Methodology development for including environmental water requirement in the water stress index considering the case of Thailand

Environmental water requirement is important for a river or a watershed to maintain the ecosystem functions and services. Thus, it needs to be an essential component in water demand calculations for maintaining water resources. This study proposes to explicitly account the environmental water as a part of water withdrawal in the withdrawal to availability ratio of the water stress index. A revised equation is formulated and calibrated using Thailand as an example. This incorporation allows flexibility in changing different amounts and setting different priorities of environmental water requirement based on a local context. The results obtained are satisfactory for explaining the actual stress situation incorporating environmental water requirement. The method and approach proposed in this paper can also be applied to other countries based on their priorities for water allocation to various water demand sectors. This paper is proposed as a step towards developing a sustainable tool for assessing the impact on freshwater resources.