Hydrogeology Lecture 3- Water in the subsurface Flashcards
What % of the Earth’s atmosphere is water vapour
4%
What element in water is slightly negative?
Oxygen
What element in water is slightly positive?
Hydrogen
Density of ice at 0C
0.91674 g cm-3
Maximum density of water at 4C
1.0 g/cm-3
Specific heat, amount of energy needed to rise water temperature by 1K
= 4187J
Compressibility of water
Very low
Location of groundwater- unsaturated zone
Vadose
Location of groundwater- saturated zone (below water table)
Phreatic
Flow and storage of water in soils?
Aeration zone–> Capillary water zone–> Ground water zone
Why can’t plants grow roots into the water table?
They lack free oxygen needed for respiration
Capillary fringe
Water is retained here at less than saturation meaning plants roots can grow here
What does capillarity arise from?
Wettability and interfacial tension(surface tension)
Hydrophilic
Substances that prefer to be surrounded by water than air- those surfaces exert a suction on the water until water has displaced all air (or other fluid) from the surface. e.g. glass, geologic media, paper etc.
Hydrophobic
Water/rust proofing, surfactants, oils can make surfaces prefer non-water fluids
How is wettability measured?
By the contact angle
Fluid molecules liking to stick together
Creates fluid/fluid interfaces with tension
Surface tension in capillaries and soil pores
The surface tension pulls the pore water up as the film is being pulled along the solid surface
What acts against wettability and surface tension pulling the fluid up?
Gravity pulling it down
Height of capillary rise
Governed by the balance of wettability, surface tension and gravity
