Ramani Thakuria
(The author is the former Chief Scientist, Water Management, Assam Agricultural University, Jorhat. Currently, he is working as a Principal Scientist at Khanapara Campus, AAU, Guwahati-22. Email – thakuriark@gmail.com)
Globally and more particularly for many developing countries, including India declining water availability has already been recognized as a major concern. The agriculture sector is the highest consumer of water, and maintaining the future growth of the sector is going to be tougher because of the emerging water-scarce situation. Efficient management of available water thus is urgently necessary. It is clear from the study that the declining situation of water availability both in terms of quantity and quality are the results of various factors like increase in population and industrial growth, changing lifestyle of people, change in climate i.e. rise in average atmospheric temperature, temporal and spatial rainfall variability, decrease in the number of rainy days with more frequency in intense rainfall etc. It has been estimated that globally the water demand has increased annually by about 2.4 per cent for which the present water stress value in many countries is expected to be increased by double within a short time. Statistics show that in India per capita availability of water has come down from 5300 m3 in the year 1955 to 1967 m3 in 1997, which is projected to further decrease to 1500 m3 by 2025 with wide inter-basin variations. Agriculture is the largest consumer of water, action on better management options will help in delaying or overcoming such a critical situation. Better water management which is officially referred to as Good Water Management (GWM) is the application of available knowledge in utilizing the water for sustainably enhancing crop production. The underlying theme is one of knowing, understanding, planning, measuring, recording and managing the water used to achieve identified social, environmental and production goals. This requires a sound and comprehensive management strategy and the capability for responsive tactical adjustments as circumstances change. Success depends upon developing the skill and knowledge bases, continuous recording and analysis of performance and the use of expert advice.
In general, GWM practices are maximization of water infiltration by minimizing the unproductive efflux of surface waters from watersheds, management of ground and soil water by proper use or avoidance of drainage where required and by building up soil structure and soil organic matter. Avoidance of contamination of water resources with production inputs, avoidance of unproductive irrigation water losses and adoption of water-saving measures and recycling of water where possible are some other practices. Specifically, GWM in agriculture is the application of the optimum amount of water scheduled at right time with the highest water application efficiency. The application of too little water is an obvious waste as it fails to produce the desired product. Excessive flooding of the land is, however, likely to be still more harmful as it tends to saturate the soil for a long time, inhibit aeration, leach nutrients and induce greater evaporation. Therefore, apart from wasting water, excessive irrigation contributes to the problem of waterlogging. The best irrigation methods are designated to apply a small measured volume of water at desired frequent intervals to where the roots are concentrated. The aim is to reduce fluctuations in the moisture content of the root zones. Moreover, an irrigation system should convey water to the field in concrete line channels to avoid seepage losses or preferably in closed conduits that avoid pollution. The objective of water management in the field is to provide a suitable moisture environment to crops to obtain maximum yield with high water use efficiency. It is an integrated process of diversion, conveyance, regulation, measurement and distribution at a time when the crop requires with requisite quantity of water. Efficient water management is depicted simply following the basic principles of irrigation water management as summarized with a simple relationship of the soil–plant–atmosphere continuum.
The agricultural water management practices are classified under surface, sub-surface and micro (sprinkler, drip) irrigation. Every irrigation practice has got its merit, demerit and limitations depending upon water availability, cropping pattern, water quality, soil types, topography, climate and socioeconomic status of the farmers. It is told that an irrigation system that may prove to be most appropriate in one location may not be suited in another location due to specific local physical conditions and cropping patterns. The economic background and government support for the farmers are also major factors. The modern irrigation methods (sprinkler and micro-irrigation) are efficiently used in developed countries, but various alternatives concerning their possible applicability in developing countries need to be given special attention. The scientists are confident that low-cost best practices with high water use efficiency could be brought into practice provided that the human resource component and farmers' training are planned systematically. The definition of 'HELPFUL Irrigation' is very innovative as mentioned by FAO as it denotes: High frequency (H), Efficiency (E), low volume (L), partial area (P), Farm (F), Unit (U) and Low cost (L).
In the past, traditional agricultural water management (AWM) was concerned with improving the efficiency of water use in large-scale irrigation schemes in which the objective was to control, not to manage water. In contrast, improved AWM is more holistic and aims to mitigate the environmental costs and risks of irrigation. Now, as larger numbers of farmers are investing in small-scale irrigation systems, the need for improved practices in small-scale systems is essentially evident. With small-scale irrigation now advocated as a way to increase food security and increase resilience to climate variability and change, it is even more important to increase farmer awareness, knowledge, and practice of improved AWM. Legal enforcement of laws to address the unchecked proliferation of water abstraction from both surface and groundwater sources also needs to be emphasized.
The GWM with the location specificity is now inevitable for sustainable rural and agricultural development. Rain-fed agricultural lands are low in productivity and sustainability and are more prone to risk as compared to those in irrigated areas. Considering the location specificity, different GWM technologies for our state have been developed by Assam Agricultural University along the lines - to provide irrigation as per water and irrigation need of the crops, providing irrigation with proper scheduling and method, rainwater harvesting and conservation. The technologies have already been recommended for our state and can be benefitted by the farming community by improvement of their income. It is high time that to achieve a second green revolution in the state, it is essential to harness the potential of the state with a strong focus on GWM in agriculture.