CWD Geology & Groundwater Hydrology 2 — Questions and Answers
Question 1: What term describes the pressure surface to which water in a confined aquifer will rise in a tightly cased well?
- Water table
- Piezometric surface (Correct answer)
- Capillary fringe
- Saturated zone
Correct answer: Piezometric surface
The piezometric (potentiometric) surface represents the hydraulic head in a confined aquifer and is the level to which water rises under artesian pressure.
Question 2: Which sedimentary rock type is MOST commonly associated with karst aquifer systems?
- Sandstone
- Shale
- Limestone (Correct answer)
- Granite
Correct answer: Limestone
Limestone is soluble in slightly acidic groundwater, creating caves, sinkholes, and conduit flow networks characteristic of karst systems.
Question 3: Darcy's Law states that groundwater flow rate is proportional to which property?
- Storativity only
- Hydraulic gradient and hydraulic conductivity (Correct answer)
- Porosity alone
- Aquifer depth
Correct answer: Hydraulic gradient and hydraulic conductivity
Darcy's Law (Q = K·i·A) shows that flow is directly proportional to both hydraulic conductivity (K) and hydraulic gradient (i).
Question 4: A formation that transmits water but yields it slowly, often acting as a leaky boundary, is called a(n):
- Aquitard (Correct answer)
- Aquifer
- Aquiclude
- Aquifuge
Correct answer: Aquitard
An aquitard restricts but does not completely prevent groundwater flow, and can contribute water to adjacent aquifers through leakage.
Question 5: What is the primary mechanism by which an artesian well flows at the surface without pumping?
- The water table is perched above ground level
- Hydrostatic pressure in a confined aquifer exceeds the land surface elevation (Correct answer)
- Capillary action draws water upward
- Tidal forces create upward pressure
Correct answer: Hydrostatic pressure in a confined aquifer exceeds the land surface elevation
A flowing artesian well occurs when the potentiometric surface of a confined aquifer lies above the ground surface at the well location.
Question 6: During a pumping test, the cone of depression expands outward until it reaches:
- The water table
- A recharge boundary or equilibrium (Correct answer)
- The bedrock surface
- The unsaturated zone
Correct answer: A recharge boundary or equilibrium
The cone of depression expands until inflow from recharge or hydraulic boundaries equals the pumping rate, achieving steady-state conditions.
Question 7: Which rock characteristic makes fractured crystalline bedrock a viable but unpredictable water source?
- High primary porosity
- Secondary porosity from fractures and joints (Correct answer)
- Intergranular flow paths
- High clay content
Correct answer: Secondary porosity from fractures and joints
Crystalline rocks like granite have very low primary porosity but can yield significant water through secondary porosity created by fractures, faults, and joints.
CWD Geology & Groundwater Hydrology 2
What term describes the pressure surface to which water in a confined aquifer will rise in a tightly cased well?