Sound & Music Generated by Freshwater

We all are very familiar with freshwater's role in generating electricity, changing weather, growing food and improving health. But few of us are aware of how our ancestors used water to make sounds and music.
Playing a glass partially full of water

Source - invigorate.royalsociety.org

We have all tried this in our home one time or another. Fill a glass partially full of water and wet its rim and rub one finger along the rim.

Source - exploresound.org

The speed with which we move changes the sound that is produced. The sound produced also changes depending upon the amount of empty volume in the glass.
Lining up a few glasses with varying amount of water in them, creates a musical organ.
Water Driven Pipe Instrument - The Hydraulis

hydraulis circa 1,000 BC
Source - en.wikipedia.org

Water Organ
Source - en.wikipedia.org

With water supplied from some higher point above the instrument, air is introduced in the water stream that is turning a musical cylinder quite like in today's music boxes. 
As the air produces pulses in the water stream, the stream changes the rotation of the musical cylinder to produce changes in sounds - changes that together produced music as early as 3rd century BC.
The Hydraulophone

A Hydraulophone
Source - en.wikipedia.org

Blocking the flow of water can also be done with the fingers somewhat like the plucking of guitar strings. When a stream of water is stopped by a finger it changes the sound the instrument makes.
In the hydraulophone, water is also sometimes used to make the sound

Water, a most abundant substance on the planet, also has a vast abundance of uses.

Water + Gravity = Tools to Tell Time

The sundial and water clocks are probably the oldest instruments whose function was to tell time. As long-ago as 4,000 BC, we were using gravity and water to measure time.
Inflow Timekeepers - The ghati

A Coconut Shell with a hole
Source - sciencephoto.com

These timekeepers measure time by how long it takes for water to fill a container.
In India, the standard water clock was a 'ghati' that measured time in 24 minute intervals - 60 of which together made up a 21st century 24-hour day.
The ghati was half a coconut shell with a hole drilled to just the right size in it. When floated in a tank of water, the shell would slowly take on water till it sank.
The size of the hole and the coconut half-shell were such that it took 24 minutes for the shell to sink.
The ghati was in use for over 5,000 years all over the ancient world.
Outflow Timekeepers - The Klepsydra

A Klepsydra
Source - depthome.brooklyn.cuny.edu

These time keepers measure time by long it takes for water to empty a container of fixed volume.
The jar at the higher elevation is filled to a fixed height. Water flows out of the hole at the bottom into another jar.
The klepsydra was made in the conical shape (a wide top and a narrow bottom) so that it would also be used to measure the passage of time. The conical shape ensured that the pressure at the bottom of the jar (that pushed out the water) remained constant as the water level dropped - A greater amount of water would flow out when the jar was filled, so that the surface level of the water in the jar would drop at a steady rate.

Water, a most abundant substance on the planet, also has a vast abundance of uses.

Freshwater and Radio Waves = A Security Tool!

We depend on adequate supplies of freshwater for our food, energy, health and every other artificial creation of ours. Now, with advances in science and technology, freshwater is also key to our security needs.
Full Body scanners at Airports

Image from Full Body Scanners
Source - en.wikipedia.org

Full Body Scanner Equipment
Source - au.ibtimes.com

Transportation authouroties around the world have adopted a tool, the full body scanner, to ensure that no travelers take board prohibited items on board aircraft, trains and other mass transportation vehicles.
There are many technologies used to create images that can reveal prohibited items.
Terahertz Radiation

Terahertz radiation band
Source - teranova-ist.org

Light with wavelength between 300GHz and 10THz is known as Terahertz Radiation.
This radiation exists naturally and falls between infrared and microwave radiation.
A characteristic quality of Terahertz radiation is its ability to penetrate clothing and the human body but only to a very limited extend - freshwater just below the human skin stops and absorbs particular terahertz radiation
Absorption by Freshwater 

Terahertz Radiation absorbed by water vapor
Source - en.wikipedia.org

One form of body scanner works by firing radio waves of Terahertz length onto the human body and capturing the pattern of reflected and absorbed waves.
This pattern creates a body image of the kind full body scanners create to identify the existence of banned items.
As most metals do not absorb terahertz radiation, their existence can be confirmed in the pattern and the image. As most banned items are made of metals, the pattern can identify items hidden in clothing that could be one of the items banned from being transported on planes and trains.
Commercial Use of Terahertz Radiation

A Custom Clothing Machine
Source - digitalstyledigest.com

The first commercial application of freshwater-based body scanners is a set of machines that have been deployed in some specialty clothing stores.
These machines create an exact outline, in 3-D of the human body so that fitting clothes, for each of our individual body contours, can be found or manufactured.
These machines fire radio waves in the Terahertz range and catch the returning waves to build a true 3-D outline of a body.

Can terahertz radiation be used to locate new sources of freshwater?

Perspective & Predictability Define Scarcity!

Source - cartoonstock.com

"One person's junk is another person's fortune" goes the old adage.
The difference between "junk" and "antique" is predominantly one of perspective.
Perspective is, of course, itself influenced by many factors that vary widely because these factors are very individual and extremely personal in nature.
It's much the same condition with safe drinking water:
- Those that have enough cannot see how they could ever do with less 
- Those that don't have enough seem to find a way to survive with what they can get
Of course those that can only get less than the necessary minimum suffer ill heath and other debilitating impacts.
Is piped water available 365/24/7 the definition of no scarcity?

Bathroom plumbing
Source - avivimprovements.wordpress.com

In the middle of the twentieth century, piped water was the norm not the exception for most of humanity.
Now, at the beginning of the twenty-first century, a large part of humanity does not get piped water 365/24/7 although all permanent houses have the necessary plumbing in place - for these house dwellers, supply of water may be intermittent or only available for a few hours a week on a unpredictable schedule.
Using the definition of 365/24/7 piped water supply, a large part of humanity already is experiencing scarcity with more people joining this group daily.
Perspective is ruled by Existing Circumstances

Esher's Waterfall
Source - en.wikipedia.org

Esher's depiction of a waterfall is a great example of perspective. Only people who happen to be in the left tower and in the big house on the left, are the ones who experience the waterfall.
The former see water dropping from where they are, while the latter see water falling to where they are.
For everyone else, water is simply moving at the same level as, of course, water cannot rise against gravity.
When asked if receiving freshwater 365/24/7 is necessary, most people who don't have 365/24/7 water supply do not label regular continuous unavailability a problem. From their perspective, they can live with much less than 365/24/7 piped water supply. 
The opposite is true for those that are used to having water run out of a tap when they turn the tap on. For them scarcity has arrived, if there is no water, even for a few seconds, running out of any tap.
Unpredictability creates scarcity

Women fetching water
Source - artwolfe.photoshelter.com

Those with and without continuously piped water agree on one thing: water availability must be predictable.
Once predictability is assured, scarcity disappears for most every individual wherever they may live and under whatever circumstances.
Take the case of people, mostly all of whom are women and girls, who make daily long difficult treks for drinking water.
In their minds, fetching necessary drinking water is just a necessary chore they must perform daily. That's just part of their life.
They don't even consider fetching water a burdensome chore. It is those with piped water that call fetching water an unnecessary and unfortunate chore.
What is the Absolute Minimum amount of freshwater for Humans?

Water Meter
Source - caes.uga.edu

Humans loose water when they breathe and when they perform virtually any movement. Even the process of being alive (not counting breathing, uses up water.
At a United Nations conference in 1977, it was decided that an average human being requires 3 liters (3.2 quarts) of water under average conditions i.e. an person living in an average climate and doing the things that people do on an average.
But, of course, there is no average human being or average climate or average life condition. And, the 3 liters do not include water needed for cooking and sanitation and human hygiene.
Adding up these numbers in a practical way, the minimum required freshwater per capita is 50 liters (13.2 gallons) per day, it was agreed, for maintaining a person's body water balance and ensuring acceptable healthiness.
Is 50 liters/day/person truly enough?
Yes, if we ask those 2+ billion who live on less than 50 liters per day!
No, if we ask those that live on more than ten times the 50 liters per day!

So what's should be the freshwater supply target per head per day?

Freshwater's Supply Chain is Unlike that of Any Other Resource!

Freshwater is a resource like no other. While differences between freshwater and other renewable and non-renewable resources are many, freshwater's supply chain makes freshwater a most unique natural and renewable resource. Nature delivers freshwater in ways it doesn't do for any other resource. 
Freshwater's Current 3-Source Supply Chain

Source - willoughby.nsw.gov.au

3 sources of freshwater exist for most human settlements. These are:
1. Rainwater that naturally falls on the settlement
2. Freshwater transported from near and far locations  to the settlement, and
3. Locally obtained water, usually from a combination of sources located at ground level (e.g. rivers and lakes) and below ground (e.g. wells that tap the local water table).
Some locations do not, of course, have all 3 sources available to them -  but most do, because this 3-source approach was seen as the most prudent and dependable one.
Threat's to the 3-Source Supply
All three sources can be threatened today in a variety of ways for human settlements in different locations:
1. Climate change has impacted the frequency, amount and location of rainfall.
2. The ability to bring water from remote locations is threatened by both dwindling resources at the remote location and the assertion of communities along the transportation route to the freshwater being transported.
3. Continued extraction of groundwater has lowered water table levels, in some cases to depths that are difficult to access.
Rainfall - Resource delivery on a near-regular schedule

Source - diswaterdrams.com

Other than freshwater, nature delivers no other natural resource on a fairly regular schedule to locations where the resource may also be ingeniously available in bulk. 
Delivery of freshwater as rain was probably of little value while humans were migrating all over the globe. Rainfall's value only became evident about 10,000 years ago, when humans chose to settle down in one place (and grow the food they needed) instead of moving around in search of food. Humans, in a sense, became dependent on rainfall at the start of the agricultural age.
Rainfall Dependency
Once reliant on rain to grow their food, humans became subject to the impacts of any change in rainfall delivery frequency, amount or location. And it is, in large part, this dependency that is shaping a crisis in freshwater supply - supply of rain is simply too undependable.
The one unique feature that defines freshwater delivery is today the one unique force behind freshwater scarcity and water security.