The Policy and Water Resources Management Committee found that in 2015, Thailand's total water demand was about 152 billion m³, concentrated in agriculture (75%), industry (3%), consumption and tourism (4%), and ecological conservation (18%) (Water Resources Policy and Management Committee 2015). As shown in Table 1, the amount of annual surface runoff calculated from rainfall, evaporation and infiltration was about 285 billion m³, while the available surface water that could be retained to serve demand was about 60 billion m³. Another available water resource, representing about 68 billion m³, was groundwater, resulting in a total available water supply of approximately 128 billion m³ with only 103 billion m³ being achieved for allocation. Thus, it still was not enough to supply the country's water needs in 2015, as mentioned above, especially the allocation of water to the agricultural area outside the irrigation area and some consumer water, about 49 billion m³. In addition, due to the expansion of the service and tourism sectors as well as local and regional commerce over the next 10 years, the expected water demand of the community, tourism and industrial sectors is likely to increase annually by about 16 billion m³ on average (Water Resources Policy and Management Committee 2015), leading to further water shortages in the country.