Evapotranspiration Assessment in the Context of Food, Energy, and Water Nexus in the Lower Mekong River Basin

The Mekong River is the 7^th largest river in Southeast Asia and supports a population of more than 60 million people. The food security of such a large population is dependent on agriculture production. Irrigated wet season rice is the primary crop, which is grown throughout the year in the Mekong Delta region. At present, the major land transformation is observed in the basin in form of conversion of forest and grassland areas to the agricultural land. The increasing intensity of the irrigation in the region is causing high fluctuation in the evapotranspiration estimates. The basin also contains the enormous untapped hydropower potential. The crop water requirement, dominated by the evapotranspiration, is the crucial factor in segregating the available water for the irrigation and hydropower generation purposes. This study focuses on the estimation of the water distribution for different purposes under the influence of the changing irrigated area and intensification of the crop cycles per year. Six different scenarios were analyzed comparing the increased water demand from the irrigation sector using the water evaluation and planning (WEAP) model. The variable infiltration capacity (VIC) model was used for the assessment of the water budget and streamflow for the selected dams in the basin. The effect is dominantly observed in the small storage capacity dams which supply 70% of the total water requirement with the loss of 9% of the energy generation, while large dams were able to withstand the growing needs, delivering 90% of the demand and marginal effect on the energy generation. The increase in the number of crop cycles per year has the dominant effect on the supply and energy generation as compared to the expansion of the irrigated area.