Moisture Circulation Systems

Question 1

What is the hydrological cycle?

Answer 1

The circulation of water from the oceans, or to the land, and then to the oceans again by overland and subsurface routes.

Question 2

How does the hydrological cycle flow?

Answer 2

Water in the oceans evaporates under the influence of solar radiation and the resulting water vapour is transported by the atmospheric circulation to the land areas, where precipitation may occur in a variety of forms including rain, hail and snow.
Some infiltrates rocks/soil where it travels slowly beneaht surface to river channels/the sea.
What remains on the surface evaporates.

Question 3

What is the hydrosphere most simply?

Answer 3

A global system consisting of four reservoirs linked by the hydrological cycle.
The world ocean, polar ice, terrestrial waters and atmospheric waters.

Question 4

What does the fact that the main areas of evaporation, mostly over oceans, does not coincide with major precipitation regions imply?

Answer 4

An atmospheric flux of water vapour from the oceans to the land masses.

• precipitation originated from distant oceans and circulated over land by low-lying winds.
• Formed of locally evaporated water.

Question 5

Evaporation rates over land masses are relatively low, only about 50% of the global average (Brutsaert, 1982). Why is this?

Answer 5

Mostly linked to the moisture holding capacity of the land surface soils, and the annual distribution of precipitation and net radiation.

Question 6

Evaporative losses from land surfaces have three components…

Answer 6

• Transpiration
• Interception loss
• Soil surface evaporation

Question 7

Transpiration is strongly controlled by what?

Answer 7

The nature and condition of the vegetation.

Question 8

What is interception loss?

Answer 8

During rainfall, water is intercepted in vegetation canopies and evaporated back to the atmosphere during and just after the rainfall event. This re-evaporated water is termed interception loss.

Question 9

Provided there is rainwater on the plant leaves, the rate of interception loss is…

Answer 9

independent of the vegetation state but strongly dependent on atmospheric conditions.

Question 10

What is evapotranspiration?

Answer 10

The sum of transpiration, interception loss and soil surface evaporation.

Question 11

What is evaporation from the ground surface dependent on?

Answer 11

The net radiation, which supplied the energy for the latent heat of vaporization, and also the vertical gradient of water vapour pressure.

Question 12

What is transpiration?

Answer 12

The removal of water from plants.

Question 13

flux rate =

Answer 13

conc difference of property/ resistance to flow exerted by system

Question 14

What is a drought?

Answer 14

A drought is considered to be a period of abnormally dry weather that causes serious hydrological imbalance in a specific region.

Question 15

What do the definitions of ‘serious’ and ‘abnormally dry’ depend on?

Answer 15

The nature of the local climate and the impact of the drought on the local society.

Question 16

Define meterological drought

Answer 16

If atmospheric conditions result in the absence or reduction of precipitation over several months or years the result is a meteorological drought.

Question 17

Define agricultural drought

Answer 17

A few weeks’ dryness in the surface layers (vegetation root zone), which occurs at a critical time during the growing season, which can severely reduce crop yields, even though deeper soil levels may be saturated.

Question 18

Define hydrological drought

Answer 18

Precipitation deficits over a prolonged period that affect surface or subsurface water supply, thus reducing stream flow, groundwater, reservoir and lake levels.

Question 19

Define socio-economic drought

Answer 19

Associates the supply and demand of some economic good with elements of meteorological, agricultural and hydrological drought.