India’s Irrigation Needs & Strategies for Development- 2 Notes | EduRev

Irrigation Engineering

Civil Engineering (CE) : India’s Irrigation Needs & Strategies for Development- 2 Notes | EduRev

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Command Area Development Programme (CADP) 

This scheme, sponsored by the central government was launched in 1974-75 with the objective of bridging the gap between irrigation potential created and that utilized for ensuring efficient utilization of created irrigation potential and increasing the agricultural productivity from irrigated lands on a sustainable basis. The programme envisages integrating various activities relating to irrigated agriculture through a multi-disciplinary team under an area development authority in a coordinated manner. The existing components of the CADP are as follows:- 

  1. On farm development works, that is, development of field channels and field drains within the command of each outlet, land leveling on an outlet command basis; reclamation of water logged areas; enforcement of a proper system of rotational water supply (like the warabandi) and fair distribution of water to individual fields; realignment of field boundaries, wherever necessary (where possible, consolidation of holding are also combined)supply of all inputs and service including credit; strengthening of extension services; and encouraging farmers for participatory irrigation management.
  2. Selection and introduction of suitable cropping patterns.
  3. Development of ground water to supplement surface irrigation (conjunctive use under minor irrigation sector)
  4. Development and maintenance of the main and intermediate drainage system. 
  5. Modernization, maintenance and efficient operation of the irrigation system up to the outlet of one cusec (1ft3/sec) capacity. 

 For an overall appreciation of an entire irrigation project it is essential that the objectives of the CAD be kept in mind by the water resources engineer. 

Participatory irrigation management (PIM) 

Any irrigation project cannot be successful unless it is linked to the stakeholders, that is, the farmers themselves. In fact, people’s participation in renovation and maintenance of field channels was the established practice during the pre independence days. However, the bureaucracy encroached on this function in the post independence period and a realization has dawned that without the participation of farmers, the full potential of an irrigation scheme may not be realized. Though a water resources engineer is not directly involved in such a scheme, it is nevertheless wise to appreciate the motive behind PIM and keep that in mind while designing an irrigation system. 

The national water policy stresses the participatory approach in water resources management. It has been recognized that participation of the beneficiaries would help greatly for the optimal upkeep of irrigation system and utilization of irrigation water. The participation of farmers in the management of irrigation would give responsibility for operation and maintenance and collection of water rates from the areas under the jurisdiction of the water user’s association of concerned hydraulic level. Under the command area development programme (CADP), presently a provision exists for a  one-time functional grant to farmer’s associations at the rate of Rs. 500 per hectare of which Rs. 225 per hectare is provided by the central government and state government each, and Rs. 50 per hectare is contributed by the farmer’s associations. 

It may be mentioned that so far, that is by year 2004, the state governments of Andhra Pradesh, Goa, Karnataka, Tamilnadu, Rajasthan and Madhya Pradesh have enacted legislations for the establishment of the water user’s associations.

The sustainability and success of PIM depends on mutual accountability between the water user’s association and the irrigation department of the concerned state, attitudinal change in the bureaucracy, autonomy for the water user’s associations, multifunctional nature of the water user’s association and the choice of appropriate model for PIM with appropriate legal and institutional framework. If the farmers have to take over and manage the system, then the system must be rectified by the irrigation department to a minimum standard to carry the design discharge before it is handed over to the water user’s association. The success of the PIM is also linked to the introduction of rotational water supply and water charges with rationalized establishment costs. Unlined field channels need to be manually constructed in a ‘V’ shape which is considered stable and efficient for carrying water. 

Management of water for irrigation

Of the two resources –land and water, management of the former is largely in the domain of agricultural engineers. Management of water, on the other hand, is mostly the purview of the water resources engineer who has to decide the following: 

  • How much water is available at a point of a surface water source, like a river (based on hydrological studies)
  • How much ground water is available for utilization in irrigation system without adversely lowering the ground water table?
  • For the surface water source, is there a need for construction of a reservoir for storing the monsoon runoff to be used in the lean seasons?
  • What kind of diversion system can be constructed across the river for diverting part of the river flow into a system of canal network for irrigating the fields?
  • How efficient a canal network system may be designed such that there is minimum loss of water and maximum agricultural production?
  • How can excess water of an irrigated agricultural fields be removed which would otherwise cause water logging of the fields?  

In order to find proper solution to these and other related issues, the water resources engineer should be aware of a number of components essential for proper management of water in an irrigation system. These are:- 

1. Watershed development: since the water flowing into a river is from a watershed, it is essential that the movement of water over ground has to be delayed. This would ensure that the rain water falling within the catchment recharges the ground water, which in turn replenishes the water inflow to the reservoir even during the lean season. Small check dams constructed across small streams within the catchment can help to delay the surface water movement in the watershed and recharge the ground water. Measures for the water shed development also includes aforestation within the catchment area which is helpful in preventing the valuable top-soil from getting eroded and thus is helpful also in preventing siltation of reservoirs. Other soil conservation methods like regrassing and grass land cultivation process, galley plugging, nullah bunding, contour bunding etc. also come under watershed development.

2. Water management: surface water reservoirs are common in irrigation systems and these are designed and operated to cater to crop water requirement throughout the year. It is essential, therefore, to check loss of water in reservoir due to  

Evaporation from the water surface

Seepage from the base

Reduction of storage capacity due to sedimentation

3. Water management in conveyance system: In India the water loss due to evaporation, seepage and mismanagement in the conveyance channels (for canals and its distributaries) is exceptionally high-nearly 60%. Some countries like Israel have reduced this loss tremendously by taking several measures like lining of water courses, lining not only reduces seepage, but also minimizes weed infestation and reduces overall maintenance cost though the initial cost of providing lining could be high depending on the material selected.

4. On farm water management: Though this work essentially is tackled by agricultural engineers, the water resources engineers must also be aware of the problem so that a proper integrated management strategy for conveyance-delivery-distribution of irrigation water is achieved. It has been observed from field that the water delivered from the canal system to the agricultural fields are utilized better in the head reaches and by the time it reaches the tail end, its quantity reduces. Often, there are land holding belonging to different farmers along the route of the water course and there is a tendency of excess withdrawal by the farmers at the upper reaches. In order to tackle this kind of mismanagement a proper water distribution roster has to be implemented with the help of farmers’ cooperatives or water user’s associations. At times farmers are of the opinion that more the water applied more would be the crop production which is generally not true beyond a certain optimum water application rate. Education of farmers in this regard would also ensure better on-farm water management.

5. Choice of irrigation method: Though irrigation has been practiced in India from about the time of the Harappa civilization, scientific irrigation based on time variant crop water need within the constraints of water and land availability is rather recent. It is important to select the right kind of irrigation method to suit the particular crop and soil. For example, following is a short list of available methods corresponding to the kind of crop. 

 

Method of irrigationSuitable for crops 
Border strip methodWheat, Leafy vegetables, Fodders 
Furrow methodCotton, Sugarcane, Potatoes 
Basin methodOrchard trees 

Other methods like sprinkler and drip irrigation systems are adapted where water is scarce and priority for its conservation is more than the consideration for cost. Although most advanced countries are adopting these measures, they have not picked up as much in India mainly due to financial constraints. However, as time passes and land and water resources get scarce, it would be essential to adopt these practices in India, too. 

6. Choice of cropping pattern: Scientific choice of cropping pattern should be evolved on the basis of water availability, soil type, and regional agro-climate conditions. Crop varieties which give equivalent yield with less water requirement and take less time to mature should be popularized. Scientific contribution in the form of double or multiple cropping can be achieved if the sowing of crops such as paddy, groundnut, arhar etc. is advanced, if necessary, by raising the nurseries with the help of groundwater. Selection of crops planting sequence per unit weight of water applied. 

7. Scheduling of irrigation water: Traditional farmers engaged in crop production are aware of some kind of scheduling of water to the crops, but their knowledge is based mostly on intuition and traditional wisdom rather than on any scientific basis. Modern scientific study on crop growth has shown that a correlation can be established between the climatic parameters, crop water requirement and the moisture stored in the soil especially in the root zone. It has now been established by scientific research that the application of irrigation should be such that the available water in the soil above the permanent wilting point is fully utilized by the crop before requiring application of water to replenish the depleted moisture in the soil. Since any canal would be delivering water at the same time to different fields growing different crops, the demand of the various fields have to be calculated at any point of time or a certain period of time(days, weeks),and the water distributed accordingly through the canal network. 

8. Development of land drainage: Due to improper application of water and inadequate facilities for drainage of excess water from irrigated lands, large tracks of land near irrigated areas have been affected with water logging and excess salt concentration in soils. Adequate drainage measures like surface and subsurface drainage systems, vertical drainage, bio-drainage etc. should be developed as an integral part of the irrigation system. 

9. Command area development: We have already seen that the government has initiated the command area development programme (CADP) which would ensure efficient water utilization and integrated area developments in the irrigation command. 

10. Canal automation: At present, the water entering the canal network through the headworks as well as the water getting distributed into the various branches and finally reaching the fields through the outlets are controlled manually. However, if these operations are carried out through automated electro-mechanical systems which can communicate to a central computer, then the whole process can be made more efficient. This would also help to save water and provide optimal utilization of the availability water. 

Classification of irrigation schemes 

The classification of the irrigation systems can also be based on the way the water is applied to the agricultural land as:

  1. Flow irrigation system: where the irrigation water is conveyed by growing to the irrigated land. This may again be classified into the following.
    • Direct irrigation: Where the irrigation water is obtained directly from the river, without any intermediate storage. This type of irrigation is possible by constructing a weir or a barrage across a river to raise the level of the river water and thus divert some portion of the river flow through an adjacent canal, where the flow takes place by gravity.
    • Reservoir/tank/storage irrigation: The irrigation water is obtained from a river, where storage has been created by construction an obstruction across the river, like a dam. This ensures that even when there is no inflow into the river from the catchment, there is enough stored water which can continue to irrigate fields through a system of canals.
  2. Lift irrigation system: Where the irrigation water is available at a level lower than that of the land to be irrigated and hence the water is lifted up by pumps or by other mechanical devices for lifting water and conveyed to the agricultural land through channels flowing under gravity. 

Classification of irrigation systems may also be made on the basis of duration of the applied water, like: 

  1. Inundation/flooding type irrigation system: In which large quantities of water flowing in a river during floods is allowed to inundate the land to be cultivated, thereby saturating the soil. The excess water is then drained off and the land is used for cultivation. This type of irrigation uses the flood water of rivers and therefore is limited to a certain time of the year. It is also common in the areas near river deltas, where the slope of the river and land is small. Unfortunately, many of the rivers, which were earlier used for flood inundation along their banks, have been embanked in the past century and thus this practice of irrigation has dwindled. 
  2. Perennial irrigation system: In which irrigation water is supplied according to the crop water requirement at regular intervals, throughout the life cycle of the crop. The water for such irrigation may be obtained from rivers or from walls. Hence, the source may be either surface or ground water and the application of water may be by flow or lift irrigation systems.  

Pricing of water  

This is more of a management issue than a technical one. After all, the water being supplied for irrigation has a production cost (including operation cost and maintenance cost) which has to be met from either the beneficiary or as subsidy from the government. Since water is a state subject (as the matter included in entry 17 of list 11 that is, the state list of the Constitution of India), every state independently fixes the rates of water that it charges from the beneficiaries, the remaining being provided from state exchequer.

There are wide variations in water rate structures across states and the rate per unit volume of water consumed varies greatly with the crop being produced. The rates charged in some states for irrigation vary even for different projects depending on the mode of irrigation. The rates, at present, also vary widely for the same crop in the same state depending on irrigation season, type of system, etc. 

As such, right now, there is no uniform set principles in fixing the water rates and a wide variety of principles for pricing are followed for the different states, such as: 

  • recovery cost of water
  • capacity of irrigators to pay based on gross earning or net benefit of irrigation
  • water requirement of crops
  • sources of water supply and assurance
  • classification of land linked with land revenue system

In some states water cess, betterment levy, etc. are also charged. Hence, there is an urgent need of the water resources planners to work out a uniform principle of pricing irrigation water throughout the country, taking into account all the variables and constraints. 

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