Deficits within the hydrological system

Question 1

What are sea surface temperature anomalies?

Answer 1

Sea surface temperature anomalies relate to how much temperatures of the sea surface, recorded at a particular time, differ from the long-term average. Anomalies may be positive or negative.

Question 2

What is a positive sea surface temperature anomaly?

Answer 2

A positive anomaly occurs when the observed temperature is warmer than the average.

Question 3

What is a negative sea surface temperature anomaly?

Answer 3

A negative anomaly occurs when the observed temperature is cooler than the average.

Question 4

Sea surface temperature anomalies are an important causal factor is short-term or long-term precipitation deficits.

Answer 4

Short-term

Question 5

Temperature anomalies provide the key to which event in the Southern Pacific Ocean?

Answer 5

El Nino-Southern Oscillation (ENSO)

Question 6

How often do El Nino events usually occur?

Answer 6

Three to seven years

Question 7

For how long does an El Nino event usually last?

Answer 7

18 months

Question 8

In what way does the water temperature change in the Pacific Ocean during an El Nino year?

Answer 8

Cool water normally found along the coast of Peru is replaced by warmer water.
At the same time, the area of warmer water further west, near Australia and Indonesia, is replaced by cooler water.

Question 9

What conditions does an El Nino year seem to trigger throughout the world and in which year? And what is the example to suggest this?

Answer 9

Dry conditions and usually in the second year.

The monsoon rains in India and South East Asia often fail.

Question 10

What event may, but not always, follow an El Nino event?

Answer 10

La Nina

Question 11

What is a La Nina episode?

Answer 11

Build up of cooler than usual subsurface water in the tropical part of the Pacific.

Question 12

Which conditions can a La Nina event cause?

Answer 12

Severe drought conditions, particularly on the western coast of South America.

Question 13

What does desertification mean?

Answer 13

Desertification is the process by which once-productive land gradually changes into a desert-like landscape. It usually takes place in semi-arid land on the edges of existing deserts. The process is not necessarily irreversible.

Question 14

What desert is an example of desertification?

Answer 14

The Sahel

Question 15

What is the downward spiral of causes of desertification?

Answer 15

1. Changing rainfall patterns with rainfall becoming less reliable, seasonally and annually. The occasional drought year sometimes extends to several years.
2. The vegetation cover becomes stressed and begins to die, leaving bare soil.
3. The bare soil is eroded by wind and an occasional intense shower.
4. When rain does fall, it is often only for very short, intense periods. This makes it difficult for the remaining soil to capture and store it.

Question 16

What are the four human factors encouraging the over-abstraction of surface water from rivers and ponds, and of groundwater from aquifers?

Answer 16

Population growth: Puts pressure on the land to grow more food. Migrants fleeing from one disaster area help to make another.
Overgrazing: Too many goats, sheep and cattle destroy the vegetation cover.
Overcultivation: Intense use of marginal land exhausts the soil and crops will not grow.
Deforestation: Trees are cut down for fuel, fencing and housing. The roots no longer bind the soil and erosion ensues.

Question 17

In the Sahel, why have crops, livestock and homes been deliberately destroyed?

Answer 17

Frequent civil wars

Question 18

What is grey water?

Answer 18

Waster bath, shower, sink and washing water. It can be recycled, but not necessarily for human consumption.

Question 19

What is ecological resilience?

Answer 19

The capacity of an ecosystem to withstand and recover from a natural event (such as drought and flooding) or some form of human disturbance.

Question 20

What percentage of Earth’s lands is covered by wetlands?

Answer 20

10%

Question 21

What are the important functions of wetlands?

Answer 21

Acting as temporary water stores.
Recharging of aquifers.
Giant filters trapping pollutants.
Providing nurseries for fish and feeding areas for migrating birds.

Question 22

What is the impact of drought on wetlands?

Answer 22

With less precipitation there will be less interception (as vegetation becomes stressed), as well as less infiltration and percolation.
Water tables will fall. Evaporation will also increase. This, together with the decrease in transpiration, will reduce the valuable functions performed by wetlands.