Depletion and Pollution of Water
The world is facing extraordinarily serious fresh water depletion and pollution, both exacerbated by ever rising demand. Over the next 40 years estimates are that demand for water will rise 50% while demand for food will rise 70%, all in the same period that we’ll be forced to confront climate change and depletion of rivers and aquifers.
Farming (and to a lesser extent, other human activities) are the main culprits. Growing food for an average human diet requires an estimated 320 gallons of water a day. For an average American diet the number is closer to 900 gallons of water a day. Agriculture depends on water, consuming fully 70% of the world’s fresh water. To produce that water, we’re draining rivers, lakes, and fossil water aquifers at an unsustainable rate. Runoffs of pesticides and fertilizers are the largest sources of pollution in US lakes and rivers, directly responsible for an 8,000 square mile dead zone in the Gulf of Mexico.
Beneath the American high plains of Nebraska, Kansas, northern Texas, and five other states lies the Ogallala Aquifer, a giant underground reservoir of fresh water that farms and people in the region depend on. Ogallala is full of ‘fossil water’ – the remnants of the glaciers and ice sheets that retreated from this area more than 10,000 years ago, melting and filling underwater basins as they went. That fossil water is used to irrigate 27% of the farmland in the United States. In two months the water we withdraw from Ogallala is enough to fill a cube a mile on a side. As a result, the aquifer’s water level is dropping, in some places as fast as three feet per year. On current course and speed, it will run dry before this century is over, and possibly much sooner.
The rate at which we consume water – particularly for agriculture – exceeds the rate at which we can capture it from rain or from sustainable withdrawals from rivers.
The Indus River Valley aquifer is being drained at a rate of 20 cubic kilometers a year. Water tables in Gujarat province are falling by as much as 20 feet a year. The giant North China Plain aquifer, which provides irrigation for fields that feed hundreds of millions, has been found to drop as much as 10 feet in a single year. A World Bank report cautions that in some places in northern China, wells have to be drilled nearly half a mile deep to find fresh water. Hebei province, one of five atop the aquifer, has seen more than 900 of its 1,052 lakes dry up and disappear due to dropping water tables. In Mexico’s agricultural state of Guanajuato, the water table is dropping by 6 feet a year. In north eastern Iran, it’s dropping by as much as 10 feet a year.
Water is being withdrawn from rivers as well. Seasonal water levels are dropping on China’s Yellow River, on the Nile in Egypt, on the Indus as far north as Pakistan, and on the Rio Grande in the US. Parts of the Colorado River are a stunning 130 feet below their historic levels. The river no longer reaches the sea. Nor does the Yellow River or dozens of others around the world that have been tapped for irrigation. The rivers that flow through Central Asia have been so massively drained for agriculture that the vast Aral Sea they once fed, once the fourth largest freshwater lake in the world, is now little more than a dry, salty lake bed, its former shore dotted with abandoned fishing villages and the bones of beached boats.
70% of the world’s surface is covered in water. Yet the vast majority of that water – around 97% of it – is salt water. Another 2% is locked up in ice caps and glaciers. Only around 1% of the world’s water is fresh, and of that, humanity can only easily access about a tenth, or 0.1%.
If we could efficiently convert salt water to fresh, we’d have access to a vast supply of water to use in growing crops and sustaining human civilization. For decades, desalination has been considered a deeply anti-environmental process, primarily because it consumes enormous amounts of energy and releases huge amounts of greenhouse gases.
However, with sufficient cheap renewable energy from technological discoveries, our featured solution could create water supplies many times larger than any projected human need.