4DHydro website

 4DHydro is a project that came out from a call for tender by  ESA to which we had the pleasure to participate. All the making of the project is, since last week documented on the 4DHydro website that you can find following this link.

Not yet available, soon you'll see here a video explaining what the website is supposed to contain. 

Modelling and Hydrological Modelling

These lecture are actually part of the 2024 course in Hydrological Modelling. However because they can be of some more general interest, I am grouping them also here. They try to review the concepts of modelling in general and when applied to hydrology. In the series of lectures there is also a concise overview of catchment processes. The first lecture image, see below, it a Maurizo Cattelan artwork entitled "A donkey among doctors" which is my attitude when I approach the topic. 

• Models in Science (Vimeo2024)
• Catchment processes (Vimeo2024)
• Further References
• Gao, Hongkai, F. Fenicia, and H. Savenije. 2023. “HESS Opinions: Are Soils Overrated in Hydrology?” Hydrology and Earth System Sciences, July. https://doi.org/10.5194/hess-27-2607-2023.
• Ying Zhao, Mehdi Rahmati, Harry Vereecken, Dani Or. “Comment on ‘Are Soils Overrated in Hydrology?’ by Gao et Al. (2023).” Egusphere -. Accessed March 8, 2024. https://egusphere.copernicus.org/preprints/2024/egusphere-2024-629/.
• Hydrological Models (Vimeo2024)
• Seven steps in hydrological modelling: I - clarifying the purposes, II-geomorphology, IV-pre-analysis of input data (Vimeo2024)
• Integral Distributed Model or Hydrological Dynamical Systems, HDSys  (Vimeo2024)
• Zoom2020, Vimeo2021,Vimeo2022, Vimeo2023
• The representation of Hydrological Dynamical System (Vimeo2024)
• Zoom2020,Vimeo2021,Vimeo2022,  Vimeo2023
• Seven steps in hydrological modelling: IV- setup, V - model calibration/execution/validation (Vimeo2024)
• Seven steps in hydrological modelling: VI- delivery the results, VII- final deployment to stakeholders (Vimeo2024)
• DARTHs (Digital Twins of Earth System)
• A new way to do models
• A final view on Hydrological Dynamical Systems and their application to catchments.
  • Hypothesis testing in Hydrological Modelling with HDSys (At the whiteboard)
• Further readings:
•  a blogpost from EGU
• Opinions

The final idea about the practice to do model is expressed in the paper and in the various posts that regard DARTHs which can be find here.  Among people that more reflected on Hydrological Modelling there is certainly Keith Beven [GS]. To get a glimpse of his contributions, please see this other post which contains some of his relevant papers. 

Stock and flow diagrams, a different way to represent dynamical systems

Stock and flow diagrams (see also here) are  a way to represent dynamical system which is the same area covered by EPN ((Extended Petri Nets). They were brought to my attention by the talk John Baez gave at  Edinburgh Mathematical Society last December. Fortunately the talk is available on Youtube.

Although I find that the visuals of EPN are more expressive and the accompanying infrastructure is easier for engineers to comprehend, I have come to realize that listening to the talk is incredibly instructive when it comes to realize that EPN falls in the objects of category theory. An intriguing aspect explored in the talk is the representation of open systems within stock-flow graphs. In EPN, it is assumed that a flow box not originating from a place indicates that the system is open. Additionally, when one EPN features an outgoing flow labeled A and another EPN has an input flow with the same label, they can be combined to create a composite graph. However, in this presentation, a new rectangular symbol is introduced for the same purpose.

Personally, I find the solution in EPN more intuitive, although it may be considered less abstract. Nevertheless, I have come to realize that a similar graphical approach could prove beneficial in extending EPN to represent not only ODE systems but also PDE systems.

On Hydrological Models and their choice (and a use of the AboutHydrology mailing list)

Initially, I was captivated by the visuals that I could incorporate into my presentations. To my pleasant surprise, I discovered that the AboutHydrology mailing list served as a valuable data source. Remarkably, this platform has been active for approximately a decade (I need to verify the exact date of its inception) and has amassed a wealth of information.

Reproduced from Melsen, 2022

Subsequently, I came across two intriguing papers authored by Melsen, delving into the "sociology of selecting a hydrological model." These papers proved to be quite engaging. Additionally, there are other noteworthy publications exploring similar themes. Notably, among the more recent works, Hamilton et al., 2022, and Horton et al., 2023, deserve special mention.  Please find their citation below. In the paper you can easily recover previous relevant literature. 

References

Hamilton, Serena H., Carmel A. Pollino, Danial S. Stratford, Baihua Fu, and Anthony J. Jakeman. 2022. “Fit-for-Purpose Environmental Modeling: Targeting the Intersection of Usability, Reliability and Feasibility.” Environmental Modelling & Software 148 (February): 105278. https://doi.org/10.1016/j.envsoft.2021.105278.

Horton, Pascal, Bettina Schaefli, and Martina Kauzlaric. 2022. “Why Do We Have so Many Different Hydrological Models? A Review Based on the Case of Switzerland.” WIREs. Water 9 (1). https://doi.org/10.1002/wat2.1574.

Melsen, Lieke A. 2023. “The Modeling Toolkit: How Recruitment Strategies for Modeling Positions Influence Model Progress.” Frontiers in Water 5 (May). https://doi.org/10.3389/frwa.2023.1149590.