Contents preface (VII) introduction 1—37

190 IRRIGATION AND WATER RESOURCES ENGINEERING
5.11.1. Warabandi
Warabandi is an integrated management system from source (river or reservoir) down to the farm gate, i.e., nakka. In the Warabandi system (Fig. 5.10), the water from the source is carried by the main canal which feeds two or more branch canals (which operate by rotation) and may not carry the total required supply. This is the primary distribution system which runs throughout the irrigation season with varying supply. The secondary distribution system consists of a larger number of distributaries which too run by rotation but carry full supply. They are fed by the branch canals of the primary distribution system. The distributaries supply water to the watercourse through outlets. These watercourses run full supply when the supplying distributary is running.

				Flow
	Headworks		e	r
		i		v
		R
			canal
			Main	(Primary system)
Distributary		canal		Branch	canal
	Branch
				(Secondary
		Ungated		system)
		outlet
Branch	Distributary			Distributary
Legend
	Managed by state				Watercourse
Managed by farmers				(Tertiary system)
Outlet
Nakka
Watercourse				Nakka
Chak boundary
	Holding boundary

Fig. 5.10 Typical warabandi distribution system (4)
Water is then allocated to various fields (or farms) situated along the watercourse by a time roster. This is the tertiary distribution system.
Warabandi is a distribution system whose main objective is to attain high efficiency of water use by imposing water scarcity on every user. The system ensures equitable distribution and safeguards the interest of the farmer whose field is located at the tail end of the conveyance

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191

system. Such a system is a classic example of the joint state-farmer management of the irrigation system. The segment upstream of the outlet is managed by the state whereas the farmers manage the segment downstream of the outlet.

In the warabandi system, each unit of culturable command area is allocated a certain rate of flow of water, termed water allowance, whose value is generally a compromise between demand and supply. The carrying capacity of distributaries and watercourses is designed on the basis of water allowance. Whenever distributaries run, they are expected to carry their full supply. The outlets to watercourses are so planned and constructed that all the watercourses on a distributary withdraw their authorised share of water simultaneously. For the Bhakra project covering Punjab, Haryana, and Rajasthan, the value of water allowance at the head of the watercourse is 0.017 m³/s per 100 hectares of culturable command area.
To check the dangers of waterlogging and salinity, no distributary is allowed to operate all the days during any crop season. The ratio of the operating period of a distributary and the crop period is called the capacity factor of the distributary. For the Bhakra project, the capacity factors of Kharif and Rabi are, respectively, 0.8 and 0.72 which means that each distributary would receive its full supply for a period of about 144 and 129 days, respectively, in a crop season of 180 days.
Because of the limits on the supply of irrigation water as well as other factors, it is generally not possible to irrigate all culturable command area. The ratio of the resultant irrigated area to the culturable command area is termed intensity of irrigation. Its value is 62 per cent for the Bhakra project. The intensity of irrigation is an index of the actual performance of the irrigation system.
In the warabandi system, the design of distributaries and watercourses is related to the culturable command area (which is fixed) rather than the variable cropping pattern. The total amount of water available at the source has its own limitations and it may not always be possible to expand or augment the supply to keep pace with the ever-increasing demand of the cropping pattern. Therefore, there is an obvious advantage of relating the design to the culturable command area rather than to the needs of the cropping pattern.
5.11.2. Management of Warabandi System
The distribution of water in the warabandi system is a two-tier operation and each is managed by a separate agency. The state manages the supply in distributaries and watercourses which, when running, always carry their full supply discharge. This reduces their running time and, hence, the conveyance losses in the distributaries and the watercourses. The distributaries are generally operated in eight-day periods. The number of these periods would depend on the availability of water and crop requirements. In a normal year, it is possible to run the distributaries of the Bhakra project for 18 periods during Kharif and 16 periods during Rabi.
The second stage of managing the distribution of water coming out of an outlet and flowing into a watercourse is the responsibility of the cultivators themselves. The distribution is done on seven-day rotation basis with the help of an agreed roster (or roster of turns) which divides 168 hours of seven days in the ratio of the holdings. The eight-day period of distributary running ensures a minimum of seven days running for each watercourse including those which are at the tail end of the distributary.
Each cultivator’s right to share water in a watercourse is guaranteed by law and the Canal Act empowers canal officers to ensure this right for everyone.

192 IRRIGATION AND WATER RESOURCES ENGINEERING
Whenever a distributary is running, watercourse receives its share of water at a constant rate round the clock and water distribution proceeds from head to tail. Each cultivator on the watercourse is entitled to receiving the entire water in a watercourse only on a specific weekday and at a specific time (during day and/or night). There is no provision in this system to compensate a defaulting farmer who has failed to utilise his turn for any reason.