Water scarcity due to climate changes and growing human population is a major concern for the world. Adaptation strategies should be developed for water scarcity in the future. Previous studies assessed the future water availability by hard technology as adaptation strategies. On the other hand, soft path such as water law would also be important for adaptation strategies. Water trade is reallocation of water among water users. If water trades are permitted in these areas, water can be moved from surplus areas/sections to critical need areas/sections. However the factors that determined the establishment of water transfer are not clear. Here we reviewed the several water trades in Australia, California and Chile to find factors that affecting water trades. Our results suggested that climate character that dry summer and humid winter, and social factor that separation of land and water owner may affect the foundation of water trades. It could be used to estimate in which areas the water trade would come into existence.
