Surface geological processes and associated deposits
BRGM'S SCIENTIFIC ADVANCES IN 2020
SURFACE GEOLOGICAL PROCESSES AND ASSOCIATED DEPOSITS
One of the stakes of the Géo SIS programme concerns surface formations.
- Hello, Hélène Tissoux.
- Hello. You are a researcher in the Georesources Department and will present your work on geological surface processes. First, can you explain what a surface formation is?
- Of course. There are two types. There are weathered formations on top of rocks in contact with the atmosphere and water. Then there are sediments. Sediments transported by rivers and streams, glaciers, the wind or the sea, and sediments such as river sand or silt in Beauce. They can be pebbles on beaches or scree on mountains. You can see these sediments on screen. They were formed by different agents: ice, gravity, wind, water... There is a weathered profile bottom right. These surface formations can be found almost everywhere. Their presence, nature and distribution are linked to external processes, external factors, such as climate, glacial and interglacial cycles and tectonics, but not seismic tectonics. I'm talking about orogens that form reliefs. Orogens? Orogeny is the primary mechanism by which mountains are formed. Subsidence causes sinking and the formation of basins, the filling of basins, such as the Sologne Basin. These sedimentary formations are usually less than 3 million years old. That is very recent as Earth is over 4 billion years old. But they are important because we live above them. We exploit them. For water, for example. And we build infrastructures on top of them. High-speed rail tracks, bridges or motorways. So the work of a surface geologist is to study these surface formations and the processes by which they form. Why is it important to study them? I'll answer in questions. Why did the Loire river which flowed here 400,000 years ago migrate several kilometres to the north? For what reasons? What were the constraints, what are they now and what will they be? If we understand how these surface formations came to be, how they evolved due to different processes and constraints, we'll be better able to predict the behaviour of these formations in the future, as regards global change in particular. What will happen if rainfall increases, more extreme events occur, forests disappear, or the sea level changes? To better understand the processes. Absolutely. To better understand them, in order to better represent them. The idea is to produce maps, maps for ourselves at BRGM, but also for students, academics, local authorities and mineral mining companies. Maps have always existed. Why make new ones? Today, we have almost complete coverage of the territory in geological mapping. The well-known 1:50 000 geological maps. There are around 1,100 for mainland France. There are also the harmonized departmental maps, the BD Charm maps. These maps feature the geological knowledge of the 1:50 000 maps but harmonize and represent it for each department. We made two observations. First, we realized that for present uses and needs, the 1 : 50 000 scale does not always suffice. It's not always suitable. The other observation is...
- we've known this for a long time
- there are significant gaps concerning surface formations on these maps. Significant gaps and major discrepancies, especially on the oldest maps. 50 or 60 years ago, concerns were different. We searched for resources deep in the bedrock. It was considered of little interest to map the surface formations that were often very thin, heterogeneous, complex and which masked what we wanted to see. So there is a real lack of knowledge which we want to address. A great deal of work. What are the recent developments? Recent developments... The idea with our current projects is to use our knowledge of processes to produce predictive mapping, to be able to predict the possible presence of these surface formations in places we have no knowledge of. The advantage of working on the surface is that the formations are on the surface and are therefore visible and they have a shape associated with the landscape. We know that a shape can often be associated with a process. So what we are trying to do is to use this shape in the landscape, this morphology, to try to predict the presence of surface formations.
-Do you have an example?
-Yes. On screen is an example of work carried out in 2020, for the first time, on granite. There is granite in the Massif Central, Brittany, the Vosges. As you can see on the left, granite, when exposed to external conditions, to weathering, will start to crack and deteriorate further as it weathers. This results in balls of granite within a matrix that has changed. This takes a very long time. Millions of years. The balls are broken down over time and become sand...
- As pictured.
- You see the process.
- Exactly. And this sand no longer has the competences... the physical or chemical competences, or the characteristics of granite. But on the geological map, granite is represented. So we use these different degrees of weathering and the resulting forms to try to estimate their presence. Granite can form a very steep slope and appear as cliffs. When it becomes sand, it has no cohesion and will no longer be in the form of a cliff. It will be found on slightly sloping or flat surfaces. So we decided to associate each degree of weathering with a slope found in the landscape. We worked on a digital model of the land. And each degree of weathering corresponds to a type of slope in the landscape. This is the result, when represented on a map. On the pink map, top left, are granites as they are represented on maps at present. Bottom right you can see the result if we use the new process. Everything in orange represents slight slopes associated with arenaceous granite. So everything in orange on the map is very probably covered with sand not granite.
- That changes everything.
- Right. This is a predictive map which must be validated in the field. It's an aid. But nevertheless, its impact on geotechnics, for example, is huge. There is a real evolution between before and after. What will be its actual use? I have presented the preliminary results. This work was carried out as part an exploratory BRGM project, which started last year. The first test was carried out on granite in the Massif Central. We will test it in different contexts, be they geological or regional. We also plan to work on other types of forms and geological processes, to have a wider range. But our aim is to publish new maps. And these maps will be lithological maps. They will indicate the nature of the surface. Is it sand, clay, marl? They can be used as such or transposed. This data could be used to improve maps of the shrink-swell of clays, of seismic risks, in particular for seismic microzoning, to help BRGM and other users to make decisions. So for all that concerns geoscience in the broad sense. For multiple uses. Thank you very much.
Application of electromagnetic techniques to natural hazards
BRGM'S SCIENTIFIC ADVANCES IN 2020
APPLICATION OF ELECTROMAGNETIC TECHNIQUES TO NATURAL HAZARDS
On line with us... Hello, Aude Nachbaur.
- Can you hear us? Perfectly. And with us here is Mathieu Darnet. Hello to you both. Aude Nachbaur, you are a researcher at the Directorate of Territorial Actions. Mathieu Darnet, you're a researcher in the Risk and Prevention Department. As for risk management, you are developing a new electromagnetic geophysical method. Can you explain what it is? Of course. The previous speakers have already said a lot about geophysics. We focus on electromagnetic methods. It's one of many geophysical methods. BRGM has been developing this technique for several years. As regards natural hazards, we are developing specific techniques for natural risks, by method acquisition, processing or imaging of this data. In recent years, we have worked a lot on heliborne methods. On screen, you can see an illustration of this. With heliborne methods, the geophysical transmitters and receivers are towed by air, by helicopter in this case. Another method that has been largely developed recently is magnetotellurics for high-risk applications. This is a different method. It is used on the ground with transmitters that measure the variations of Earth's electromagnetic field. These two methods enable us to map the subsurface. What we learned was how to develop algorithms and interpret the data to better characterize different hazards: volcanic, landslide and seismic. What are the results? The results... It's important to know that these electromagnetic methods enable us to characterize a physical property of the soil: the electrical conductivity of rocks. Why does this interest us? The electrical conductivity of rock shows how easily rocks can conduct electricity. As you know, water, mineralised water in particular, conducts current very well. Measuring this parameter indicates the nature, the quantity and the degree of mineralization of fluids present in the soil. Another parameter that changes the electrical conductivity is the presence of clay or weathered clay-like substances. When measured together, these two parameters enable us to assess the nature of the rocks in the subsoil and determine the presence of fluids. Thanks to these two static parameters, we can evaluate the dynamic properties and see if these fluids change over time. The characterization of the subsoil by electrical conductivity is done using heliborne methods to make a 3D map of the subsoil and electrical conductivity in particular. As regards magnetotellurics, we track the evolution of this electrical conductivity and try to discover variations of hydrothermal and magmatic fluids when assessing volcanic risks. Can you give us an example of the data collected in France regarding these natural risks? I'll let Aude answer. Go ahead, Aude. For example, I could talk about French overseas territories that are highly exposed to a number of natural risks for which the electromagnetic data mentioned by Mathieu is extremely useful. The risks may be close to the surface - landslides soil liquefaction, erosion - but also much deeper down. The acquisition mode is pertinent because the new data provided by these means concern a large area and provide homogeneous information that is adapted to risk management and we can prioritize sensitive areas on an island. So the geophysical data is very important and can be applied to risk zones or on development project areas. With the heliborne method, the whole territory is covered and each municipality has access to the same information. Can we hope for promising results? Yes, a lot of risk projects use this data concerning the nature of the rocks. Take landslides. Data can be used to calculate the risk of a major landslide. Hazard maps took them into consideration, but it was difficult because they concern areas 10, 20 or 30 m below the surface, so hard for geotechnicians to study without employing expensive and extensive measures. Yet this is a huge problem for land-use planning. We are lucky that plastic horizons, ones that are deformed irreversibly, which cause major landslides, correspond to the most altered parts of our volcanic rocks. And as they have a very high clay content, they will be easier to distinguish with conductivity data. The MVT Mar project, for example, in Martinique, uses this conductivity data and geological data. Geologists have done a survey on surface formations, regolith, in order to be able to identify the areas where major landslides are possible and pinpoint the threat on a territory-wide basis. This project is in addition to the one currently underway on Reunion Island, RenovRisk, which uses the same heliborne electromagnetic data to explain the mechanisms that trigger major landslides in the Cirque de Salazie. In this zone, there are a lot of constraints of geotechnical and historical calibration when interpreting the geophysics. There are promising results as regards the volcanic risks that Mathieu mentioned, the deep imagery of these techniques. BRGM implemented this expertise in magnetotellurics in Mayotte... in the context of the current crisis. It enables us to visualise the presence of magnetic reservoirs beneath the island and to identify at what depth the reservoir is situated. That is very important. This reservoir is situated at a depth of less than 20 km. And in terms of operationality... There is, in fact, a monitoring network to monitor magma movements and reveal any magma surges when the volcano erupts. A lot of data has been collected thanks to heliborne electromagnetism and this serves many projects. That's right. Other than those mentioned, it's used for other natural hazards. We mentioned seismic risks. When we want to characterize seismic risks, site effects are often mentioned. These are particular geologic conditions that amplify seismic waves. It is therefore important to identify them in order to adapt land use. At present, electromagnetic data is used to clarify seismic hazards in Mayotte. We use this data to have a 3D view of the basins and site effects. And we can spatialise geophysical point data which is indispensable for characterizing this seismic amplification. We can spatialise and interpret it thanks to this 3D imaging. Great prospects for development. Thank you for these explanations and for being with us.
- A pleasure.
- Thank you.
Aquanes and Eviban, controlled groundwater recharge
BRGM'S SCIENTIFIC ADVANCES IN 2020
CONTROLLED GROUNDWATER RECHARGE: AQUANES AND EVIBAN EUROPEAN PROJECTS
I'll hand over to Géraldine Picot and Marine Pettenati.
- Hello, Elodie.
- Hello to both of you. Thank you for being here. Marie Pettenati, you are the public research scientific correspondent in the Department of Water, Environment, Processes and Analysis and a project manager. Géraldine Picot, you are a hydrogeologist. Today, water is crucial. Will we lack water in the future? As Dominique said, water is crucial. We need it. Nature does too. Ecosystems. It has different uses and we must share it. We use it for agriculture, industry, energy, leisure and as a supply of drinking water. Where does this water come from? In mainland France, mainly from underground sources. And it comes from aquifers: bodies of porous rock saturated with groundwater. We draw this water in order to use it. This can result in imbalances in groundwater if the water removed is not replaced. If more water is removed than replaced, the groundwater becomes imbalanced. The quality of the water can also change, because this water may be polluted or not fit for usage. That's another problem. And this is exacerbated by climate change that modifies rainfall which is the main supply source of groundwater. We know how changeable the climate is!
- It's complicated.
- As well as this, our usage will change. Our needs will change due to rising temperatures and droughts, etc. All that will lead to imbalance. Will we lack water in the future? Yes, we will. It's already the case. To compensate this lack of water, to respond to needs all over the world, not just in arid countries, solutions exist, hydrogeological solutions. This range of solutions is what we call integrated water resources management. Among these solutions, there is one that Géraldine and I work on, and all the BRGM geoscience teams: managed aquifer recharge. Explain to us what that means. We don't want to lack water. One solution is managed aquifer recharge. Imagine that the aquifer has a huge storage capacity and the water flows rather slowly in comparison to other surfaces. The flow rate of rivers is higher. So the idea is to conceptualise water storage. When there's too much, it is kept for later use. This concept of recharging is known as managed recharge or artificial recharge sometimes. In any case, it is a strategy designed to better manage water stress and water quality. Because when we artificially recharge aquifers, we use a wide range of technical solutions such as basins or recharge wells. There are many solutions. We use available sources of water, of all kinds: groundwater. desalinated water, river water, treated wastewater. The aquifers will purify water that is not of good quality. Even wastewater becomes drinkable? It's treated wastewater. It depends on the treatment carried out before recharge. But aquifers supplement this treatment. So it can be used for that. But also to increase the water levels, which will enable us to continue to draw the water we need. Or maintain wet zones on the surface. Because surface water and groundwater are connected. This can also prevent saline intrusion as we saw earlier. When fresh water or good quality water is lacking, we can stop this salinization. These managed recharge techniques depend on the land, the stakes and the aims. So a context more or less favourable to this strategy. You have carried out European projects for several years on this subject. We have participated in major European funding programmes. They are very competitive calls for projects and we've worked on them for about 15 years. The FP6, FP7, HVA20 programmes. What is now Horizon Europe. It is a real challenge for us to participate. And there are also funding tools such as JPI and the PRIMA projects, more focused on the Mediterranean belt, which enables us to collaborate with teams from those countries. But we also have backing from domestic support funds for development projects, which enable us to participate in all these projects and develop techniques that make us competitive when bidding for projects. The major projects that financed research on managed aquifer recharge are also a means for us to keep up with European expertise on these themes, which are complex and involve many professions, multidisciplinary research. Themes with high societal stakes. As Géraldine said, water is crucial.
- We all need it.
- It can run out. Today we're going to focus on an experimental site in Normandy, in Agon-Coutainville, where a dune aquifer is recharged with treated wastewater. We've monitored this site since 2016 thanks to two major projects: HVA20 Aquanes and the JPI Water Eviban project, which is currently underway. Géraldine is going to tell us more about this site. The site in Agon-Coutainville is... I don't know if you can see the video we prepared. It is a coastal area where municipal water...
-That's the plant. This water treatment plant treats the water with classical methods, like all treatment plants in France. But instead of pumping it into rivers, they decided to release the treated wastewater into the dune aquifer through this reed bed. The vegetation that you can see here. Does it recuperate the water? It's not recuperated but injected from the surface through the reeds. This water then continues to flow into the aquifer. On this site, the decision was made to set up this recharge system quite a while ago. It was in 2006. And on this site, the stakes were environmental. The coastal waters had to be protected as they received the residual pollution from the treatment plants. So the decision was taken to use this wastewater to artificially recharge the aquifer. Thanks to the Aquanes and Eviban projects, we were able to set up a monitoring system of the groundwater that receives the treated wastewater, in order to monitor the evolution of the water quality, the water levels, and the impact on saline intrusion. All this data enables us to learn more about the processes. Quentin Guillaume Hautot's thesis will help us to clarify this. We've understood how to recharge an aquifer. And we know what it is now. We've had three years of drought in France. What is the outlook now in research terms? What more can be done in terms of water management? Thanks to this research, we collaborated on the book "Managing Aquifer Recharge: A Showcase for Resilience and Sustainability". It is a compilation of over thirty recharge projects, which are described in order to set up sustainability indicators. There are three pillars: economic, societal and environmental. We helped set up these indicators and shared our expertise on the Agon site as well as BRGM know-how with the working groups of the International Association of Hydrogeologists. As Géraldine said, BRGM now has visibility in Europe and internationally. We are experts on the subject and have tools that we developed to meet national challenges. Now, because of our territorial actions, we are contacted by manufacturers, water managers and farmer groups. We also have very specific requests about the lack of water and managed aquifer recharge. In fact, last year, we organized specific training, Géraldine, me, and Jean-Christophe Maréchal, from the DEPA/NRE team in Montpellier, to teach agents how to go about setting up such projects, in order to share our expertise in terms of prefeasibility modelling of sites, and models for managing these sites, and our mapping tools. You are often called upon to share everything you have put in place, not just in France but internationally. We congratulate the teams and hope that we won't have water shortages in the years to come.
- We'll take care of that.
- You're working on it.
- Thank you.
- Thank you. Thank you.
Predictive mapping of tsunami-related coastal flooding in Mayotte
BRGM'S SCIENTIFIC ADVANCES IN 2020
PREDICTIVE MAPPING OF TSUNAMI-RELATED COASTAL FLOODING IN MAYOTTE
Welcome, Anne Lemoine. You are a seismologist, a researcher for the Risk Management Department, and one of the specialists working on Mayotte's seismic risks. What is going on in Mayotte? Thank you. Since May 2008, Mayotte has been affected by an exceptional phenomenon on a geological level, starting with earthquakes that were very strong for the area, which isn't used to such strong seismicity. Diverse phenomena were observed, leading to the discovery of a new volcano, the largest active volcano found since 1783. So it's quite a big structure. And it so happens that BRGM was the only institution to have seismic stations on the island and to have a regional office. The time it took for the community to get organized to establish the REVOSIMA, a dedicated monitoring network, BRGM was charged with monitoring these phenomena. A great source of pride. I can imagine, in light of your discoveries, the issue of risk was raised. What can you tell us about that? Yes, the risk factor was an immediate issue. Especially because, as Gilles said, BRGM is sensitive to these issues, to seismic risks, tsunamis, etc. And from the start of this phenomenon, we wondered about its potential impacts. I'll be talking about tsunamis but as a seismologist, I was on the team that monitored the seismic sequences from the start and I'm also on BRGM's tsunami team. On the tsunami team, a colleague, Rodrigo Pedreros, had previously worked on cyclone-induced flood forecasting. So he knew the field and had the necessary data to understand the specificities of properly simulating flooding due to a cyclone. As early as March 2019, preliminary tsunami models were developed. And after the discovery of the new volcano in May 2019, the Ministry of the Environment tasked BRGM with an exploratory research project for the assessment of tsunami impacts through models of three tsunami source types: earthquakes, submarine landslides, and the potential collapse of magma reservoirs. What results did you find through this research? In this exploratory research project, we proposed 60 different scenarios and for each scenario, we built a different tsunami model. This video on the screen depicts the tsunami's propagation near Mayotte. So this is one of the scenarios? Yes, it's a model. A digital model. We imagined a tsunami source, a landslide, to the east of Mayotte. A rather large landslide. We maximized each hypothesis in order to remain conservative. Each colour represents a wave's amplitude. The small arrows represent the water's speed. And what we see on this video is that... the reef is outlined by... the tsunami's propagation, for when it hits the reef at the edge of the lagoon, some of its energy is dissipated. In this kind of video, we can see how a tsunami behaves. We made a model for each of the 60 scenarios and for the scenarios with the biggest impact, we made high-resolution versions so as to estimate, as realistically as possible, the possible flooding it would entail. Mayotte, as a land mass, is a particularly... difficult for creating tsunami models. Elaborating models of tsunamis as we should ideally be doing presents a certain number of technical challenges. On the one hand, this is an active phenomenon with tsunamigenic sources that potentially...
- It's always changing?
- Yes. And some sources are close to the island, so we must not overlook a hypothesis. And technically, in terms of hydrodynamics, we are impeded by the use of certain... rules. Because the sources are very close, we must use certain tools in our models that are highly detailed and specialized. For example, the fact that tsunamigenic sources are rather small compared to the water's thickness above these sources, forces us to use highly-detailed models and to carry out rather complex numerical modelling. In conjunction with this exploratory project, other research projects were conducted, namely in collaboration with our colleagues at the Institut de Physique du Globe de Paris, based on Pablo Poulain's doctoral thesis, which was codirected by Gilles, Rodrigo and colleagues at the Institut de Physique du Globe de Paris. This added another layer of complexity. This layer can be seen on this video. The picture on the top left represents the source, in red. This area of the slope has been destabilized and it is sliding down the slope. On the video, we can see, below the water, the progress of the destabilized sediments as they slide down the slope and at the same time... The fact that the sediments are sliding down the slope will destabilize the water column, generating a tsunami, and the tsunami will spread across the basin. What we see here is that in this hypothesis, which integrates the dynamics, or the landslide flow history, before the landslide has even finished sliding down the slope before the first waves appear. So the phenomenon's dynamics are quite complex and require adapted digital tools or we risk miscalculating the impact... Of course, and having false predictions. This leads to my next question: are these tools fully developed? The tools... To carry out this simulation, there was an initial development. In other words, model codes were coupled. A model that focused on how the landslide rushed down the slope was coupled with a code that focused on how the tsunami spread across this basin, with a reef upon which waves unfurl and the unique specificities of the coastline. To take things further, we need to have a more integrative effect, with codes that are satisfactory for a generation of complex sources and that account for the land's specificities using hydrodynamic codes. As well as this... All the work we've done so far has also allowed us... It's like a case study. It has allowed us to focus our efforts and to understand how we could develop our tools. And BRGM's team members who are working on this type of model also collaborated with INRIA, namely for the development of a code called UHAINA. This code allows us, thanks to one of its interesting characteristics called an "unstructured grid"... This code has many other qualities, but the reason it interests us is because we can use detailed data for areas with particular challenges to make highly-detailed simulations, or to have a higher resolution for a specific source. Because it is very difficult to simulate a source with complex data. So we can hone our models based on the sites we're focusing on. Furthermore, another characteristic of the island of Mayotte that is subjected to such phenomena is that it is unknown from a geological standpoint. But in recent years and months, we've seen a great number of acquisition campaigns, on land and at sea, for a better comprehension of the terrain, the materials, and the active structures. The next step will be to continue developing tools by adapting them to these factors, for better, high-resolution simulations of the effects of a tsunami, of flooding in particular, and to integrate, to the best of our knowledge, geological objects and active structures in order to have realistic sources and models. Another step will be to push these models further, to integrate these models... To integrate damage factors to our models. Damage to infrastructures and buildings. To protect the population, of course. But we're seeing wonderful progress. Looking at these models, we can imagine how they'll look after these factors have been developed for even more precision. The interesting thing about this issue is... The subject we're discussing is very integrative in the sense that it is multidisciplinary. In Mayotte, as Gilles said earlier, this issue has mobilized many specialists and institutes and a whole team of researchers from very different fields.
- It is cross-disciplinary.
- Exactly. Thank you. Thank you both.
Characterisation and prediction of contaminant transfer in relation to erosion in a post-mining context
BRGM'S SCIENTIFIC ADVANCES IN 2020
CHARACTERISATION AND PREDICTION OF CONTAMINANT TRANSFER
We're here with Thomas Grangeon from the Risk Management Department and Mathieu Debure from the Water, Environment, Processes and Analyses Department. You're conducting a project called Transport. It's innovative because it unites two scientific communities that aren't necessarily made to work together. Could you tell us more about it? One of the real advantages of this project is that it unites two communities: Mathieu's community studies and has an excellent understanding of contaminant transfer in the environment and the environment's chemistry. And my community works on soil erosion. We focus on trying to understand how particles are eroded and then transferred into the environment. The issues related to this field are quite varied but our special focus is on food security. When there is soil erosion from the impact of rain that suspends these particles and washes them away... When it rains, the water turns brown. This is what we study and it has a serious impact. Our research has shown us just how significant this phenomenon can be. We have observed erosion rates, that is, local soil loss, of various magnitudes superior to the natural production rate. We're losing soil faster than it is produced. As soil is used for farming, it clearly has a huge impact. Another impact of soil erosion, which concerns in this project, is associated contaminant transfer. We tend to admit, without necessarily understanding, that these particles contain chemical substances. We don't know how, if they're attached or integrated. This is the core work of an entire community, namely Mathieu's. which studies it in depth. So this project aims to help us communicate and have a more global understanding of contaminant transfer in the environment. As Thomas said, what principally interests us is geochemistry. In geochemistry, you have "geo" for rock-related things and "chemistry"... Try to think back to junior school, to Mendeleev's periodic table with all the elements. That's what we study, and mostly in water. We talk a lot about water and it's great to have it, but it has to be water you can drink, bathe in, etc. Potable water. Among the various chemical elements, there are elements we'd like to get rid of. We don't want to find them in the environment. Examples include lead, arsenic and zinc. You find all these things in anthropogenic, or human, activities. These could be mining activities or industrial activities. We study this mainly, as Thomas said, in dissolved form and don't pay much heed to solids. We mainly observe solids for the interactions these chemical elements can have with solids. But we don't study the transport of solids in the environment. By transport, I mean carrying matter from point A to point B, as you might take a train from Paris to Marseille. We study the migration of these elements in water but without the complexity of particle transport. The only particles we do study are microscopic particles, less than 1 micron, generally called colloids. These are the only ones we look at. As for the rest, we know they exist, but we tend to look past them. That's why this project is advantageous, for having two distinct communities collaborate. We know that particle transfer impacts the transfer of pollutants in the environment and dissolved forms, too. But we don't know how they interact. You are studying very specific sites: mining sites. That's right. Our work focuses on mining sites for two reasons. As Dominique said, one of BRGM's missions is to manage these mining sites. When you think of mining sites, you think of... Well, personally, I thought of northern France and its spoil tips. But spoil tips exist all over. They're here and we must live with them. The DPSM's mission is to manage these sites. In this project, we're here to clarify the dynamics of these sites and ultimately create tools to help manage these sites. The second reason we're interested in spoil tips is because in terms of erosion, we don't understand them well. The process that generates erosion isn't clear to us. One reason for this is that spoil tips are very dynamic in terms of erosion. When you see a spoil tip like this... To give you an idea, this spoil tip is 100 metres long and about 20 meters high. It is crisscrossed with gullies. So there is intense particle transfer. This is a problem for us because it invalidates our tracking methods. One obstacle we overcame was quantifying this erosion, understanding how it works. And to do this, we used a 3-D laser scanner. We took digital pictures of the tips at various points in time, to see how they changed and deduce the existence of transport. Only two of us are here today, but it was a collaborative effort involving many people. There are two communities, and we can imagine the numbers. We couldn't invite everyone. But it involves many researchers. You were saying that this erosion has a considerable environmental impact. Yes, and to that effect, we have an illustration in which we can see a lovely mining spoil tip in the background. It's rather pretty and full of vegetation that grew over the spoil tip. As Thomas said, they're found in southern France. There are various activities. In Abbaretz, until recently, you could mountain bike and hike on the tip without considering the many pollution problems. In the foreground, you can see a stream that has an orangey colour. This colour is mainly due to iron hydroxide. You'll see the same thing in your garden if you leave an iron bar out in the weather. It eventually rusts. This is similar. The problem is, there isn't just iron hydroxide. There are also pollutants, including those mentioned earlier: lead, arsenic and so on. These can be transported inside old mines. But as sites are not sealed off, they do not stop at the edge. They can be carried into the environment and end up in rivers. Another important point, as we see in the middle, is that it looks as if the spoil tip is covered in gashes. They are actually gullies. This is mainly due to rainfall events that were rather intense or to a lack of stability in the spoil tip. This brings even more elements into the environment. By this, I mean elements in particle form and in dissolved form. We're trying... As for the source, we know the mine is the source and we know more or less the different modes of transfer, but not all of the processes. And that is what we're trying to describe in this project. I thought you wanted to speak. So this project hasn't yet been completed. What are the future prospects? Is there a way to stop this flux? How can we preserve our streams? The project is still ongoing. Globally, it centres around... First, we had to clear the land to take measurements. The goal of this phase was to understand the first process and to be able to quantify things. This was our achievement in the first year. And now, in this next phase of the project, we'll be developing the conceptualization of the processes we measured to integrate them into a digital model that takes into account the transfer of particles and the associated contaminants, which Mathieu and his colleagues can describe better. So we'll be... trying to integrate this data into a digital tool which will eventually help us develop strategies for managing sites. OK. Thank you. Thank you, gentlemen.
New models for assessing the impact of the energy transition on the environment
BRGM'S SCIENTIFIC DEVELOPMENTS
ASSESSING THE IMPACT OF ENERGY TRANSITION ON MATERIAL AND ECOLOGICAL FOOTPRINTS
To talk about the MINTECO project, we'd like to welcome Gaëtan Lefebvre, an economist in the Georesources Department and Daniel Monfort-Climent, a researcher in the Water, Environment, Processes, and Analyses Department. In 2020, you conducted a project. Can you tell us about this SURFER project? Hello, everyone. First of all, I didn't do it alone. There were several of us. Hello to all of them. There were several of us at BRGM, within the DEPA, but also within the DGR. So the project was conducted by two departments. The project was coordinated by BRGM and co-financed by ADEME and a partnership with the CNRS, ISTerre, a geosciences laboratory in Grenoble. The initial question raised by this project on energy transition was: what is the growing demand for materials, metals, as Patrick pointed out, in this energy transition? Are we moving away from a somewhat historical dependency on an energy mix of fossil fuels, oil, coal, gas, towards a growing dependency on metals? As well as questions like "Is there a transfer of impacts?", as Patrick said. Many of these metals and materials will be extracted elsewhere. That was the project's initial question a long time ago. We're now completing the final report, but the project started in 2017. And it isn't over yet. The question remains...
- Completely topical.
- Exactly. And how was this project born? One of our initial questions...
- well, my colleagues', because I joined the team later on
- was the matter of data. Everyone was using this data for prospects in various materials. We realized that everyone was using the same data but without doing a critical analysis of this data, in terms of the facilities' material content. We knew how much steel was necessary for a wind turbine, how many rare-earth metals for a generator, and everyone was using the same data without wondering about origin, disparity, heterogeneity and so on. So we were a bit... You starting asking. We started raising these questions. We collected as much data as possible from scientific and technical literature, in reports and documents, and we gathered them in a database based on the database of a previous project, ProSUM. A European project. And in the end, this work... It was a lot of work to gather and read all those papers. We put all the steel together, the copper, rare earths, cobalt for electric batteries... Because the subject is energy transition. So of course this included the generation of electricity, but we were also interested in batteries, mainly for electric vehicles, as well as equipment you wouldn't necessarily think of: anything that generates heat, heating networks, geothermal energy, heat pumps, and even pellet stoves, to give you an idea. It ranges from nuclear power plants to pellet stoves. Once we had gathered all this data, the goal was to find common unity regarding what is called intensity of matter, which is the amount of matter, let's say steel, brass, copper or aluminium, needed for a unit of energy performance or a unit of energy. In general, we use megawatts, the output capacity of a power plant, allowing us to compare them. Do we have a visual? Yes. To give us a better idea. Can you tell us about it? We made this graph for the SURFER project. It details the amount of steel, in tons per megawatt, of the various power plants that produce electricity. We see a high level of dispersion for certain technologies, which can be explained in many ways. Because you're comparing very different things. We can still see that there is gas, coal, nuclear energy... They're very centralized power plants. There is a lot of steel in these plants. But compared to the power of these plants, the material intensity is rather low. And we see that hydro... Hydro is a special case. But with wind power, in particular, the material intensity for steel in megawatt-hours is considerable. One of the conclusions we can draw from this graph is that an equivalent nuclear reactor, at about 1,000 megawatts, would need... A wind turbine is between 2 and 3 megawatts. That's a huge difference. And in terms of the amount of steel, to replace a nuclear reactor that rotates with a load factor of about 80%, while wind turbines are at 30%... When we started to do these kinds of calculations, we realized there was an issue regarding materials. Not only for steel, but also for concrete and copper, materials and metals that are present in all infrastructures. We tend to focus on rare earths, etc., that concern only a few technologies. But copper, aluminium and steel are used a lot more. Meaning we're promoting certain forms of energy, like using wind turbines rather than controversial nuclear power, but there are other stakes at hand, meaning there are no single, neutral solutions. Absolutely. That is the question behind this project. It's all about nuance and contextualization. You can't make something out of nothing. That was the project's answer. And the issue of matter goes hand in hand with circular economy. For the question we are asking ourselves is: What role does circular economy have? Can we recycle to reduce the use of primary resources? Thank you, Daniel. Gaëtan, you led another project that is part of the mineral resources and low-carbon transitions programme. Tell us about this project called CGDD. Yes, CGDD, because it is conducted by the French Advisory Committee for Sustainable Development. BRGM was solicited along with other partners, including the CEA. The project is slated to last 2 years. Sorry, 3 years. Between 2019 and 2021. It is ending in 2021. There were four different working groups over this period. The first two, between 2019 and 2020... The first worked on photovoltaics and the second on power grids and energy storage. The issues in this project are similar to the SURFER project's. It aims to characterize the material needs for low-carbon energy-transition technologies. You have wind power, solar power, and energy storage. That is the first goal, but it aims for more politically-related results. We wanted to have a vision of the environmental and societal impacts of choosing certain technologies. That's how the project was presented to us. We quickly realized that answering these questions is much harder than it looks and, as we saw with Daniel, it isn't just about choosing one technology or another, it involves many different aspects. Material aspects, but also environmental and societal.
- Are there societal obstacles?
- Of course. We can see it with photovoltaics, for which... BRGM mainly contributed its expertise on supply chains. In photovoltaics, for example, we compare silicon technology with cadmium tellurium technology. The materials are different. And so... the energy used, for example, for silicon panels is greater than the energy used for cadmium tellurium panels. Yet cadmium is reputed to be a more toxic metal than silicon. So which is the correct choice? An analysis of the supply chain allows you to see that, for example, silicon technologies are mainly dominated by Chinese companies. Cadmium tellurium is rather controlled by a single company that is American. So this reveals all the hidden issues at stake. All right. Thank you very much. So BRGM, in all this... Beyond just the research it conducts, how can it become involved and put its research to use to help unravel these societal issues? It does seem as though BRGM focuses more on the production of information and knowledge. In terms of this project, they could try to influence recommendations in public reports that are available to everyone. And BRGM's role is to shed light on these issues and to make them available to the state as well. And in this sense, they can try... In the aftermath of a project like this, they can guide investments, to have targeted investments in start-ups to improve the sovereignty of these supply chains... that we know rather well, and perhaps try to improve regulatory incentives on that subject. These are the two main objectives we hope to accomplish. Which illustrates one of the themes you talked about in terms of economic strategy. I just brought it up because it helps us to visualize what a concrete project like this can hope to accomplish. Thank you, gentlemen. Thank you.
Estimating the geothermal potential of shallow aquifers, an innovative method implemented in the Orleans metropolitan area
BRGM'S SCIENTIFIC ADVANCES IN 2020
ESTIMATING THE GEOTHERMAL POTENTIAL OF SHALLOW AQUIFERS
I give the floor to Charles Maragna, a researcher on an innovative project, which he will present to us. But first, perhaps he can explain shallow geothermal energy. Shallow geothermal energy consists in exploiting thermal energy stored below the surface at a depth of 0 to 200 metres. So it is a shallower system than those Sylvie mentioned to heat, air condition, or cool off buildings, or to provide sanitary hot water. While this heat pump consumes some electricity, ultimately, this system is relatively efficient. 60 to 80% of the energy that comes into the building is extracted for "free" from the ground. This technology is mature, silent, does not emit fine particles, invisible on the surface, and it even provides almost free cooling in summer. On the left, we can see how the heat pump works. We can extract thermal energy from the subsurface in different ways. On the top left, we see a vertical probe. It is a borehole with pipes in which a combination of water and antifreeze warms or cools on contact with the ground. You can have several hundred for large buildings. This is called a probe field. For individual homes, if you have enough space, you can use horizontal exchangers that take up 1 or 2 metres of land. And another system is the doublet with two wells. As with deep geothermal energy, you have a well to pump groundwater. It can be hot or cold depending on what we want. And this water is reinjected via a second well farther off. That's how it differs from what Sylvie Gentier presented. The depth and techniques are different. In terms of innovation, you have begun researching geothermal potential in the city of Orléans. We partnered with Orléans for this project to develop a map of geothermal energy potential by combining data, data regarding surface energy needs, buildings' energy needs, taking into account geological and hydrogeological properties as well as the various regulatory and implementation constraints. We worked at the IRIS scale. IRIS is an acronym of ‘aggregated units for statistical information’. There are 117 in the city. And these IRIS units had the largest... Are these locations? Yes, quite variable in size, ranging from Saint-Cyr-en-Val to small areas in the centre. It's generally based on the number of inhabitants, so it can be more or less extensive. Interestingly, energy data was available to us for these units. And for each unit, we estimated the amount of heat vertical geothermal probes and geothermal doublets could provide. I see. So it's a large study with 117 points. And what are the results? On these 117 points, we determined consumption rates... We used the energy consumption rates estimated by the Artélis research bureau. They used the IRIS scale. We see that Saint-Cyr-en-Val, for example, is a single IRIS unit. So we had energy data for the entire unit. The first challenge we had to overcome was the redistribution of energy needs to different areas... To built-up areas. We combined urban planning data and energy data. On the map, is dark blue good or bad? Those are the areas where energy consumption is the lowest. So, basically, on the outskirts of the city. And in central Orléans...
- High consumption.
- Yes, it is much higher. In the end, we divided the 117 zones into 536 zones where we consider consumption to be homogeneous. And are there constraints in terms of regulations? Regulations are relatively unrestrictive. It does not stop the development of projects in most of the city. The Mining Code is a declarative system, sometimes with the opinions of experts for most of the city. You only need to submit applications or request an investigation for larger projects, typically, big buildings connected to geothermal heat sources. There is one additional constraint, which is taking into consideration the protection zones covering drinking-water catchment areas, in which case, you cannot use this simplified system. You must apply for authorization, which can be quite long. And there are a few constraints regarding groundwater drinking water sources. Is it a large portion of the area? A good part of the city... Here you can see the protection zones in orange, on the map. These are areas in which the simplified system does not apply. You must have authorization. It represents only a small percentage of the total area. You mentioned the Mining Code, as it's underground. Are local development plans also integrated in these regulations? We simply looked at the regulations for the subsurface. However, local development plans encourage building owners and developers of new areas to develop this or that form of renewable energy. So this can also be a way to develop geothermal energy. And thanks to this research, I'm sure you've had results, good or bad. What progress was made in 2020 for this geothermal energy project? I'll talk about that, but first I'd like to address one last point: we also collected data pertaining to aquifers and to the thermal and hydrodynamic properties of the subsurface. We collected pump test data. There were only about 20 points throughout the city, but even with the least-productive wells, the main aquifer formations are able to supply a sufficient flow for even the largest operations. Following this, we conducted... Using the same methods, we conducted a study... We modelled an aquifer doublet. Here we can see the two formations, Pithiviers Limestone and Etampes Limestone, at a depth of 12 metres, which can supply large amounts of water to feed the geothermal heat pumps. And on the next slide, on the top left, you can see our doublet model with its various characteristics: subsurface flow, various needs, etc. We made a model of the wells that pump groundwater to heat or cool a building. There is a lot of groundwater flow, as we can see on the left. And it tends to send the temperature plume in the direction of the water's flow. We used groundwater flow modelling software. We were able to deduce the size of capsules, the size of plumes of zones impacted by a doublet. We then used a map processing tool to estimate how many doublets the city needed to meet its energy needs. As for the results, we reached the conclusion that the first aquifer layer could cover 25 to 30% of the city's energy needs. And the Etampes Limestone could cover 30 to 40% of energy needs. I won't go into the details, but we also did a study on vertical geothermal probes, by developing methods that allow for available land. In this case, we could cover 55% of the city's energy needs with 100-metre-deep probes, and even more with 200-metre probes. Who will be using the results you have obtained? We gave the data to the city and they're integrating it into their energy development plans to compare it with other renewable energy sources. So the city may turn to shallow geothermal energy in the near future? Yes. This energy source is put forward in their PCAET plans, the Climate, Air and Energy Territorial Plans. Thank you very much.
Artificial intelligence and groundwater level prediction, BRGM challenges the French-speaking community
BRGM'S SCIENTIFIC ADVANCES IN 2020
ARTIFICIAL INTELLIGENCE AND GROUNDWATER LEVEL PREDICTION: BRGM CHALLENGES THE FRENCH-SPEAKING COMMUNITY
We'll be talking about artificial intelligence. We're here with Vincent Labbé and Abel Henriot. V. Labbé, you are a researcher in the Digital Infrastructure and Services Department and Abel Henriot, you are a hydrogeologist. We're going to talk about data, AI, and other words that hurt my head, as well as groundwater prediction. To begin, Vincent Labbé, what is artificial intelligence? Hello, Élodie. Artificial intelligence, for BRGM, are digital methods that aim to give a machine intelligent behaviour. In other words, it automates tasks that were too complex for a machine, and that were carried out by humans, or even too complex to be carried out by humans. AI has several meanings: it's an expression with another meaning, a discipline in computer science with a very active community. Some say it's a major technological revolution, others a buzzword of the moment that is very useful to get funding, and you can also describe it as an intelligent program like this one. But in any case, for 10 years now, due to repeated success in deep learning, AI has become the cornerstone of data science. What is deep learning and the relationship between AI and data science? Data science refers to two things. It's data analysis without considering the trades behind the data. It sounds like statistics, which is one of the components of what we call data science. But there is another complementary component that is more factual, experimental and operational. And that is where AI fits in with all of this. For example, today, deep neural networks, we can't mathematically explain why they work so well but we do know for a fact that they work better in some cases than conventional techniques that are theoretically controlled. The second aspect of data science is data-driven programming and organization. As Matthew said, data volume is exploding in every organization today. Organizations understood they could find value in these data by analysing them, sometimes in real time, to make decisions. This decision-making, is called data-driven management. We used to have, and still have, dashboards in decision-making information systems to help decision-makers make decisions. But today, within the operational information system, decisions are taken automatically, more and more. So you save time and can go faster.
- What about deep learning? Deep learning is a branch of machine learning, which is central to AI. This branch has had the most success these past 10 years. That's why everyone is talking about AI. It makes it possible to extract information from images and texts. This is called unstructured data. Today, it is a key technology and companies and even states have understood this. and are heavily investing in deep learning and AI in general. So mastering AI is a crucial issue today? Yes, it's crucial, because AI is undoubtedly what will make the difference in competitive terms. AI promises to bring productivity by automating more and more things. That's... the first promise. That, and increasing quality or do things we didn't know how to do before. For BRGM, AI can bring both opportunities and threats. In terms of opportunities, it gives value to data which until today were not fully valued, like the ones I mentioned: images like stratigraphic columns, and texts, like BRGM's reports. It's also about scaling up in terms of predictivity, being able to automate the creation of predictive models and to scale or mesh an entire territory. This is what AI promises to bring to BRGM. As for the threats... Well, it's a new form of competition. And this means there are new players on these fields that are rather historical in BRGM's case. Today, we'll sometimes see IT players enter a field...
- IT, yes. Information and technology. The digital domain. Actors like Atos, for example, enter fields that apply to the environment through AI methods. So it is a new emerging competition. So is AI a necessary step for BRGM? Yes, it must do so quickly and BRGM has started to take this step. I'd like to list a few points. Today, there are over 40 current or upcoming projects that present an AI component at BRGM, distributed in all operational offices. A bottom-up organization was recently created, an open online team space called Artificial Intelligence, Data Science and Big Data. I invite all interested parties to connect to the site. There are open "Data Science Gossip Meetings" every two months. To my knowledge, there are at least 10 data scientists, you might call them, in each of our "DOs", two training courses in the second half of 2021 and computer resources, especially with the new data centre, which will reinforce our IT calculations to serve AI. It's clear to see that BRGM is also surfing on technology and mastering artificial intelligence. Abel Henriot, how can artificial intelligence be used for predicting groundwater levels? Good question. First of all, why we would want to use AI to predict groundwater levels? This need has existed for a long time. It stems from the fact that we can foresee the use of water resources and for different uses. We saw that it could be important. Exactly. And today, BRGM already knows how to do it, but does not master the techniques that relate to AI. Yet we are competing against or being challenged by our partners or competitors in these areas. In the large sense, it simply creates a link between input variables and output variables. And the algorithms of artificial intelligence, including the neural networks branch, can create this input-output connection, with the promise of doing it quickly and "well" over larger territories and with less interventions by the user. This offers large perspectives for the BRGM. What we have put in place as part of the AI exploratory project to try to reach this target of being able to simulate piezometric levels with artificial intelligence, is based on a testbed that aims to compare and document different approaches to predicting groundwater levels, classic and AI-related approaches, so as to evaluate them following different prisms, such as the capacity of automatically recovering data, all or part of the data, the ability to exploit all or part of the data, and the ability to predict what the end user expects, which is to reproduce the evolution of piezometric levels. We took advantage of the exposure of this testbed to work with our partners, in particular for the publication of a challenge with university partners, like the University of Tours. This challenge is called Niña and it'll end with a forum in early January, 2022, to which you are invited, of course. With pleasure. Well, thank you very much. Thank you for this presentation on digital evolutions at BRGM. Thank you very much.
Advances presented in the framework of the scientific programme “Knowledge of geological systems”.