Deficit in the Water Cycle

Question 1

Water deficit

Answer 1

when precipitation is lower than combined loss of water from runoff and evapotranspiration

Question 2

water imbalance

Answer 2

balance between evapotranspiration, run off and precipitation

Question 3

equation for drainage basin balance

Answer 3

P = Q + ET + C
P = precipitation
Q = discharge
ET = evaporation 
C = +/- changes in water storage

Question 4

meteorological causes of deficit (drought conditions)

Answer 4

meteorological drought = extended period of low/absent rainfall relative to regions average
agricultural drought = insufficient moisture for average crop production
hydrological drought = available water reserves fall below acceptable levels, can arise even when there have been recent rains

Question 5

human causes of deficit

Answer 5

• aquifer depletion (removal of permeable rock layer that contains water)
• over extraction of surface water resources
• population growth, agricultural demand and use of water in industry
• total demand projected to exceed 5,000km3 by 2025

Question 6

Agriculture, food and drink production influences

Answer 6

• Ogalla aquifer lowers at a rate of 90-150cm per year, impacting grain supplies and prices
• kerala, aquifer tapped by Coca Cola subsidiary firm, water shortages reported

Question 7

Industry influences

Answer 7

• second largest use of water

- growth in industrial activity worldwide, puts extra pressure on water supplies in recent decades

Question 8

Household water consumption influences

Answer 8

• decrease in poverty, increase in emerging economies increased water consumption
• more people have access to bathing, showering and domestic appliances

Question 9

What is an Aquifer?

Answer 9

permeable and porous water-bearing rocks such as chalk and sandstone

Question 10

How are aquifers naturally recharged?

Answer 10

by percolating rainwater, if too much water is taken, they dry out before recharging

Question 11

Where do artesian aquifers develop?

Answer 11

where sedimentary rocks formed syncline (basin-like) structure, with aquifer confined between impermeable rock layers

Question 12

AQUIFER EXAMPLE: London Basin

Answer 12

• saturated layer of chalk between two layers of impermeable clays
• rainwater enters chalk aquifer, groundwater flows by gravity through chalk to centre of basin
• if groundwater tapped by a well, water flows to surface under own pressure
• level water rises is naturally determined by height of water table in areas of recharge
• over exploitation in 19th century caused drastic fall by 3m per year, water seep into railway tunnels and building foundations