This blog is written by Mike Simpson, a Senior Water Scientist at HR Wallingford*. Mike works in water resources and water planning.
Water, water, everywhere…?
Water doesn’t look too exciting. It’s clear, there’s a lot of it, it doesn’t taste of anything. When it’s raining outside it doesn’t seem like you would ever run out. And people sometimes have too much of it, when it flows through their house or garden as a flood. But it does a lot more than come out of your tap – it grows your food, it is used in making electricity, it keeps you clean.
Probably the only time you would think about water is when it’s not there. Unless you live in an arid area that might seem pretty unlikely, but every year some cities get caught out and have to restrict water use. In 2017/2018, Cape Town in South Africa almost completely ran out of water after years of falling dam levels, and had to enforce dramatic reductions in water use.
In times of drought, the obvious answer is to bring in water from somewhere else, but this is not straightforward. One problem is that you use a lot of water. On average every person in a household uses 140 litres of water a day (a modern shower uses 10 litres per minute). The other thing is that water is very heavy. So the challenge is finding that much water somewhere nearby, finding someone who is prepared to give you that water, then finding a way of transporting it to your house, every day. In reality, during a drought, people have to use a lot less water. People who can’t shower stop going to work. Farming, power and industries may have to shut down. As you might expect, the people most affected are those who can’t afford to buy private water supplies. This inequality is most stark in developing countries, but also impacts on water use in the USA and the UK.
Climate change will only make water shortages worse. So how do we keep water supplies secure? The good news is that there are well established systems for researching and planning for water, much of which depends on geoscientists and roles closely aligned with geoscience.
The most basic element we need to understand when planning for water is the difference between how much we have (supply) and how much we need (demand).
How much we have
Supply encompasses anywhere we can get water from. Mostly rivers and lakes (surface sources), but also from groundwater sources. Geoscientists assess multiple sources to understand how much water we can sustainably take from groundwater, even under drought, and how this might change during climate change. Groundwater will often be more reliable that surface sources, and cleaner, but it is hidden. It is therefore difficult to work out how much we have, and critically whether the quality of the water changes due to natural toxic substances such as arsenic or uranium, or pollution. Perhaps the most widespread contaminant is seawater, which can be sucked into coastal groundwater sources if these are over-used, so determining what can be taken sustainably is critical. Understanding the local geology and the location of aquifers (layers of porous or fragmented rock that can contain water) and aquicludes (denser, finer material that prevents water moving) lets us develop computer models of where groundwater might be.
Aside from river, lake and groundwater sources, locally important water supplies can include desalination of seawater (often too expensive and polluting to be a major source), melting glaciers (although there is a risk that these may melt entirely) and rainwater, although the available volumes produced can be small.
How much we need
Demand for water is challenging to measure and has typically relied on very rough estimates of how much water people use, based on broad assumptions on standard households. Now, with improved communications and sensors, water meter data can be used to give a clearer idea of how much water is used and how the water is used. We can also use ‘big data’1 and statistics to test assumptions of how water is used.
With an understanding of the supply and demand for water, it’s possible to work out if we have a surplus (more than enough) or deficit (not enough) of water available. Equally importantly, by considering factors like climate change and population, we can figure out if it looks like we will move into deficit in the coming decades. This process has to include seasonal effects on river flows and demands. Perhaps we also want some spare capacity in our water system in case one supply fails, or we know that there is a new development such as a large industry moving into the area. We might also want more water to support resilience in the water supply against drought.
Wimbleball Dam, England, built in the 1970s. The creation of new concrete infrastructure is now much rarer when planning water resources (Photo credit: Lewis Clarke via Wikimedia) .
What to do about it
So, we know if there is a problem, or if there will be a problem in the future. The traditional response was to work out the shortfall, find a valley, build an enormous dam, and move on to the next problem. This didn’t take our understanding of the environment into account, or of the needs and concerns of the people who live in the valley. Decisions on water are now much more ‘bottom-up’ – suggestions from all members of the community have to be considered, and the public can also comment on any scheme proposed by water planners. The effect of this is that new concrete infrastructure is much rarer, and there is far more careful use of water as a resource. Systems for desalination of seawater become more common, and the use of treated wastewater for public water supply is considered.
There is a real pressure to lower the use of water, both through household and industry or agricultural water saving. It’s also very possible to reduce water lost to any leaks in the distribution system, although as these networks can be huge and are usually buried, renewing a network can take many years.
The Future
Understanding the best way to plan water provision in the future depends on a team of social researchers, engineers and geoscientists. There are lots of opportunities for research as well as in the operational and planning sector, which will need many more staff in coming years. If you are interested in using geoscience to protect the environment and safeguard against the risks of water shortage, it’s a great field to get involved in!
1 ‘Big Data’: extremely large datasets that can be analysed by computers to reveal patterns relating to human behaviour and interactions.
* Please note that this short introduction to water planning is based on my experience in a range of contexts and different projects and is my own perspective, not that of HR Wallingford.
Feature image from mrjn Photography at Unsplash