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Revisit our report on water: interview with Emma Haziza, hydrologist

On 11 May IFGR organised a dialogue with Emma Haziza, hydrologist, PhD, graduated from the Ecole des Mines de Paris, specialist in territorial resilience strategies against climatic risks and expert in managing risks linked to floods and drought. A lecturer and founder of the research centre Mayane and the start-up Mayane Labs, she answered our questions on climate change and the challenges represented by the necessary adaptations regarding water.


Water is a marker of climate change. Extreme meteorological events are increasing and becoming more and more frequent, with repercussions in terms of human and financial impacts. What are your observations in France? 

There have always been climatic variations in the world, for example, people could cross the Rhine on foot in 1303. The Middle Ages were marked by food riots linked to periods of drought and famine. However, a rupture has occurred in recent years with the acceleration of heatwaves. 

If I take the example of France, we have observed since 2017 an alternation of heatwaves and extreme drought, then floods equally as remarkable, with in particular a historic flood in the Seine basin. In 2018, the 16 days of heatwave in the summer pushed France into a state of hydric stress, with ever lower low water levels. It was a year of historic drought.

Regarding 2019, temperatures reached record levels, up to 46°C in Gard, winegrowers lost their harvests due to a sudden drought that acted like a blowtorch. Twenty departments were faced with water supply problems. The harvest fires that struck Picardy in 2020, another year of historic drought, demonstrated the unpreparedness of the territories and the need to develop adapted tools to manage future crises. Reinforcements had to be sent to the Mediterranean coast to control the wildfires there.

What lessons should we draw from these extreme heatwaves and droughts? 

France is absolutely unprepared: no major decision has been taken in favour of adapted territorial development. As in 2019 when 85% of departments had to severely restrict consumption, this year could follow a similar path. It’s both the drying up of rivers and soils that have to be taken into account.

These extreme climatic events confront us with our reality and our capacity to adapt as a society. 

In cities, cooling and air-conditioning systems generate heat islands and thus warming. We have to question the capacity of our buildings and cities to adapt, and how we manage these heat islands: by expelling hot air outside, we merely heat the ambient atmosphere. Despite 16 consecutive months of absolute record temperatures between 2019 and 2020 and 4 historic years of drought, France still imagines that, all said and done, everything will be better next year.

You speak of the acceleration of the water cycle. What do you mean?

Take 2021 to understand this phenomenon. Summer was wet in France; it rained a lot and the water tables were recharged. France was placed in a kind of blue bubble mainly linked to the descent of a cold front from the North Pole. Depressions generated by successive cold droplets came into contact with masses of warm air from the Mediterranean and Adriatic Seas. Blocked by an anticyclone over Scandinavia, the depression had no choice except to travel northwards to Germany and then Belgium with the dramatic floods seen by all.

Vue aérienne des inondations dans la Vallée de la Roya, octobre 2020 (Valery HACHE / AFP)

These extremes are totally linked: masses of warm air will trigger even more violent processes. It’s the water cycle that is speeding up, in the image of our societies. The precipitant capacity of clouds increases, giving rise to the disastrous floods that swept through the valleys of the Vésubie and the Roya in Alpes Maritimes in 2020. We reached 500 millilitres of water, meaning 500 litres of water per square meter, whereas the models forecast 250.

Inondations à Erftstadt-Blessem, près de Cologne, juillet 2021 (REUTERS/Rhein-Erft-Kreis)

We also see that the position of anticyclones tends to shift towards the poles, that’s to say that the heat is rising massively towards the poles, where one least expects to experience these climatic extremes. Remember the temperatures reached in Lytton and Vancouver (western Canada), with the heat dome that struck in summer 2021: 46.6° instead of an average of 18-19°C.  90% of the town of Lytton disappeared within a period of three hours due to huge wildfires.

It’s important to understand that as the northern hemisphere deems that it has a plentiful supply of water and is protected, it is poorly adapted because it is unaware of the risk that is turning into a reality.

It’s necessary to understand that the great water cycle is accelerating to the detriment of a smaller water cycle that permits wetting soils and filling water tables. Thus, France, a temperate country, receives about 512 billion cubic metres of water a year, of which 65% evaporates immediately into the atmosphere. A portion of about 26% runs off the surface and only 9% succeeds in infiltrating the soil. In the present context, this share of infiltration is decreasing drastically.

So, storing water has become unavoidable? 

Yes, it’s an essential issue that has become conflictual due to disputes over use between industry, energy, agriculture and domestic use. It brings into question the governance of water. At present, we observe the massive development of large PVC water tanks. These are not hill reservoirs as they do not belong to the hydrographic network. The aim is to capture groundwater and bring it to the surface to permit continued irrigation. The water withdrawn via these tanks is subject to very high evaporation accentuated by heatwaves, resulting in heating the local atmospheric column and accelerating drought.

One must also be aware that groundwater is connected to our rivers and streams: it’s a balance in which one drains the other. When the discharge of a river decreases, it will rely on the groundwater. But if the level of the groundwater is too low, it causes the decoupling of the groundwater from the river, pushing the level of the river ever lower. It took me a very long time to understand why we make massive withdrawals from the groundwater whereas we could have made these withdrawals by boring wells during summer to continue irrigation. The reason is simple: it allows bypassing Prefectural rulings. During crises, only persons with access to these basins can continue to irrigate their land.

Using water recovery tanks calls into question the prevailing model of agriculture and monocrops with high water consumption developed after the war. 

As for hill reservoirs, also developed massively, they recover rainwater and break the links in the hydrological network. They make farmers believe that they will always have water and fail to push them to reduce their consumption: this can be a solution that supports local but over exploited agriculture, but it can become a trap by preventing rivers from having a discharge sufficient to sustain the entire surrounding ecosystem.

What can we expect in 2022, given that the first restrictions on water consumption have been taken in France? 

Vancouver dans un brouillard de chaleur en juin 2021 (DON MACKINNON_AFP)

2022 is still a new year that must be monitored carefully because we have suffered from a winter drought in France. That’s something new. Up to now we’ve had droughts that started in May or June. A scientific publication has shown the mode of diffusion of these droughts. They present the same modes of propagation as forest fires, very dry and warm winds on the surface of the soil that gradually spread and dry land located further away. This leads to hydric stress that spreads within several days. The scientific literature now speaks of lightning droughts. Droughts are in the process of occurring everywhere, on every continent. Canada and Brazil, two giants of water, imagined they were protected, but they too have been affected. 

The economic impacts will be considerable, in particular for energy…

Yes, it’s the issues of energy and food that come into play once the water cycle is completed disorganised. Brazil is no longer 90% dependent on hydraulic energy as it was twenty years ago but this dependence remains above 60%. Once water levels have fallen to extremely low levels, there is a risk of energy shortage. As for China, it was struck by a historic drought last year in the southeast, leading to a shortage of reserves of around 80%. This limited its economic activities, so it turned massively to coal. However, extracting coal requires considerable quantities of water, so China came up against a new limit in its extraction capacities and then turned massively to liquified natural gas from Qatar. In Europe, the Netherlands also turned massively to Qatari natural gas, due to the absence of wind in the North Sea which stopped its off-shore wind farms from operating.

If one looks at the question of energy from the viewpoint of water and droughts that will undoubtedly increase in frequency, it is vital to rethink our model of society. Nuclear energy, considered as a carbon-free energy, seems to be good solution. However, the operation of nuclear power plants, which need water to cool their reactors, is fragile: they are affected by the temperature of rivers.  Only a few days ago, a temperature of 30° was reached in the Gironde estuary and production had to be reduced at the Blayais power plant. At a given moment, a choice has to be made between electricity production and the ecosystem: do we prefer the eutrophication of rivers, their suffocation, with the loss of biodiversity that implies, or maintain these energy systems in a period of peak demand linked to air-conditioning systems?

You are a specialist in territorial resilience strategies against climatic risks. What are your recommendations for building a more resilient society? 

The acceleration of forever more acute droughts and more violent and powerful floods, with massive runoffs, requires us to rethink our territories by considering the exploitation of farmland.

Agriculture represents 93% of the territory used at the global level: rethinking its use of water is vital. 

France, Drôme (Camille Moirenc)

In OECD countries, 70% of our land is used to feed cattle. Since the post-war period, we have developed monocrops like maize that massively rely on water. It should be borne in mind that in France, 80% of our available water is reserved during summer for agricultural purposes. I think that we should ask the question: In a period of shortage, can we continue with this model of agricultural yield? By preserving these fields subject to constant sunlight, with a maximum albedo*, we merely accelerate this water cycle and our loss of water.

Water is multitalented: it heats us, cools us, it’s used for eating and preserving biodiversity. We are ourselves composed of water: it is our greatest ally and is part of us at every level. We must understand the water cycle, the phosphorous cycle, that of nitrogen, all these cycles that compose Earth. We ourselves belong to these cycles and we must question ourselves about how we conceive our future, our territories and our societies.

It should be borne in mind that water is part of a natural system that includes us. 

What should we do so that water remains our ally? 

We have to ask the question: What contributes to what? We now know very well that all the water withdrawn massively from the ground will be transferred to another reservoir because the quantity of water always remains the same on Earth.

It will end up in the atmosphere and in the oceans: it contributes to raising the level of the oceans and to the greenhouse effect. 95% of the world’s greenhouse gases are due to water and 4.1% to carbon. We never speak of this because water is unstable in the atmosphere, it ends by falling: we can’t measure it like we measure CO2 in ice cores taken from glaciers.

Should the problem of CO2 be considered as a cause or a symptom? I believe that it’s a question we should ask today. Luckily, we have this greenhouse effect on the planet and this atmospheric belt that protects us. But in reality, our atmosphere is terribly narrow and fragile: all the atmospheric water included on the scale of the planet amounts to only 1/7th  of the Caspian Sea. Mathematically, if you add more water in the layers of the atmosphere, you increase the greenhouse effect.

What are the concrete solutions for managing this volume of water as well as possible? 

The solution lies in the development of the territories, to capture water and carbon. One may feel helpless and incapable when taking into account global deforestation and the massive loss of our wetlands. However, we can propose a new model at the European scale. One should never forget that at the global scale, 63% of our rainwater comes from the continents: it does not come from the seas and oceans. This means that rain is renewed from the land. But our land must be able to conserve this water.

So, it’s necessary to replant and recreate water cycles at a smaller scale. Plenty of solutions exist everywhere: from agroforestry to sponge cities and the restoration of wetlands. It’s time to act by implementing solutions that are specific to each territory, and by assisting farmers and territorial actors to carry out these transitions. 

We should stop speaking of climate change in terms of deadlines like 2030, 2050 or 2100. We are in the midst of climate change; we are living it now and we can act massively to change our territories. It requires that we act differently, consume differently, maybe better and less. We have to leave this world and frenzy that incessantly pushes us towards to a totally senseless system in which we are rushing headlong towards a cliff.

*share of sunlight reflected by a surface and transmitted into the atmosphere

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