The Global Water Picture
What is meant by water shortages? How much water is available to support humans? And how does water availability vary across the globe?
Linda Vanasupa takes us on an educational journey all about water with these videos (transcriptions by me.)
We will look at these questions in this video about half the world’s population face a scarcity of water. This is about seven plus billion people on such a large planet with so much water. Even when you include residential irrigation, how is this possible? Well recall that the earth is for all intents and purposes a closed thermodynamic system. This means it can exchange energy with the surroundings, such as incoming solar radiation, but to a great degree it cannot exchange a large amount of mass with the surroundings to affect its temperature pressure and volume.
What this means is that matter that is needed for living must be on earth already. Well, what about water is there shortage of water? We know that more than 75 % of the surface of our earth is covered with water. So why is there any talk of water shortages? The global stock of water is stored in three primary forms. 2.5 percent of this water volume is fresh water from lakes, rivers, and streams, and only about 0.1 % of the earth. Water is dissolved in the atmosphere, so this gives you a sense of where the water actually is and in what form it’s in.
So, when you hear talk about water shortages, water means freshwater saltwater is not fit for human consumption. Much of natural water also is not fit for human consumption. For example, the typical contaminants found in natural water in that developed country include major in organics minor in organics. Naturally, occurring organic compounds and anthropogenic organics now notice that some of these constituents are toxic, others simply affect the odor, taste and color of the water.
So quality measures of water include things like odor taste, temperature, color and total dissolved solids as well as turbidity and turbidity is the measure of the optical clarity of water and is caused by suspended particles in water. So natural fresh water also needs treatment prior to human consumption. However, treatment is not always available.
This figure shows the population by regions that are lacking improved water supply and sanitation.
There is a greater percentage of the population that still lacks access to improve sanitation. 2.5 billion people lack access to any type of sanitation equipment compared to the global population that lacks access to improve water supply. Not having access to an improved water source and lack of access to improve water, sanitation can lead to disease, causing agents to be transmitted through contact with air water and solid waste.
How do we look at these issues on a larger scale? One method is through the water footprint tool. If we look at the global picture, we see that some regions do not experience a scarcity of water. However, many regions have water scarcity several months out of the year. This graphic depicts the regions throughout the world where the amount of water needed to sustain human life and dilute pollutants to acceptable levels exceeds what is available through rivers and groundwater.
Although the Earth’s surface is more than 75 % water, only fresh water can support the life of non-oceanic beings. Even fresh water must be treated in developed countries. Fresh water typically contains a range of contaminants, including trace concentrations of biotoxins. Almost a billion people do not have access to improved water up to three times, as many do not have access to sanitation. There are many regions where the water needed exceeds the available water. Several months out of the year in the next video we look at measuring water needs.
The Hydrologic Cycle
The hydrological cycle, what is the natural cycle of freshwater replenishment, where is fresh water stored for our use and how does increase global temperature affect fresh water storage? These are the questions that We will be considering in this video.
The hydrologic cycle consists of the pathways for how water moves and is distributed on the planet recall that we’re largely focused on fresh water, so the oceanic water is not considered. Let’s begin by thinking about water in the atmosphere, our atmosphere naturally absorbs water vapor. We refer to this as humidity. The water vapor is provided by evapotranspiration from Earth’s land, surface and evaporation from Earth’s water surface, the concentration of water vapor that can be absorbed in the atmosphere increases with increasing temperature.
The term relative humidity is the percentage of water vapor. In the air relative to the concentration that the air can hold when it’s saturated, when the temperature drops sufficiently to cause the water concentration to exceed the saturation limit of water and air water will do one of two things: either condensed a small liquid or small ice Particles which we recognize as clouds or precipitate out in the air, it is this precipitation of water from the atmosphere that refills our natural freshwater reservoirs. As shown in this image, precipitation can be stored directly in reservoirs such as streams, rivers, or lakes, or it can infiltrate the soil and end up in the underground aquifer. This image shows the source of various types of water from a developed country viewpoint.
The type of water treatment required for human consumption depends on whether the water is collected directly from precipitation, reclaimed, surface water or groundwater. This image shows the approximate distribution of fresh water in various reservoirs at the time of creating this video, our best science estimates over two-thirds of the fresh water is in the form of glaciers and permanent snow cover of the remaining most is in groundwater, and one percent of the total is estimated to be in these more or less accessible forms.
Well, note that the volume of glaciers is shrinking dramatically each year, as indicated by in taken by NASA. One of the issues with global warming is that the combination of warmer surface temperatures in a warmer atmosphere has the effect of drawing more water vapor into the atmosphere. Shifting the storage of water from more accessible forms to less accessible forms freshwater is critical to all life forms so depleting these natural reservoirs of water jeopardizes all life forms, including the life forms that create the biological services to support life.
Freshwater is stored in the atmosphere through evaporation and evapotranspiration. The release of atmospheric water is regulated by temperature, sensitive processes. Global warming has the effect of increasing the water vapor solubility of the atmosphere and increasing both evapotranspiration and evaporation rates. The result is that easily accessible water is moved to the atmospheric reservoir, which is generally less accessible, depleting the accessible water reservoirs jeopardizes all life forms and biological services which depend on water.
Accounting for our Needs
How do we account for water use? What is the difference between water consumed and water withdrawn? What is the water footprint tool? We will look at these questions in this video fresh water is the basis of all life.
This image shows that there are regions throughout the world where the amount of water needed to sustain human life and dilute pollutants to acceptable levels exceeds what is available through rivers and groundwater. That is, there’s a scarcity of freshwater in different regions in the world. How do we account for the stock of freshwater available in the amount that we need?
The traditional method of measuring water has two categories of use: consumption or withdrawal. This image depicts the differences between the two accounting categories of water when the water is used and then returned to the closed system. As is often the case for water used in residential homes, we consider this water withdrawn.
The water returned to the municipal system then requires treatment to be used again when the water is used in exits. The closed water system that water is consumed consumptive water use, is defined as use that removes massive water from the local water supply.
This image shows the difference in the water withdrawn and the water consumed in the United States recall that the water withdrawn will return for treatment and reuse. While the water consumed is lost from the freshwater storage system, a newer method of accounting for water has been developed by Hoetrksa and others. This method is called the water footprint.
It’s a method that accounts for the volume of water associated with human economic activity. The water footprint tool differentiates between three types of water, green water, from precipitation, blue water from groundwater and surface water and grey water, which will be explained.
The water footprint tool recognizes that all goods and services have a life cycle and that each stage of the life cycle water is used as a resource and pollutants are emitted in the water footprint model, volumes of fresh water are needed to dilute or assimilate the load Of the pollutants to the natural background concentrations and existing ambient water quality standards in the water footprint rattle, this volume of water required to dilute the pollutants to the acceptable levels is called gray.
As a Product
The water that is used to create a product is used in directly and the water footprint tool accounts for direct use and indirect use. An example of direct water use would be the water you use each day for cooking, cleaning, watering your plants and sanitation. The indirect use is associated with the embedded water in goods and services that you use. Traditional measures of water use are also shown on the slide note that the traditional measures do not account for the systemic use of water, nor do they account for pollutants.
This chart of water scarcity is based on national water footprints. Let’s consider how the water footprint tool examines national water footprints within a country, production activity results in goods and services that are internally consumed or exported. There is also trade activity consumed in the country or react sported into goods and services.
The Virtual Budget
This results in what is called the virtual water budget. As you can see, the virtual water budget is a sum of the water footprint of national consumption and the virtual water exported. You might wonder why it’s called virtual water, not simply water. Note that these volumes of water are the volumes required not actually the volumes used, for example, the water footprint tracks water needed to dilute pollutants, but it is not always the case that water is used to dilute pollutants to acceptable levels.
This image is a case study on coffee and tea for the Netherlands, as shown because coffee, tea or water intensive crops, they result in a large virtual water footprint.
Traditional methods for water use consider only the volumes of water withdrawn from local water supplies and not returned in the United States.
Five percent of the water consumed is through irrigation and livestock use. The water footprint tool is more holistic than traditional accounting methods and considers the volume of water needed for both direct and indirect use. Indirect use consists of water embedded in goods and services throughout the lifecycle. The water footprint tool also considers the water needed to dilute the pollutant load to acceptable quality standards. The water footprint allows a picture of national virtual water budgets associated with economic activity.
The Energy Connection
The water energy connection, how is water use related to energy use? Why is energy needed for water when water is needed for energy? Is one liter of water equivalent, regardless of how it is used? These are the questions that will be addressing in this video in developed countries.
Water and energy use can be closely connected, especially if processes rely on industrial era methods. For example, in the United States, every million gallons of treated water delivered requires 300 to 3,800 kilowatt hours of electric energy. Eighty to ninety percent of this energy is used simply for pumping the water extraction.
Transformation and delivery of energy in turn requires water. Let’s look at two cases: energy in the form of electricity and energy in the form of fuels. In both cases, the delivery requires an insignificant amount of water compared to the extraction and transformation steps, so we will just focus on extraction and transformation.
With respect to a life cycle picture, we are only considering the water input for the equivalent of material production and manufacture of the energy in terms of the water footprint, we are neglecting the water needed to absorb the pollutant load, that is, the gray water. In some cases, the gray water load may be as much as the water input required.
Here is a look at the use of water to extract and transform energy resources to electricity. The vertical axis represents the leaders of water per gigajoule of energy extracted. The horizontal axis represents liters of water per gigajoule. Electricity transformed, so energy resources in the bottom left represent the least water used in the combined processes.
You can think of processes lying on an arc of equivalent radius as being equivalent in the amount of water used per gigajoule of electricity. Produced notice that electricity from photovoltaics require the least water per gigajoule, while in general, fossil fuels and nuclear power represent the largest.
Water consumed per gigajoule electricity produced coal and geothermal, are about the same hydroelectric uses about an equivalent amount of water per gigajoule produced as fossil fuels. If you consider the water that is evaporated from the open surface of a body of water, evaporation from bodies of water is a natural process, and you might ask yourself if, even though the quantity of water use per gigajoule is the same, is the quality of the use equivalent?
For example, evaporation removes water from water reservoirs, but this water would be removed anyway, because of the nature of a reservoir in fossil fuel transformation. Water is contaminated and requires energy to treat the water. For this case, you can see that the water footprint tool would be helpful because it would consider the whole lifecycle water needs as well as distinguish between the type of water needed.
When we consider a comparison of liquid fuels, we see that the most water intensive fuels are the biofuels for these fuels. The majority of the water required in the growth stage for the soy and corn crops. As with the case for electricity, it’s important to consider not just the quantity of water used for fuel production, but also the impact of the water use again, the water footprint tool would be helpful.
Reflecting on the Data
These data illustrate that one must use reflective judgment and systems thinking when considering numbers. The numbers only tell part of the story. In this case, the data show the connection between energy production water use, but they only tell part of the story since it neglects the water needed to deal with the emissions from the extraction and transformation processes in developed countries that rely on industrial era technologies.
Water uses closely tied to energy use in the United States. Most of the energy used in water treatment is for pumping energy production, storage and delivery requires water. The amount of water required per quantity of energy produced varies widely depending on the energy resource. However, one leader of water consumption is not equivalent in its impact when it excludes the water needed to assimilate toxic emissions associated with the consumption. Therefore, it’s critical to use reflective judgment when examining and comparing data