Estimation Of Irrigation Efficiency

Water use efficiency – The water utilized by crop is evaluated in terms of Water Use Efficiency. This water use efficiency can be classified into:

• Crop Water Use Efficiency

• Field Water Use Efficiency

• Physiological Water Use Efficiency, and

• Irrigation project efficiency

(i) Crop water use efficiency – It is the ratio of Crop yield (Y) to the amount of water used by the crop for evapotranspiration (ET).

CWUE = ——- and expressed as kg/mm/ha

(ii) Field water use efficiency (FWUE) – It is the ratio of crop yield (Y) to the total amount of water used in the filed (WR)

FWUE = ——– and expressed as kg/mm/ha

(iii) Physiological water use efficiency (PWUE) – The physiological WUE is calculated in terms of the amount of CO2 fixed per unit of water transpired

Rate of photosynthesis

PWUE=———————————–

Rate of transpiration

(iv) Irrigation efficiencies of irrigation projects – Many irrigation projects throughout the World operate with 25-40 per cent overall efficiency. Thus perhaps one third of the water released at the Project headwork is actually beneficially used for evapotranspiration by crops. In many areas increased irrigation efficiency would result in increased irrigation average and production as well as decreased problems with salinity and drainage. The decrease in efficiency can be attributed to losses occurring at various stages.

Some of the reasons are:

• Inadequate design of the project.

• Inadequate design of the Farm Irrigation System.

• Lack of maintenance.

• Inadequate management of the system.

A typical Irrigation System consists of

• head works

• main canals

• field channels

• farm