Glossary

A

Aerosphere

The gaseous sphere over the earth's surface also called earth's atmosphere.

Arid climate (desert climate)

It is talked about arid climate, if the potential evapotranspiration is higher than the precipitation. (ET_pot > P).

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C

Catchment area

Cohorent area, from which precipitation flows into a stretch of water. The boundary of the catchment area is determined by the topography.

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D

Depth of run-off

Run-off converted in mm height on one square metre. It indicates the run-off in a catchment area within a specified period of time. Unit: mm / time unit

Desert climate

see arid climate

Dry savannah

Transient area from the desert zone to the tropical rain forest with an average annual precipitation of 500 to 1,000 mm and a humid climate during 4½ - 5 Monaten in a year.

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E

Evaporation

Evaporation from not overgrown soil and from free surfaces of water.

Evapotranspiration

Sum of evaporation and transpiration. It is also called evaporation of an area.
The evapotranspiration depends only on physical factors, especially on solar energy, air temperature, humidity and topography and underground conditions.

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G

Ground water

Ground water is according to DIN 4049 a permanent consequence of the changing of state and location in form of precipitation, run-off and evaporation.

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H

HDI

Human Development Index. The Human Development Index shows the state of development of a country. It is published for every country every year in the HDR of UNDP.

HDR

Human Development Report. Annual come out report, which is published by UNDP.

Humid climate

In a humid climate the precipitation is higher than the evapotranspiration.

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I

Interception

Evaporation of precipitation, which is collected by plant (leaves). This precipitation does not reach the ground.

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P

Potential evapotranspiration

The potential evapotranspiration ist die maximum possible evapotranspiration. The actual evapotranspiration can only be equal to the potential evapotranspirationkann over free surfaces of water.

Precipitation

Water which falls in solid or liquid form from the clouds down to earth or which is released from the aerosphere e.g. dew.

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R

Run-off

Quantity of water (volume of water), which flows through a catchment area by the influence of gravity.

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S

Savannah

Savannah means Steppe. It is the transient area between the desert zone towards the tropical rain forest, which is characterised by arid climate. The savannah is characterised by grass growth with trees in regulary intervals. It is distinguished by the number of humid months and the average annual precipitation:

• wet savannah
• dry savannah
• thorn savannah

Semi-arid climate

The precipitation is smaller than the potentielle Evapotranspiration (N < ET_pot) during six to nine months of a year.

Steppe

see savannah

Sub-Sahara-Africa

The area of Africa south of Sahara.

Subtropics

The area between 23,5° N and 40° N as well as between 23,5° S und 40° S are named subtropics.

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T

Thorn savannah

Transient area between the desert zone and the tropical rainforest with an annual average precipitation of 250 to 500 mm and a humid climate during 2-4  months of a year.

Transpiration

Evaporation of water by plants.

Tropical rain forest

The tropical rain forest is located between 10° N and 10° S. The climate of the tropical rain forest is characterised by all–the–year precipitation which are especially intensive during the rainy season. The precipitation is in the annual average higher than the evapotranspiration (N > ET_real).

Tropics

The tropics are the area between the Tropic of Cancer (23,5° N) and the Tropic of Capricorn (23,5° S).

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U

UNDP

United Nations Development Programme with headquarters in New York.

UNEP

United Nations Environemtal Programme with headquarters in Nairobi.

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V

Virtual water

The necessary quantitiy of water which is used to produce a product, e.g. wheat or rice.

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W

Water shortage

It is talked about water shortage if there is less than 1,000 m³ water per person and year available for his disposal.

Water stress

Of water stress is talked if is between 1,000 m³ and 1,700 m³ water per person and year available for his disposal.

Water stress, susceptible for

Of susceptibility for water stress is talked if for each human between 2,500 m³ and 1,700 m³ per person and year available for his disposal.

Wet savannah

Transient area from the desert zone to the tropical rain forest with an average annual precipitation of 1,000 to 1,500 mm and a humid climate during 7-8  months of the year.

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