31 ref. IIMI research report no. 12 IIMI, POB 2075 Colombo - Sri Lanka. E-mail: r.desilva@cgnet.com

This report is based on several years of IIMI research at the Tambraparani Irrigation System, much of which carried out in collaboration with the Centre for Water Resources, Anna University in Madras, and with the Irrigation Management and Training Institute in Tiruchirapalli. This report makes two arguments about the relationships of water distribution rules to water distribution performance. First, it argues that if water delivery does not match technically feasible goals of the water users, then the users will subvert the rules. This will lead to poor water delivery performance and increases in the cost of irrigation to the users. Second, it argues that inconsistency in the water distribution rules creates difficulties in system operations that are likely to lead to inefficient and inequitable water distribution performance. Data from the Tambraparani Irrigation System in Tamil Nadu, India, are used to demonstrate these points. Specifically, the allocation rules do not provide for the irrigation of bananas although farmers want to plant them. Farmers take a variety of actions to get water for their bananas. In addition, inconsistencies in the Tambraparani rules makes it difficult to operate the system according to the rules. For example, the rules for the operation of the system reservoirs limit flows to less-than-required for irrigation during some periods. The various inconsistencies lead to unpredictable water deliveries. The resulting inefficiencies and inequalities are demonstrated using data for the year 1994-1995. It is argued that problems at Tambraparani arise from fundamental issues that apply to all large irrigation schemes. In particular, increasing demands on irrigation systems from both farmers and other users make it essential to modify water distribution rules over time. Resolution of these problems requires devising a system by which responsible persons review system performance and can initiate changes to water distribution rules as needed. It is further argued that involvement of the users in these changes is essential to ensure that the distribution rules serve their desires and that the users accept the limitations on uses imposed by water availability and the features of the system

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