Why is Steam White?

Ever wonder why you cannot see the water vapor in the air around us?
Water in Vapor form

Source - scienceprojectideasforkind.com

Water molecules when in vapor form are transparent.
That's one reason why we cannot see the moisture in the air.
Another, of course, is the tiny size of water molecules, so tiny that our eyes cannot make them out or the loose chains that they form.
Yet another, is that the vapor molecules are randomly arranged and so present no discernible shape to the human eye.
Water Molecules in Liquid Form

Source - crazykitcheninventions.co.uk

Steam is essentially a lot of liquid water molecules suspended in a mixture of air and water vapor molecules.
As light rays that hit these randomly arranged liquid water molecules is a mixture of all colors (i.e. white light), the light exiting from the many liquid molecules appears as white - the color we attribute to steam.
If a different color light, say, red were to be falling on steam, the steam would appear to be red in color.

Definitions Matter for Water Scarcity to be Seen as a REAL Issue?

Everyone sees every problem from their own perspective - a perspective built from mostly their understanding, experience and interests. And when many definitions exist, the probability of getting a consensus decreases. Maybe, this lack of a common definition is the cause of lackluster progress against water insecurity!

Different Ways to define Water Scarcity

Which Regions are Under Stress" has many answers!
Source: globalwaterforum.org

Why a consensus is necessary and matters is clearly seen in the result of applying differing (the following of many others) indexes to West Africa and Europe!

As the different colors clearly indicate, different approaches - to describe water insecurity- do lead to different conclusions and, thus, different actions will be deemed necessary to alleviate this insecurity.

Water security: for Who?

Source - oxforddictionaries.com

Whose insecurity is to be eradicated is complicated by the following kinds of competing interests:

• Do the needs of people override the needs of the environment? Or must both go hand-in-hand?
• Does the need of industry override the needs of agriculture?
• When must human migration be the preferred option over staying put?
• How do the needs of different human settlements sharing water resource sources get balanced?
• ... ... ... 
• ... ... ...

Water Stress Index
The regional adequacy of natural sources of water for the "population residing in the region" is measured for each person:

• > 1700 cubic meters per person per year signifies NO Stress
• < 1700 cubic meters per person per year signifies a population experiencing stress from inadequate water supplies
• <1000 cubic meters per person per year signifies a population experiencing water scarcity
• < 500 cubic meters per person per year signifies a population under dire scarcity

These Water Stress definitions lead to some interesting conclusions depending upon the geographical definition of "Region", e.g.:

• If the "region" is the Whole Planet, then there is NO Stress
• If the "region" is a Continent, there is NO Stress
• If the "region" is a country, there may or may not exist enough stress worthy of remediation
• ... ...

Virtually every scenario we can dream up can be identified through the application of the numerical criteria underlying the definition of Water Stress!
Water Demand-vs.-Supply Index

In recognition of the fact that different people use different quantities of water, this index looks at regional water insecurity as defined through unmet need e.g.:

• If water demand is <20% of the supply, the region has NO scarcity
• If water demand is 20-40% of supply, the region is deemed water scarce
• If water demand is >40% of supply, the region is deemed to be under severe scarcity

Usually applied at the country level, this index can be adapted to anyone's interests by including man-made water sources, by emphasizing recycling and a number of other actions.

Water Infrastructure Index

Having water resources but not being able to get our hands on the water is the perspective behind this index. 

Water Poverty Index

This approach factors in prosperity of the population in a selected region. As the definition of prosperity varies widely, this index is extremely complex and thus easily manipulated to support the interests of individuals preferring to use this Index.

We surely need a way to build consensus!!


Source: http://www.globalwaterforum.org/2012/05/07/understanding-water-scarcity-definitions-and-measurements/