Chapter: Civil : Water Resources and Irrigation Engineering : Irrigation Engineering

Environmental Effects of Irrigation

Irrigation is to agriculture as blood is to the human body. Introduction of irrigation results in changes in vegetation, the fauna and the flora thereby altering the ecology of the command area.

ENVIRONMENTAL EFFECTS OF IRRIGATION

Irrigation is to agriculture as blood is to the human body. Introduction of irrigation results in changes in vegetation, the fauna and the flora thereby altering the ecology of the command area. These improvements have added advantage of a chain reaction in many spheres which lead to a more prosperous life for the people of the area. Lands which were once barren, infertile and sandy hum with activity with green pastures, verdant forests and teeming population. The human environment

I. (iv) Porous soils should be treated before sowing crops to reduce seepage of water. II. (v) Alkaline soils should be properly leached before sowing

III. (vi) Manure fertilizers should be added to increase water holding capacity of the soil.

IV. Rotation of crops should be preferred, as this will ensure increased crop yields with minimum use of water.

(2) Precautions in handling irrigation supplies:

(i) The source of irrigation water should be situated within the prescribed limits, and be capable of good quality of water.

(ii) Canals carrying irrigation supplies should be lined to reduce seepage and evaporation.

(iii) Water courses may preferably be lined or R.C.C. pipes may be used for the same.

(iv) Free flooding of fields should be avoided and furrow irrigation method may preferably be adopted, if surface irrigation is restored to.

(v) Sub surface irrigation and Drip irrigation may be preferred to ordinary surface irrigation.

(vi) If canals are not lined, then two canals running side by side may be preferred to a single canal, as this will reduce the FSL, thereby reducing percolation losses.

(vii) Irrigation supplies should be economically used by proper control on its distribution, volumetric assessment, and by imparting proper education to the farmers.

The above distinction of seasons is well applicable to North India, but in South India, there is no such marked distinction between the different seasons. In fact, in South India, there is no clear cut winter, spring, summer and autumn seasons, as they are in North India. Except Bombay

�'Deccan, where there are five crop seasons, there are only three crop seasons in the remaining parts of the country. These three classifications of seasons are:

(i) Hot or Kharif season. (ii) Winter or Rabi season. (iii) Monsoon season

When a crop requires water for its crop season and also for some time in the beginning of the next crop section, allowance has to be made for this overlap. This allowance is known as overlap allowance, Sugarcane is an example of this kind of crop. Some important Indian crops, their periods of growth, water requirements, seed requirements, yields, etc, are shown in table

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Civil : Water Resources and Irrigation Engineering : Irrigation Engineering : Environmental Effects of Irrigation |