Water resources. All civilizations started with agriculture, and agricultural water accounted for most of the total water resources after all the efforts had been put into the irrigation business. However, in many developed countries, such as Taiwan, Japan and Korea, due to the development of the industry and businesses, the improvement of living standard has led to the demand for more public, domestic, as well as industrial water supply. Again, due to the difficulties of developing new water sources as well as the environmental protest problems, the demand to transfer agricultural water resources to nonagricultural sectors has been increasing. In addition to the decrease in quantity as a result of transferring to nonagricultural purposes, agricultural water quality is decreasing owing to the discharge of domestic and industrial waste water. In many cases, contaminated agricultural water has not been suitable for irrigation purposes.