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.

8. Inland Navigation: Large canals can also be used for inland navigation, and thus transportation of agricultural products to the mandis.

9. Improvements of communication: Almost all the irrigation channels are provided with inspection roads. These roads can be metalled, and be used as means of communication.
10. Canal Plantation: The stripped area along the canal is always damp, and therefore, trees etc, are planted along the canals banks, water courses and field boundaries. The increases timber wealth of the country and also checks the soil erosion.
11. Improvement in ground water storage: Due to the constant percolation and seepage of water, the ground water table is raised in the area where irrigation facilities are prevalent. So long as this water table remains well below the root zone of the crop, this improvement in the ground water storage is beneficial.
12. Aid in Civilisation: Due to the introduction of river valley projects, the violent tribes adopt irrigation as their profession, and settle peacefully. Also, due to the increased yield and vale of the crop, the standard of living of a common cultivator is improved, and he becomes more civilised.
13. General Development of the Country: The most important benefit derived from the irrigation is the general development of an agricultural country such as ours in which majority of people live in villages and have agricultural as their profession. Due to the increased yield and value of the crop, means of communication, such as road-ways, railways and post and telegraph facilities are introduced. Due to the increase in agricultural revenue of the state, and due to rise in living standard of the people, school, hospitals and other facilities are provided. All these in turn have direct influence in making the people netter citizens. There are instances in which the most dry and backward areas have become prosperous and civilised, mainly due to the introduction of irrigation facilities.

Ill Effects of irrigation: Excess irrigation and unscientific use of irrigation water may give rise to the following ill-effects:

1. Breeding places for mosquitoes: Due to excess application of water, and due to leakage of water, ponds and depressions get filled up with water and create breeding places for mosquitoes. Also, if the canal is leaky, mosquitoes breed all along the canal and spread malaria conditions.
2. Water- Logging: If the water table is near the ground surface, over-irrigated may raise the water table. This saturates the crop root-zones completely, causes efflorescence and the whole area becomes waterlogged.
3. Damp Climate: The area which are already damp and cold, become damper and colder due to irrigation.