Assessment of irrigation water charges can be done in one of the following ways:
(i) Assessment on area basis
(ii) Volumetric assessment
(iii) Assessment based on outlet capacity
(iv) Permanent assessment
(v) Consolidated assessment.
In the area basis method of assessment, water charges are fixed per unit area of land irrigated for each of the crops grown. The rates of water charges depend on the cash value of crop, water requirement of crop and the time of water demand with respect to the available supplies in the source.
Since the water charges are not related to the actual quantity of water used, the farmers (particularly those whose holdings are in the head reaches of the canal) tend to over irrigate their land. This results in uneconomical use of available irrigation water beside depriving the cultivators in the tail reaches of the canal of their due share of irrigation water.
However, this method of assessment, being simple and convenient, is generally used for almost all irrigation projects in India. In the volumetric assessment, the charges are in proportion to the actual amount of water received by the cultivator. This method, therefore, requires installation of water meters at all the outlets of the irrigation system.
Alternatively, modular outlets may be provided to supply a specified discharge of water. This method results in economical use of irrigation water and is, therefore, an ideal method of assessment. But it has several drawbacks.
This method requires installation and maintenance of suitable devices for water measurement. These devices require adequate head at the outlet. Further, there is a possibility of water theft by cutting of banks or siphoning over the bank through a flexible hose pipe. Also, the distribution of charges among the farmers, whose holdings are served by a common outlet, may be difficult. Because of these drawbacks, the method has not been adopted in India.
Assessment of canal water charges based on outlet capacity is a simple method and is workable if the outlets are rigid or semi-modular and the channel may run within outlet’s designed range of parameters. In some regions, artificial irrigation, though not essential, has been provided to meet the water demand only in drought years.
Every farmer of such a region has to pay a fixed amount. The farmers have to pay these charges even for the years in which they do not take any water. A farmer has also to pay tax on the land owned by him. In the consolidated assessment method, both the land revenue and the water charges are combined, and the cultivators are accordingly charged.