By -Sanjay Kumar : Water on the earth is moving through the hydrological cycle. The utilization of water for most of the users – human, animal or plant involves movement of water. The dynamic and renewable nature of the water resources and the recurrent need for its utilization requires water resources be measured in terms of its flow rates.
What is effectively available for consumption and other uses is a small proportion of the quantity available in rivers, lakes and ground water. The crisis about water resources development and management arises, because most of the water is not available for use and secondly it is characterized by its highly uneven spatial distribution. Accordingly, the importance of water has been recognized and greater emphasis is being laid on its economic use and better management.
Global and Indian Water Scenario
70 per cent of the earth’s surface is covered with water and many have an image of the world as a blue planet. The reality, however, is that 97 percent of the total water on earth of about 1400 Billion Cubic Meter (BCM) is saline and only 3 percent is available as fresh water. About 77 percent of this fresh water is locked up in glaciers and permanent snow and 11 percent is considered to occur at depths exceeding 800 m below the ground, which cannot be extracted economically with the technology available today. About 11 percent of the resources are available as extractable ground water within 800 m depth and about 1 percent is available as surface water in lakes and rivers. Out of the 113,000 bcm of rain and snow received on the earth, evaporation losses account for about 72,000 bcm, leaving a balance of about 41,000 bcm, out of which about 9000-14000 bcm is considered utilisable.
The annual precipitation including snowfall in India is of the order of 4000 bcm and the natural runoff in the rivers is computed to be about 1869 bcm. The utilisable surface water and replenishable ground water resources are of the order of 690 bcm and 433 bcm respectively. Thus, the total water resources available for various uses, on an annual basis, are of the order of 1123 bcm.
Although the per capita availability of water in India is about 1869 cubic meters as in 1997 against the benchmark value of 1000 cu m signifying ‘water-starved’ condition, there is wide disparity in basin-wise water availability due to uneven rainfall and varying population density in the country. The availability is as high as 14057 cu m per capita in Brahmaputra/Barak Basin and as low as 307 cu m in Sabarmati basin. Many other basins like Mahi, Tapi, Pennar are already water stressed.
India is a vast country with very deep historical roots and strong cultural traditions. These are reflected in our social fabric and institutions of community life. We have retained the spirit and essence of these traditions and have remained attached to our roots in spite of social movements of varied nature through the millennia. Some of our traditions, evolved and developed by our ancestors thousands of years ago have played important roles in different spheres of our life. One of the most important among these is the tradition of collecting, storing and preserving water for various uses.
The tradition probably started at the dawn of civilization with small human settlements coming up on the banks of rivers and streams. When, due to vagaries of nature, rivers and streams dried up or the flow in them dwindled, they moved away to look for more reliable sources of water. In due course of time, large settlements came up along the banks of perennial rivers that provided plentiful water. As the population increased, settlements developed into towns and cities and agriculture expanded.
The Satavahanas (1st Century B.C. to 2nd Century A.D.) introduced brick and ring wells for extraction of water. Lake and well irrigation techniques were developed on a large scale during the time of Pandya, Chera and Chola dynasties in south India (1 st–3 rd Century A.D) and large dams were built across Cauvery and Vaigai rivers. A number of Irrigation tanks were constructed by developing large natural depressions. Water resources development on a large scale took place during the Gupta Era (300-500 A.D.). In the south, the Pallavas expanded the irrigation systems in the 7 th Century A.D. The famous Cauvery Anicut was built during this period. Large-scale construction of tanks (Tataka) for harvesting rainwater was also done during this period in Tamil Nadu. The Chola period (985-1205 A.D) witnessed the introduction of advanced irrigation systems, which brought about prosperity in the Deccan region.
This included not only anicuts across rivers and streams but also a number of tanks with connecting channels. This new system was more reliable in terms of water availability and provided better flexibility in water distribution. The Rajput dynasty (1000-1200 A.D) promoted irrigation works in Northern India. The 647 sq km Bhopal Lake was built under King Bhoja. In Eastern India, Pal and Sen Kings (760-1100 A.D) built a number of large tanks and lakes in their kingdoms. Rajtarangini of Kalhana gives a detailed account of irrigation systems developed in the 12th Century in Kashmir.
The Medieval period, encouraged the farmers to build their own rainwater harvesting systems and wells. The Western Yamuna Canal built in 1355 to extend irrigation facilities in the dry land tracts of the present-day Haryana and Rajasthan. Emperor Shahjahan built many canals, prominent among them being the Bari Doab or the Hasli Canal. Under the rule of Rangila Muhammad Shah, the Eastern Yamuna Canal was built to irrigate large tracts in Uttar Pradesh.
The Vijaynagar Kings (1336-1548 A.D.) in the south took keen interest in building large and small storage tanks. Anantraj Sagar tank was built with a 1.37 km long earthen dam across the Maldevi River. The well-known Korangal dam was built under King Krishnadevaraya. The Bahmani rulers (1388-1422 A.D.) introduced canal irrigation for the first time in the eastern provinces of the Deccan. Sultan Zain Uddin (1420-1470 A.D.) introduced extensive network of canals in Utpalpur, Nadashaila, Bijbihara and Advin areas of Kashmir.
Pre – Independence
Agriculture has been the backbone of the Indian economy since time immemorial as bulk of the population in rural areas depended on agriculture for its livelihood. References to irrigation abound in the folklore and ancient literature of the country. The physiographical features of the area largely conditioned the nature of these works. In the arid and semi-arid plains of North India, perennial rivers like Indus and the Ganges easily diverted floods through inundation channels. In the peninsular part, where rivers are not perennial and rainfall is scanty, the practice of trapping storm water in large tanks for agricultural and domestic purposes was popular. In areas where high ground water table permitted lift irrigation, wells were common. The Grand Anicut across Cauvery River still remains by far one of the greatest engineering feats of ancient India. The Viranrayana and Gangaikondacholapuram tanks in Tamil Nadu and Anantaraja Sagar in Andhra Pradesh were constructed in the 10th and 13th centuries. The Western and Eastern Yamuna Canals and Hasli Canal in the Ravi were dug in the 16th and 18th centuries.
Under the British rule, irrigation development continued with renovation and improvement of existing irrigation works and with this experience, more new diversion works such as Upper Ganga Canal, Upper Bari Doab Canal, Krishna and Godavari delta systems were taken up and completed between 1836 and 1866. By the second half of the 19th century, irrigation potential to the tune of about 7.5 million hectares (m. ha) had been developed.
Based on recommendations of the First Irrigation Commission, the period during 1900-1947 saw more irrigation development and the potential created increased to 22.5 m ha at the time of independence. There was a distinct shift from diversion works to survey, investigation and implementation of storage works during this period. Dams like Krishnaraja Sagar and Mettur were constructed across Cauvery River during this period. Storages were identified on Tungabhadra, Krishna, Narmada, Sabarmati, Mahi and Sutlej rivers. One reason for this shift was the realization that cheap diversion sites had already been exhausted. The need for productive irrigation and not merely protective irrigation was another. It was also realized that arid and drought areas could be benefited only by transferring water from other areas, which would be possible only with storage dams.
Post – Independence
After independence, the tempo of irrigation development was sharply accelerated with the objective of attaining self-sufficiency in food grains to meet the needs of a growing population. Construction of large storages like Bhakra, Hirakud, Nagarjunasagar -called by Pandit Nehru as ‘Temples of Modern India’, were taken up and completed. The criteria for economic evaluation of storage projects were changed from the financial return evaluation to a benefit- cost ratio evaluation. The return to the Government on investment was, thus, no more relevant but benefit to the farmer (at a cost to the Government) became the main evaluation criterion.
The development of irrigation potential took place in successive plans by leaps and bounds and reached an impressive 89.5 m ha by the end of the Eighth Five Year Plan. The country achieved self-sufficiency in food grains by producing 200 million tones and import of food grains became a thing of the past.
The Second Irrigation Commission, set up in 1969, while not advocating any major change in the policy of irrigation development, cautioned in its report that areas like conjunctive use of surface and ground water, command area development, watershed development, increase in water rates to meet Operation and Maintenance (O & M) costs as well as a part of the interest on investment also needed attention.
The Government took a number of policy decisions in pursuance of the above recommendations, relating to command area development, protection of environment and forests, conjunctive use, flood plain zoning, regulation on use of ground water, preservation of water quality and the like. These measures have met with varying degrees of success and have had a bearing on the irrigation development achieved so far and also in shaping the future strategy in this sector.