The ability of individuals to ease the world water crisis is very limited due to the nature of the crisis.
The crisis has three basic elements elements:
The first aspect of the water crisis is the water is not where people need it. This is the quantity part of the problem
People have been diverting water and transporting it by canals and aqueducts for thousands of years. This has always been accomplished by large groups of people working together under some sort of management structure, whether it be a government (Rome), irrigation districts (The Salt River Project in Phoenix, Arizona), or cities with reservoirs and pipelines. We don't know, for example, what sort of management systems were used by the people in the Tigris and Euphrates valley or by the ancient Hohokam Indians in the Phoenix area, but the vastness of the irrigation canal systems makes it obvious individuals did not accomplish this.
What is clear is that there is a very strong link to water transportation systems and civilization itself.
The problem in many areas is there is not an entity with the ability to store and transport large quantities of water.
Efforts are needed in conjunction with governments at all levels, as well as the United States, the UN, the EU, wealthy Asian nations, as well as other entities to create the ability to accomplish this in areas which lack a supply of water.
The second aspect of the water crisis is water quality. For millions and millions of people, the quality of the water available to them is a serious health problem.
In the first world nations, this problem was solved by a combination of stringent governmental regulation over water quality, and public funding of potable water systems which protected water quality.
In many parts of the world there are not governmental entities with the resources to provide potable water. This is where grants from rich nations to poorer nations are vital.
We spend far more on military assistance to other nations than we do in the United States on assuring people have safe drinking water. The US could make a lot more friends in the world by providing water treatment plants instead of bombs.
The water quality problem is the most amenable to more local solutions, with small level technologies available to treat water. But, again the problem is lack of funds and an institutional framework to make this happen.
The third aspect of the water crisis is affordability. In many cases water is being made available, but it is too expensive for the users, especially farmers. In the United States we developed the irrigation district system with tax exempt financing available to construct water storage and transportation systems in the early 1900's, and expanded this concept to entities which did the same for cities, such as the Metropolitan Water District of Southern California.
In many areas, such as Mexico, drinking water is sold by water trucks or people buy bottled water. The cost of this water is extremely high.
To depend on private corporations to do this works against affordability. The best way to keep water affordable is to not turn water into a commodity provided for a profit.
Governments are uniquely able to address the problems of quantity, quality and affordability of water. The main problem is many governments default this responsibility either for lack of funds, or lack of political will.
Looking to the private sector to deal with the water crisis is not a very good solution, because of the need for a rate of return on investment.
The private sector can provide the technology and the ability to solve the problems, but governments must play the lead role in making sure everyone has access to water and that it is affordable.
In order to provide quantity, quality and affordability, tax subsidies or grants are absolutely essential.
We are now looking at a world where wars may be fought over water.
In the United States we have our own version of water wars for over a century. Initially solving one area's water problem came at the expense of another area. Take for example Los Angeles drying up the Mono Lake Valley for LA's growth. At one point when the MWD was building its aqueduct from the Colorado River to LA, the state of Arizona sent out its National Guard to halt construction of the diversion dam. We have an elaborate legal system to resolve disputes over rights and access to water.
Where one country (i.e. Turkey) can intercept the flow of a river and dry it up to the downstream people, there will likely be serious consequences.
The UN and other international agencies are absolutely essential to create international solutions for water issues where the disputes can be resolved without resort to force.
Ultimately the role of the individual is to demand quantity, quality and affordability of water as a basic human right.
And it is the duty of governments at all levels to assure people of that basic human right.
[Note: I practiced law in the area of water quantity, quality and affordability since 1974, and have been involved in water projects in both the United States and Mexico.]