Yield failure is often caused by the uncertainty of supply or the shortage of water at the critical period of crop growth. This situation compels farmers and engineers to find ways to efficiently use the available resource. Reduction of irrigation depth or extension of irrigation interval are the methods commonly adopted. Another alternative is the application of the rotational irrigation technique instead of continuous irrigation. The question is how to adjust the water supply to minimize crop yield losses. Water supply itself is a dynamic parameter depending on farm size, canal capacity and crop growth stages. The distribution factor (DF) is a technique of water distribution based on the dynamic character of the supply over the growth stages. It allows categorization of the allocation of the available water in the farm within the limit of the channel capacity to satisfy crop water needs. The procedure was applied to a set of 24 farms in 2006 in the Chianan Irrigation Association which frequently experiences water shortages. The results showed that if a uniform reduction of water supply could be applied during moderate water shortages, DF made it possible to rationally distribute water among rotational groups in severe shortage conditions.