Unit 3: Water Cycle Flashcards
(15 cards)
What is a Water Deficit?
A water deficit is experienced when an area lacks sufficient water to meet its needs.
Water deficits can be caused by both natural (meteorological) and human causes.
What is a drought?
Drought is generally defined as an extended period of low or absent rainfall relative to the expected average for a region.
Therefore, it means different amounts of rainfall in different regions.
What is Low Pressure?
Where warm air rises.
What is High Pressure?
Where cold air descends (sinks) through the atmosphere it warms, no condensation occurs and consequently no precipitation.
Causes of the 1976 UK Drought?
• During the spring and summer of 1976, the jet stream was positioned further north than normal, and a blocking high pressure system was located over the UK. This resulted in an extended period of dry weather.
• The summer of 1976 had been preceded by a dry winter
• High summer temperatures of over 32 °C occurred for two consecutive weeks. Temperatures peaked at 35.9 °C in Cheltenham in July. The high temperatures resulted in high rates of evaporation.
Why does demand for water increased?
Demand for water has increased due to:
• growth in global population
• increased per capita consumption due to increased
affluence
What is Water Scarcity?
Water scarcity is the lack of available fresh water resources to meet demand.
• Water stress is increased by:
- Climate change
- Population growth/increased affluence/consumption
- Increase water withdrawals.
What is an Aquifer?
An aquifer is a body of permeable rock which can contain and transmit fresh groundwater.
What is Water Scarcity?
Water scarcity is the lack of available fresh water resources to meet demand.
• Water stress is increased by:
- Climate change
- Population growth/increased affluence/consumption
- Increase water withdrawals.
What is an unconfined aquifer?
An unconfined aquifer lies directly below the water table.
What is a confined aquifer?
A confined aquifer lies below a layer of impermeable rock or sediment such as clay and is therefore confined under high pressure.
Summarise the California Central Valley Aquifer:
• As covered earlier in the unit, the western USA, including California, is experiencing ‘megadrought’.
• California is one of the USA’s agricultural centres and Central Valley is where 1/3 of the USA’s fresh food is produced!
• 80% of California’s water use is in Central Valley and due to recent droughts, there has been increasing pressure on the Central Valley Aquifer to meet the water needs
What is Artificial Recharge?
Artificial recharge involves capturing excess runoff during periods of heavy precipitation and diverting this water into recharge basins or recharge canals.
• These basins have porous bases that allow the captured water to percolate down to the aquifer.
What is Natural Ground Water Recharge?
Aquifers can be recharged (replenished) naturally over time through precipitation, river bed seepage, flooding and other natural processes including seasonal snow melt.
When the rate of percolation is greater than the rate of groundwater flow the water table will rise
Summarise the Aral Sea Case Study.
• The Aral Sea is located between Kazakhstan and Uzbekistan, in Asia
• In 1960 it was the 4th largest body of inland water, fed by two main rivers: the Syr Darga entering from the northeast and the Amu Darya entering from the south.
• By 2014 it was covered just 10% of it’s original size
