The process of fuel ethanol production from cassava root is connected to a chain of impacts on the water resource of the country where the cassava plant is grown and the root processed into fuel ethanol. The paper assesses the impact of the domestic production of 5 per cent ethanol (E5) needed under the Nigerian biofuel programme from cassava root on the water resource of Nigeria. Using the 2007 Premium Motor Spirit (PMS) consumption as the baseline, Nigeria will require about 0.49 hm(3) of ethanol to blend 9.32 hm(3) of PMS to arrive at the 2007 consumption estimates. The impact of the domestic production of this ethanol requirement translates to about 6.0 km(3) of water; out of which about 48 per cent is green and about 52 per cent is blue. Addressing future impact typical of a developing economy like Nigeria, a three-scenario analysis was adopted to examine the impact of future growth in cassava-fuel ethanol requirement on the water resource of Nigeria, and also, the impact of improved water use on the future water footprint of ES. The projected water impact of cassava-ethanol production into the future ranges from 6.02 to 7.28 km(3), while improved water use could lower these values by about 0.04-2.35 km(3) for the same period, 2010 to 2020, under the projection assumptions made. (C) 2010 Elsevier Ltd. All rights reserved.