Hydrogeology Flashcards
7 cards from real ASBOG practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Hydrogeology flashcards as text
Which of the following conditions will cause the water table to decline even in the absence of pumping wells?
Answer: Both B and C
Both high ET losses from the capillary fringe and reduction in recharge due to impervious cover can cause the water table to decline without pumping.
A well installed in a leaky (semi-confined) aquifer is pumped. Compared to the Theis solution for a confined aquifer, drawdown in the leaky aquifer will:
Answer: Reach a steady state at smaller drawdown due to vertical leakage from the aquitard
Leakage from an overlying or underlying aquitard provides additional water, limiting drawdown and allowing a steady state to be reached at a shallower level than Theis predicts.
The specific capacity of a well is defined as:
Answer: Pumping rate divided by drawdown in the pumped well
Specific capacity (Q/s) is pumping rate divided by the drawdown in the well; it is a practical field measure of well performance.
Darcy's Law becomes invalid at high groundwater velocities primarily because:
Answer: Turbulent flow develops, violating the linear relationship between flux and gradient
At high velocities (Reynolds number > ~1–10 in porous media), inertial forces cause turbulence and the flux-gradient relationship becomes nonlinear, invalidating Darcy's Law.
Which map product is used to show the configuration of the potentiometric surface of a confined aquifer and delineate groundwater flow directions?
Answer: Potentiometric surface map based on piezometric levels in the confined aquifer
A potentiometric surface map contours the static water levels in wells completed in a confined aquifer, with flow directed perpendicular to contours from high to low head.
A NAPL (non-aqueous phase liquid) that is denser than water (DNAPL) behaves differently than LNAPL in the subsurface because it:
Answer: Sinks through the saturated zone and may pool atop aquitards below the water table
DNAPLs sink through the unsaturated and saturated zones due to their high density, pooling on low-permeability layers deep in the aquifer and forming persistent source zones.
The cone of depression created by a pumping well will be steeper (greater drawdown per unit distance) in an aquifer with:
Answer: Low transmissivity and low storativity
Low transmissivity means greater head loss is needed to convey water to the well, and low storativity means little water is released per unit head decline, both steepening the cone.