As the global population continues to rapidly grow, the demand for fresh water is growing with it. Even without accounting for shifting weather patterns driving regional droughts like those seen recently in California and the Horn of Africa, demand for fresh water for agricultural, industrial and municipal use is predicted to increase by 50% globally between 2000 and 2030.
However, the supply of water is not keeping pace with demand. By 2030, scientists project there will be a 40% gap between the expected need for and availability of water.
This situation is unsustainable. If we are to support a growing, increasingly demanding world, we must tackle the water scarcity crisis –so where can we find the water we need?
Tapping into the planet’s reserves
One way of finding more fresh water is improving how we get our water in the first place.
For most purposes, we need fresh water – salt water is largely toxic to plants and animals, and corrodes machinery, so fresh water is needed for almost every agricultural, industrial and household use.
Unfortunately, only 3% of globally available water is fresh water, and most of this is frozen in glaciers and in the ice caps. In fact, just 0.5% of global water supplies are actually available for practical uses.
However, science is helping us tap into that remaining 97% – primarily through increasing experiments with desalination, removing salt from sea water. There are three main techniques – thermal, electrical, and pressure – to purify water, but until recently doing this at scale proved highly impractical and expensive.
It still is difficult to desalinate at scale, but recent advances have improved the practicality to the extent that it is already a major industry in the middle east. In 2015 Israel got 40% of its fresh water via desalination, and that figure is expected to hit 70% by 2050.
Fresher fields: Water scarcity solutions for agriculture
One of the most important functions of fresh water is to help us grow the food that sustains us. Roughly 69% of total fresh water withdrawals globally is used for agricultural purposes, a figure that rises to more than 90% in most of the world’s least-developed countries. With water consumption by farms expected to increase by about 20% globally by 2050, a more efficient use of water in agriculture is needed.
Part of the problem, though, is the inherent difficulty of irrigation inefficiency – a challenge that has plagued farmers since the dawn of agriculture, some 12,000 years ago.
Typical irrigation works by spraying crops equally with water – or by applying inefficient flood irrigation techniques, where water is run through fields in channels. But a field isn’t just a uniform patch of land – there can be variability in soil quality, nutrient availability, topography, and crop type, often within the space of a few meters – all of which can determine how much water will be needed.
Until recently, farmers would have to judge this by experience and knowledge alone. The vast amounts of data that could have informed more efficient application of water to crops would have been too much to measure, let alone analyze. But with the spread of data and analytics technology, it’s allowing farmers an unprecedented level of insight into their land and their water needs.
But all that data and analytics is no use without cutting-edge irrigation technologies to get the water to where it’s needed. Drip irrigation, for instance, can provide water-use efficiency of more than 95%, “that translates to a water-use reduction of more than 60% over traditional flooding methods,” says Holger Weckwert, Global Segment Manager, Fruits & Vegetables and Insecticides at Bayer. The system works through pipelines running along the ground that can deliver precise quantities of water, nutrients and protective products exactly where they are needed.
Or you can target the crops themselves. Not all plants are created equally thirsty – some have substantially lower demand for water than others. By focusing on less water-intensive crops, farmers can maintain yields whilst improving water usage. And the addition of certain microbes to the soil can actually help encourage root growth, enabling plants to thrive on far less water than they would usually require.
With the application of genetic science, this gets even more sophisticated. Rice comes in two varieties: lowland rice and upland rice. Lowland rice needs to be grown in extremely water-intensive paddy fields. Upland rice, on the other hand, can be grown in much drier soil.
By identifying, isolating and transferring the genes that confer this resilience in upland rice to lowland rice, agriculturists can tailor crops to available conditions, rather than bringing water to the crops. In the language of economics, they can develop a demand-side solution to water management.
Urban water sustainability
Urban areas also use a huge amount of water, and this too is putting considerable strain on the planet’s resources. One of the first steps towards securing reliable fresh water for the future will be renovating existing water infrastructure.
In the US, much of the existing water infrastructure (like pipelines and dams) was laid down nearly a century ago and is approaching the end of its operational life. Renovating it is no small task – the American Water Works Association estimate that this could cost around $1 trillion over the next 25 years.
Another common response to water shortages has been reallocation of water from irrigated agriculture to non-agricultural water uses, principally in urban areas – but this can have a devastating impact on rural communities. A more sustainable solution is for cities and industry to pay farmers to modernize their irrigation infrastructure, enabling farmers to grow the same amount of crops using less water, giving the cities the extra water they need to grow
Over 80% of the world’s wastewater – and over 95% in some least developed countries – is released to the environment without treatment. However, finding a way to reuse treated wastewater means it could become a reliable water supply, independent from seasonal drought and weather variability and able to cover peaks of water demand.
Historically, sewage water has been treated by microbes. Bacteria are introduced to the wastewater, who break down the harmful products in the water so that the water can be safely reintroduced into the water supply. But this produced a sludge by-product that needs to be treated before it can be disposed, and this requires a significant amount of energy – for example 35% of U.S. municipal energy budgets is spent on water treatment.
However, certain microbes emit electrons or heat as they break down waste products, turning the whole process into an energy source. By containing this process in a microbial fuel cell, the act of breaking down sewage itself can power the process – thus becoming a self-sustaining system. Microbial fuel cells could effectively reduce that energy use to zero, giving millions access to cheaper, cleaner water.
A thirst for new ideas
These kinds of innovative approaches will be vital as the world looks for new ways to feed its thirst for water. A solution that may work in one situation may not be appropriate for others, and in many cases we’ll need a combination of approaches to overcome this growing challenge.
But progress is being made, and scientists around the world are actively exploring new concepts and water scarcity solutions to help turn the potential for a global crisis as a catalyst for creating a more efficient, effective, sustainable society.