Assessment of climate change impact on rice yield and water footprint of large-scale and individual farming in Thailand.

Large-scale farming (participation in large-scale agricultural extension program) and individual farming (no participation) are two farming management practices of rice cultivation in Thailand, both of which cause significant water consumption and degradation and are vulnerable to climate change. However, given that climate change will influence both grain yield and water resource availability, it is not fully understood which type of farming management practice is more adaptive to climate change. This study aims to evaluate the adaptation capabilities of large-scale and individual farming by simulating rice yield changes under future climatic conditions and estimating the climate change impact on the water footprint (WF) of rice production. Rice management practices were obtained from large-scale and individual farming. Five General Circulation Models of RCP4.5 and RCP8.5 scenarios under four future time periods were used as future climate projections. Simulation results show a remarkable increase in rice yield of individual and large-scale farming under RCP4.5, ranging from 1.3 to 29.8% and 2.0 to 30.8%, respectively, whereas it fluctuates from 11.7 to -29.0% and 8.3 to -20.8% under RCP8.5 for individual and large-scale farming, respectively. The projected total WF of rice production under RCP4.5 will decline, ranging from -10.0 to -43.0% and -0.5 to -67.0% for individual and large-scale farming, respectively. Conversely, the RCP8.5 shows a fluctuation in projected total WF of -26.5 to 63.3% and -51.1 to 60.0% for individual and large-scale farming, respectively. The total WF, mainly grey WF, in large-scale farming is lower than in individual farming. The increase of rice yield under RCP4.5 is due to an increment of temperature and precipitation, resulting in a decrease of the total WF and vice versa for RCP8.5. The large-scale farms are highlighted as adopting appropriate management practices for rice production in which they can maintain rice yield and reduce grey WF.