Prof. Dr. P. K. Jena in Bhunbaneswar, February 6, 2021:Further, nearly two third of water available in the country is being improperly transported and used carelessly in 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 agricultural sector should be the most important one to mitigate the water crisis in India. The 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 enter into the main delivery system.

The WUE should be considered from three aspects namely: (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 topography, type of soil, materials used for lining the canal and also on the efficiency of 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. In order to save irrigation water, instead of using 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 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 loses can be reduced from 4 – 30% 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 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 maximization 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 in the world. For example, in United State of America from the experience of pricing, it has been noticed that, with a 10% increase in water price, the decrease in water use in agriculture sector is about 6.5%.

Ecological Efficiency: The term ecological efficiency of water use implies its environmental sustainability. This means that water should be managed in such a way so that it should not diminish its opportunity for potential use by future generation. Further, the available water should be allocated in such a manner so that it has no adverse effect on the ecological health of the surroundings. For example, the diversion of large amount of river water for irrigation purpose may affect the ecological aspect of the region. Sometimes, it may have a negative impact like water logging, salination, soil erosion etc. Similarly, in case of using ground water for irrigation purpose, if the total water withdrawn exceeds the sustainable supply of water to the aquifer then it would have a negative effect on the environment. As such, all these can affect the potential water needed for the future generation. For improving water use efficiency, an integrated approach combing all these factors mentioned above are necessary.

Some possible Areas of Water Conservation

a) Water conservation through cultivation of selected varieties of crop.
It is necessary to grow crops which need less water. Some crops need less amount of water than others. For example, potato requires much less amount of water than rice per unit quantity. Some of the plants suitable for water scarce area with shorter growth period and high yielding plants which require less water should be popularized.

b) Use of water in irrigation from treated used water

In agricultural sector, in some localities, it is possible to utilize 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 waste water for various agricultural purposes after removing the toxic materials.

c) Steps to reduce 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 shelter belt of trees and bushes along the sides of agricultural field 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.

d) 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. The silt and weed removal should be done at intervals to maintain the water holding capacity of the canals. The irrigation tank should be filled up to meet the requirements of the water whenever required. Many times the encroachment of canal takes place which has to be avoided by proper inspection and under taking timely remedial measure.

e) Changes in methods of irrigation
As in India, nearly 70% of the total water is consumed in agricultural sector, it is necessary to encourage farmers to economize 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%. 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 popularized by giving proper incentive and know how to the farmers. The supply of water by using such economic methods of irrigation with the amount of water available, more agricultural production can be achieved.

f) 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. The farmers can participate in management of water supply, distributing for agricultural purpose 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 practice, administration and execution of water supply. Electronic system should be used to monitor the supply and distribution of water to users as well as for maintenance.

g) Pricing of water:
Water pricing for irrigation purpose is essential to avoid wastage of water. In most part 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 case of volumetric pricing, the charge is made according to the amount of water provided where as for a 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. The 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 for sustainable management of the water resource. While doing so, the following facts have to be taken into consideration i.e. (i) Nearly 70% of the total water resource 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 ground water (iv) By improving irrigation efficiencies it would be possible to conserve the water and get financial benefits and (v) The system for procuring water for irrigation is becoming capital intensive.

In addition to implementation of above programmes, it is necessary to undertake some additional programmes for mitigating the water crisis with zero waste approach as given below:

1. Rain Water Harvesting projects at suitable sites both in rural and urban areas should be planned and implemented scientifically for increasing both surface and ground water resources.
2. Existing wetlands should be developed and new ones should be created to enhance both surface and ground water resources.
3. Programmes to keep the rivers and other water bodies away from wastes and effluents from point and non point sources should be undertaken.
4. It should be mandatory for all the mines and major industries to harvest rain water to meet most of their requirements particularly during summer and winter months and recycling waste water for various purposes. They should also be motivated to develop wetlands.
5. High priority should be given to provide drinking water to all, preferably extracted from deep aquifers.
6. A network of water quality monitoring system should be developed and executed periodically.

Government agencies at different levels should have the resources and responsibility to implement the above programmes with the help of experts in the concerned areas and also bring awareness amongst the public regarding proper management of water resource.

• Former Director General, Council of Scientific and Industrial Research, India