Hydrological models and model evaluation
21 important questions on Hydrological models and model evaluation
What is the difference between plotting Q on a log scale vs a normal scale in a hydrograph? How can you use this to differentiatie between quickflow and baseflow?
Log is non-linear transformation.
Drawing linear line/inflection point, from this point, all Q is assumed to originate from (slow) linear GW reservoir.
Plot baseflow separation line.
Everything that behaves more non-linear than that (above this line), should be fast non-linear runoff processes.
All flow above this line is quickflow (=fast nonlinear runoff processes).
Baseflow: maybe GW, should behave like linear reservoir, so should decay exponentially in time, so plotting on log scale it should be straight.
Why are hydro models generally poor when predicting extremes? Why is this a problem?
Bc those are conditions that cause damage and are scientifically interesting.
Models have different levels. Assumptions/preconceptions/theories/physical laws can already be considered models. They are a form of ... Model? And what could they grow into?
- Higher grades + faster learning
- Never study anything twice
- 100% sure, 100% understanding
For my 1st exam I got a C. Then, I started looking for ways to learn better and I came across Study Smart. Since then I have scored a A+, A, A- and another A. I highly recommend it to everyone who wants to hear it. I am so happy with it!!
I was struggling to finish all my first-year subjects for 3 years. Then I discovered Study Smart, which helped me to finish all of them within 3 months.
Because of StudySmart, things are going well in many ways. Before, I always had study stress and no time for anything. Now I feel calm and confident (because of the program). I used to score a B, now I usually score an A or A+.
Hey Chris, I really want to thank you very much for developing the platform, I usually got around C for my exams, now I scored an A+, an A and a A- !!
Since using Study Smart, my average has increased significantly. I even completed a statistics course with a A+ while I'm bad at statistics. I took on extra courses this year, because of Study Smart. Thanks so much!
Ever since I started studying with StudySmart I passed all my exams !!! No more re-sits!! At first, I was happy with a pass and now I only get good grades. Many thanks!
I aced all the courses I studied with Study Smart. For law, I first scored a D, and now an A! I’m 100% sure that I’ll pass all the courses I study with Study Smart.
I always thought I studied well. My grades were fine. I could never have imagined that applying these study skills would have such a huge and direct impact on my grades, my speed and the pleasure I have in learning.
For the first time, I finally feel totally confident about the way I learn. I have the perfect overview and make great progress in terms of speed and the grades I get. Thanks, Chris!
I immediately started to enjoy learning again, and my grades soared. All of a sudden, everything went better. I highly recommend Study Smart to all students..
Being able to create my materials online made the process of studying so much smoother and quicker. I no longer have to spend a huge amount of my time on creating my summaries.
At first, my notes were a mess. Now I use Study Smart to take my notes in a perfectly structured way. It helps me to save a lot of time and do other things I enjoy.
Students that study with Study Smart get better grades. The system applies all the learning methods in such a way that both well-performing students and students who struggle perform much better.
Hi Chris, I would like to thank you very much. Last year I scored C on a course, and this year I got an A+ thanks to your method! Thank you very much!
The largest effect is that my child is more enthusiastic about school! Every parent wants their children to be happy at school, Study Smart made it happen.
In high school, I failed several exams, and that has really changed now. I actually needed this tool very much back then. Since I started studying with StudySmart, I haven't had any D's. My average score is now an A and those are results I would have never had in the past
With my old method, I passed only 3 out of 8 courses. Since I started taking my notes digitally in Study Smart, I have passed all my courses on the first try. For me, StudySmart takes away the stress of wondering if I will pass or not.
Thanks to StudySmart, I passed all my exams, and with better grades than before! On top of that, I have mastered a very good study method now, which I am confident will help me earn my degree.
What is the main difference between conceptual and physically-based model and what do they have in common?
Physically-based model have differential equations, which does not make them necessarily better.
They both solve the same mass balance, and are in that sense both equally physical.
We'll mainly use conceptual models - lumped version.
Name the 5 steps of model development
2. Numerical implementation: details very important for model outcome
3. Code verification: does your model reflect concepts you had in mind? During step 2 your model concept might change.
4. Model parameter calibration or optimization: optimize your parameters (based on training dataset)
5. Model output validation: what's the value of your model outcome (rest of splitted dataset used for validation)
With which factors can an optimum in model complexity be achieved?
- Predictive performance
- Data availability
- Model complexity
>Optimum: more complexity reduces predictive performance
Explain the difference between accurate and precise (and inaccurate and imprecise)? Use dartboards in your explanation. Which statistical concepts do they represent?
Variance = precision
What is Occam's razor (law of parsimony)?
Entities should not be multiplied without necessity.
When presented with competing hypotheses that make the same predictions, one should always select the solution with the fewest assumptions. Note: the razor is not meant to be a way of choosing between hypotheses that make different predictions(!).
Name 3 implications of Ockhams' razor?
- Determine how many assumptions and conditions are necessary for each explanation to be correct.
- If an explanation requires extra assumptions or conditions, demand evidence proportional to the strength of each claim.
- Extraordinary claims require extraordinary evidence.
Name the 3 inputs and two outputs of a model simulation
- model parameters/variables
- initial conditions (for all model state variables, typically have a differential equation behind them)
- Model/atmospheric forcing (e.g. P, T, RH)
Output:
- Model variables (e.g. Q, ET)
- State variables (e.g. S - left side differential eq)
What would leaf area index be in model input?
In many models, it would be an input, e.g. Parameter that varies per month and influences ET. Vegetation could also be a state variable (as the thing you want to predict), co-evolving with water storage.
How to quantify how well a model fits the data?
What is the difference between Nash-Sutcliffe and Coefficient of determination/R^2?
Nash-Sutfcliffe goes from - infinity to +1 in same equation
If you use R^2 you do that on a linear fit (so you've already optimized the fit, the fit can never be worse than optimal/average?)
Min 70!!
Explain the drawbacks of NSE, based on slide 23 and 25 (paper by Schaefli and X)
25: Seasonality - maybe not using the mean as benchmark anymore due to seasonality. Nash values would take only average over the whole year.
What do Schaefli and Gupta suggest to improve the precipiration-based benchmark efficiency? Explain this in 4 steps
4 steps as zero hypothesis
What is KGE and how does it differ from NSE?
How can NSE be deconstructed?
Smt with unequal weighing
Name and summarize the 3 issues with NSE and their current solutions.
2. Seasonality - solution suggested by Gupta and Schaefli(?)
3. Unequal weighing of bias/variability and correlation - KGE proposes equal weighing.
What's a constrain of modelling all non-linear flow as runoff processes in a hydrograph, as is often done in models?
What happens when you do a log transform on a hydrograph (Q-axis)? Give a mathematical example of a non-linear process.
A non-linear process would be exponential decay.
How do accuracy (bias) and precision (var) behave in relation to model complexity and why? How can this be practically used?
Try our study magic for free
a PDF, study it super fast
- No sign up, email or credit card needed!
- AI makes unlimited flashcards
- Get unlimited quizzes and tests
- Ask AI anything
- No sign up, email or credit card needed!
- Have and keep perfect overview
- Make flashcards, notes and mind maps
- Review, test and score!
The question on the page originate from the summary of the following study material:
- A unique study and practice tool
- Never study anything twice again
- Get the grades you hope for
- 100% sure, 100% understanding
