Can we meet the water demand of future generations?

Water - we all need it, but is there enough?
Image credit: fox_kiyo

Approximately one in eight of the world's population don't have access to clean water^[1]. The situation is only expected to worsen with increasing water demand and diminishing sources. Population growth and higher water consumption per capita are to blame for greater consumption. The amount of water most of us use has grown mainly due to changes in diet, the increase in use of water intensive biofuel crops, and acceleration of energy demand which in turn requires water. Water is such an essential part of life it's thought to be one of the main reasons why the Earth is the only planet we've found to be inhabited so far (but we're still searching).

It's hard for anyone to try determining how bad our water shortage is or will be when basic things about water sources still remain a mystery. For example we are clueless about how much water is available and how the water supplies that are obtainable to us may reduce in the future.

Currently most of the water on our planet is not available to us, although it is still not known how much fresh water may be available to us. The water that is available is derived mainly from two origins - surface water such as lakes and river, or groundwater which is stored in underground reserves known as aquifers. On-going work involves exploring how large these reserves may be and how deep we may hope to extract water. For example recent surveys of Africa show there may be extensive groundwater reserves^[2], and the first attempt to map water reserves was made a year ago^[3]. In the future improved and more detailed maps are expected as scientists try to answer the basic question of how much water is left? Without this knowledge it is impossible to try and understand fully the extent of water scarcity.

World Groundwater Resources, 2008.
Image credit: UNESCO's World-Wide Hydrogeological Mapping and Assessment Programme (WHYMAP)

The water available to us is not the only unknown - how changing climates may affect the water that is available is still largely disputed. It is known that higher temperatures cause the atmosphere to hold more water, so for some areas this will mean more and heavier rainfall. Heavier rainfalls are not such a good thing, as sudden large increases in rain water cannot be stored effectively - leading to further problems such a flooding. Ideal rainfall for collection is a consistent low level. It is also expected that even though there may be increases in global rainfall, drier regions will experience less rain. These localised trends and patterns are very difficult to predict. In most climate models there is agreement that higher temperatures can be expected, but the knock-on effect on weather and rainfall is more difficult to determine and so is still a matter of debate^[4]. Difficulties arise from not being able to distinguish the effects of climate change from natural variations; feedback systems associated with a change in temperature are also very complicated and still not fully understood. Scientists work using new satellites and equipment to improve the reliability of climate models. Even if the extent is uncertain, it is still predicted that in arid areas changing climate is most likely to cause higher evaporation levels and less rainfall, leading to the depletion of precious water sources.

It's not good enough to have water - it has to be clean.
Image credit: woodleywonderworks 

Understanding ways in which we can protect our water stores is key, and pollution is an important example of this. Pollution means that sources require more intense purifying, or mean a decreased supply to those that don't have the necessary means to do so. New studies in the UK aim to follow how pollutants move through the river before working with the farmers to develop methods that reduce pollutants due to agriculture. The methods being trialed vary in complexity from using GPS to guarantee efficient spreading of fertilisers to simply planting a few trees^[5]. Other research programmes also study pollutants, their causes, effects and test possible preventions.

One of the key roles of scientists is to firstly understand fully what the problem is and how it is caused - which will then hopefully enable solutions to be found. Much in the same way as if you were trying to navigate your way around an obstacle course blindfolded, it would be very helpful if someone were to remove the blindfold.

Being blindfolded tends to make things harder.
Image credit: Louise Crusoe

Many areas worldwide already experience the devastating repercussions of water deprivation, with untreated water causing widespread disease. While countries that are used to a seemingly endless supply of water are beginning to notice the falling water tables, leading to harder extraction of groundwater. We also must not forget that it is not only us that rely on water for survival. Our polluting and overuse of water sources will impact all other forms of life. The lack of water can force species to migrate to unfamiliar territories and may have other consequences such as reducing breeding potentials. There are several different types of pollutants that can cause a range of damage to wildlife, one example is mercury which is thought to cause deformation of developing animals.^[6] It is difficult to study the possible effects that may be caused to species in the field as other contributing factors are impossible to control.

Some don't think they need to worry about water shortage, but it is a global issue and the implications will be far reaching. There has been a lot of worry about energy security, but with growing tensions over water policies and ownership should more concern be given to the possibility of water wars?^[7]

With the threat of what could be in store there is increasing pressure on scientists and engineers to come up with a solution to the crisis. The first key problem to address is that millions of people do not even have clean water to drink or cook with.

There are several solutions that already exist that can provide drinking water including desalination which involves turning seawater into drinking water. Ninety five percent of Earth's waters are salty^[8] - desalination could hypothetically make this water available to use.There are several setbacks associated with the use of desalination, however. If waste salt is dumped back into the ocean this may cause problems for marine life and will make the desalination more difficult in the future, so what should we do with it? More complex issues concern the amount of energy required to run the current processes of desalination. Not only are these costly to the countries running the plants, they also rely on the burning of fossil fuels which contributes to climate change - which in turn could cause further droughts. The obvious problem is that places far away from the sea can only get desalinated water if it is transported large distances, so perhaps this is not a solution for everyone.

Desalination isn't always popular with the locals. Image credit: Takver

Researchers not only hope to continue improving the methods of desalination that are already available but also look for new techniques. There is currently hope in several different areas; nano-osmosis is a process that achieves desalination using carbon particles^[9], and watercones are small portable devices that use the Sun's energy to purify salty or brackish water^[10]. Watercones are being increasingly used in developing countries, although the amount of water they produce (like many processes) is not enough.

Moringa oleifera - also known as a "miracle tree"
Image credit: Forest & Kim Starr

Super sand (graphite coated sand) and "miracle tree" seeds are two examples of a way in which nature can be exploited to provide sanitary water. A new study^[11] combines the positively charged microbe killing protein from the seeds and negatively charged sand to cheaply produce clean, storable water. In order to be used outside of the labs current research aims to scale up the process.

Otherwise distillation units or machines that take water vapour from the air can be used to produce drinking water. Unfortunately these machines are expensive and often cannot be run or maintained.

The problem with all the current techniques is that they are expensive, require a lot of energy or only produce a very small amount of clean water. As drinking water is required for the world's poorest countries it is imperative that the solution be economical. The race is still on to find a way to provide a solution. In order to solve the needs of those without water the best solution will probably involve combining many different technologies, as certain processes may be better suited to specific environments.

Water shortage isn't just a problem for developing countries
Image credit: Koshyk

But water is not only sparse in developing countries; even some of the wealthiest nations are predicted to experience water shortages. With increasing problems it will become necessary to consider that about ninety five percent of the water entering our homes goes down the drain. A large percentage of water goes into growing our food and producing all the products we use. Methods that recycle household water ready for use on fields or in industries would reduce the amount of wasted water. It would also be beneficial to improve the efficiency of crop irrigation.

Nano technology could provide us with effective new filtration systems that enable our waste water to be recycled. While developing methods such as drip irrigation could massively reduce water lost during watering crops. A possible way of replenishing ground source water is being used in India; it involves taking rainwater that would otherwise run off and using it to refill the aquifers.

Science can only go so far towards helping the water predicament. After techniques are developed it is up to governments and worldwide authoritative bodies to ensure that these systems are implemented locally and overseas to areas without potable water. People and authorities often don't act without at least a little push. This is where the role of policy comes in. Water policies, laws, incentives and treaties are required to ensure that we protect our water sources at home^[12]. But also to guarantee that abroad water is safe-guarded and shared.

Further improvements of current methods could definitely help the situation. For many, however, the quest for one truly successful method and source of water is not over.

This article was written by Things We Don’t Know's summer physics science writing intern Johanna Blee, from the University of Southampton.

References
why don't all references have links?

[1] World Health Organization and UNICEF (2013). Progress on sanitation and drinking-water.
[2] MacDonald, A, Bonsor, H Dochartaigh, B and Taylor,R. (2012). Quantitative maps of groundwater resources in Africa. doi:10.1088/1748-9326/7/2/024009
[3] Hoekstra, A. (2012). Global Monthly Water Scarcity: Blue Water Footprints versus Blue Water Availability. PLoS One 7.2 (2012): e32688
[4] IPCC (2008). Technical Paper on Climate Change and Water.
[5] Department for Environment, Food & Rural Affairs (2010). New research project to tackle water pollution from agriculture. [6 ] US Geological Survey (2000). Mercury in the Environment. US Geological Survey Fact Sheet 146-00.
[7] Struck, D. (2007). Warming Will Exacerbate Global Water Conflicts. Washington Post.
[8] American Water Works Association. (2002). Water on Earth.
[9] National Academy of Engineering. (2012). Provide access to clean water. NAE grand challenges for Engineering.
[10] Richard, M. (2010). This Device Provides Clean Water for Pennies a Day, TreeHugger
[11] Huda A. Jerri, Kristin J. Adolfsen, Lauren R. McCullough, Darrell Velegol, Stephanie B. Velegol. Antimicrobial Sand via Adsorption of Cationic Moringa oleifera Protein. Langmuir, 2011; doi: 10.1021/la2038262
[12] Commons Science and Technology Committee (2013). Innovative solutions to improve water quality and reduce water bills are needed, UK parliament.