Lots and Lots of Water in the Atmosphere!

Total moisture in the atmosphere
In total there exists, at any one moment, 12,900 cubic kilometers of water in the atmosphere. 
Liquid water in air
98% of this moisture exists as vapor while 2% exists as liquid i.e. there are:
~ 258 cubic kilometers of water in liquid form in the atmosphere, and
~ 12,642 cubic kilometers of water in vapor form in the atmosphere
Using 1 cubic kilometer = 2.64172052 × 10¹¹ US gallons, there are:
~ 681.56 x 10¹¹ US gallons of water in liquid form in the atmosphere, and
~ 33,396.63 x 10¹¹ US gallons of water in vapor form in the atmosphere
Moisture in air replenishment rate
All the moisture in the atmosphere is, however, replaced every 9 days i.e. 12,900 cubic kilometers of water is delivered to the surface of the Earth from the atmosphere every 9 days i.e.
~ 681.56 x 10¹¹ US gallons of liquid water falls on Earth every 9 days, and
~ 33,396.63 x 10¹¹ US gallons of vapor water falls on Earth every 9 days
Water deposited on Earth from the atmosphere every day
~ 3,787 x 10¹¹ US gallons every day
For a 10 billion human population, this is ~ 37,870 US gallons/person/day
What's behind global water scarcity?
Recognizing that ~ 37,870 US gallons/person/day is just NEW water and does not include water from rivers, lakes, underground aquifers and other sources, the question arises:
Why do we have a water scarcity issue in most places around the globe, today?
Granted, we cannot capture every, or even most, drops for humanity's use, water scarcity remains a challenge for human ingenuity in two ways: How do we capture precipitation in locations that nature chooses and how do we transport the collected water to where we want or desperately needs to have it?

Freshwater Innovations Fuel Population Growth!

While we may never know with absolute certainty the answer to the question: "Which came first, the chicken or the egg?" we can be reasonably sure that human population grew and thrived because required amounts of freshwater became available necessary to sustain growing numbers of people.
Human Population Growth

Source - Adapted from Page 15, of book titled
"Pandora's Seed" authored by Spencer Wells

Approximately 200,000 years ago, our breed of human (aka Homo Sapiens) originated in Africa. Only 60,000 years ago Homo Sapiens started to grow in number.
Some 10,000 years ago, however, this rate of growth accelerated dramatically - Human population grew thousand-fold, from 1 million people to 1 billion people, in less than 10,000 years. 
Role of Freshwater

Source - Ommato LLC

When key water-related innovations are superimposed on to the population graph, it becomes clear how these innovations influenced growth in numbers of people. Key water-related innovations included:
- About 10,000 years ago, humans dug a well to capture water they saw disappearing into the ground
- Some 7,000 years ago, irrigation was born when humans figured out that water would, on its own accord, move from higher levels to lower levels
- About 5,000 years ago humans made the artificial lake when they built a dam to stop a river from flowing
- Approx 4,000 years ago humans began to raise water from lower levels to higher levels with the invention of a Shaduf. This was quickly followed with the Archimedes Screw and the Waterwheel all increasing the height to which water could be raised.
- Around 300 AD, 1900 years ago, the Romans built their gigantic aqueducts to bring water from many miles away to their cities.

Impact of Innovations
Each innovation had its incremental impact. But as is evident from the chart, the greatest impact on human population numbers came from the inventions that raised water to very high levels and that transported water over long distances.

What innovations lie in the wings or are possible today, that will bring abundance to safe drinking water in the 21st century?

Overcoming Distance is Humanity's Fundamental Freshwater Challenge

Transportation of water to where people have chosen to live or forcing people to live in close proximity to freshwater supplies are two solutions that mankind has practiced ever since the beginning of civilization. This "transportation" issue is still the heart of our current and future freshwater crises.


Places with Meager Freshwater Supplies
The story and images of women spending their day carting water from sources far, far away from where they live, are well known and publicized as a scourge on the already poor. 

Source - newstimeafrica.com

Source - workworthdoing.com

Innovators have developed devices, like the rolling container that makes water transportation a less physical activity, but does not address the basic issue - the water is far away from where the people who need it are.

Ancient Roman Aqueduct
Source - think2020.tripod.com

In the richer parts of the world the solution to this basic issue is no different, except in scale and institutionalization - the formation of an organization which exists for the sole purpose of supplying needed freshwater.

Source - planetforward.org

Source - spannertech.com

Without such costly and massive creations, most of the population centers in the developed world would also be susceptible to water shortages and supply disruptions.
Covering the distance problem is still the most basic issue behind the supply of freshwater.
Places with Abundant Freshwater Supply
Humanity's Freshwater crisis would disappear in an instant if people lived in locations where there currently exists an abundant natural supply of freshwater and where future freshwater supplies were assured.

Source - worldatlas.com

Unfortunately, however, the two locations with the most freshwater resources (the areas around the North and South Poles) are too inhospitable for long human existence.


And there are no other locations that have necessary freshwater supplies for the existing and future mega-cities that are projected to house nearly 50% of the world's population.


The Distance Eliminating Solutions
The only "local" bodies of freshwater, that can eliminate or, at least, drastically shorten the distance, are the bodies of water located in the "local" air (the atmosphere) and under the ground over which people live. The reality that local underground supplies are already non-existent or under severe stress of becoming extinct, leaves only the option of finding ways to harvest water from the local atmosphere.