POTENTIAL EVAPOTRANSPIRATION - SOURCE DATA

Data ID

Description:

Potential evapotranspiration

Chapter:

Additional data

File name:

pet

File type:

Excel file

Geographical area:

Namibia

Keywords:

evaporation

evapotranspiration

water

Notes on data, analysis and

Potential Evapotranspiration (PET) is a concept widely used in Agrometeorology to indicate the water requirements of

compilation:

crops, rangeland or natural vegetation. It represents a combination of the potential evaporation from the soil and the

transpiration of the crops calculated according to the relevant weather conditions. The weather elements that are used

to calculate the PET are solar radiation, air temperature, wind speed and humidity of the atmosphere. Often, data for

these elements are not available, and proxies must be used, for example, duration of sunshine instead of solar radiation.

Some estimation of the suitability of any area for crop growth can be determined by comparing the PET with the actual

rainfall which occurs. By convention, Agrometeorologists often compare actual rainfall with half PET, since crop

growth (though not maximum possible crop growth) can be reasonably successful when rainfall equals or exceeds half

PET. Plotting these on a graph also indicates the length of the growing season.

This file contains PET data for 26 stations in Namibia taken from the Agro-ecological zone project (Ministry of

Agriculture, Water and Rural Development). Data are in the format: station name, latitude, longitude, altitude, PET.

Monthly data for 6 stations (Keetmanshoop, Luderitz, Windhoek, Tsumeb, Gobabis, Sesheke) are also provided. These

data were extracted from the FAO CLIMWAT database and are in the following format: month, PET, 1/2 PET, rainfall.

Data quality and organisation

Positional Accuracy:

co-ordinates for stations

Spatial reference

Projection:

N/A

Source/Distribution

Data Source:

Ministry of Agriculture, Water and Rural Development; FAO CLIMWAT database

Contact:

Marina Coetzee

Online/Offline Address:

Ministry of Agriculture, Water and Rural Development

Private Bag 13184

Windhoek

Distribution notes:

Unrestricted