Catchments - Rainfall-runoff processes

16 important questions on Catchments - Rainfall-runoff processes

Precipitation that falls on vegetation is categorized in interception (until interception capacity is reached) and throughfall. How does a part of intercepted precipitation still reach the soil?

Via stemflow - the rest of intercepted precipitation will evaporate.

What happens when the precipitation intensity is below the infiltration capacity?

All rain will infiltrate. The precipitation intensity can be directly related to the infiltration speed mm per h^-1 and the maximum infiltration speed is the infiltration capacity, so if the speed of rainfall is lower than speed of infiltration there is no water excess.

What is the interception capacity dependant on?

The type of vegetation and the type of precipitation.
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Why is soil compaction disadvantageous for the infiltration capacity?

The porosity of the soil will decrease, which makes the soil less permeable.

Why can soil become hydrophobic?

Water increases the transport capacity of the soil, which means the soil can become hydrophobic when it is dried out.

What is the infiltration capacity dependent on?

Land cover, soil type, soil wetness and the presence of vegetation. Vegetation improves stability and structure.

What is soil compaction?

Small soil particles are transported to and deposited on the soil surface, closing the pores and hampering infiltration.

What is the water in the soil called?

In the unsaturated soil, it is called soil moisture/soil water and in the saturated soil it is called groundwater. They are separated by the capillary fringe, which is located just above the groundwater table.

Why does the infiltration capacity of the lower layer of soil increase during a rainfall event?

Then the soil doesn't get hydrophobic. In that situation the ic.  is quit small.

What are the upward and downward flows of water between saturated and unsaturated zone?

Percolation (caused by gravity) and capillary rise (caused by negative pressure from evapotranspiration in topsoil)

What facilitates percolation through the soil matrix?

Macropores

What causes an overrun of water?

-impermeable land surface
-infiltration excess (infiltration capacity is exceeded)
-saturation excess
-seepage (groundwater flows upwards to the surface

What causes the delayent of waterflow towards the catchment outlet?

Depression storage (the occurence of ponding in low-lying areas) and snow storage.

When does surface runoff, or overland flow, occur?

It occurs when ponding has occured on a sloping surface and it is raining or has just rained.
(saturation excess overland flow&infiltration excess overland flow)

What does water level management in the netherlands look like? And why is it important?

They use weirs in ditches (structures that block the water flow.

It is important because it prevents sibsidence of peat soils, inundation (overstroming), brackish seepage (upwelling of deep salty groundwater), and a shortage of water for crops.

What is upward seepage?

Water enters an area via deeper sil layers and subsequently moves upward towards the soil surface.

The question on the page originate from the summary of the following study material:

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