Groundwater Overview

Groundwater: A Vital Resource

• Distribution of Earth’s Water
  • 97.2% Salt Water
  • 2.8% Fresh Water
  • 2.15% Glaciers/Ice
  • 0.63% Groundwater
  • 0.02% Surface Water
  • Groundwater is crucial as it holds the largest reservoir of accessible fresh water, approximately 26 times more than all streams and lakes combined.

Groundwater Storage and Transport

• Defining Groundwater
  • Groundwater is water stored in rock and soils below the Earth's surface.
  • Porosity: This refers to the volume of empty space relative to the volume of sediment particles, influencing how much groundwater can be stored.
  • Well-sorted sand has high porosity, while poorly sorted sand has low porosity.
• Permeability: This is a measure of how easily a fluid flows through a network of pores and cracks within sedimentary materials.

The Water Table

• Water that seeps into the ground creates two main zones:
  1. Zone of Aeration:
  • Comprised of sediment that is partially saturated with both air and water.
  1. Zone of Saturation:
  • Contains sediment with all pore spaces filled with water.
• Water Table:
  • Acts as the boundary between the zone of aeration and the zone of saturation. Wells must reach below this level to access groundwater.
• Water table levels fluctuate based on precipitation, with recharge occurring from rainfall and discharge happening via springs or wells.

Aquifers and Groundwater Flow

• Aquifers:
  • Rock bodies or layers of sediment capable of easily transmitting and storing water.
  • Two Types:
    • Unconfined Aquifer:
    • Surfaces coincide with the water table.
    • Confined Aquifer:
    • Water-bearing rocks are sandwiched between impermeable layers, allowing pressure to build up.
• Artesian Wells:
  • These wells draw water to the surface without pumping due to the pressure from the confined aquifer.
• The flow rate of groundwater can be slow, traveling a few centimeters per day, but can reach up to 15 centimeters per day in gravel.

Heated Groundwater Features

• Hot Springs:
  • Heated groundwater rises naturally to create pools of warm water.
• Fumarole:
  • Vent that releases steam where heated groundwater turns to steam.
• Geysers:
  • Features that periodically release super-heated water explosively.

Springs and Caves

• Formation of Springs:
  1. Recharge: Rainfall replenishes groundwater.
  2. Percolation: Water moves downward through rocks.
  3. Speleogenesis: Chemical weathering of rocks forms caves.
  4. Groundwater Flow: Driven by gravity.
  5. Sinkhole Formation: Result of cave collapse, leading to openings that may connect to springs.

Groundwater and Human Impact

• Cone of Depression:
  • Results when groundwater is extracted faster than it can be replenished, creating a cone-shaped depression near wells.
• Contamination:
  • Saltwater Intrusion: Happens when freshwater is over-extracted, allowing saltwater to encroach into aquifers.
  • Human activities like landfills, agriculture, and sewage contribute to groundwater contamination.
• Groundwater Usage:
  • Various sectors withdraw water, including agriculture, public supply, and recreational use, putting pressure on freshwater resources.
  • Over-extraction leads to issues such as surface subsidence and reduced water supply.

Climate Change Effects

• Climate change can exacerbate droughts, reducing freshwater availability globally.
• The increasing temperatures and changing precipitation patterns threaten groundwater recharge and availability, contributing to water stress, particularly in arid regions.

Important Considerations:

• Groundwater management is critical for sustainability and preventing resource depletion.
• Awareness and conservation efforts are necessary to protect this vital resource against contamination and overuse.