Could you describe how your professional and/or personal experience relate to water? Where does your interest in water come from? What influenced your decision to focus your work in the water sector, more precisely, in groundwater?
I always wanted to do something constructive with a positive impact. As a young person, it was difficult for me to choose one career path because I am interested in many things, but at some point I thought that civil engineering was broad enough to cover what I liked from a technical perspective. I would love to say that it was only that, but of course opting for such a traditional career path was a way of “securing my future”. It was during my studies that I found out that I could work with water, something that truly connects everything I could possibly be interested in: we all need it, and nothing can be sustained without it.
At first, I was interested in sanitation, to be able to provide clean water to everybody in need (a big ideal, I know). Unfortunately, I couldn’t find a job directly related to this topic after my graduation. In my first job, I was as a project engineer in the area of road safety, and later, during my second job, I worked on a couple of environmental projects. In one of them I had to design an industrial landfill. Here I spent quite some time learning about the different types of isolation layers needed to prevent leachates to reach the bare soil, and in this case, the underlaying aquifer. That was the first time that I somehow had to deal with groundwater at work, learning that it was so important to protect this resource, of which I knew almost nothing about.
Later that year, I got an email about the GroundwatCh programme, an Erasmus Mundus master’s degree to study groundwater in a global context, and I just went for it. For me it was a big deal and a huge adventure to get a scholarship to study in Europe.
Somehow at that time I haven’t realised that this master would lead me to dedicate 100% of my working hours specifically to groundwater, but here I am, and I love it.
Which gaps do you see in the management of groundwater resources overall?
Groundwater management is based on two pillars: groundwater assessment and groundwater monitoring. Both activities require human and financial resources, and this is where one of the biggest gaps is.
In general, there is a lack of groundwater specialists, either because there are no financial resources to hire them, or because there are very few people with the right training available, i.e., hydrogeologists, or people interested to study groundwater. This poses a problem, because, establishing a groundwater monitoring network or a groundwater sampling campaign, to name just a few examples, requires specifical technical knowledge that only an specialist can provide. Setting up such a network would also require the economic means to, for instance, buy equipment and/or drill, if necessary. But unfortunately, in many cases, there are other priorities that are, or at least appear, more important than installing monitoring stations.
In your master’s thesis, you have investigated the effects of climate change on a coastal aquifer in Cape Verde. Could you explain how changes in climate are expected to affect groundwater resources quality and quantity globally? Besides climate change, which other factors can impact groundwater resources? Is it possible to attribute observed groundwater change to individual factors? If so, how?
One effect of climate change is a change in precipitation patters. This affects renewable sources of groundwater directly, because most of it comes from precipitation. In some places it is raining less and less, which means less water is available to recharge aquifers (i.e. there is less water available to infiltrate the soil and percolate the rock, reaching the aquifers, where groundwater is stored). In some other places, precipitation events are getting very intense. In such events, water is rapidly flushed away as runoff, having not enough time to recharge the aquifer.
Another direct effect of climate change is a rise in air temperature, which can cause more evapotranspiration. This means an increasing amount of water returns to the atmosphere before going all the way down through the soil layers to reach the aquifer.
Other effects are less direct. In the case of a drought, for instance, when surface water become less available, the reliance on groundwater increases, which can lead to an overexploitation of the resource and to aquifer depletion.
Groundwater is greatly affected by other global changes, namely, overpopulation and changes in land use. Overpopulation translates into more people needing water, and hence, overexploitation of the resource. In some other cases, an increase of population occurs faster than sanitation infrastructure is built to cope, which means that groundwater quality gets rapidly deteriorated in and around these areas. Land use change can have significative effects in recharge processes. For instance, an area that once was a native forest and now is a monoculture might experience an increase in recharge on the short term, but in the longer term there is a high risk of soil erosion, especially in sloping ground, which can lead to an eventual loss of recharge. These effects are much worse when the source of groundwater is not renewable, which is the case of fossil aquifers. This type of aquifers were recharged many decades ago, and nowadays do not receive enough rain (sometimes not at all) to compensate for the water that is extracted. In these cases, once the aquifer is depleted, it’s over. There won’t be any more water for our generation or even the next one.
And yes, groundwater changes can be attributed to individual factors: after all, groundwater is a local resource. It is indeed possible to establish what the sources of contamination in a certain area are, or the reason why groundwater is being depleted. An established groundwater monitoring network or campaign is essential to determine these factors.
Could you explain the main applications of space technologies in the groundwater sector? What are current limitations and potential opportunities in using space technologies for sustainable management of groundwater resources?
I would say that the most popular application of space technologies in the groundwater sector is the use of the GRACE (Gravity Recovery and Climate Experiment) and GRACE-FO (Follow On) satellites to estimate terrestrial water storage anomalies, and from it, derive groundwater storage anomalies. There are other space technologies and applications as well, for instance, a recent study presented a novel approach to mapping terrestrial groundwater-dependent ecosystems (GDEs) by using data derived from Landsat-8 data. In other studies, InSAR has been used to investigate groundwater extraction-induced subsidence.
The main limitations are related to the fact that groundwater is a hidden resource that is literally under the ground. Since groundwater cannot be “seen” from space, we cannot benefit from remote sensing applications in the same way as we do for assessing water above the ground, such as those used for surface water studies. A lot of the work in this field depends heavily on other datasets.
Filling data gaps represents an important challenge for water resources management. How do initiatives like the Global Groundwater Monitoring Network (GGMN), and G3P contribute to close this gap for groundwater? Which further actions could be developed to speed up this process?
The GGMN aims at improving the quality and accessibility of groundwater monitoring data and information. One aspect of the programme is the portal (https://ggmn.un-igrac.org/), by which we are trying to create the largest global dataset of groundwater level measurements, based on updated data shared by national authorities. The GGMN programme also focuses on shedding light on groundwater monitoring practices around the world. At the end of 2020, the International Groundwater Resources Assessment Centre (IGRAC) published the first edition of the report 'National groundwater monitoring programmes: A global overview of quantitative groundwater monitoring networks', which is a compilation of all the information available on national groundwater monitoring networks in 80 countries. It represents the only global overview currently available on this topic.
In the case of G3P, the product is a tool that will allow to easily see trends in groundwater storage over the past 20 years. This product, in combination with in-situ groundwater level data, could provide a very accurate picture of where groundwater is being overexploited, which is crucial information if we want to take action to protect this resource.
One action to speed up this process could be to collect more data, but I believe that nowadays there is an immense amount of data that is not accessible for different reasons. For example, private data collected by drinking water companies, or private data collected by countries that do not have an open data policy. In some cases, there is publicly available data, but because it is not managed properly, it is very difficult to be used. In that sense, I think that more effort should be put in sharing and preserving the data that we already have.
The G3P is the first data source worldwide that provides operational Earth observation-based information on changing groundwater resources in a consistent way. Could you explain how the G3P data source was developed and how it works? What is its spatial and temporal resolution? How did you contribute to the development of this product ?
The G3P approach has already been applied in many studies. Groundwater storage anomalies are derived from terrestrial water storage anomaly values which are estimated from data collected by the GRACE and GRACE-FO satellites, as well as from other water storage compartments such as soil moisture or surface water. In most cases, this analysis is done via case studies in various parts of the world.
The added value of G3P is that it is a global product, published monthly from 2002 until present, that not only makes use of data from GRACE and GRACE-FO but also from water storage data that are based on the existing portfolio of Copernicus services. This global gravity-based groundwater product (G3P) is developed with the aim to later implement it at operational level as an Essential Climate Variable (ECV) on Groundwater into the Copernicus Climate Change Service, Lot Land hydrology & cryosphere.
I have been working on the project from the very beginning, the writing of the proposal to be precise. I am leading Work Package 5, which is dedicated to dissemination, exploitation and use cases. I am also contributing to Work Package 4, dedicated to the development of the groundwater product. Specifically for this work package IGRAC has the task of validating/evaluating the product using in-situ groundwater data, coming for instance from the GGMN.
What steps need to be taken to fit a global model on groundwater based on GRACE/GRACE-FO data to a local aquifer ? How can we assess the amount of in-situ data necessary for fitting the model or to validate it, and verify space-based observations? Can a locally trained model then improve the global product again?
One of the main limitation of groundwater data derived from GRACE/GRACE-FO is that the resolution of the data is not high enough to be used in local studies. The amount of in-situ data needed to validate/verify space-based observation will depend on the study area.
Yes, in theory a locally trained model can improve the global product again. But this beyond the scope of the project, as we are first aiming at developing the global product.
Can you think of a way to also use space-based data and technology to contribute to an assessment of an aquifer’s water quality? Would it be worth exploring for example land use land cover, the mineral composition in the surrounding geology, IoT equipped sensors, or other ways?
This is a very interesting question. As you can imagine, it is not possible to observe the quality of groundwater directly using space-based technology, but satellite-derived data can be used as proxy data to, for instance, predict the occurrence of certain contaminants in an area. One example of this is the study conducted by the researcher Chloé Poulin and her colleagues, who combined satellite, census and hydrological data with secondary measurements of groundwater quality in Uganda and Bangladesh, to determine areas of possible microbial contamination. I believe that it is important to pursue this type of study, especially in areas where it is still very difficult to establish a groundwater quality monitoring programme or campaign.
If you had three free wishes to be fulfilled by a space agency, what would they be?
I definitely do not know enough about the whole range of work of space agencies, but maybe for this reason I wish that these institutions could communicate better to the public why it is important that they exist, and how satellite-based products can help us to understand and adapt to the rapid changes that our planet is experiencing. At the same time, I think that it is also important to make clear what the limitations of this type of products are, and that they are not “sold” too much as to make us believe that we do not need in-situ monitoring stations anymore. There must be a balance.
What is your favourite aggregate state of water and why?
Liquid! I love being in water, especially in the ocean.