A rotation method among irrigation groups has been implemented to counter water-shortage problem. However, the conventional rotation irrigation method lacks a procedure for practical implementation of water distribution to mitigate effects of the water shortage. In this study a rotational method of irrigation is proposed using a parameter which is defined as a ratio between effective water supply and effective water demand and also designated as a K-factor to provide a stepwise procedure for water distribution method that can take into account the presence of variable sources of water supply. The irrigation area of the Chung-tan working station located at the Kaohsiung Irrigation Association in Taiwan was used as an example to demonstrate the practical application of the K-factor. The results showed that using the developed K-factor as an index of water distribution is an expedient means and stepwise procedure to achieve a water distribution scheme for varying water supplies.