Islands have many problems due to their isolation and many islands lack domestic water for everyday use. However, there are few studies of forms of water intake and water use in such islands. Such research is necessary. The study regions in the present research are the Nada Area of Nandan Town, Mihara County and the Kaminada Area of Sumoto City. These regions are situated on steep slopes at the southern foot of the Yuzuruha Mountains in Awajishima Island and the different water intake and water use in each village have been evolved according to the geomorphological conditions. The aim of this research is to clarify forms of domestic water intake and changes in the spatial structure of water utilization in the region where water utilization conditions are unfavorable. This research is summarized as follows: 1. There are 5 types of water intake as shown in Table 1. Type A: in which water is diverted from mountain streams cooperatively and a small water supply system functions for the exclusive use of the village. Type B: in which water intake from mountain streams is carried out by individual households. Type C : in which water intake is from a spring (called Kawa or Hori) or a well. Type D: in which water is distributed from a town-managed small water supply system, and type E: in which water is diverted from an irrigation pond. 2. Type A water intake is being used in 14 out of 17 villages and type D is being used in 2 villages. One village is situated in a transition zone between type A and type D and uses types B, C and E. 3. Type A water intake is further classified into 2 type: A1 type having many water utilization groups in a village and A2 type having only one water utilization group in a village. A1 type occurs in 6 villages and A2 type in 8 villages. 4. Due to the geomorphological conditions that houses locate dispersedly on small marine terraces, type A1 is seen in Yudani, Yamamoto and Sogawa. Type A1 occurs due to social factors that social groups originate wate rutilization groups and is seen in Yoshino, Kuroiwa and Shirosaki. In 3 villages where many water utilization groups are formed by such social factors, water intake is taken per Rinpo which is a small territorial group and has various social functions. It is thought that in Yoshino and Kuroiwa the distribution of Rinpo is strongly influenced by the topography. In Shirosaki, 2 water utilization groups are formed by 2 Rinpos which hold conflicting views on water utilization methods. So only these water utilization groups in this village can be said to be formed just by social factors. 5. The reason why many water utilization groups are not unified as one group is that it has not been necessary to alter the forms in the water utilization until now, even in order to meet high costs for construction, so long as no drought occurs. When a drought occurs, water utilization groups may become unified, as in the case of the village of Shirosaki. 6. In type A2 joint diversions of domestic water, no clear-cut rules concerning utilization procedures, distribution, and maintenance labor exist such as are found in agricultural water utilization groups. To a certain degree, however, a management rule is established, since facilities in this form often break down. For example, persons on duty for the water work are selected and these persons manage the water works facilities. When things break down on a large scale, all households contribute to repair works. There are villages which collect expenses for repairs every month. Further, with respect to the source of water supply, the degree of distress in a dry period is quite different between villages which have the water right on the mountain stream and those that don't, have it. Such villages as Habu have often changed the source of their small water works.