Assessing Green and Blue Water: Understanding Interactions and Making Balance between Human and Nature

Abstract. Water resources assessment is crucial for human well-being and ecosystem’s health. Assessments by considering both the blue and green water are of great significance as the green water plays a critical but often ignored role in the terrestrial ecosystem, especially in arid and semi-arid regions. Many approaches have been developed for green and blue water valuation, while few of them considers the interrelationship between them. This study proposed a new framework for green and blue water assessment by considering the interactions between them in an arid endorheic river basin where hydrological cycling is dramatically altered by human activities. Results show that even though the green water is the dominant water resources, the blue water is also critical. Most of the blue water are transformed to green water through physically and human induced processes to meet the water demand of ecosystems. Time and spatial variability of water supply and consumption forms totally different blue and green water regimes in different ecosystems. We also found that human use an increasing share of water with the decrease of the water availability. The massive water use by human reduces the water use for natural ecosystems. This indicates that natural ecosystems will take a higher risk of freshwater use when the water use competition increases. This study provides crucial information to better understand the interactions between green and blue water by assessing water resources in an explicit way. It also provides crucial implications for water management aiming to make the balance between humankind and nature.