Hydrology Notes

I. Porosity

  • Porosity is the percentage of open spaces (pores) in a material compared to its volume.
  • Example: Sediments like sand have pores.
  • Factors affecting porosity include:
    • Shape: Rounded sediments tend to have higher porosity.
    • Sorting: Well-sorted sediments have higher porosity.
    • Packing: Loosely packed sediments have higher porosity.
  • Size is NOT a factor of porosity.

Factors That Affect Porosity

  • Sediment characteristics and their relationship to porosity:
    • Rounded vs. Angular:
      • Rounded sediments: High porosity.
      • Angular sediments: Low porosity.
      • As sediments become more rounded, porosity increases.
    • Sorted vs. Unsorted:
      • Sorted sediments: High porosity.
      • Unsorted sediments: Low porosity.
      • As sediments become more sorted, porosity increases.
    • Closely Packed vs. Loosely Packed:
      • Closely packed sediments: Low porosity.
      • Loosely packed sediments: High porosity.
      • As sediments become more closely packed, porosity decreases.

II. Permeability

  • Permeability is the ability of water/liquids to pass through the pore space of rock.
  • Impermeable: Water cannot pass through (e.g., pavement).
  • Permeable: Water can pass through.

A. Infiltration

  • Infiltration is the process by which water on the ground surface enters the soil.
  • Experiment demonstrating infiltration rate:
    • Setup: Graduated cylinder with tubes containing different-sized beads (4mm, 7mm, 12mm).
    • Results:
      • 4mm beads: Infiltration time = 5 minutes.
      • 7mm beads: Infiltration time = 2 minutes.
      • 12mm beads: Infiltration time = 30 seconds.
    • Conclusion: As particle size increased, infiltration time decreased and infiltration rate increased.
    • Infiltration Rate:
      • 4mm beads: Slow
      • 12mm beads: Fast

Factors That Affect Infiltration

  • Slope of the Land:
    • As the slope of the land increases, the rate of infiltration decreases.
  • Rate of Precipitation:
    • As the rate of precipitation increases, the rate of infiltration decreases.
  • Permeability of the Soil:
    • As the soil becomes more permeable, the rate of infiltration increases.
  • Saturation of the Soil:
    • As the soil becomes more saturated, the rate of infiltration decreases.
  • Temperature of the Soil:
    • As the soil becomes more frozen, the rate of infiltration decreases.

III. Capillarity

  • Capillarity is the upward movement of water against the force of gravity.
  • Relationship to Particle Size:
    • As particle size increases, capillary action decreases.