Ever wondered what Global Hydrological Models (GHMs) are … or perhaps you have never even heard of them? A few weeks ago, Alexandra Murray, a Water Resources Engineer working at DHI, co-published a key scientific article in the Journal of Hydrology about DHI’s own GHM. This week, Alex sat down with Gareth James Lloyd from the UNEP-DHI Centre to have a chat about these game-changing tools and their application.
Gareth: Hi Alex! Thanks for agreeing to meet up. Perhaps we could make a soft start by you explaining what a Global Hydrological Model, or GHM, is?
Alex: In simple terms, a Global Hydrological Model is a tool for looking at hydrology from the perspective of the Earth as one interconnected system, rather than disconnected and isolated parts. They are basically used for better understanding, predicting and managing water resources on a global scale.
Gareth: Are GHMs something new?
Alex: Yes, they are a relatively new field. The first one was developed in 1989, but they’ve only got really good in the last 10 years, because of the growing availability and accuracy of global remote sensing datasets. There are currently something like 20 GHMs around, of which about half are for research, and a handful, including DHI’s, are for more practical applications.
Gareth: What is so special about the DHI’s GHM?
Alex: Firstly, DHI’s model is unique in the way it handles areas with limited or no local observations. Because it directly accounts for the detailed physical characteristics of landscapes using satellite data, we can really trust the results from these data-scarce areas. Secondly, we can get results much more quickly than before. We can run the entire world within one hour, which means we’re ready for the next weather forecast one hour later. This is extremely fast compared to other models!
Gareth: That all sounds very promising, but what about the downsides?
Alex: Well, each GHM is designed to serve a slightly different purpose. DHI’s ambition is to have the very best operational model that can be used directly for very practical purposes for measuring and managing water. To be honest, some models, especially research models, better account for water use on a global scale. The reality is that it is local water managers who are interested in models that take account of water use. DHI can make local models that combine data from the GHM with other types of local data more relevant for local water management.
Gareth: So how is the DHI’s GHM being used?
Alex: It is being used in so many ways. That’s what’s kind of cool about it. It’s a super versatile tool. For example, we have used it to help make a rapid assessment, with recommendations on how to reduce the vulnerability of drought-prone areas of Kenya. We are using it to provide operational forecasts and calculate nutrient loading in the Baltic Sea. And we are using it to predict plastic waste in the world’s rivers to help countries develop strategies to combat plastic pollution on a global scale. This global model lets us dive head- first into new applications of all kinds in a way we just couldn’t 10 or even five years ago.
Gareth: How can the GHMs support water diplomacy?
Alex: In transboundary collaborations where data sharing can be sensitive, these models can help provide information that can be used as the starting point for a discussion. Even in places where data sharing is happening, they can provide an overview for everyone involved – perhaps from a more neutral perspective.
Gareth: Where are GHMs in general heading? What’s the future?
Alex: This is a hot topic – at least in the world of GHMs! There are so many opportunities, but right now GHMs in general are heading down a path of finer resolution. So, knowing everything about everywhere, all the time. This is because the input data is just getting better and better and can support finer resolution modelling. At DHI, our GHM could be developed to replace some existing tools or further strengthen their capabilities. It can also be, in its simplest form, a data generator and could power a global platform for hydrology, water level, drought, and water quality for the world. The future of GHMs is very exciting!
The DHI-GHM publication is a collaborative work, produced by Alexandra Murray, Gregers Helge Jørgensen, Peter Nygaard Godiksen, Jannik Anthonj, and Henrik Madsen
UNEP-DHI Centre on Water and Environment
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