The study assesses the implications of the bioethanol policy mandate in Thailand of producing 9 M litre ethanol per day by 2021 on water use and water deprivation. The results reveal that water footprint (WF) of bioethanol varies between 1396 and 3105 L water/L ethanol. Cassava ethanol has the highest WF followed by molasses and sugarcane ethanol, respectively. However, in terms of fresh water (especially irrigation water) consumption, molasses ethanol is highest with 699-1220 L/L ethanol. To satisfy the government plan of bioethanol production in 2021, around 1625 million m(3) of irrigation water/year will be additionally required, accounting for about 3% of the current active water storage of Thailand. Two important watersheds in the northeastern region of Thailand are found to be potentially facing serious water stress if water resources are not properly managed. Measures to reduce water footprint of bioethanol are recommended. (C) 2013 Elsevier Ltd. All rights reserved.