India is in a water-stressed region of the world. In recent years, climate change due to global warming is causing irregular rainfall. In addition to this, a large number of water bodies getting polluted due to various anthropogenic activities like the release of urban sewage water and industrial wastes effluents.
Many wetlands have vanished due to the construction of roads and buildings. Further, nearly two-thirds of the water available in the country is being improperly transported and used carelessly in the agriculture sector. In the present practices of irrigation, a large proportion of water is lost in the soil as well as evaporated. Water conservation in the agricultural sector should be the most important task to mitigate the water crisis in India. Water Use Efficiency (WUE) is defined as the ratio of water volume actually applied at the crop root area to the total amount of water, which enters into the main delivery system.
WUE should be considered from three aspects (i) Technical efficiency (ii) Economic efficiency and (iii) Ecological and environmental efficiency
Technical Efficiency
The technical efficiency of irrigation water use is measured by the ratio of total water taken by the plant to the total water supplied by the system. This involves the physical layout of the canal system such as conveyance, distribution and application.
These are influenced by the nature of the topography, type of soil, materials used for lining the canal and also on the efficiency of the water being distributed in various areas of farming and the exact method of water application, adoption of modern irrigation technology such as low volume irrigation.
To save irrigation water, instead of using the flooded irrigation system, high pressure and sprinklers for irrigation can save a lot of water from evaporation. Similarly, it is possible to increase infiltration and reduce the wet surface area by excavating a column of soil from directly below the drip emitters and back-filling with coarse sand. It is reported that, by this process, the evaporation losses can be reduced from 4 per cent -30 per cent of the water applied.
Economic Efficiency
The economic efficiency of irrigation water used is measured as the ratio of the price of the crop produced to the cost of the unit of water applied or overall financial return in terms of net benefits obtained in the project. As usual, it is a cost-benefit ratio. This economic efficiency should involve the maximisation of overall socio-economic benefits. It is reported that management of water as an economic good is now being done in various countries of the world. The pricing of water has helped in improving water use efficiency in most of the countries. For example, in the United States of America, from the experience of pricing, it has been noticed that, with a 10 per cent increase in water price, the decrease in water use in the agriculture sector is about 6.5 per cent.
Ecological Efficiency
The term ecological efficiency of water use implies its environmental sustainability. This means that water should be managed in a way that it should not diminish its opportunity for potential use by future generations. Further, the available water should be allocated in such a manner that it has no adverse effect on the ecological health of the surroundings.
For example, the diversion of a large amount of river water for irrigation purposes may affect the ecological aspect of the region. Sometimes, it may have a negative impact like water logging, salination, soil erosion etc. Similarly, in the case of using groundwater for irrigation, if the total water withdrawn exceeds the sustainable supply of water to the aquifer then it would have a negative effect on the environment. All this can affect the potential water needed for future generations. For improving water use efficiency, an integrated approach combing all these factors are necessary.
Some possible areas of water conservation
- Water conservation through the cultivation of selected varieties of crops.
It is necessary to grow crops that need less water. Some crops need less water than others. For example, potato requires much less water than rice per unit quantity. Some of the plants suitable for water-scarce areas with shorter growth period and high yielding plants, which require less water should be popularised.
- Use of water in irrigation from treated used water
In the agricultural sector, in some localities, it is possible to utilise domestic and sewage water as well as industrial effluents after suitable treatment. Particularly those agricultural lands which are near urban areas and industrial units should explore the possibility of using wastewater for various agricultural purposes after removing the toxic materials.
- Steps to reduce the loss of water
Steps should be taken to reduce the loss of water in agricultural land through various techniques like mulching by application of organic materials, compost etc. by covering the soil through a shelter belt of trees and bushes along the sides of agricultural fields and also through contour farming, which is mostly adopted in hilly areas. In this farming, soil and water conservation takes place to a great extent.
- Improvements in water loss in canals
In India, most of the irrigation systems are through earthen canals where a large amount of water is lost due to seepage, evaporation and leaks to other areas. Therefore, it is necessary to make cement lining of irrigation canals to prevent seepage losses. Silt and weed should be removed at intervals to maintain the water holding capacity of the canals. The irrigation tank should be filled up to meet the water requirement whenever necessary. Many times, the canal is encroached upon. This has to be avoided with proper inspection and taking timely remedial measures.
- Changes in methods of irrigation
Since in India, nearly 70 per cent of the total water is consumed in the agricultural sector, it is necessary to encourage farmers to economise the consumption of water. It is reported that technologies like sprinkle and drip irrigation systems are being increasingly used in different parts of the world, particularly in most of the developed countries with an increase of irrigation efficiency as high as 90 per cent.
Drip irrigation system is now being used to grow cotton in parts of California (USA). In India and other developing countries, such irrigation systems should be popularised by giving proper incentives and know-how to the farmers. More agricultural production can be achieved with the supply of water by using such economic methods of irrigation.
- Institutional innovation
All over the world, it has been experienced that by involving farmers through Water Users Association (WUA), appreciable conservation of water is possible. Farmers can participate in the management of water supply, distributing for agricultural purposes and also collecting water fees from the users in time. The WARABANDI system which is a rotational system of using and allocating water to the farmers located at different areas of the canal system should be practiced. There should be transparency in irrigation practices, administration and execution of water supply. The electronic system should be used to monitor the supply and distribution of water to users as well as for maintenance.
- Pricing of water
Water pricing for irrigation purposes is essential to avoid wastage of water. In most parts of the world, the pricing of water is being done on the basis of either volumetric pricing or non-volumetric pricing or market-based pricing. In the case of volumetric pricing, the charge is made according to the amount of water provided whereas for non-volumetric pricing, the water supplied is calculated either on a flat rate or per acre of the farming land or according to the crop produced. Market-based pricing is fixed on the demand and supply of water based on the market rate in the area.
Pricing of water in case of irrigation has to be done by properly framing and implementing sustainable management of the water resource. While doing so, the following facts have to be taken into consideration (i) Nearly 70 per cent of the total water resources are used for irrigation sharing a major chunk of public investment (ii) Irrigation of water brings some financial gain to the farmers and can be considered as an economic good (iii) Irrigation attracts private investment particularly for groundwater (iv) By improving irrigation efficiencies, it would be possible to conserve water and get financial benefits and (v) The system for procuring water for irrigation is becoming capital intensive.
In addition to the implementation of these programmes, it is necessary to undertake some additional ones for mitigating the water crisis with a zero waste approach as given below:
- Rainwater harvesting projects at suitable sites both in the rural and urban areas should be planned and implemented scientifically for increasing both surface and groundwater resources.
- Existing wetlands should be developed and new ones created to enhance both surface and groundwater resources.
- Programmes to keep the rivers and other water bodies away from waste and effluents from point and non-point sources should be undertaken.
- Rainwater harvesting should be mandatory for all the mines and major industries to meet most of their requirements particularly during summer and winter months and recycling wastewater for various purposes. They should also be motivated to develop wetlands.
- High priority should be given to provide drinking water to all, preferably extracted from deep aquifers.
- A network of water quality monitoring systems should be developed and executed periodically.
Government agencies at different levels should have the resources and responsibility to implement these programmes with the help of experts in the concerned areas and also bring awareness among the public regarding the proper management of water resources.
