Geology for Global Development

Water series

Tracking water consumption: how you can help fight climate-change-driven water stress

Tracking water consumption: how you can help fight climate-change-driven water stress

How much water do you think you’re using? When you eat 200 g of beef, you are using more than 3,000 liters of water. Regular blog author Bárbara Zambelli helps us understand how we can alleviate climate-change-related water stress in countries around the world, just through our choices of consumption. [Editor’s note: This post reflects Bárbara’s personal opinions. These opinions may not reflect official policy positions of Geology for Global Development.]

This month our blog theme is resources, and I chose to write about water, not only because it is our most basic need but also as it is the basis of all goods, products and resources that we use.

Freshwater, like any other natural resource, is unevenly distributed on Earth’s surface, leading to physical scarcity in many parts of the globe, while other regions are suffering from floods and heavy rain events. So, we have to deal with water scarcity problems every time that water is too little, too much or too dirty.

The largest share of water is used in agriculture and industry, whilst direct uses (such as drinking, cooking, bathing, cleaning and so on) are responsible for only a small amount

Another reason to be alert is that, according to the Organization of Economic Cooperation and Development, 47% of the world’s population will suffer from water shortage by 2030. In this article, in order to better discuss sustainable water usage, I want to explore some important concepts in the following paragraphs.

Virtual water is the first one: it is related to indirect water used for different purposes, such as growing crops, energy production or transportation. Let’s take an example from food production – Do you know how much water is necessary to produce 1 kg of beef? The global average is about 15,400 L/kg.

On the other hand, to produce the same amount of vegetables, only 322 L are needed, for cereals 1,644 L/kg and for milk 1,020 L/kg. With that in mind, do you feel you really know your own water consumption? Would you like to find out? In this link, you can calculate your water footprint.

Here we come to the second important concept: water footprint. A water footprint reveals water consumption patterns, from individual to national level, communicating its expenditure in the manufacturing and production of goods. In addition, it reports the amount of water contaminated during those processes.

When a country is exporting some product (cereals, vegetables, oil, ores, clothes, technology and so on), it is also exporting virtual water needed to produce that product.

If we take a look at a list of highest water footprint by country, the United Arab Emirates leads the way, followed by the U.S. and Canada. Brazil appears at number 6.

It is important to point out that nowadays the largest share of water is used in agriculture and industry, whilst direct uses (such as drinking, cooking, bathing, cleaning and so on) are responsible for only a small amount. On this website, you can find many more interesting statistics about virtual water.

Another important concept is the international virtual water trade flow. When a country is exporting some product (cereals, vegetables, oil, ores, clothes, technology and so on), it is also exporting virtual water needed to produce that product.

Big virtual water exporters are most of the Americas, Asia, Australia, and Central Africa while big importers are in Europe, Japan, North and South Africa, the Middle East, Mexico, and Indonesia.

One problem related to this trade happens because the indirect effects of water exploitation are externalized to other countries. Moreover, consumers are generally not aware and do not pay for the water problems in the overseas countries where their goods are being produced.

So, how can we take action, at an individual level, to reduce our water consumption and, at the same time, tackle climate change?

 First of all, we need to think outside the box. Reducing water consumption means way more than closing the tap while brushing your teeth. We need to re-think our lifestyles, diet, our choices for daily commutes and more.

A good start would be cutting off meat one day of the week (meatless Monday, for example). Instead of buying new clothes every year, look for some in second-hand shops, flea markets or swap with friends. Choose public transportation or bikes over private cars. When you need to shop anything, always check for local products instead of imported ones. Overall, always be a conscious citizen!

**This article expresses the personal opinions of the author (Bárbara Zambelli). These opinions may not reflect an official policy position of Geology for Global Development. **

Water Series (3): Arsenic Contamination in Drinking Water

Following our post about fluoride contamination last week, our water series is now focused on the equally serious problem of arsenic contamination.

Some arsenic is present in all groundwater sources (see table 1). Of course this is only a problem if the arsenic has the chance to leak into groundwater as it filters through the rock. Arsenic leaching is more likely to occur in groundwater that is hot, oxygen-depleted, alkaline or extremely acidic.

Table 1: table of different geological rock types and their associated arsenic content (from UNICEF arsenic report, 2008)

Rock or sediment type Average arsenic content (parts per million) Range of arsenic content (parts per million)
Sandstone 4.1 0.6 – 120
Limestone 2.6 0.4 – 20
Granite 1.3 0.2 – 15
Basalt 2.3 0.2 – 113
Alluvial sand 2.9 1.0 – 6.2
Alluvial silt 6.5 2.7 – 15
Loess 5.4 – 18

A 2008 UNICEF report found that over 137 million people in more than 70 countries are probably affected by elevated arsenic levels in their drinking water (above 10 parts per billion is considered a risk to health). Arsenic can be transferred into the body through drinking contaminated water, or eating food that was irrigated using contaminated water.

There is no available treatment for the suite of health problems, collectively known as arsenicosis, caused by the build up of arsenic in the body over several years. Arsenic exposure can cause cancer, as well as vomiting, blindness and paralysis. High arsenic levels are a major problem in SE Asia. In Cambodia concentrations of up to 250 parts per billion have resulted in cases of arsenicosis so severe that amputations are required.

Small child using a well in Bangladesh. Photo taken by Donald John Macallister whilst working on a water project.

Arsenic poisoning can often remain undetected for a long time, as the symptoms do not occur until after a long, slow period of toxin build-up in the body. It is often health workers that have the first opportunity to identify the problem, but many are not trained to recognize the effects of early arsenicosis – lesions on the skin.

Once a high-risk area is identified, water samples can be taken over a wide area to map contaminated wells. The samples can be analysed in the field or sent back to a permanent laboratory. Field testing is cheaper and the results can be conveyed back to the relevant communities immediately, but laboratory testing may be necessary if more precise results are needed.

The most effective way to reduce exposure to arsenic is to identify contaminated wells and explain to the affected communities why they should avoid them. Communicating the severity of arsenic poisoning can be difficult, as arsenic in water can’t be seen or tasted, and there are no immediate consequences of drinking arsenic-contaminated water.

In cases where a local, uncontaminated well cannot be identified, the only option may be to remove arsenic from drinking water by passing it through an ultrafiltration membrane. Polyelectrolytes (long-chained molecules that acts like salt and dissociate in water) form complex molecules with arsenic that are too large to pass through the membrane. These large molecules form more efficiently at higher pH (8.5), as arsenic becomes more negatively charged (-2) and so is more attracted to the positive polyelectrolyte. Conveniently, groundwater often has a slightly elevated natural pH. The filter should have grains with a high surface area and high absorptive capacity. Goethite amended sand works well, with added iron oxide.

Filtering out arsenic can cause the concentration of other elements to drop as well, some of which, such as chromium, may be beneficial. It is always more desirable to source water from an alternative well than to filter water from an existing well.


UNICEF have produced an excellent and extensive report documenting their knowledge and experience of working with arsenic contaminated wells. To learn more, you can read it for free online.

Water Series (2): Fluoride Contamination in Drinking Water

This week, as part of our ‘water series’ we will focus on fluoride contamination in drinking water. In some parts of the UK we add fluoride to our drinking water, because small amounts can help to protect your teeth. However, too much fluoride (>1.5mg/L) can lead to a serious medical condition called fluorosis, affecting the development of teeth and bones. This strong dosage dependency can lead to real battles in science communication. Even in the UK, where our fluoride levels are carefully controlled and maintained at a level that benefits us, there are public concerns and conspiracy theories about fluoride.

In places where water is not regulated at a centralised plant, many people have to drink from wells that have dangerously high levels of fluoride.  The main source of fluoride is contaminated groundwater, but other sources should also be taken into account when assessing safe concentrations. In the UK, toothpaste provides an extra source of fluoride, whereas in Ethiopia, the tea people drink is high in fluoride. Fluoride poisoning affects two hundred million people worldwide, and is a particular problem in Ethiopia.

The underlying control on fluoride concentration is geological. Fluorine appears in almost every kind of rock. The highest concentrations of fluoride occur in connection with intercontinental hot spots and along rift zones. In geologically unstable regions fluoride enriched fluids rise from the Earth’s crust or mantle up towards the surface sediments.

Rifting breaks apart continents and forms new oceans, often beginning with a 3-armed structure, such as the one in the Middle East/East Africa highlighted by the red lines. Normally the rift axis is underwater, but here one rift occurs on land, through the centre of Ethiopia. Source: Google Earth

The great rift valley cuts across the centre of Ethiopia with a NE-SW strike, pulling the country in two. The rift is an important geological site as this process normally occurs on the seafloor, and can rarely be observed above ground. Rocks in the valley are mostly young volcanics. Samples of drinking water from along the length of the valley have been analysed for their elemental concentrations using  ion chromatography and an ICP-MS and (a mass spectrometer that is common in most Earth Science departments, used for measuring the concentration of a whole range of elements in a liquid sample). Seventy eight per cent of the samples would fail EU drinking water regulations, and this is predominantly due to high fluoride levels. The contamination is a result of the water passing through the volcanic rocks in the rift valley.

To remove fluoride, water can be passed through a cleaning system at the point of access or within the home. One cost effective and widely available method for removing fluoride is to filter the water through charred animal bones. Fish bones or eucalyptus wood work just as well for communities that have an ethical objection to the use of animal products. Crushing and heating the bones increases the surface area, and so improves the absorbance capacity. The temperature that the bones are heated to is critical, and the ideal lies between 400 and 500 degrees centigrade. In Ethiopia large kilns are already in place, so most people have access to the necessary technology to remove fluoride from their water. The temperature can be monitored with waxed candles, as the fuse breaks when the temperature is too high, and can be controlled by altering the balance between extra fuel and air supply. The addition of simple ligands can double the Fluoride uptake, so if possible the charred material is treated with Aluminium oxides or sulphate to improve the efficiency.

The technology to remove fluoride from people’s water supply is well developed and easily accessible. However, the science alone is not enough. Collaborations between geologists, engineers, anthropologists, sociologists and entrepreneurs is needed to make a project a success. Social surveys and group discussions are used within communities to determine the best way to deliver the water purification treatment. In some cases it makes sense to treat the water centrally as this is more cost effective. However, in some communities it is more beneficial for families to treat their own water at home. A family can be issued with equipment the size of a bucket and can last up to 6 months. Entrepreneurs can also be involved in financing the scheme, aiming to transform it into a business that can continue to fund itself. This is a truly multi-disciplinary issue.

Water Series (1): The Quantity and Quality of Groundwater

The water available in or near your home can vary dramatically over short distances. In Manchester, there is a robust supply of fresh water from the Lake District, whereas in London (only 200 miles away) the water has passed through limestone, leaving it with a cloudy taste and causing limescale build-up. Signs up on the London underground at the moment are encouraging people to save water by taking the “4 minute shower challenge” and this summer we have had a series of localised droughts and floods. Food prices are expected to rise because there was too much rain this summer, leading to widespread crop failure. Even in the UK, where we have plenty of year-round rainfall, controlling the quantity and quality of water is an expensive and precarious business.

It was in London that the connection was first made between water and health. John Snow noticed that the cholera outbreak in Soho was being caused by a contaminated water supply from the broad street well. In the UK there is now a secure and safe water supply. However, the water available to people around the world is much more variable. Over two million deaths a year are caused by poor water hygiene – equivalent to AIDS or malaria.

The primary control on precipitation (water that falls as rainfall, sleet or snow) is the large-scale convection cells in the atmosphere, which vary systematically with latitude – are you in a tropical zone or a desert zone? Groundwater levels, however, follow more complex patterns. Groundwater maps of Africa produced by a team at UCL show surprising levels of groundwater in unexpected places, such as deep beneath the sahara desert. The primary control on the quality of water is often geological – what rock and sediment does the water pass through between the source and the point of access?

NASA’s landsat educational archives: Latitudinal bands of tropics and deserts across the globe are driven by large scale atmospheric circulation cells.

In developing countries projects often have to work on a local scale, because there is no centralised water supply. Lack of access to water often has a disproportionate impact on women, who are normally expected to walk long distances to collect water from uncontaminated wells. Babies and small children are then the most vulnerable to health problems if the water supply is contaminated. Provision of clean water  is the single most important factor in reducing infant mortality.

Clean groundwater is being extracted from a deep borehole in Ethiopia – giving local communities a better chance of staying healthy. (c) Geology for Global Development 2012

Surface water is more susceptible to contamination from bacteria, but groundwater is more susceptible to heavy metal contamination. Two of the most worrying contaminants are Fluoride and Arsenic, and we will discuss each of these in depth in future blog articles. GfGD has discussed problems relating to water supply in the past, such as our winning entry in last years blog competition, and Donald John MacAllister’s guest blog sharing his practical experience in Bangladesh. Look out for more on our ‘water series’ over the coming weeks.