Thursday, February 1, 2024

Hydrological modelling 2024

Welcome to the 2024 Hydrological modelling class. To understand better what is below: 
  • A storyboard is a summary, usually in Italian, of the lecture
  • A whiteboard is an explanation of a particular topic made on the whiteboard (using Notability on the iPad)
  • Slides are commented in English (since 2021)
  • Videos are available to comment the slides. They are usually recorded during the lectures with no editing at all (which would be too much time expensive). 2024 Videos are uploaded to a Vimeo Showcase that can be found here. 
  • Additional  information (only for the brave or the curious) and references are in italics
 

2023-02-19 - I  - Syllabus - Introduction 2 Hydrological Modelling 

Here  I introduced the class. Its learning by doing philosophy (altered by the necessity due to COVID-19 times that impose to do first the all the theoretical parts and subsequently all the practical parts hoping that they can be done in presence). 
To begin is also worth to have a little (philosophical) analysis of what a model is. This is what done in the following parte of the lecture
2024-02-22 - Geomorphometry   - Discussion of previous lesson topics. The rational of introducing these concepts  is that catchments are spatially extended and in this course we are interested to deal with catchments hydrology. 

In this first part we deal with the geometrical (differential) characteristics of the topography. Elevations, slopes, curvatures. They will be necessary later to extract the river network and the parts of a catchment.
In this class we define also what the drainage directions are and how they are computed in the case of DEMs (a topography discretized over a regular grid).  From drainage directions are determined the total contributing areas in each point of  a DEM. These two characteristics are eventually used to determine  the channels head and extract the river network. In turn, the extraction of the channel network allows for the extraction of hillslope and a first definition of  the Hydrologic Response Units (HRU). 
    2024-02-26
    Q&A - 

    2024-02-29 -  Interpolations 
    This lecture, assuming that now you have at least the concepts of what a catchment is and theoretically you know how to extract it and subdivide it in parts, deals with the data to feed catchments hydrology models. Because catchments have a spatial distribution, then also the driving data must be distributed. We need therefore methods of interpolation. 

    2024-03-04 -  Interpolations part II. 
    In this class we try to understand how to estimate the errors over the estimates. Besides we introduce a method (the Normal Score) to avoid to obtain negative values when positive interpolated values are required.
    Q&A - 
    Spatial Interpolation (Vimeo2023)

     Hydrological Models. This is a class about hydrological models, so what are they ?

    The title is self-explanatory. A theoretical approach to modelling is necessary because we have to frame properly our action when we jump from the laws of physics to the laws of  hydrology. Making hydrology we do not have to forget physics but for getting usable models we have to do appropriate simplifications and distorsions. The type of model we will use in the course are those in the tradition are called lumped models. Here we also introduce a graphical tool to represent these models.
    2024-03-06-Hydrological Models 

    For old material give a look to Hydrological Modelling 2023
    2024-03-11
    2024-03-18
     Linear Models for HRUs

    Once we have grasped the main general (and generic) ideas, we try to draw the simplest systems. They turn out to be analytically solvable, and we derive their solutions carefully. From the group of linear systems springs out the Nash model, whose derivation is performed.  Obviously, it remains the problem to understand how much the models can describe "reality". However, this an issue we leave for future investigations.
    • Summarizing the previous class results at the blackboard(Vimeo2022)
    2024-03-21
     A little more on the IUH and looking at the variety of HDSys models

    We introduced previously without very much digging into it the concept of Instantaneous Unit Hydrograph. Here we explain more deeply its properties, Then we observe that there are issues related to the partition of fluxes and we discuss some simple models for obtaining them. Not rocket science here. The concept that we need those tools is more important than the tools themselves. We also observe that linearity is not satisfactory and we give a reference to many non linear models. Finally we discuss an implementation of some of the discussed concepts in the System GEOframe. 
    2024-03-25
    2024-03-28
    Intermediate exam (2024-04-22)

     Travel Time, Residence Time and Response Time
    Here below we started a little series of lectures about a statistical way of seeing water movements in catchments. This view has a long history but recently had a closure with the work of Rinaldo, Botter and coworkers. Here it is presented an alternative vie to their concepts. Some passages could be of some difficulty but the gain in understanding the processes of fluxes formation at catchment scale is, in my view, of great value and deserves some effort.  The way of thinking is the following: a) the overall catchments fluxes are the sum of the movements of many small water volumes (molecules); b) the water of molecules can be seen through 3 distributions: the travel time distribution, the residence time distribution and the response time distributions; c) the relationships between these distributions are revealed; d) the relation of these distributions with the the treatment of the catchments made through ordinary differential equations is obtained through the definition of age ranked distributions; e) The theory this developed is a generalizations of the unit hydrograph theory. 
    2024-04-04
    Some References (advanced)
    Additional material

    Digressions I - A Glimpse on distributed process-based models

    Digressions II - Radiation -  After all radiation moves it all.
    Digressions III 
    Equations for disease spreading (Out of schedule)
    Digressions IV

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