Initial discussions in this chapter on population may look strange, raising the question: what has the evolution of the world’s population got to do with vital water graphics? The answer is everything, because the world’s population growth is the key to the whole equation of water availability and its use. But the importance of population is not the only factor to consider. The brutal challenge of climate change resulting in changes in rainfall regimes, threatening surface water and the regularity of aquifer recharge, and the contamination of aquifers in expanding urban areas, are other factors that contribute to making water resources scarcity a reality.
Going back in history, before the industrial revolution, it was possible to withdraw and consume water to everyone’s satisfaction However, times have changed as demographic pressure in the last three centuries (for example, 1 billion inhabitants in 1800, 2 billion in 1900 and 6.6 billion at the end of 2007) no longer allows for the management of water without cooperation among communities.
It is a known fact that water, in a geographic sense, is unequally distributed on earth and population growth varies on every continent. Projections show that the demographic patterns of developing countries are becoming more and more significant, in particular in sub-Saharan Africa and South East Asia, where access to clean water is already a challenge for the current population, presenting a high risk of increasing, and irreversible, water scarcity