Until recently many areas of the world treated fresh water as an inexhaustible resource. It isn’t. The 2015 NASA study identifies 37 major aquifers in the world, and found that water is being extracted from 21 of these at greater than the replacement rate. Not surprisingly, the 21 are in areas of high population and water use or in areas with little rainfall or other water sources.

The world population is growing. More population requires more water. The water needs of developing nations will grow even faster than their population, as standards of living improve, industry and energy needs increase, and per capita food consumption grows. More efficient use of water can help reduce the need for additional water, but cannot eliminate it. Three recent expert studies of the situation have reached very similar conclusions. These are that, even with adjustments to allow for future increases in the efficiency of water use, global water requirements will increase by over 50% by 2050 and supplying this quantity will necessitate increased use of desalination and water reuse. Both are essential to satisfy 21st century water needs.

Desalination is used to convert seawater (97% of the world’s water) or saline water from aquifers into usable water. There are concerns with the effects of seawater desalination on the marine environment and marine life, but these can be greatly reduced by proper design and location of intakes and brine discharge processes. The more serious problem with desalination is that it is energy intensive, currently requiring large quantities of fossil fuel.

The solution most likely to allow more extensive use of desalination is the use of renewable energy, solar or wind, to power desalination plants. This greatly reduces operating costs and does not cause atmospheric pollution. This is a promising area for development and demonstration.

Water reuse involves the processing of wastewater to produce usable water. This can even produce drinking water. Water reuse processing requires significantly less energy than desalination. Water reuse has high potential to make a significant contribution to meeting global water needs, particularly for agricultural uses, which currently account for 70% of global fresh water use.