Aquifers, ground water reserves, abstraction

Question 1

What are aquifers?

Answer 1

layers of permeable rock (sandstone, limestone) containing significant quantities of water- great reservoirs of water. water moves very slowly through aquifer, acts as a natural regulator in the hydrological cycle by absorbing rainfall- which would otherwise reach streams rapidly

Question 2

Example of an aquifer

Answer 2

under Sahara, Ganges and Indus in Asia

Question 3

How are they formed?

Answer 3

sand or gravel laid down in depositional environment on top of impermeable bed

Question 4

Where are they found?

Answer 4

porous permeable rock (sandstone~) or open cavities and caves

Question 5

How does groundwater move within them?

Answer 5

when new surface water enters, recharges groundwater supply (e.g. downward from mountain slopes)

Question 6

benefits of aquifers?

Answer 6

cheap to develop
useful water supplies- store huge volumes
where water table is 3m deep, little loss through evapotranspiration

Question 7

issues of aquifers

Answer 7

subsidence- ground sinks because of ground water pumping (irrigation)
salt water intrusion/biological contaminant/industrial chemical risk

Question 8

What is ground water?

Answer 8

water that is beneath the earth’s surface in pores and crevices of rocks and soil

Question 9

what is ground water balance?

Answer 9

change in storage= recharge to groundwater- discharge from groundwater

Question 10

Why are ground water reserves important?

Answer 10

97% in underground, up to 1500 million people rely on it for drinking
base flow component to many rivers, especially in upper reaches of catchment

Question 11

How human activity affects ground water?

Answer 11

inadequate abstraction control, pollutants, soil and rocks filter and purify water (they may be polluted), salt water intrusion is a problem for small islands such as the Maldives as it is there only source of water, water irrigation

Question 12

Where may demand exceed the amount of water available?

Answer 12

low rainfall, high population density, intensive agricultural/industrial industry

Question 13

example of where saline intrusion has limited groundwater use

Answer 13

Malta- cannot be used for domestic consumption or irrigation

Question 14

Water abstraction in the London Basin?

Answer 14

water has been extracted from wells and boreholes in chalk- exploitation in 19th century- 1960= 88m below sea level (depression)
recovering 3mm/year since early 1990s- London underground at risk