Hydrological Modelling Flashcards
Which database (only hydrological and meteorological data) is necessary to
(I) Simulate and calibrate a simple conceptual Rainfall-Runoff-Model (MInimum requirement)?
(II) Simulate and calibrate a physically based hydrological model like WaSiM (with process based modelling of evapotranspiration)?
(I) Black Box - precipitation
(II) Precipitation, temperature, wind speed, humidity & global radiation
Generation of a catchment including subcatchments with TANALYS:
(I) What information/which data is necessary to generate a catchment and water network with TANALYS (name and explain three)?
(II) Name and explain at least three reasons for defining a gauge in a hydrological model and therefore to create a subcatchment.
(I) TANALYS (topographic analysis tool) –> for analysing Wasim data required to generate a catchment
- Slope/flow direction: helps to delineate drainage areas, length of flow
- Flow accumulation: ultimate flow path, identifying stream channels
- Outlet/interpolation grid: helps identifying pour points of discharge- confluences of major streams found out
(II) 3 reasons for defining a gauge
- separate data in subcatchment (define land area)
- to calculate the time interval & flow times
- model a land use change and other essential parameters
Draw a schematic structure of a physically based hydrological model with at least six usual model components/submodels. Say for each of them whether it describes a vertical or horizontal process.
Which problems can be investigated with a process based hydrological model like wasim? How can this be done?
- based on time series, predict flood
- land use changes based on spatial data
- climate change phenomenon like extreme precipitation events can be investigated
Which calibration parameter in Wasim influences
- baseflow (amount)
- baseflow (dynamics)
- interflow (amount)
- interflow (distribution/shape)
- surface runoff (distribution/shape)
- baseflow (amount) Q0
- baseflow (dynamics) KB
- interflow (amount) dr
- interflow (distribution/shape) Ki
- surface runoff (distribution/shape) KD
Name at least five possibilities to check the quality of your model run
- Comparison of modelled data & observed values
- Nash Sutcliffe Model Efficiency
- Percent Bias
- Root mean square error
- RMSE observed standard deviation ratio
- Explained variance
Name the hydrological balance equation:
Precipitation = Evaporation + Run-off + Change of storage
Given diagram:
- How is this diagram called?
- What is the name/labeling of
- Draw into the diagram:
- Field capacity (FC) : 1.7
- Permanent wilting point (PWP) : 4.2
- Soil moisture retention / soil parameterization / pF diagram
2.
x-axis: % volume of water
y-axis: water tension
Soil type a: Sand
Soil type b: Silt
Soil type c: Clay
Name and compare two methods to calculate the runoff coefficient/effective precipitation distributed over time. Which do you prefer? Why?
- SCS method
- Φ - Index method
- Constant percentage
- Exponential percentage (prefered)
There are different types of hydrological models. Explain two of them with at least two advantages and two disadvantages each
- (white, grey and black box models)
Black box model: Only relation between input and output is considered. The system is assumed to be linear
Grey box model: Different parts of the water cycle are interpreted separately. More calculations possible.
Disadvantages:
- Black box: Natural processes arent directly displayed
- Grey box: More time, data and cost intensive. But more calculations/szenarios possible
Describe the difference between model calibration and validation. name and explain three of the primary Wasim calibration parameters and their main influence on the modeled hydrograph
Calibration:
- trying to reach the purpose of the model (trying to describe the reality as good as possible)
- Data is used to modify parameters (e.g. sensitivity analysis)
- Goal is to trigger as many model processes as possible
Validation:
- Purpose of the model is reaches
- Parameters are not modified anymore
- Goal is to test the performance of the model in different time series for checking the correctness of the calibration
Parameters : Explanation
kd : surface run-oof storage coefficient
kb : baseflow storage coefficient
ki : interflow storage coefficient
Thiessen-Polygon –> Name at least one other method to calculate area precipitation. Compare this method with the Thiessen-Polygon method (two advantages, two disadvantages each)
- Arithmetic mean value
- Isohyet method
- Inverse distance method
- (Thiessen Polygon method)
Arithmetic mean value is simple & easy to calculate.
Useful for the flat lands where gauges are placed at uniform distances. Not useful for short-time intervals. Also it is highly sensitive to extreme values.
Explain the term runoff generation. What is it influenced by (at least two parameters)?
- Components: Interception, Evapotranspiration, Infiltration, Snowmelt
Parameters: Effective precipitation (Precipitation which causes immediate runoff) Neff
Runoff coefficient: Ψges = NEff / NTotal
Describe the conditions in a catchment/characteristics of a catchment to get the following runoff coefficients:
- Ψ = ca.1
- Ψ = > 1
- Maximum infiltration is reached and all the precipitation is observed in surface run-off.
- In addition to the above, there is observed snowmelt which makes the coefficient greater than 1.
Determination of the runoff-coefficient
Koaxialdiagramm
SCS method
