MAJOR AND MEDIUM IRRIGATION SCHEMES OF INDIA

Major irrigation schemes are those which have culturable command area (C.C.A.)* quite 10,000 ha. Irrigation schemes having C.C.A. between 2,000 and 10,000 ha are classed as medium irrigation schemes (8). The important schemes of the primary two plan periods include Bhakra- Nangal, Rajasthan canal, Gandhi Sagar dam, Gandak, Kosi, Nagarjunasagar, Hirakud, Tungabhadra, Malaprabha, and Ghatprabha projects. Later, the multipurpose Beas project, Ramganga dam and canals, Sri Ramsagar, Jayakwadi, Ukai, Kadana, Sardar Sarovar, Tawa, Teesta, etc. were haunted for utilising the monsoon waters.

The performance of major and medium irrigation schemes was examined by the National Irrigation Commission (1972), the National Commission on Agriculture (1976), and a number of other other committees. it had been found that the available irrigation potential was not fully utilised. The difference between the available and utilised irrigation potential exceeds 4.0 Mha. Waterlogging and salinity damaged large areas. Moreover, the return in terms of increased agricultural production was far below the expectations. For of these deficiencies, the subsequent causes were identified (8).

(i) Need for modernisation of the pre-Plan and early-Plan systems to supply water at the outlet delivery points to farmers at the proper time and in the right quantity.
(ii) Lack of adequate drainage leading to waterlogging conditions due to excess water used in irrigating crops as well as due to soil characteristics.
(iii) The absence of a distribution system within the outlet and therefore the non-introduction of rotational distribution of water to the farmers.
(iv) Inadequate attention to land consolidation, levelling and every one other aspects which can promote a far better on-farm management of water.
(v) Lack of anticipatory research on optimum water use, particularly in black soils with considerable moisture retention capacity.
(vi) Lack of suitable infrastructure and extension services.
(vii) Poor coordination between the concerned Government organisations within the command areas.

Irrigation projects constructed before 1965 were designed to meet the irrigation demand of traditional crops. With the utilization of high-yielding varieties of seeds since 1965, many of the earlier projects became inadequate to satisfy the exacting demands for water in respect of highyielding varieties of crops.

Table 1. State-wise ultimate irrigation potential and potential created and utilised upto 1992–93 (6)

(Unit: Thousand Hectares)

Modernisation of the old irrigation systems listed in Table 2. has, therefore, become necessary (8). The weaknesses within the old structures, adequate capacity of the canals to cope with the newest cropping patterns, deficiencies within the control structure system, causes of heavy losses within the irrigation channels, methods to reinforce canal supplies in tail reaches, and other aspects of modernisation are being looked into for a few important projects.

Table 2. Old irrigation systems needing modernisation (8)

The drainage problem is acute within the states of Punjab and Haryana. It also prevails in the command areas of a number of the irrigation projects of UP, West Bengal , Gujarat, Madhya Pradesh, and Maharashtra. Serious waterlogging and consequent salinity problems have arisen in the Chambal Project areas in Madhya Pradesh and Rajasthan, the Kosi and Gandak Project areas in Bihar, Tungabhadra in Karnataka, Nagarjunasagar in Andhra Pradesh , and the Kakrapar system in Gujarat. Inadequate drainage and consequent waterlogging prevails in the Purna, Pravara, and Neera projects in Maharashtra, Dantiwara in Gujarat, Barna and

Tawa in Madhya Pradesh, Lower Ganga canal in UP, Malampuzha in Kerala, Periyar-Vaigai in Tamil Nadu , Tungabhadra in Andhra Pradesh and Karnataka, the Sone system in Bihar, Ranbir and Pratap canals in Jammu and Kashmir, Hirakud and Mahanadi Delta in Orissa, and Krishna Delta in Andhra Pradesh . consistent with the estimates of the National Commission on Agriculture (1976), a complete area of about 6 Mha is waterlogged .

* Gross command area of an irrigation system is the total area which can be economically irrigated from the system without considering the limitations of the quantity of available water. Area of the cultivable land in the gross command of an irrigation system is called the culturable command area (C.C.A.).