4.3 effects of water extraction

Question 1

what is an aquifier?

Answer 1

An aquifer is a body of porous and permeable rock capable of storing and yielding significant amounts of water just underneath the surface.

Question 2

What is the water stored in an aquifier called?

Answer 2

groundwater

Question 3

what is the water table?

Answer 3

The water table is the level of groundwater within the aquifier

Question 4

How do aquifiers alter seasonally?

Answer 4

^ winter as less evapotranspiration/ ^ precipitation etc

Question 5

why are aquifiers vulnerable

Answer 5

• overuse / urbanisation (oil spills ) can cause pollutants into the aquifer
• Construction of infrastructure
• Farming

Question 6

Example of a aquifier - Barbados

Answer 6

Relies on limestone aquifers → natural springwater found here purest in the world

• BWA (barbados water authority limited) = supplier → aquifers provides 90% of this supply of water
• With decline rainfall in 90s had to turn to coastal desalination → highlights the need for aquifers - so seasonal variations / climate change is a threat

Question 7

what is an artisean basin?

Answer 7

a layer of confined porous rock sandwiched between layers of impermeable rock.

Question 8

what is the term where this artisean wells form?

Answer 8

A syncline - (earth is U shaped with layer of impermeable - aquifer - impermeable again)

Question 9

Why does the water come to the surface naturally ?

Answer 9

the water comes to the surface naturally → due to this artesian pressure - the level to which it rises is the - potentiometric surface (height of the water table in areas of recharge)

Question 10

Define potentriometric surface

Answer 10

An imaginary surface that defines the theoretical level to which water would arise in a confined aquifer.

Question 11

Explain how london is located on a syncline

Answer 11

London is built on top of one → OG water in trafalgar square came naturally from basin due to artesian pressure

Question 12

What are the extraction pressures of London Artisean Basin

Answer 12

Overexploitation in 20th century (early) → caused drastic fall in the water table fell 90m in central

• In the past 50 years industry is declined demand for water have allowed the table to recover
• Since 1992 thame water have granted extraction licences which has slowed rise of the water table

Question 13

Explain the case study of River kennet catchment - why was it needed and for how many people?

Answer 13

Water is needed as many local urban areas rely on the water from the basin to meet the public supply → swindon 200,000 ppl

Question 14

explain the impacts on the localised water cycle and drainage system

Answer 14

• Rates of groundwater extraction > than the recharge
• Water table decreased 10-14% flows
• Lower flows = reduced flooding and temporary wetlands on floodplain
• Lower groundwater levels - springs and seepages dried up - reduced incidence of saturated overland flow of chalk