Geology & Groundwater Hydrology Flashcards

What is the primary concern with upconing in a coastal aquifer?

Answer: Upward movement of the freshwater-saltwater interface toward a pumping well

Upconing occurs when pumping draws the denser saltwater interface upward beneath a well, potentially leading to saltwater intrusion and well contamination.

Hydraulic head in a groundwater system is the sum of:

Answer: Pressure head and elevation head

Hydraulic head (h) = pressure head (p/ρg) + elevation head (z), representing the total mechanical energy per unit weight of groundwater.

Glacial outwash deposits are valued as aquifer materials primarily because they consist of:

Answer: Well-sorted sands and gravels with high permeability

Glacial outwash is deposited by meltwater streams and consists of well-sorted, coarse-grained sands and gravels that form highly productive aquifers.

What is the Ghyben-Herzberg relationship used to estimate?

Answer: The depth of the freshwater-saltwater interface below sea level in coastal aquifers

The Ghyben-Herzberg relationship predicts that the saltwater interface lies approximately 40 feet below sea level for every 1 foot of freshwater head above sea level.

In a pumping test, residual drawdown is measured to:

Answer: Calculate aquifer properties during the recovery phase after pumping stops

Recovery test analysis uses the rise in water levels after pumping ceases to calculate transmissivity and confirm aquifer parameters obtained during the pumping phase.

Which depositional environment typically produces laterally discontinuous, heterogeneous aquifer units?

Answer: Alluvial fan and braided river systems

Alluvial fans and braided streams deposit sediments in rapidly shifting channels, creating complex interbedded layers of varying grain size and permeability.

Groundwater age dating using tritium-helium methods is most useful for determining:

Answer: Whether groundwater was recharged before or after 1952 (nuclear testing era)

Tritium from nuclear weapons testing peaked in precipitation around 1963, so its presence (or decay product helium-3) indicates modern recharge after 1952.