Groundwater and Aquifers Quiz

Groundwater

• Groundwater is a vital freshwater source found at varying depths underground, but is limited by the amount extractable and its quality.
• An aquifer is a rock formation containing usable groundwater. A good aquifer needs both porosity (open space to hold water) and permeability (connected spaces for water flow).

Porosity and Permeability

• Porosity is the percentage of open space in a rock. Primary porosity is the space between grains, while secondary porosity is from fractures or dissolved spaces.
• Permeability is the connectivity of the open spaces in a rock, allowing water to move. Well-sorted sediments have higher porosity.
• Compaction and cementation during rock formation reduce porosity. Clay-rich shales often have high porosity, but poor permeability due to poorly connected pores, limiting water flow.

Aquifers

• Aquifers are rock layers with sufficient porosity and permeability that allows both water containment and movement.
• For aquifer suitability, pores must be at least partially filled with water and permeable for water transmission. Potable water is also a requirement for drinking water aquifers.
• Aquifers can vary significantly in size and scale.

Groundwater Flow

• Infiltration or seepage of surface water first enters the unsaturated (vadose) zone, where pore spaces are not completely filled with water.
• Water pressure in this zone is less than atmospheric pressure.
• The capillary fringe is below the vadose zone, saturated with water, but fluid pressure is still less than atmospheric.
• The saturated (phreatic) zone sits below the capillary fringe, with fully saturated pore spaces where water pressure is equal to or higher than atmospheric pressure.
• The water table is the boundary between the zone of saturation and the unsaturated zone.
• Wells are conduits that extract, measure, or add water to aquifers.

Discharge

• Discharge areas are where the water table or potentiometric surface intersects the land surface.
• Discharge areas include springs, flowing wells, gaining streams, and playas in arid regions.

Groundwater Mining and Subsidence

• Groundwater mining occurs when water extraction exceeds recharge, leading to declining groundwater levels and potentiometric surfaces.
• Reduced spring and stream flow and subsidence can result.
• In these situations, groundwater is akin to a mine, with depletion over time.

Water Contamination

• Water contamination can result from natural features (mineral-rich formations) or human activities (agriculture, industries, landfills, and sewage).
• Contamination can be categorized as organic and inorganic chemicals, or biological agents.

Remediation

• Remediation refers to cleaning up contaminants.
• Techniques include biological remediation (bacteria), chemical remediation (reactive barriers), and physical remediation (pump-and-treat).
• Point source pollution comes from specific sources (like waste disposal sites), while nonpoint is from dispersed sources (like lawn fertilizers).

Karst

• Karst landscapes form from dissolution of soluble bedrock like limestone, creating features like sinkholes, caves, and disappearing streams.
• Groundwater dissolving limestone results in these karst features.

Test your knowledge on groundwater, aquifers, and the concepts of porosity and permeability. This quiz covers essential characteristics of aquifers and the qualities necessary for effective water storage and movement. Challenge yourself to understand the science behind this vital freshwater resource.