Reasons for optimism - desalination
Technological advances make it highly likely that the world will soon have no shortage of water of potable quality in the places where it is needed. Although there have been disputes between countries over available supplies, the likelihood is that there will be enough for everyone. On the small scale much is being done to dig new wells and to adopt local water purification techniques that diminish the spread of water-borne diseases. The big advances, however, are being made in desalination.
The world is not short of water; it covers seven-tenths of its surface. The problem is one of removing the salts from it to render is usable for drinking and for agriculture. The most promising developing technology uses seawater reverse osmosis (SWRO desalination) to push seawater through membranes that admit pure H20 molecules, but prove impervious to the salt and other molecules dissolved in it.
It has had problems associated with it, notably the high energy inputs needed, and the high costs this brings, together with the environmental impact on the localized marine ecology, but these are being solved. It has been shown that the local impact can be mitigated by creating or restoring suitable habitats or by restocking with affected species. And the high costs associated with abundant energy use is being resolved as the costs of renewable energy sources decline. The current cost curve for solar and wind energy suggests that energy will become cheaper as time progresses, making osmotic desalination ever more attractive economically.
As energy does become cheaper, it will be possible to move the desalinated water to the places where it is needed by pumping it long-distance though pipelines, much as oil is currently piped across thousands of miles. Lower energy costs will render this viable. The rapid development of desalination technology indicates that water shortage problems can be resolved. This will make it possible to cultivate in currently inhospitable areas. It will enable hydroponic farming to take place in areas lacking fertile soil, further reducing pressure on the land needed to produce food.
Far from facing shortages and possible conflict situations, the likelihood is that fresh, clean water will be both abundant and cheap in the future