Earth is home to over 1,386,000,000 km3 (the amount of water to fill 565 trillion Olympic sized swimming pools) of precious water. Water is abundant, and can be readily found in all three of its physical states: as ice, liquid, and gaseous water vapor. However, most water occurs as saltwater in the oceans, which cover over 70% of the Earth’s surface. Saltwater cannot be consumed by humans because the salinity causes our body’s cells to dehydrate. The left column in Figure 11 shows the distribution of all water on Earth.
You will learn in the Water and Ethics section that water is a ‘human right’. You can imagine why this would be the case as you see here how water is essential for life and in short supply.
Only 2.5% of the total water supply is fresh water, the form needed to support animal and plant life including essential human activities like drinking, cooking, cleaning, bathing, agriculture, and industry (figure 12).
As you study the middle and left-hand columns in Figure 11 you see that almost 69% of the Earth’s freshwater is frozen in glaciers and ice caps. The remaining 31.4% is found in underground aquifers and surface bodies of water. With the rapid melting of glaciers and polar ice caps, much of the Earth’s stored fresh water is melting and mixing with the oceans, making it unavailable for human use.
Other than frozen water stored in glaciers, there are three primary sources of stored liquid freshwater on Earth. The first is surface water, or water found in lakes, wetlands, or rivers. Surface water is created by precipitation collecting in a drainage basin or watershed. The second source is ground water, which collects in the small spaces between gravel and soil or within underground aquifers. Ground water is recharged by both precipitation and the third source of freshwater: under-river flow. Under-river flow is the water moving through the hyporheic zone which lies just beneath the sediment surface of a floodplain or riverbed. Under-river flow is very dynamic. When the ground water table is low, under-river flow recharges it or replenishes water to the water table. When ground resources are completely saturated, water is forced back up through the hyporheic zone and into the river itself, a process called discharge.
In the upcoming Action section you will learn about actions being taken in Indonesia to deal with flooding caused by deforestation.
Clean, accessible freshwater is rare and unevenly distributed across the globe. We have already encountered this problem in the Ganges case study that opened this chapter. The availability of clean water varies widely from place to place for two reasons. The first is natural variation in the hydrologic cycle, which was discussed above. The second is human intervention which will be discussed below. Human activities have greatly impacted the natural distribution of water. These interventions include division of water for agriculture, deforestation, industry, and the burning of fossil fuels. Over time, human activity has also contributed to global climate change, which also greatly alters water distribution. Higher global temperatures cause:
- increased evaporation from the surfaces of oceans and land
- increased precipitation over oceans and land; increased rain intensity
- ocean acidification due to dissolving of carbon dioxide from the atmosphere into H2O
- less snow; less rebuilding of glaciers and high altitude snow pack
- frequent, intense storms; hurricanes, tornadoes, monsoons, typhoons
- ice cap melting; higher sea levels
Of course, human communities have also directly manipulated water flow for socio-economic reasons. Technologies built to ensure reliable water access for human use have changed the paths of rivers, created and depleted surface resources, and drained aquifers, as we have seen with the River Ganges. The following chapter on food systems will thoroughly discuss how modern industrial agriculture has impacted water resources in these ways.
Human Access to Water
Environmental ethics must give special attention to the water needs of the poor.
Humans obtain the majority of the water they use from their local drainage basin or watershed. People often collect that water by extraction from sub-surface aquifers (groundwater wells), direct diversion from rivers, and removal from reservoirs or retention ponds. Groundwater provides 20% of water for all uses worldwide. In Europe, groundwater provides between 50 and 70% of the potable water. In the United States, 75% of municipal supply systems draw from groundwater. The majority of countries outside the tropics rely on groundwater for agricultural production. In Saudi Arabia and the Libyan Arab Jamahiriya, 90% of the water used in agriculture is drawn from groundwater. India has nearly this degree of reliance at 89%, followed by Tunisia (85%), South Africa (84%), Spain (80%), Bangladesh (77%), Argentina (70%), the United States of America (68%), Australia (67%), Mexico (64%), Greece (58%), Italy (57%), and China (54%).
Human reliance on groundwater resources in many regions is so extensive that the rate of extraction greatly exceeds the natural rate of replenishment through the hydrologic cycle. This causes various problems. Rapid removal of water from aquifers has resulted in serious water shortage and health problems in countries like India and Bangladesh where the demand for water to irrigate crops has been so great that it has been necessary to dig deeper wells for potable water. The deep wells bypass the rechargeable layers of soil where water is naturally purified, and reach into non-rechargeable layers containing water which is sometimes contaminated with arsenic. Likewise, as the water table drops, many poor farmers’ hand-dug wells run dry and they are unable to afford to dig a deeper, bore well. Unfortunately, many families have lost their basic livelihood and slid into poverty this way.
Environmental ethics must give special attention to the water needs of the poor.
Another problem occurs in regions resting over limestone formations. Limestone geology contains large subterranean caverns that hold groundwater. This is called karst topography. Excessive extraction of groundwater can result in the collapse of the cavern and the sinking of surface layers, creating sinkholes sometimes large enough to swallow up buildings (see Figure 14). From 1972-2000 over 42 Karst sinkholes opened underneath homes and roadways in Moscow, Russia alone.
River diversion provides water to areas that are without natural water sources. Because river flow is uni-directional, river diversion also reduces water availability to those living downstream, or can cause the water level downstream to fall so low that lake and river ecosystems can suffer or collapse. The Colorado River in the western United States, for instance, no longer flows into Mexico due to a century of water diversion by seven U.S. states. This has deprived Mexican people of water they had relied on for centuries.
Artificial reservoirs are created by damming river water into an artificial lake. Reservoirs are created for three main purposes: 1) for hydroelectric power production, 2) for flood control and 3) as a reliable water source for local communities. While reservoirs make water more accessible for local human use, they can create several local as well as down-stream water shortage problems. Primarily, dam construction increases the surface area of the retained water. This means that more water is directly heated by the sun and subsequently lost through evaporation. In every decade since the 1970’s, the amount of water lost through evaporation from reservoirs worldwide has exceeded the amount of water used for domestic and industrial consumption. Dams can also prevent nutrient-rich sediments from being transported downstream where they are necessary to build river deltas and maintain the fertility of floodplain soils. Water held in the reservoirs for use during low water periods can greatly reduce the water source to communities living downstream.
Finally, as reservoirs fill, they submerge dry land and its plant cover. Once submerged, the plants die and bacteria decomposes the plant material producing methane, a potent greenhouse gas. The decomposing vegetation can provide the ideal conditions for bacteria to convert elemental mercury (Hg) to methyl mercury (CH3Hg). This latter form of mercury is toxic to wildlife and humans. Even small amounts of methyl mercury in fish consumed by humans can impair the nervous system, especially in the developing fetus.
Human Uses and Consequences
Human use of freshwater is often divided into three categories: domestic, agricultural, and industrial. The amount of freshwater consumed by each of these activities is not uniform across the globe (see Figure 15), but generally agriculture accounts for 70% of global freshwater use, industry 20%, and domestic use only 10%. Regional water consumption differences are influenced by population density, level of development, and geographical factors like the types of available water resources.
Many projects are underway in Africa to improve water access for domestic use. You will learn about one such project in the upcoming Action section.
Domestic water use is water used for household tasks like drinking, washing, cooking, or watering a garden. Domestic water use was the first of the three categories to develop historically. Nomadic human communities first gathered and temporarily settled around sources of freshwater that could meet their daily subsistence needs.
The amount and quality of water a person can access greatly determines his or her health and economic opportunity. Humans require about fifty liters (50L) of clean water a day to maintain health. This is called our Basic Water Requirement (BWR). Fifty liters is enough water to ensure that a person will be able to replace the amount they lose every day through regular activities (about 1 liter per 1000 calories expended) and enough additional water to maintain hygiene, household needs for preparing food and avoid disease. The water used for the food we grow, the livestock we raise or the consumer goods and services we produce is called embedded (or virtual) water. The annual volume of embedded water that is consumed worldwide is nearly 1,625 billion cubic meters, or about 40% of all water consumption. Embedded water is not included in the BWR.
When water use is examined as amount used per person, or per capita, it becomes clear that individuals across the globe do not have equal access to water resources (see Figure 16). In 2011, over 11% of the global population (768 million people) had no access to a clean source of drinking water. Worldwide, 84% of those with no access to safe domestic water live in rural areas.While water access differs widely from place to place, so too does the rate of domestic consumption. Though the ratio of water use to Gross Domestic Product (GDP) has fallen in many countries, the average American uses over 500 liters of water (not including embedded water) at home every day; that’s thirty-five times more water than the average person living in sub-Saharan Africa, and twice the amount of the average German (Fig. 16).
Clean water access is closely linked to sanitation and hygiene. Together, dirty water and a lack of proper sanitation and hygiene contribute to over 80% of infectious disease worldwide, much of it from contamination by human and animal feces. A single gram of feces can contain over 10,000,000 viruses, 1,000,000 bacteria, 1,000 parasite cysts, and 100 parasite eggs. 7 Diseases caused by contaminated water kill over 4,500 children a day, causing more death since World War II than all global armed conflicts combined. Poor domestic water and sanitation access affect nearly every aspect of a person’s daily life.
Agricultural water use was the second of the three categories to develop, as nomadic peoples began to plant, harvest, and store crops. As irrigation practices improved, agricultural output could support growing human populations. Today, large-scale farming is a vast, mechanized process in many parts of the world and constitutes 70% of the world’s freshwater use, more than any other human activity.
Clean water is essential for growing food and raising animals, but agricultural water consumption also accounts for nearly 80% of all embedded water; the water used to harvest, process, refrigerate, and transport food to market. Growing, harvesting, and shipping food to market is an extremely water-intensive process.
John Williams is an Australian hydrologist and founding member of the Wentworth Group of Concerned Scientists. Williams is a leader in developing water-saving solutions in agriculture. Williams is also a practicing Christian who sees a relationship between his faith and his work as a scientist. 9
According to the Food and Agriculture Organization of the United Nations (FAO), it takes 2,000 to 5,000 liters of water to produce one person’s daily food. As we’ve seen, a person only requires 50 liters of clean water a day to live healthily. You may be surprised to learn that a pound of steak requires over 7,500 liters of water from farm to table.
In some places, scarce water resources have prompted governments to buy large tracts of land in countries with more abundant access, sometimes thousands of miles away. The practice is called a land grab. In 2008, for instance, Qatar made a deal for 40,000 hectares in Kenya to grow food it could then export back to Qatari markets. According to 2018 rankings, Qatar is the third most water stressed country in the world; Kenya is “low risk” at number 123.
Agricultural production has increased substantially since the 1960’s with the introduction of synthetic fertilizers, chemical pesticides, and herbicides. Most of these chemicals find their way back into the hydrological system through runoff into lakes, rivers, and streams. They then re-enter the food system and begin to build up in living organisms, a type of contamination called bioaccumulation.
Agricultural runoff contains fertilizers which collect in rivers and ultimately flow into the sea ( step 1 in Figure 18), providing an unintended boost to single-celled aquatic plants called phytoplankton or algae. The algae utilize the fertilizer and reproduce abundantly, forming massive algae blooms (step 2). Small crustaceans called zooplankton feed on the algae (step 3). The uneaten algae die and, along with the zooplankton feces, sink to the bottom to be rapidly decomposed by bacteria (step 4). These bacteria use oxygen in their decomposition process (step 5), leaving very little oxygen in the water for other marine life. The water becomes hypoxic (low oxygen) and, as marine life suffocates, an oceanic dead zone is created (step 6).
The number of oceanic dead zones around the globe (such as those in Figure 19) has risen from just a few dozen in the 1960’s to over 400 today due to an increased use of fertilizers in agricultural practices worldwide.
Industrial water use includes the vast amounts of water necessary for manufacture, fabrication, washing, conveyance, cooling, extraction, and service provision. Just as every agricultural product has a ‘water footprint’ which accounts for all of the embedded water used to grow, harvest, process, and deliver the product, so too does every industrial product. If you are wearing a cotton shirt, for instance, your shirt took approximately 2,500 liters of water to produce.
Water pollution by industrial processes is also an important concern. The semi-conductor, steel, chemical, paper, metals and mineral mining, and fossil fuel mining and refining industries produce waste material that can leak into surface and groundwater, presenting human and animal health risks and having a profound effect on aquatic life. Percolation of rain water through industrial waste piles produced by coal mining, for instance, can introduce toxic cadmium, arsenic, mercury, and lead into groundwater aquifers that are used for drinking.
Hydraulic fracturing (called fracking) is a new and controversial mining technology used to extract natural gas (methane, CH4) from oil shale deposits in the United States. Fracking involves high-pressure injection of a mixture of water and over 500 different solvent chemicals into deep underground wells, expanding crevices in oil shale and releasing natural gas for collection. Between 70 and 140 billion gallons of fresh water are injected into fracking wells annually in the U.S. In addition to its enormous consumption of water, there are two primary concerns about the effect of fracking on water quality. One problem is the harsh fracking chemicals that contaminate groundwater. The second is that methane released during the fracking process also contaminates aquifer drinking water. While natural gas is a source of fossil fuel energy, it is also an extremely potent greenhouse gas; 20 times more potent per molecule than carbon dioxide (CO2). As you will learn in the energy and climate change chapters, fracking causes leaking of CH4 directly to the atmosphere, exacerbating the effects of global climate change.
Water is a basic human right, necessary for the ‘common good’ and water privatization raises serious questions about equitable distribution of water.
Finally, corporations license water rights from national governments to operate manufacturing plants, beverage companies or private utilities. For example, an estimated 200 billion bottles of drinking water were extracted, bottled and sold in 2008 alone, many of them transported long distances to their final destinations, which itself requires high quantities of water. In South Asia, beverage producers have illegally overdrawn the ground and surface water resources on which local communities rely. During the 1980s, the International Monetary Fund (IMF) and World Bank encouraged the privatization of water utilities in developing countries that were receiving IMF loans.
While private utilities can be a viable option if properly regulated, unregulated water privatization can lead to massive price increases for water, disruptions in service, and cutoffs for poor families. For example, Cochabamba, Bolivia famously led public demonstrations against its private water service industrial provider, Bechtel, finally expelling them from the country.
Water Stress and Water Crisis
The difference between water’s distribution and consumption can create issues of water scarcity in some regions. Difficulty in accessing freshwater is called water stress.
With a rising global population, increasing water use per capita, and depleting reserves of groundwater, there’s no doubt that blue gold, as water is sometimes called, is an increasingly precious resource. Read more about global water stress and scarcity, and explore an interactive map.
In addition to the amount of rainfall a country receives each year, the way a country manages its water is also very important. This process involves a series of policies and practices collectively called Water Resource Management (WRM). Water stress is usually measured by comparing the amount of renewable water in a particular place to the amount withdrawn per capita. When the amount withdrawn is greater than the renewable amount, a country is water stressed. When water stress reaches the point that the available clean water can no longer meet the needs (domestic, agricultural, industrial) of the local community, that community experiences a water crisis.
Many countries are withdrawing water at a non-sustainable rate, meaning that water resources will not be able to naturally regenerate through the hydrological cycle at the rate in which they are being depleted. Kuwait (like Qatar) is one of the most water stressed countries in the world, consuming over 2,400% of its renewable water every year. Globally, the renewable supply of freshwater per person decreased 58% in the second half of the 20th century, as the population grew to over 6 billion. As that number expands to 8.7 billion before predicted stabilization around the year 2050, it will continue to drive increasing demand for ground and surface water resources.
The scientific study of water reveals a substance of extraordinary life-giving qualities. Water is essential to all living and non-living things on Earth, from the smallest organism to the vast patterns of global weather. It is no wonder that since human beings emerged as a species, they have placed a high value on water and have faced many challenges about water protection and distribution. It is to these challenges that Healing Earth now turns.
Questions to Consider
- Imagine that a technology was invented to change enough salt water into fresh water to serve the needs of life on Earth. Would this solve the water crisis? Learn about desalination efforts at the Scientific American website.
- What are the major global impacts on water quality and quantity today?