Groundwater - Groundwater level

21 important questions on Groundwater - Groundwater level

What is the capillary fringe?

Part of the saturated zone, but not of the groundwater sinch the water particles are sticking to the soil particles rather than sitting on top of the water below.

What is a synonym for groundwater table?

Phreatic plane

How works a piezometer?

Tube with holes in the end, stick in in the soil with end below the groundwater table. Water seeps into the tube and rises to the groundwaterlevel.
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Which two components does the hydraulic head of a piezometer consist of?

Hydraulic head (H in m): water column height corresponding to the potential

-Elevation head (z in m)
-pressure head   (h in m)

Formula: H = z+h

How compares the pressure head to atmospheric pressure?

Pressure head is always higher than the atmosperic pressure below the groundwater table.

What are dredged ditches?

Ditches from which sludge is taken and placed on the edges of the fields

Why is the hydraulic head the same everywhere in the piezometer?

Because when you go down ;
- pressure head increases
- elevation head decreases

What is a gully

It is a ditch of a few decimeters in depth, dug in the middle of a field to avoid ponding in the middle of the field during winter.

What happens in summer with the flow direction of groundwater and the groundwater level?

Water flows towards river, gw level drops, gw level in river is higher, water flows out of the river into the land.

What is the definition of hydromorphic characteristics?

Soil characteristics which are present as a result of wet soil conditions

Why are groundwater level classes used?

To visualize the effect of groundwater level variation and to communicate it to others. They are based on the Average Highest Groundwater Level (AHG) and the Average Lowest Groundwater Level (ALG)

For nature conservation purposes an additional level is used: average sprig groundwater level (ASG)

What causes (upward) seepage?

The hydraulic head of the top layer is lower than the hydraulic head of the lower layer and so water flows downwards.

When is the pressure head zero?

At atmospheric pressure

Why does the presence of peat indicate wet conditions during the soil formation?

The prodcution of soil organic matter is much larger than it's degradation in wet conditions.

What parts of the soil are always saturated with water?

The zone below the groundwater table and the zone on top of that, which has pores that are completely filled with water

What tells the distance between drainage networks about the groundwater level?

If the distance between ditches is large, groundwater levels are deep.
If the distance betweeen ditches is small, the groudwater levels are high.

What are the head characteristics of the heads at the groundwater table?

At the groundwater table, since the water is in contact with the atmosphere, the pressure head is 0. H=h+z, so H=z - hydraulic head equals elevation head

What happens when the groundwater level drops in a peat field?

The peat starts to oxidize in the middle of the field, causing this area to lower.

What is the main force behind groundwater flow?

Solar energy.
It leads to an evaporation of water at one location while precipitation is formed and falls at another location. These cause differences in hydraulic head, which in turn causes groundwater flow. Hydraulic resistance affects flow but doesn't cause it, differences in land surface level don't affect the groundwater table, unless it drops deep enough for plant roots to extract water or groundwater surfaces and a channel is formed/constructed to discharge the waters. Seasonal changes cause temporal differences in hydraulic head but this does not cause flow since water flows in space and not in time.

What is able to permeate the filter of the piezometer

Water and air

What are HG3 and LG3?

The mean of the three lowest and highest groundwater levels every year (April 1st till March 31st)

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