Contaminated Water

   An astonishingly small part (less than 2.5%) of the world’s water is freshwater, and of that small part, the vast majority is locked up in ice or snow.That means only a small, fixed amount of freshwater is available for drinking, washing, agriculture, industry, and ecology. Furthermore, most freshwater is far from population centers. Rivers, lakes and groundwater basins are the primary source of the freshwater for human use, but less than one percent of this water is safe to drink. In fact, microbe contaminated water is still the greatest cause of global human sickness and death. Freshwater readily carries disease and toxins, so it must be kept clean and/or treated for it to be potable. Unfortunately, humans continue to pollute water and have not achieved universal access to clean water and sanitation.

    Worldwide, over a billion people do not have access to safe drinking water, and approximately one-third of the world’s population lives under water stress. Water stress occurs when the demand for water exceeds the amount of water available, or when poor water quality restricts its use.Water stress will become increasingly severe as human numbers increase and more waste is discharged into our rivers, lakes, and groundwater. Since water is a vital necessity for all of us to survive, we humans must be very careful about the future availability and quality of freshwater resources for both current and future generations.      
    Water is a shared and finite resource. Our glass of water today may have come from a well, a lake, or the local river, but it has been in many places in the world, and in many forms, such as snow, ice, clouds, rain, ocean water, and groundwater. In fact, it is millions of years old, and this same water will be in use for millions of years more. Driven by energy from the sun, water is in constant motion, cycling through the Earth’s atmosphere, oceans, and continents according to the hydrologic cycle, depicted below in Figure 1.

    It is through the hydrologic cycle that our water resources - our rivers, lakes and groundwater - are continuously replenished. Very little new water is formed, and very little existing water is removed or destroyed; water is used and re-used in nature and by humans. However, we can, and we are, reducing the amount of usable freshwater by polluting it and withdrawing it faster than it can be replenished by rain and snow. While we can also make more freshwater available by desalinating sea water, the process requires large amounts of energy.
      Our Future Water Needs
   A primary goal of this chapter is to present projections to 2150 when the grandchildren of today’s young people will be living on the freshwater that is available to them. We relied mainly on the Global Environmental Outlook 3 and 4 (GEO3 and GEO4) report from the United Nations Environment Programme.
As noted in the UN's Global Environmental Outlook (GEO4) report, scarcity of water and sanitation facilities will increasingly be a major problem for future generations. Currently, per capita availability of freshwater is decreasing and contaminated water is still the greatest environmental cause of human sickness and death. Water resources are being threatened by increased consumption, increased pollution, and increasing population. These threats are likely to become worse during our lifetimes and those of our children.