 Basically, I'm going to very briefly present the research I made for my master thesis in IHE, which later became a paper in environmental research letters, which is about estimating the extent of groundwater dependence for urban self-supply in continental Africa. Moving into some context, as you might know, since 2014, half of the world population is urban. So, especially in developing countries, this undergoing urbanization is happening mostly or often in informal settlements, which means that public service infrastructure is not growing as fast as CVs are. And so water utilities capacities are overpassed. So as a consequence, people have to source water from wherever they can find it outside the water distribution of the public networks. And this is how we defined self-supply. And of course, this can come either from wells in the backyards or buying water from a neighbor who has a borehole or from vendors. There's many, many strategies out there. And those that can use groundwater, well, that really depends on the local hydrogeological conditions, on the climate, on availability of other resources and how the city was developed. We know that this is quite widespread, this use of groundwater. However, it's not really, it's really underestimated when you look at the monitoring data, especially for SDG6 and for these international platforms. And we find that the biggest reason for that is that national service collect the primary source for domestic water, where in reality, it is often a combination of multiple sources. There's different strategies to get water. And so that, yeah, of course, it's not reflected. And so because of this, the objective of this research was to present a method and estimates of urban population using groundwater obtained by a self-supply for the entire African continent that is without islands. Here is the published paper in case you want to dig further. These are just 10 minutes. So I'm just going to briefly explain a little bit of it. So how did we do this? Basically, we took a lot of literature in the field, people observing how were people obtaining groundwater for self-supply. We talked to experts and so we developed two ways to approach this. The first one was the maximum urban population to use groundwater obtained by a self-supply. That is the maximum total amount of people that could possibly use groundwater only based on the hydrogeological conditions on areas densely enough to be considered cities. So for these, we took groundwater search, groundwater productivity, and depth to groundwater. And then in a second phase, we calculated the likely urban population to use groundwater obtained by a self-supply. For these, we used 10 sample cities. And for these, we considered variables that could limit or condition the use of groundwater for self-supply. Like, for example, proximity to surface water, as it is often referred, if it's closer and more accessible. The area of public water supply, of course, if you are outside of the area of the public water supply, you're more likely to have to search other sources like groundwater. Like distribution, we see how that changes the technology used. As in, if you're very rich, you probably can afford to build a borehole within your property. But if you have really low income, then probably you depend on springs or shallow groundwater to access it. Of course, there are some cities where there are restrictions to use groundwater, so we took that into account. So that's basically the two measures we calculated. All of the input data was spatially distributed, open data that you can all find. This was all prepared in a GIS environment where we then used conditional algorithms to evaluate how these things interacted. So now jumping into the big results we got, so basically the potential self-supply groundwater use, we estimate that only considering hydrogeological conditions, approximately 79% of total urban population could potentially use groundwater to meet their domestic needs. Here's the map of the distribution of that population. Again, it's urban population that we're looking at, and that's assumed near Nigeria and Uganda, Tanzania and Kenya. And then the 10 cities we took into account were Arusha, Kampala, Kano, Addis Ababa, Kinshasa, Lagos, Nairobi, Maputo, Dodoma and Lusaka, because they had these available data, were big cities. And so basically from these results we obtained that about 32% of the urban African population are likely to use groundwater obtained by a self-supply. Earlier studies from 2011 pointed that an estimated of 30% or more of the urban population depends on wells, boreholes or springs as their primary source of drinking water. These also considered South Asia. So in this context, our result resembles this previous estimation. And about this method that we developed, of course it has some limitations. For example, even in cities with very favorable groundwater, very favorable hydrogeological conditions, they not necessarily use the groundwater because there are other sources. So that's difficult to take into account in these kind of methods. Of course, the possibility of using the groundwater taking into account the quality was not taken into account. Local deviations or groundwater or water governance arrangements are not captured by these simplified urban analysis. And also the hydrogeological input data has a resolution of 25 square kilometers, which often means that there's just like three or four of these in a medium-sized city. So of course it does not capture the heterogeneity of hydrogeology. As we know, it's quite heterogeneous. But however, it's a first attempt to get data from open data that's in a large scale that can tell us something about the region, but could also be helpful in telling us what's happening in the city. And so what are the implications of this study? First, it helps us understand the scale and magnitude of potential and likely groundwater use in urban and sub-Saharan Africa. Clearly, household investments are significant and they should be recognized as such. What we mean by this is that, yeah, to access hand-off wells in the backyard or to pay for neighbors selling water from their boreholes or so and so requires some investment that it's not just that we're not realizing of groundwater use, but we're not realizing of what it entails. And also from what we observed in many urban African contexts, self-supply using groundwater for domestic water is here for the foreseeable future. So, yeah, for the immediate future, maybe instead of assuming that self-supply will no longer be needed, we should aim at making it safe and sustainable. So, yeah, basically that's it. Thank you very much. Thank you, Arthur. Thank you very much. Yes, and while we are waiting, maybe a number of questions from the audience or from co-panelists, of course, if there are any, I would have one to start with. Perhaps, and that's not maybe for the audience, a bit nice to understand a bit better. What is the difference between the likely and potential use of groundwater, these different numbers? Yeah, I think 79% is potentially potential self-supply. And so what can you repeat or explain a little bit more on what that number, the figure means, actually, that almost 80% has that potential? Yeah, by potential, basically what we wanted to see is if just by looking at hydrogeological conditions, what was the percentage of people who could live in cities use self-supply, like, okay, I'm just here and how many people could just hand dug a well or install a borehole, just based on the, let's say, hydrogeological availability, so that's the potential. Exactly, and so what you're saying is that that potential, which is very large, what would be the way forward to then optimize that potential? I mean, I know that that depends, of course, on resources, technical support, etc., right? But what do you think would be a large game changer to increase that use or that potential? Yeah, I think that's a very good question. And I guess it has a lot of nuances, but I think that it's important to look at it because as we conclude, self-supply is kind of there to stay in a sense of it allows people to access water when it's not really available in the public networks, just because infrastructure is not possible to grow it as much. So if there was a way to make policies into instead of spending a lot of money and trying to extend the infrastructure more like spending resources on, okay, let's find a way to make self-supply safe and sustainable by, I don't know, either education sources or different approaches, maybe this this potential figure could help to see like, okay, maybe in places that haven't realized they have a lot of water availability, we could do more. So I think that's one way to interpret it. You're actually indirectly responding to Rafael Abines' question on how do you make ground water safe and sustainable given that there's no policy to manage its abstraction? And I think you're trying to say that, right, through awareness-raising education. Anything you want to add to that? Yeah. Yeah, for sure. For sure that's a big thing. For sure that's a big thing. Pollution is a big thing. We tried to consider it in the study, but there was just not enough data to go with it, but for sure the safe part of it is, of course, maybe the most urgent one. And unfortunately, I don't have an easy answer for that, but it's definitely maybe the most important criteria to offer safe water for all. But yeah, I mean, even in these urban ground water environments, there's a lot of study on how to make it more so that the urban environments don't pollute water as much. Yeah. Yeah, that's also Gopah, Kumar was mentioning the same from the audience that for urban population to use ground water for self-supply, we need to ensure that sources are free of pollution. And that's also where awareness-raising and also technical training and support can definitely play a big role. Besides having availability to water, it also has to be, of course, water free of contamination, microbiological and chemical contamination. For sure. Yeah, we are maybe last question and then we need to move on. Is there any projection made that Olawala is asking in the research in terms of the number of people that will be depending on, I think, yeah, as self-supply, of course, in the future. So projections on the number of people that will be depending on self-supply in the future. Do you follow the question? Yeah, I think I do. We didn't look into the future. Actually, the figures I showed, I forgot to mention, they are 2015 based, like they are based on population from 2015. Well, I think that the trends we looked at without having numbers for it, I think it will increase just because of the fact that urbanization is increasing. It is expected, I think that by 2050, that 70% of the population will live in cities. So yeah, I think urbanization is one of the biggest game changers since the last century. So yeah, I would think that that number is going to grow, but we have to see. And I guess, indeed, in having this huge issue of urbanization also calls for self-supply or finding or protecting areas of supply where we know that through hydrological studies that it is sustainable to extract certain amounts, of course, linking to low-cost infrastructure somehow would be a way to deal with this among many challenges that we need to overcome.