Groundwater & Hydrogeology Flashcards
7 cards from real CES practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Groundwater & Hydrogeology flashcards as text
Darcy's Law states that groundwater flux (Q) is proportional to which combination of parameters?
Answer: Hydraulic conductivity (K), hydraulic gradient (i), and cross-sectional area (A)
Darcy's Law is expressed as Q = KiA, where K is hydraulic conductivity, i is the hydraulic gradient (dh/dl), and A is the cross-sectional area perpendicular to flow.
A confined aquifer differs from an unconfined aquifer primarily in that it:
Answer: Is bounded above by an aquitard and water pressure exceeds atmospheric pressure
A confined aquifer is overlain by a low-permeability aquitard, and the water within it is under pressure greater than atmospheric, causing water to rise above the aquifer top in a well (artesian conditions).
The hydraulic gradient between two monitoring wells 500 meters apart, with head values of 45 m and 40 m respectively, is:
Answer: 0.01
Hydraulic gradient = Δh / ΔL = (45 – 40) / 500 = 5/500 = 0.01, representing the dimensionless slope of the potentiometric surface.
Which term describes the fraction of the total aquifer volume occupied by interconnected pore spaces through which water can flow?
Answer: Effective porosity
Effective porosity (also called kinematic porosity) accounts only for interconnected voids through which water actually moves, which is always less than or equal to total porosity.
An aquitard is best described as a geologic unit that:
Answer: Has low permeability and retards but does not completely prevent groundwater flow
An aquitard is a confining layer with sufficiently low hydraulic conductivity to restrict groundwater flow but not block it entirely; an aquiclude is the term for a completely impermeable unit.
Transmissivity (T) of an aquifer is defined as:
Answer: The product of hydraulic conductivity (K) and saturated aquifer thickness (b)
Transmissivity T = K × b, combining the aquifer's ability to conduct water (K) with its thickness (b); it represents the integrated horizontal conductance of the saturated zone.
In a three-point problem using water table elevations from three monitoring wells, the primary purpose is to determine the:
Answer: Direction and gradient of groundwater flow
The three-point method uses head values at three non-collinear wells to construct the potentiometric surface, revealing the direction of groundwater flow (perpendicular to equipotential lines) and the hydraulic gradient.