Where does rainwater enter the chalk aquifer in the London basin?
Rainwater enters the chalk aquifer where it outcrops on the edge of the basin in the North Downs and Chilterns.
In what direction does groundwater flow through the chalk in the London basin?
Under natural conditions, groundwater flows by gravity through the chalk towards the centre of the basin in the London area.
What is the importance of groundwater from the chalk in the London basin?
Groundwater from the chalk is an important source of water for the capital, London.
What caused a drastic fall in the water table in the London basin during the nineteenth and early twentieth centuries?
Overexploitation of groundwater in the nineteenth and early twentieth centuries caused a drastic fall in the water table in the London basin.
How much did the water table in central London fall during the period of overexploitation?
During the period of overexploitation, the water table in central London fell by nearly 90 meters.
What factors have contributed to the recovery of the water table in the London basin in the past 50 years?
Declining demand for water by industry in London and reduced rates of abstraction have allowed the water table in the London basin to recover in the past 50 years.
At what rate was the water table rising in the early 1990s in the London basin?
By the early 1990s, the water table in the London basin was rising at a rate of 3 meters per year.
What measures were taken by Thames Water to slow the rise of the water table in the London basin?
Since 1992, Thames Water has been granted abstraction licenses to slow the rise of the water table in the London basin.
What is the current state of the water table in the London basin?
The water table in the London basin is now stable due to the measures taken by Thames Water to control abstraction rates.
