Human impact: Lowland hydrology
15 important questions on Human impact: Lowland hydrology
Lowlands are often induced by humans. True or false?
What are lowland catchments?
Claudia: Areas where hydrological processes are influenced by shallow (less than 3 m below surface) GW.
What are differences between freely draining lowlands and polders (see slide!) - both are lowland catchments.
- Gradients are flow, so flow is slow but flow is gravity-driven
- Are influenced by people, but natural system
- Slightly sloping
- Drained by brooks
Polder:
- below land surface, water flow is pumped/levels are managed
- Manmade
- More stable GW level
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What are similarities between freely draining lowlands and polders?
Often located in river deltas
Shallow GW
Agriculturally productive
Attractive for settlement (often densely populated)
What are challenges in lowland catchments (advantages leading to challenges):
- Floods
- Climate change
- Land use change (has to do with urbanisation and agri expansion)
- Water quality detoriation (extensive agri use and population density)
- Land subsidence (peat oxidation)
- Increasing deman for information
Name (dis)advantages of parametric models (min 16)
- Representation of processes by parameters
- Easy to use
- Relatively fast
- Smaller risk of overparameterisastion than physicall
Disadvantage:
- Need for calibration of parameters
- Over-parameterization (but not as bad with physically based models, in principle you shouldnt have to calibrate your model, but in theory you do)
- No spatial information
Often used at catchment scale
What was a major problem until 2013?
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Fill the gap: WALRUS ....SEE SLIDE
Maximum soil moisture content (min 22/23)
Brown part: soil particles
Water = water part
There's a strong relation in GW depth and SM content in lowland areas. True/False?
Which lessons were learned (min 41)
dV indicates how dry it is = storage deficit
dG indicates GW depth = GW table
.....
What is lesson 2: wetnes-dependent flowroutes
- Drainpipe flow
- Ponding & overland flow
- Macropore flow
How does this work in the model?
W is related to vadose zone and dV.
...
Relation between wetness index (W)
GW - SW feedback, has to do with SWlvl management. Name two ways in which SW lvls are managed? SW = surface water
- Supply water from upstream
- Changing weir elevations
What is the 4-step effect of SW lvl management?
What is lesson 3: GW-SW feedback & how is this modelled in WALRUS?
Infiltration: SF to GW
WALRUS: Part P is led to SW and GS and SW interact. Water can also be supplied/extracted externally from SW.
What do the external fluxes fXG and fXS represent?
Draw graph
fxG = upward...
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