The Best Methods of IrrigationJanuary 31, 2022
The Defects of Well Irrigation
Deep tube wells ae not the solution to the water crisis.
Well irrigation causes the level of the water-table to drop. The continuous use of well irrigation dries up the subterranean flow of water.
Initially, the effects of continuous well irrigation may not be easy to perceive, but eventually a fertile region will be transformed into a desert.
In fact, if the subterranean water level stays at above 20-25 feet, the surface vegetation will not be affected. But if it drops below 50 feet, the surface of the earth will become a barren wasteland.
The negative effects of well irrigation include the following:
- Neighbouring shallow wells dry up.
This creates a lack of drinking water.
- Trees, orchards and large plants do not get sufficient subterranean water.
These wither and die. Green countryside will become a desert after 30-45 years of intensive well irrigation.
- In some deep tube wells, heavy minerals and mineral salts get mixed with the water, causing salinity.
The land eventually becomes infertile and unfit for cultivation. When the flow of well water stops, irrigation tanks supplied by these wells also dry up.
Well irrigation should be used only as a temporary measure because of the devastating effects it can have on the surrounding environment. Alternative methods of irrigation include river irrigation, irrigation from reservoirs, dams and small ponds, shift irrigation and lift irrigation.
Irrigation water is like the apex of a spinning top. Without it, agriculture is not possible.
The Best Methods of Irrigation
The best method of irrigation is the conservation of surface water through a system of ponds, canals, dams, lakes and reservoirs.
Take the example of Ráŕh and Orissa.
The potentialities of this region have not yet been fully developed and utilized. The major portion of the wealth is subterranean, and these treasures should be properly harnessed, but practically nothing has been done in this respect. The surface potentialities should also be properly developed, but these too have been neglected.
How should the surface water potentiality in this region be utilized?
The rainfall in this area is very meagre – rain only falls part of the year, and the rest of the year it is dry.
Well-irrigation is underdeveloped. There is hardly any lift or shift irrigation. 65% of the land is rocky and sandy. Traditionally, only coarse grain is grown there.
So in Ráŕh, we must do 2 things:
- Construct many new small-scale ponds, dams and lakes
- undertake large-scale afforestation on the banks of all water systems.
Ráŕh has undulating land, so large-scale reservoirs cannot be easily constructed.
But many small lakes and ponds can be built.
Large, deep reservoirs will not be as beneficial as small-scale ponds and should not be encouraged.
Moreover, large reservoirs rely on lift and shift irrigation to supply water to a system of canals. In such a system, the water pressure will fall because as the water travels along the canals leading from the reservoirs to the fields, the canals will be obstructed by the hilly terrain.
So, if there is a big investment in reservoirs, the money will be wasted.
Instead, many small ponds and dams can be constructed with the same investment.
If many small-scale dams are constructed at a cost of about 100,000 rupees each, this investment will give a return of hundreds of millions of rupees.
In a system of small-scale ponds and dams, any surplus water in the canals leading to the fields can be rechannelled back to a main water source to avoid wastage.
Water will only be carried a little distance in a small-scale canal system, so most of the time the surrounding fields will be properly irrigated. Sometimes however, as in the rainy season, surplus water will be created which should be rechannelled back to the water source or used further downstream.
Such a system will also help check flooding in the rainy season and avoid damage to the small-scale dams constructed along the rivers. Farmers should take care that they do not use excessive non-organic fertilizers, because the chemicals will pollute the water system and have a harmful effect on humans, animals, fish, plants and the environment. Organic fertilizers are preferable to non-organic fertilizers.
What is the method to irrigate a rain-shadow region? When the rain clouds move from the sea and strike high mountains on the land there is rain. The part of the mountain range which faces the sea gets ample rain, whereas the region on the other side of the range facing inland gets little rain. The region which gets ample rain is the rain-front area, while the region which gets little rain is the rain-shadow area. The entire Telengana region is a rain-shadow area, and so is the Pune region of Maharashtra.
How can the Pune region be irrigated?
There are 2 main methods:
- Pump water up the coastal side of the mountain range so that it can run down the inland rivers
- Dig a tunnel through the mountains from the rain-front area to the rain-shadow area.
- This method is far cheaper. A well constructed tunnel should last about 150 years.