Spain has experienced a hydrological year with exceptional figures. The country’s water reserves have reached 82.6% of its total capacity, a record after the wettest winter in almost 50 years. Reservoirs are full, and restrictions have been lifted. The drought, which meant that water had to be rationed in a number of territories just two years ago, seems to be something of the past. However, the fact that reservoirs are full does not mean that the challenge has gone away. The abundance of a year of heavy rain can relieve pressure in the short term, but it does not change the background trends that are transforming water management in many parts of the world.
Together with Spain, countries such as Chile, Colombia, the United States or Australia have faced episodes of shortages that have tested their water supply systems. We will explain why an abundance of water does not guarantee water security, and how systems are being put in place to withstand the next drought.
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Globally available freshwater is not increasing, but the pressure on it is. There are more people, more economic activity, increasingly intensive agriculture, and cities that continue to expand. All these factors push demand up, whether it rains or not. In fact, according to the last United Nations World Report on the Development of Water Resources, global demand for water is increasing by approximately 1% each year, driven by demographic growth, economic development, and changes in consumption patterns.
The key question is no longer: how much water falls from the sky? It is what is done with it, and how its use is planned well in advance.
Miguel Aritio, Director of Water Energy Resources at ACCIONA, summarises the situation as follows: “Water management is a future issue that will be essential in the world we live in. Drinking water resources are declining rapidly due to demographic, industrial and economic pressure. There are times when we receive large amounts of rainwater, which we normally manage in a more or less correct way. However, given that everything that has to do with climate is cyclical, we often return to periods of drought when we suffer from shortages of the resource over and over again.
As a result, each hydrological cycle starts from a more demanding point than the previous one. A winter can fill reservoirs up to their full capacity, but that volume has to be spread out among a wider range of uses than five or ten years ago. The room for maneouvre narrows with every turn in the cycle, even if rainfall levels remain stable. The key question is no longer: how much water falls from the sky? It is what is done with it, and how its use is planned well in advance.
Water management has been almost exclusively supported for decades by a model: fresh water catchment from rivers, reservoirs and aquifers, and then its treatment to make it potable. This conventional treatment system consists of purifying the water, removing particles, filtering impurities, disinfecting it and adjusting it until it is safe to consume. It is a well-known and effective process, but starts from a basis that is not always guaranteed.
Preparing for scenarios of greater scarcity involves acting on several fronts. Repairing ageing networks to reduce losses, reusing more clean water, and diversifying supply sources.
Not all rainwater can be stored. Not everything that is stored reaches households or crops. Some is lost along the way due to leaks from old pipes, pipes in poor condition, networks that carry raw water from reservoirs which, over the years, let more water escape than they should. When the entire system depends on that chain, any weak link reduces the safety margin.
Preparing for more scenarios of water scarcity means acting on several fronts, not relying solely on the freshwater captured, by repairing ageing networks to reduce losses, reusing more clean water, and diversifying sources of supply. No single action solves the problem on its own. Applied together, however, the room for manoeuvre improves in an increasingly demanding system.
One of the most widespread responses to improve water security is to increase the number of sources, incorporating new ones that were previously not considered usable. The most obvious is seawater. As Miguel Aritio explains: “The biggest water tank we have in the world is the sea, but we can’t drink it directly. Through reverse osmosis, which is a very mature technology, we can turn it into drinking water.”
Reverse osmosis desalination works by applying pressure to salt water and passing it through a semipermeable membrane that retains salt, separating the fresh water from the salt water. It is the most used desalination technology in the world, representing more than 60% of all the desalination capacity installed wroldwide.
If the decision to build more capacity is made when reservoirs are already at critical levels, it will be too late to tackle the next drought. The planning process needs to look further ahead
The water from desalination has no single destination. It can be potabilized for human consumption, but can also be used in agricultural irrigation or in industrial processes, sectors that often require different levels of water than drinking water. That versatility makes desalination more than just an extra source, it allows the redistribution of the water that goes to each use, freeing up better quality water for household consumption.
However, none of these infrastructures can be built quickly. A desalination plant is not a small facility. “A desalination plant, a kind of unconventional water treatment, is not built in 12 months. [...] A facility of this type can cover between five and fifteen hectares and requires between three and five years’ work,” says Aritio.
If the decision to build is made when reservoirs are already at critical levels, the plant will arrive too late to cover that drought. The planning process needs to look further ahead. What will protect a city from shortages in five years will be decided today, when it is not yet needed.
Australia has taken this logic to a consistent limit. In the industry it is known as ‘drought proofing’, i.e., even maintaining operational and prepared water infrastructures in years when they are not strictly necessary, so that they are available when they are required.
Two plants managed by ACCIONA in Australia show how this idea takes shape, from different perspectives. The Adelaide Desalination Plant has the capacity to produce up to 100 Hm3 per year in critical situations, enough to ensure water supplies for up to two million people. Its role is not to consistently produce water, but to act as a capacity reserve and be ready on the day that the rest of the system cannot deal with the demand.
The Mundaring drinking water treatment plant (DWTP) is not designed to deal with the next drought, but with several decades of dry and wet cycles.
The Mundaring drinking water plant (DWTP), in the southwest of the country, is a kind of complementary strategy. Rather than relying on a single source, it combines water from a reservoir, a nearby dam and Perth’s water supply system, which in turn incorporates desalination plants, to distribute drinking water to more than one hundred thousand people. The plant was the result of a public-private partnership with an operational commitment of at least 35 years. It is not just designed to deal with the next drought, but several decades of dry and wet cycles.
Moving from reacting to a crisis to anticipating it is, above all, a mindset change. Years of abundance do not mean that the problem goes away. It is the best opportunity to solve the problem: with time, without pressure, without the emergencies that distort any decision made under full emergency conditions. The next time the reservoirs are full, the question should not just be about how much water has recovered. It should be what is being built, now, for when that water supply fails again.