While many were focusing on energy use, carbon emissions, and climate change and buying carbon offsets, I was trying to secure a sustainable water supply. Global fresh water supply poses the real and immediate environmental risk.
According to the US Census Bureau there are 312 million people in the United States and almost 9 billion people on earth. All the water that exists on the planet is finite and always part of the water cycle or hydrologic cycle, the continuous movement of water on, above, and below the surface of the Earth. Since the water cycle is truly a "cycle," there is no beginning or end. More than 96% of Earth's water exists in the oceans where the sun, which drives the water cycle, heats water. Some of it evaporates as vapor into the air. Ice and snow can sublimate directly into water vapor. Rising air currents take the vapor up into the atmosphere, along with water from evapotranspiration, which is water transpired from plants and evaporated from the soil. The vapor rises into the air where cooler temperatures cause it to condense into clouds. Air currents move clouds around the globe, cloud particles collide, grow, and fall out of the sky as precipitation. Some precipitation falls as snow and can accumulate as ice caps and glaciers, which can store frozen water for thousands of years. Snowpacks in warmer climates often thaw and melt when spring arrives, and the melted water flows overland as snowmelt. Water is not created, it changes states, it changes locations, but it is finite.
The fresh water on the planet is stored in the glaciers (that are reported to be melting), groundwater, rivers and streams all which can be polluted. Groundwater, river and streams are recharged by precipitation. Most precipitation falls back into the oceans, but some falls onto land, where the precipitation flows over the ground as surface runoff. A portion of runoff enters rivers which all flow towards the oceans. Runoff, and ground-water seepage, accumulate and are stored as freshwater in lakes. Not all runoff flows into rivers, though. Much of it soaks into the ground as infiltration. Some water infiltrates deep into the ground and replenishes aquifers (saturated subsurface rock), which store huge amounts of freshwater for long periods of time. Some infiltration stays close to the land surface and can seep back into surface-water bodies (and the ocean) as ground-water discharge, and some ground water finds openings in the land surface and emerges as freshwater springs. Over time, all of this water keeps moving and is truely the flow of life on our planet.
As global population rises, the demand for fresh water rises for drinking, domestic use, for industry and for agriculture. The demand for food and the water that is essential to produces it grows with population and wealth. Globally, farming is estimated to account for 60% -70% of fresh water use. Irrigated agricultural is the largest consumer of water on the planet. With population growth and increase in wealth it is projected that agricultural consumption of water will increase, although its consumption growth is forecast to be slowed by more efficient water usage in the future, nonetheless, it was estimated that the water usage would grow by a third between 2000 and 2050. While there might be adequate fresh water on the planet to meet this, the available fresh water is not located where it is needed.
Irrigation has vastly improved crop yields in many semi-arid climates where the growing season is long and crop yields seem only to be limited by water availability. The development of irrigated agriculture was the first step in increasing human population. Irrigated agricultural land is two and a half times more productive than rain fed agricultural land and the limits of irrigation really are the fresh water resources, the capital costs and the saline buildup over time in the farm land and aquifers. Over 40% of the global food harvest now comes from the 17% of the world's croplands that are irrigated. More successful agriculture has allowed a larger and larger portion of the population to pursue activities beyond the direct production of food.
Social scientists and demographers predict that 70% of the world’s population will live in urban areas by 2050. Today there are reported to be 3.5 billion people living in urban areas, about half of the world’s population; however, much of this is due to urban migration because humans do not breed in captivity. In the United States in 2011 just under 80% of the population lives in urban areas many of modest size. http://www.fhwa.dot.gov/planning/census_issues/metropolitan_planning/cps2k.cfm
In the nineteenth century, the world’s most populous city was London whose population in 1900 was 7 million, today London has 9 million citizens and has been eclipsed by emerging countries of China, India and even Mexico. Shanghai has15 million people, Delhi has 16 million people and Mexico City has 20 million people. Fresh and safe water supplies are becoming critical in these new world urban centers.
To survive the average adult needs between 0.75 and 2.25 gallons of water daily, depending on climate, activity, and size. However, the production of foodstuffs involves much greater consumption of water environmental scientists estimate that, for an average vegetarian diet, 95,000 gallons of water per capita per year is needed or irrigation or rainfall. So, the annual drinking water consumption of even the thirstiest vegetarian would still represent just 1% of the water required for the cultivation of their food. Animals like humans require massive quantities of water to grow, so that an animal protein based diet requires multiples of the water used in a vegetarian diet.
Drinking water and food are basic human requirements. Other needs include personal hygiene, cooking and cleaning. The World Health Organization considers that a minimum 8-13 gallons per day is necessary for keeping up basic personal hygiene, for cooking, and for cleaning. This amount (which does not include water for flushing toilets), plus the amount consumed as drinking water, has been labeled the “basic water requirement.” Rounding, the basic requirement is 15 gallons a day. http://https://www.citigroupgeo.com/pdf/SGL72074.pdf
Of course, most humans aspire to more than just basic survival and few of us in the “first world” would be willing to live at the survival level when it comes to food and water and continue to work and produce at our current level of production. On that point, although per capita meat consumption in developing countries is still less than half the levels of developed countries as incomes rise so does meat consumption. As noted above, 95,000 gallons of water per capita per year is needed for an average vegetarian diet; a diet containing 20% meat triples that consumption (reflecting water consumed directly by animals, and water used in the production of food for livestock).
Water is used for activities beyond basic personal hygiene. Activities such as flushing a toilet, watering flowers, or washing a car increase daily per capita water needs by 8-26 gallons. Hospitals, restaurants, hotels, schools, office buildings and other institutions use considerable amounts of water either directly or in the form of energy consumption. The actual numbers vary from 5.5 gallons per capita per day in Africa, to 26.5 gallons per capita per day in Europe, and over 100 gallons per capita in North America. Though we think of North America as the home of the ornamental lawn, the truth is that approximately 80% of North America’s gross water use, the total volume withdrawn from water bodies, goes to energy, natural resources and food. The thermal power generating sector is responsible for the greatest gross water use, while agriculture accounted for the majority of consumptive water use (water not returned to a water body after use).
As the world population grows the excess capacity of water necessary to have adequate food for areas of the earth experiencing drought, flooding or natural disasters shrinks. As all civilizations have in the past our intermingled world civilization will grow to the breaking point. Technology has allowed us to surpass the limits of previous civilizations, but we are still limited by water and our ability to increase our water efficiency.