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Hydrogeology Flashcards

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  1. Which dimensionless number is used to compare advective transport to diffusive transport of solutes in groundwater?

    Answer: Peclet number

    The Peclet number (Pe) is the ratio of advective to diffusive solute transport; high Pe means advection dominates.

  2. A confined aquifer has a storage coefficient of 5×10⁻⁴. This value indicates that water release is primarily due to:

    Answer: Compression of the aquifer and expansion of water

    In confined aquifers, the storativity reflects elastic compression of the aquifer skeleton and expansion of pore water under pressure change.

  3. Which of the following best describes a perched aquifer?

    Answer: A saturated zone above the regional water table, separated by an unsaturated zone

    A perched aquifer is a locally saturated zone sitting atop a low-permeability lens above the main water table.

  4. In the context of aquifer testing, what does the term 'skin effect' refer to?

    Answer: Near-wellbore damage or improvement affecting wellbore efficiency

    Skin effect describes additional head loss (positive skin = damage, negative skin = improvement) caused by near-wellbore conditions.

  5. The Ghyben-Herzberg relation describes the depth of the freshwater-saltwater interface below sea level as approximately how many times the freshwater head above sea level?

    Answer: 40

    The Ghyben-Herzberg relation gives the interface depth as 40 times the freshwater head above sea level, derived from the density ratio of freshwater to saltwater.

  6. Which aquifer property controls the rate at which water-level changes propagate through a confined aquifer?

    Answer: Hydraulic diffusivity (T/S)

    Hydraulic diffusivity (transmissivity divided by storativity) governs how fast pressure perturbations travel through a confined aquifer.

  7. A water sample from a spring shows tritium activity of less than 0.8 TU. This result most likely indicates the water:

    Answer: Has a mean residence time greater than about 50 years

    Tritium levels below ~0.8 TU indicate the water predates 1952 thermonuclear testing, implying residence times exceeding ~50 years.