Geosciences Column: When water is scarce, understanding how we can save it is important

Geosciences Column: When water is scarce, understanding how we can save it is important

Supplies of water on Earth are running dry. The rate at which an ever growing population consumes this precious resource is not matched by our Planet’s ability to replenish it. Water scarcity is proving a problem globally, with regions such as California and Brazil facing some of the most severe water shortages on record. Used for drinking, agriculture and industrial processes, water forms an fundamental part of our day to day life, so finding ways in which to preserve this vital resource is important.

The global population now exceeds 7.3 billion people. One of the greatest challenges of the 21st century will be to feed this ever growing population – by 2050 crop production will have to double to meet demand. At the same time, agricultural irrigation currently accounts for approximately 80-90% of global freshwater consumption, while agricultural areas requiring irrigation in the past 50 years having roughly doubled. With both space and freshwater in short supply, innovative solutions and fresh approaches will be need if the increase in crop demand is to be met.

The fields in the image are farmed on seemingly vertical hillsides, terrace their fields nearly to the top of every available mountain, and plough by hand or with a draft animal. Terraces, by Cheng Su, distributed via Imaggeo.

The fields in the image are farmed on seemingly vertical hillsides. Terraced fields are  present nearly to the top of every available mountain, and ploughed by hand or with a draft animal. Terraces, by Cheng Su, distributed via imaggeo.

It might come as a bit of a surprise that current irrigations systems operate at efficiency of 50% or below. Water is wasted as it is transported to the crops as well as whilst it is applied to the plants and is affected, not only by the irrigation system itself, but also meteorological and environmental factors. A recent paper published in the open access, EGU Journal, Hydrology and Earth System Sciences, has found that improving current irrigation practices can contribute to sustainable food security.

To better understand where efficiencies might be made in irrigation systems, the scientists used a new approach: They took into account ‘manageable’ factors such as water lost through evaporation, run-off, deep percolation and that taken on by weeds. At the same time, assessing mechanical performance of the systems and the vegetation dynamics, climate, soils and land use properties of a particular region. These factors were fed into a global irrigation model implemented on the three main irrigation types: surface, sprinkler and drip.

The researchers created maps of the global distribution of irrigation systems at a country level, based on the results from their model. The maps showed that areas where surface irrigation – were water is distributed over the surface of a field – is common, irrigation system efficiency was low, sometimes registering values of less than 30%! This is particularly applicable to Central, south and Southeast Asia due to the widespread cultivation of rice. In contrast, areas where there is a high usage of sprinkler systems – similar to natural rainfall – and drip systems (were water is allowed to drip slowly to the root of the plant), such as North America, Brazil, South Africa, Ivory Coast and Europe, efficiency was above the global average.

Global patterns of beneficial irrigation efficiency (Eb, ratio of transpired and diverted water) for each irrigation system – (a) surface, (b) sprinkler, and (c) drip, calculated as area-weighted mean over CFTs (excl. “others” and pastures). This figure is based on theoretical scenarios, in which each system is respectively assumed to be applied on the entire irrigated area.

Global patterns of beneficial irrigation efficiency for each irrigation system (a) surface, (b) sprinkler, and (c) drip. This figure is based on theoretical scenarios, in which each system is respectively assumed to be applied on the entire irrigated area. From Jägermeyr et al., 2015. Click to enlarge.

To investigate how the three irrigation system types compared to one another, irrespective of their geographical distribution, the researchers produced another map. They found that surface irrigation is the least efficient of the three methods, with values at less than 29%. Sprinkler and drip systems perform significantly better, with values of 51 and 70%, respectively. Interestingly, regardless of the system used, irrigation efficiency in Pakistan, northeast India and Bangladesh is always at below global average values. Crop type can also play an important role: rice, pules and rapeseed are linked to poor system efficiencies, whilst, maize sugarcane and root crops (such as potatoes) are above average.

Jägermeyr, the study’s lead author, and his team calculated that 2469km³ of water is withdrawn yearly for irrigation purposes – that is close to 5 times the volume of water held in the Canadian/American Lake Erie. Of that, 608 km³ is non-beneficially consumed. In other words, lost through evaporation, interception (by foliage leaves) and during delivery to the plants and represents an area where substantial water savings could be made.

Replacing surface irrigation with a sprinkler or drip system proves one of the best solutions to the problem, with a potential 76% reduction in non-beneficial consumption of water. This would mean that up to 68% less water would be needed for the purposes of irrigating crops.

Therefore, irrigation system improvements could make an important contribution to sustainably increase food production. The water saved would allow for irrigated areas to be expanded and yields increased on farms where production is currently limited by an insufficient water supply.

The upgrade of irrigations systems seems a very attractive solution to the problem, but the researchers warn that its suitability must be assessed on a river basin level. Factors such as crop management, soil type and local climate may affect the suitability of this approach in some geographical areas. The study finds that regions such as the Sahel, Korea and Madagascar, as well as temperate regions in Europe, North America, Brazil and parts of China would benefit the most from irrigation system improvements.


By Laura Roberts Artal, EGU Communications Officer.



Jägermeyr, J., Gerten, D., Heinke, J., Schaphoff, S., Kummu, M., and Lucht, W.: Water savings potentials of irrigation systems: global simulation of processes and linkages, Hydrol. Earth Syst. Sci., 19, 3073-3091, doi:10.5194/hess-19-3073-2015, 2015.

Gleick, P.H., Christian-Smith, j., Cooley, H.: Water-use efficiency and productivity: rethinking the basin approach, Water International, 36, 7, doi: 10.1080/02508060.2011.631873, 2011.

Tilman, D., Blazer, C., Hill, J., Befort, B.L.: Global food demand and the sustainable intensification of agriculture, PNAS 108, (50), 20260-20264, doi:10.1073/pnas.1116437108, 2011.

Film review: Revolution

Film review: Revolution

It’s not every day you are asked to review a film, and since it’s a documentary that encompasses a few of EGU’s sciences (such as climate sciences, biogeosciences, and energy, resources and the environment), I couldn’t say no. I’ll start by giving it a rating, 3.5/5 stars, though I would probably give it more if I were part of the film’s main target audience.

Revolution, by biologist-photographer turned filmmaker-conservationist Rob Stewart, is about some of the most pressing environmental issues of our time. It aims to educate the audience about ocean acidification, climate change, overfishing and deforestation, alerting them to how these issues can impact our planet and, in turn, humanity. But it’s also about much more than that.

The film starts with Stewart telling his own story, revealing how his personal experiences lead him to make his first documentary, Sharkwater, and how researching and promoting that film made him want to tell the broader story of Revolution. This makes for good story telling, and it’s an interesting and candid introduction (Stewart says at one point that he had no idea how to make a movie before Sharkwater). But it seems a tad overly dramatic at times and not always scientific in its claims. For example, to illustrate how humans, responsible for many environmental problems, can also be part of their solution, Stewart tells a crowd in Hong Kong that the “holes in the ozone layer are almost a figment of our imagination now”, which is not exactly true. According to a 2014 NASA release, the ozone hole is still roughly the size of North America, though it has been shrinking over the past couple of decades. I should point out, however, that while there are some minor scientific inaccuracies here and there in the film (and a glaring typo in a sentence where CO2 appears incorrectly written as CO2) the majority of the facts and figures cited in the movie do roughly seem to be accurate, even if rather dramatic and seemingly exaggerated at first.

The movie becomes more exciting (though, at times, depressing too) when Stewart changes the focus from his story to the story of how life evolved on Earth, and what its future might look like. The backdrop is beautiful footage, worthy of a BBC wildlife programme. Stewart starts where life itself started, underwater, and the images showing a diversity of corals and colourful fish (and the cute pigmy sea horse) are breath-taking and work well in illustrating his points. For example, as the colourful imagery gives place to shades of grey, Stewart describes and shows how corals have been affected by ocean acidification and rising temperatures.

Coral cover on the Great Barrier Reef has declined by 36% over the last 25 years. That's an enormous loss. Photo © Rob Stewart. From the documentary film Revolution.

Coral cover on the Great Barrier Reef has declined by 36% over the last 25 years. That’s an enormous loss. Photo © Rob Stewart. From the documentary film Revolution.

If the footage, both underwater and on land, makes for a stunning background, the interviews with various scientific experts bring home the film’s key messages. To me, they are the strongest aspect of Revolution. Stewart talks to credible researchers who are able to communicate their, often complex, science in clear language. Some of the readers of this blog may be able to relate to scientists Charlie Veron and Katharina Fabricius, whose field work is shown in the film, while viewers less familiar with the effects of ocean acidification on coral reefs will likely be moved by the dramatic words of these researchers.

What the scientists tell us will happen if humans continue in the business-as-usual path is indeed gloomy: deforestation increasing, fisheries collapsing, greenhouse gas emissions and temperatures on the rise at unprecedented rates, species going extinct en masse… the list goes on. The issues of deforestation and mass extinction are addressed when Stewart travels to Madagascar: the island’s tropical dry forests are home to unique animals and plants, many of which have seen their habitats destroyed by the burning of trees to make room for pastures and crops. Humanity’s dependence on fossil fuels is illustrated when Stewart talks about the Alberta tar sands, and how resource intensive and polluting it is to extract oil from them. A key message of the film is again illustrated here by one of the experts interviewed. Hans Joachim (‘John’) Schellnhuber, a scientific advisor to the German Government and director of the Potsdam Institute for Climate Impact Research, explains how stopping the Canadian tar sands project “is one of the decisive battles in the war against global warming”.

Indeed, Stewart sets out not only to inform people about the environmental issues faced by humanity, but also to encourage the audience to act on them: “Revolution is not just about the environment – it’s a film about hope and inspiration.” As such, Stewart balances out this negative outlook with examples of people who are standing up for climate justice and fighting for an end to fossil-fuel burning (and, sometimes, with clips of flamboyant cuttlefish and jumping lemurs!). Although it may not seem like it halfway through the film, the overall message is positive.

This is most evident when Stewart talks to young people, particularly those who travelled to Cancun, Mexico for the United Nations Climate Change Conference in 2010 (COP16). It is heartening to find out how committed and courageous some young people are in fighting for our future, their future, and in wanting to make the Earth a better place by changing human behaviour. This fighting spirit is best encapsulated in a speech by Mirna Haider, from the COP16 Lebanon Youth Delegation, which is particularly bold and moving, if impatient: “You have been negotiating all my life, you cannot tell me you need more time.”

Flamboyant Cuttlefish. Photo © Rob Stewart. From the documentary film Revolution.

Flamboyant Cuttlefish. Photo © Rob Stewart. From the documentary film Revolution.

Young people are those who may have the most to benefit from watching this film, and I think are the primary target audience of Revolution (there’s even an accompanying Educator’s guide with pre- and post-viewing resources and classroom activities teachers and parents might find useful). It inspires them towards (peaceful) revolution against corporations who profit from burning fossil fuels and from destroying natural resources, and against governments who take no action to stop them. It is a shame the film doesn’t address other ways in which individuals could help fight climate change, deforestation and ocean acidification, such as divesting from fossil fuels or eating less meat. But perhaps that’s something that resonates better with older people. Children and teenagers tend to be more optimistic about their power to save the Planet through revolution, and this film is sure to inspire them to act on the most pressing environmental problems the Earth faces.

Revolution premiered at festivals in 2012/2013, but has only been widely released earlier this year. You can watch the film online on the Revolution website, or through the platforms indicated there (sadly, it’s not free, but you can either rent it or buy it for only a few dollars, so it’s certainly affordable!).


By Bárbara Ferreira, EGU Media and Communications Manager

Imaggeo on Mondays: Sunset over the Labrador Sea

Ruby skies and calm waters are the backdrop for this week’s Imaggeo image – one of the ten finalist images in this year’s EGU Photo contest.

 Sunset over the Labrador Sea. Credit: Christof Pearce (distributed via

Sunset over the Labrador Sea. Credit: Christof Pearce (distributed via

“I took the picture while on a scientific cruise in West Greenland in 2013,” explains Christof Pearce, a postdoctoral researcher at Stockholm University. “We spent most of the time inside the fjord systems around the Greenland capital, Nuuk, but this specific day we were outside on the shelf in the open Labrador Sea. The black dot on the horizon toward the right of the image is a massive iceberg floating in the distance.”

Pearce took part in a research cruise which aimed to obtain high-resolution marine sedimentary records, which would shed light on the geology and past climate of Greenland during the Holocene, the epoch which began 11,700 years ago and continues to the present day.

A total of 12 scientists and students took part in the Danish-Greenlandic-Canadian research cruise in the Godthåbsfjord complex and on the West Greenland shelf. By acquiring cores of the sediments at the bottom of the sea floor, the research team would be able to gather information such as sediment lithology, stable isotopes preserved in fossil foraminifera – sea fairing little creatures – which can yield information about past climates, amongst other data. One of the main research aims was to learn more about the rate at which the Greenland Ice Sheet melted during the Holocene and how this affected local climate conditions and the wider climate system.

“The picture was taken approximately 25 kilometres off the shore of west Greenland coast. In this region the water depth is ca. 500 meters,” describes Pearce. “At this location we deployed a so-called gravity corer and took a 6 meter long sediment core from the ocean floor. Based on radiocarbon measurements – by measuring how much carbon 14 is left in a sample, the age of the sampled units can be known – we now know that these 6 meters correspond to approximately 12000 years of sedimentation, and thus it captures a history of climate and oceanography from the last ice age all the way to present day.”


Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at

GeoTalk: How hydrothermal gases change soil biology

The biosphere is an incredible thing – whether you’re looking at it through the eye of a satellite and admiring the Amazon’s vast green landscape, or looking at Earth’s surface much more closely and watching the life that blossoms on scales the naked eye might never see, you are sure to be inspired. Geochemist, Antonina Lisa Gagliano has been working on the slopes of Pantelleria Island in an effort to find out what can make soil and its biota change enormously over just a few metres. Following her presentation at the EGU General Assembly, she spoke to Sara Mynott, shedding light on what makes volcanic soils so special…

Antonina Lisa Gagliano out in the field. Credit: Antonina Lisa Gagliano

Antonina Lisa Gagliano out in the field. Credit: Antonina Lisa Gagliano

What’s your scientific background, and what drew you to soil biota?

I am a geologist with a background in Natural Sciences and, in 2011, I started my research in biogeochemistry during my PhD in Geochemistry and Volcanology at the University of Palermo. I’ve always tried to look at the interactions between different factors in all sorts of subjects, but if you apply this concept to biotic and abiotic factors, it is particularly interesting and fascinating. I started the study on soil biota when my supervisors introduced me to the biogeochemistry of a geothermal area, thinking that I could have enough scientific background and enthusiasm to start studying something new in our team.

Tell me about your field site – what makes it a great place to study?

Pantelleria Island, a volcano located in the Sicily channel, is a really interesting place. It is an active volcanic system – at present quiescent – that hosts a high-energy geothermal system, with a high temperature gradient and gaseous manifestations all over the island. We studied the most active area, Favara Grande, sampling soils and soil gases from its geothermal field. A first look at the island’s geochemistry suggested high methane fluxes from the soil and high surface temperatures – reaching up 62 °C at only 2 cm below the surface. Indirect evidence of methanotrophic activity led us to better investigate soil biota and how it interacts with methane emissions. It is a great place to study because the peculiar composition of the geofluids is extraordinarily rich in methane and hydrogen, and because the geothermal system is stable both in space and time.

Geothermal area at Favara Grande, Pantelleria Island, Italy. Credit: Walter D’Alessandro.

Geothermal area at Favara Grande, Pantelleria Island, Italy. Credit: Walter D’Alessandro.

During the General Assembly, you highlighted key differences in soil sites that were only 10 metres apart – what did you find and why are they different?

We investigated two really close sites in the Favara Grande geothermal field. They released similar gases (CH4, H2, CO2) and had similar surface temperatures, but at the same time they showed differences in soil chemistry (in particular, pH, NH4+, H2O, sulphur, salinity, and oxides). Amazingly, one site showed high methane consumption and the other was totally inactive, despite both sites being characterised by high methane emissions.

These differences were due to the hydrothermal flux from the ground. As the gasses rise, the gas mixture is influenced by several factors including changes in soil and subsoil properties, such as fracturing, level of alteration, permeability and many others. Variations in even only one of these factors can change the flux velocity, which directly regulates soil temperature. When the temperature goes below 100 ⁰C the most soluble species (H2S and NH3), start to dissolve, releasing hydrogen ions and changing the soil’s characteristics.

The condition of one site was much more mild than the other (higher pH, lower amounts of NH4+, sulphur, soil water content and salinity). These differences were due to a lowering of the hydrothermal flux velocity in deeper layers at the milder site, leading to the depletion of soluble species in the surface soil layers. These conditions created two totally different environments for bacterial populations thriving in the two sites.

How did you identify the different species? How many did you find?

Nowadays, Next-Generation-Sequencing techniques (NGS) are available to screen the microbiota in different substrates. We extracted total bacterial and archeal DNA from soil samples and from the geothermal field at Favara Grande. We found an extraordinary diversity of methanotrophs, that use methane as sole source of carbon and energy in the milder site. In the harsher site, we found a high diversity of chemolithotrophs, that use inorganic reduced substrates to produce energy. Here, there was no methanotrophic activity, nor any evidence of the presence of methanotrophs.

On the left, the harsher site – the stains on the surface are signs of the soil alteration. To the right, the milder site – here, soil alteration is much harder to see without a microscope. Credit: Walter D’Alessandro.

On the left, the harsher site – the stains on the surface are signs of the soil alteration. To the right, the milder site – here, soil alteration is much harder to see without a microscope. Credit: Walter D’Alessandro.

Has anything like this been found before, perhaps at another volcanic site, hot spring or hydrothermal vent?

Currently, integrated studies of bacteria thriving in geothermal soils are still at the pioneer stage and few studies on similar work are available; What we found in terms of chemolithotrophic species is similar to other volcanic sites, but the diversity of methanotrophs detected in our soil samples seem to be unique, probably because the geothermal soils are still under-investigated in this regard.

What do you hope to work on next?

Several questions regarding the relationship between biotic and abiotic factors at our sampling sites are open, so our next challenge is to better investigate the dynamics in this geothermal field. We would also like to extend this research to other sites and establish new collaborations to study different areas and discover new things.

What are your biggest challenges in the field and how do you overcome them?

The first challenge is to find a good sampling site; sampling is like a closed box, particularly when you don’t have anything for comparison terms or any state of art equipment at your disposal. But we overcome these challenges with good planning ahead of the field campaign.

If you could give an aspiring biogeochemist one piece of advice, what would it be?

Biogeochemistry puts together several spheres of knowledge (geochemistry and biology, above all), so my first advice is never stop studying, because when you think to know a lot about something, it’s likely that you may completely overlook the other aspects of the argument. Secondly, go outside the scheme of classical and sectorial research and collaborate with scientists of different sectors to increase your expertise and look at problems from other points of view.

Interview by Sara Mynott, PhD student at the University of Exeter.


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