Hydrological impact of biofuel production: A case study of the Khlong Phlo Watershed in Thailand

This study evaluates the potential impact of increased biofuel production on the hydrology of a small watershed, Khlong Phlo, in the eastern part of Thailand. The water footprint of biofuel energy was estimated for three crops in order to identify the most water-efficient crop. The Soil and Water Assessment Tool (SWAT) model was used to evaluate the impact of land use change (LUC) caused by the expansion of biofuel crops on the components of water balance and water quality in the studied watershed. Several LUC scenarios consisting of oil palm (biodiesel), cassava and sugarcane (bio-ethanol) expansion were evaluated. The water footprint results indicated that cassava is more water-efficient than the other two crops considered. Simulation results revealed that although oil palm expansion would have negligible alteration in evapotranspiration (0.5 to 1.6%) and water yield (−0.5 to −1.1%), there would be an increased nitrate loading (1.3 to 51.7%) to the surface water. On the contrary, expansion of cassava and sugarcane would decrease evapotranspiration (0.8 to 11.8%) and increase water yield (1.6 to 18.0%), which would lead to increased sediment (10.9 to 91.5%), nitrate (1.9 to 44.5%) and total phosphorus (15.0 to 165.0%) loading to surface water. Based on the results, it can be concluded that land use change for biodiesel production would affect water quality, while both the water balance components and water quality would be affected by the expansion of bio-ethanol crops. Overall, the study indicates that biofuel production would have a negative impact on the water quality of the studied watershed. Further research at large scale (e.g. basin level) and on the economic aspect is recommended, in order to contribute to developing suitable land use and energy policies.