India’s Irrigation Needs and Strategies for Development (Part - 1) Civil Engineering (CE) Notes | EduRev

Irrigation Engineering

Civil Engineering (CE) : India’s Irrigation Needs and Strategies for Development (Part - 1) Civil Engineering (CE) Notes | EduRev

The document India’s Irrigation Needs and Strategies for Development (Part - 1) Civil Engineering (CE) Notes | EduRev is a part of the Civil Engineering (CE) Course Irrigation Engineering.
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Introduction 

It is known fact that India has a very large population and different studies show that it will continue to rise at least till 2050 A.D. The United Nations publication “Sustaining Water - An Update”, published in 1994 indicates that the population of India by that time could vary between 1349 million (low projection) and 1980 million (high projection), with a medium projected figure as 1640 million. At present the country’s food grain availability is around 523 grams per capita per day (though it varies significantly with the economic level). In China and USA, the corresponding figures are 980 grams and 2850 grams respectively. Assuming a population figure of 1800 million by 2050A.D, and a small rise in per capita consumption of food grain at about 650 grams, the annual requirement of the country would be around 430 million tonnes. The present productivity of irrigated land is about 2.5 tonnes/hectare and les than 0.5 tonnes/hectare for rainfed lands. Assuming that these levels can go up to 3.5 and 1.0 T/hr respectively by 2050 AD (which should be the urgent needs that has to be addressed to by the water resource engineer), it is imperative that the irrigation potential of at least 130 million hectare is created for food crop alone and 160 million hectare for all crops to be able to meet the demands of the country by 2050 AD.

Since the land and water resource of any country is not going to change much over the years, the water resource planners have to make cautious decisions on optimizing the available resources for maximum benefit. In the next section, we look into the options available and the decisions that may be taken. 

Sustainable development in Irrigation 

For the survival of the country, there is an urgent need to implement and plan irrigation strategies for now, and in future, as the population continues to grow. But that should not be at the cost of degradation of the present available resources of land and water, which means the natural resources that we have, should more or less remain the same after 50 or 100 years and beyond. This concept is termed “sustainable”, which was not much of a problem earlier when compared to the resources the demand was less. But now it is reversed and for devising any planning strategy the constraints have to be kept in mind. As an example, the utilization of ground water may be cited. In many regions of India, there has been alarming withdrawal of ground water for meeting demands of irrigation and drinking water demand than that which can be naturally recharged. This has led to rise of further problems like arsenic and fluoride contamination. Since ground water recharge by natural means takes a long time, perhaps years and even decades, there is little hope of regaining the depleted table near future. 

Next we look into the options available to the irrigation engineer for development of irrigation facilities within the constraints. 

Future directions 

The question that is to be resolved is this: Are we capable of producing the required amount of food grain for the country? Apart from spreading the network of irrigation system further into the country, there is an urgent need on research- for better seeds, better water management and distribution practices, low cost fertilizer etc., Nevertheless, the possible options available to water resource engineer to meet the future irrigation and food requirement may, therefore, include evaporation control and reduction and losses during conveyance of water through channels, recycling of water, inter basin transfer, desalination of sea-water in coastal areas, rainfall by cloud seeding, improved technology, etc. Loss of top soil due to erosion in one of the forms of degradation which can be contained on a limited scale but problems of salinity, alkalinity, water logging, etc. reduce the productivity. The future lies in considering and bringing under cultivation additional area and considering intensified production on existing good agricultural land and water resource system optimization. 

Constraints of land and water

The total geographical area of land in India is about 329 million hectare (M-ha), which is 2.45% of the global land area. The total arable land, according to an estimate made by the Food and Agricultural Organization (FAO), made available through the web-site Aquastat, is about 165.3 M-ha which is about 50.2 % of the total geographical area (the average world figure is 10.2%). 

India possesses 4% of the total average annual run off in the rivers of the world. The per capita water availability of natural run off is at least 1100 cubic meters/yr. The utilizable surface water potential of India has been estimated to be 1869 cubic kms.but the amount of water that can actually be to put to beneficial use is much less due to severe limitations imposed by physiographic, topographic, interstate issues and the present technology to harness water resources economically. The recent estimates made by the Central Water Commission indicate that the water resources utilizable through surface structures is about 690 cubic kms only (about 36% of the total ground water is another important source of water). 

Ground water is another important source of water. The quantum of water that can be extracted economically from the ground water aquifers every year is generally known as ground water potential. The preliminary estimates made by the Central Ground Water Board indicate that the utilizable ground water is about 432 cubic km.thus the total utilizable water resource is estimated to 1122 cubic km. It must be remembered that this amount of water is unequally spread over the entire length and breadth of the country.

Of the total 329 M-ha of land, it is estimated that only 266 M-ha possess potential for production. Of this, 143 M-ha is agricultural land. It is estimated that 85 M-ha of land suffers from varying degrees of soil degradation. Of the remaining 123 M-ha, 40 M-ha is completely unproductive. The balance 83 M-ha is classified as forest land, of which over half is denuded to various degrees. 

It is alarming to note that the percapita availability of land is half of what it used to be same 35 years ago. This would further reduce as our country’s population continuous to grow. At present 141 M-ha of land is being used for cultivation purposes. Between 1970-71 and 1987-88 the average net sown area has been 140.4 M-ha. The need for production of food, fodder, fibre, fuel in the crop growing areas have to compete with the growing space require for urbanization. The factors of land degradation, like water logging, salinity, alkalinity and erosion of soils on account of inadequate planning and inefficient management of water resources projects will severely constrain the growth of net sown area in the future.

Benefits of irrigation 

With the introduction of irrigation, there have been many advantages, as compared to the total dependence on rainfall. These may be enumerated as under: 

  1. Increase in crop yield: the production of almost all types of crops can be increased by providing the right amount of later at the right time, depending on its shape of growth. Such a controlled supply of water is possible only through irrigation. 
  2. Protection from famine: the availability of irrigation facilities in any region ensures protection against failure of crops or famine due to drought. In regions without irrigation, farmers have to depend only on rains for growing crops and since the rains may not provide enough rainfall required for crop growing every year, the farmers are always faced with a risk. 
  3. Cultivation of superior crops: with assured supply of water for irrigation, farmers may think of cultivating superior variety of crops or even other crops which yield high return. Production of these crops in rain-fed areas is not possible because even with the slight unavailability of timely water, these crops would die and all the money invested would be wasted. 
  4. Elimination of mixed cropping: in rain-fed areas, farmers have a tendency to cultivate more than one type of crop in the same field such that even if one dies without the required amount of water, at least he would get the yield of the other. However, this reduces the overall production of the field. With assured water by irrigation, the farmer would go for only a single variety of crop in one field at anytime, which would increase the yield. 
  5. Economic development: with assured irrigation, the farmers get higher returns by way of crop production throughout the year, the government in turn, benefits from the tax collected from the farmers in base of the irrigation facilities extended.
  6. Hydro power generation: usually, in canal system of irrigation, there are drops or differences in elevation of canal bed level at certain places. Although the drop may not be very high, this difference in elevation can be used successfully to generate electricity. Such small hydro electric generation projects, using bulb-turbines have been established in many canals, like Ganga canal, Sarada canal, Yamuna canal etc. 
  7. Domestic and industrial water supply: some water from the irrigation canals may be utilized for domestic and industrial water supply for nearby areas. Compared to the irrigation water need, the water requirement for domestic and industrial uses is rather small and does not affect the total flow much. For example, the town of Siliguri in the Darjeeling district of West Bengal, supplies its residents with the water from Teesta Mahananda link canal.

Classification of irrigation schemes 

Irrigation projects in India are classified into three categories –major medium & minor  according to the area cultivated the classification criteria is as follows:- 

  1. Major irrigation projects: projects which have a culturable command area (CCA) of more than 10,000 ha but more than 2,000 ha utilize mostly surface water resources.
  2. Medium irrigation projects: projects which have CCA less than 10,000 ha. But more than 2,000 ha utilizes mostly surface water resources.
  3. Minor irrigation projects: projects with CCA less than or equal to 2,000 ha. utilizes both ground water and local surface water resources. Ground water development is primarily done through individual and cooperative effort of farmers with the help of institutional finance and their own savings. Surface water minor irrigation schemes are generally funded from the public sector only. The ultimate irrigation potential from minor irrigation schemes have been assessed as 75.84 million ha of which partly would be ground water based (58.46 million ha) and covers about two thirds. By the end of the ninth plan, the total potential created by minor irrigation was 60.41 million ha. 

The ultimate irrigation potential of the country from major and medium irrigation projects has been assessed as about 64 M-ha. By the end of the ninth plan period, the total potential created from major and medium projects was about 35 M-ha. 

Major and medium irrigation projects vis-à-vis minor irrigation projects

While formulating strategies for irrigation development the water resources planner should realize the benefits of each type of project based on the local conditions. For example, it may not always be possible to benefit remote areas using major/medium projects. At these places minor irrigation schemes would be most suitable. Further, land holding may be divided in such a way that minor irrigation becomes inevitable. However, major and medium projects wherever possible is to be constructed to reduce the overall cost of development of irrigation potential. 

According to the third minor irrigation census carried out in 2000-01, there are about 5.56 lakh tanks in the country, with the most occurring in the following states 

  1.  West Bengal: 21.2 percent of all the tanks in the country
  2. Andhra Pradesh: 13.6
  3. Maharashtra: 1 2.5
  4. Chhattisgarh: 7 .7
  5. Madhya Pradesh: 7.2
  6. Tamilnadu: 7 .0
  7. Karnataka: 5 .0 

Due to non use of these 15 percent tanks nearly 1 M-ha of Irrigation potential is lost. Another, around 2 M-ha of potential is lost due to under utilisation of tanks in use. Loss of potential due to non use is more pronounced in Meghalaya, Rajasthan and Arunachal Pradesh (above 30%), whereas loss of potential due to under utilisation is more than 50 percent in case of Gujarat, Nagaland, Rajasthan, A&N Island and Dadar and Nagar Haveli.

It also appears that the maintenance of the tanks has been neglected in many parts of the country and their capacity has been reduced due to siltation. It has been estimated that about 1.7 M-ha of net area has been lost under tank irrigation due to drying up of tanks and encroachment of foreshore area. Some advantages of minor irrigation should also be kept in mind. These are: small investments, simpler components, labour intensive, quick maturing and most importantly it is farmer friendly.

On the other hand, it is seen that of the assessed 64 M-ha of irrigation potential that may be created through major and medium projects, only about 35 M-ha have so far been created. Hence a lot of scope for development in this sector is remaining. These may be realized through comprehensive schemes including storage, diversion and distribution structures. Some of these schemes could even be multi-purpose thus serving other aspects like flood control and hydro power. 

Outlook of the national water policy  

Our country had adapted a national water policy in the year 1987 which was revised in 2002. The policy document lays down the fact that planning and development of water resources should be governed by the national perspective. Here we quote the aspects related to irrigation from the policy. 

  1. Irrigation planning either in an individual project or in a watershed as a whole should take into account the irrigability of land, cost-effective irrigation options possible from all available sources of water and appropriate irrigation techniques for optimizing water use efficiency. Irrigation intensity should be such as to extend the benefits of irrigation to as large a number of farm families as possible, keeping in view the need to maximize production.
  2. There should be a close integration of water use and land use policies.
  3. Water allocation in an irrigation system should be done with due regard to equity and social justice. Disparities in the availability of water between head-reach and tail end farms and between large and small farms should be obviated by adoption of a rotational water distribution system and supply on a volumetric basis subject to certain ceilings and rational pricing.
  4. Concerted efforts should be made to ensure that the irrigation potential created is fully utilised. For this purpose, the command area development approach should be adopted in all irrigation projects.
  5. Irrigation being the largest consumer of fresh water, the aim should be to get optimal productivity per unit of water. Scientific management farm practices and sprinkler and drip system of irrigation should be adopted wherever feasible.
  6. Reclamation of water-logged/saline affected land by scientific and cost effective methods should form a part of command area development programme. 
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