Note: this article reprinted Xiong Hang blog since science network

Virtual Water (Vritual Water)

British scholar John Anthony Allen in 1993 put forward the concept of "virtual water", to compute the water during the course of food and consumer goods in the production and sales. The concept that people not only need to consume water in drinking and the shower, in the consumption of other products will consume large amounts of water. , for example, a cup of coffee in the cultivation, production, packaging and transportation in the process of the need to consume 140 litres of water, this is equivalent to a British person on an average day of drinking water and family life; A hamburger is need to consume about 2400 litres of water. For this he gained the Stockholm water prize in 2008.

Blue (Blue Water) and Green (Green Water)

In 1995, the concept of green water and blue water began to appear. Swedish experts put forward the concept of "green water", the so-called "green water", is mainly refers to the root of soil storing rainwater. From the perspective of the water cycle analysis, 65% of the total global precipitation through the forest, grassland, wetland and rainfed farmland evapotranspiration returned to the atmosphere, known as the green water, green water); Only 35% of the precipitation stored in rivers and lakes and in aquifers, known as the blue water. Blue water after use can be divided into two parts: the part after use consumption become water vapor into the atmosphere, no longer suitable for human use; Another part of backflow into the ecological system, but often carry large amounts of pollutants. Green water was originally defined as evapotranspiration flow, flow to the atmosphere of water vapor flow, then is defined as a specific water, green water is due to precipitation, stored in the soil and vegetation evaporation consumed the water resources, especially in the rainfed agricultural region is an important water resources.

Said simply, "green water" refers to the water, not visible "blue water" refers to water in sight.

In a first-class domain, "green water" the cycle of water (gas) supply of terrestrial ecosystems, the cycle of "blue water" (liquid) supply of aquatic ecosystem and the demand of human beings. "Green water" the cycle of "soil and plants" reflects the nature of the ecosystem of water consumption. "Blue water" in the earths surface and subsurface flow, from the top of the hill to the bottom, from land to sea.

The water resources utilization in human ways include:

1, direct use - primarily social and economic water, including the rain-fed agriculture, timber, pastures, use of green water and irrigation, industrial, life, etc. Use blue water

2, indirect use - mainly is the water ecological system, including related to "green water" terrestrial ecosystem water and aquatic ecosystems water associated with "blue water".

Blue water WB = WS + WG - WR

Green water WG = P - WB

WB blue water; WS surface water resource; WG groundwater resources; WR repeat calculation of surface water resources and groundwater resources; P precipitation