Water: Storage and Movement in Rocks Flashcards
Define Groundwater
Subsurface water contained within the pore spaces of rocks below the water table.
Where Does Groundwater Originate From?
Rainwater that has infiltrated into the soil and then percolated downwards through the space of rocks to reach the water table.
Define The Water Table
The level at which waer sits within the ground. It is the surface separating unsaturated rock above from saturated rock below.
What Do Rocks Above The Water Table Contain?
Have air and water in their pore spaces.
What Do Rocks Below The Water Table Contain?
Only contain water in their pore spaces.
What Features Does The Water Table Have?
The shape of the water table follows the surface topography and intersects the ground surface at lakes and rivers. The position of the water table may vary depending on climatic variations.
Define Prosity
The amount of pore space in a rock or sediment, usually expressed as a % of the total rock volume.
How is Porosity Calculated?
% porosity = (total volume of pore space / total volume of rock) x 100
What Factors Affecting Porosity?
- Rock type
- Degree of sorting
- Degree of compaction & cementation
- Grain shape
Define Permeability
The ability for fluids to flow through a rock.
Which Rocks Have High Porosity and Low Permeability?
- Clay
- Mudstone
- Shale
How is Permeability Calculated?
Distance / Time
What Factors Affect Permeability?
- Grain size
- Rock type
Degree of compaction & cementation
What is Hydrostatic Pressure?
It results from the weight of the overlying column of water and increases with depth.
Define Hydrostatic Head
The height of the overlying column of water.
