Groundwater Hydraulics: Storage, continuity and groundwater flow equations Flashcards
True or False
Specific yield only applies to confined aquifers.
False (It applies to unconfined aquifers)
Specific yield is the volume of water released per unit area due to a unit drop in the _______ elevation.
water table
What does storativity in a confined aquifer represent?
A) The volume of water per unit volume of aquifer that is drained due to gravitational forces
B) The volume of water released per unit area over the entire thickness of the aquifer as a result of a unit fall in the potentiometric surface
C) The increase in water content due to capillary action
B) The volume of water released per unit area over the entire thickness of the aquifer as a result of a unit fall in the potentiometric surface
What causes the change in storage in an aquifer?
The change in storage is caused by effective stress and fluid pressure, where an increase in effective stress results in a decrease in porosity, and a change in fluid pressure affects the fluid density.
True or False
The specific storage coefficient is determined only by the rock compressibility.
False (It is determined by both rock and fluid compressibility)
In the equation S_s = nρg(c_R+c_F), c_R and c_F represent the compressibility’s of the _______ and the _______, respectively.
rock, fluid
Which formula represents the effective porosity related to specific yield in an unconfined aquifer?
S_y = V_{water released}/V_{areaxdrop}
True or False
Storativity is dimensionless and calculated as
S=HS_S, where H is the aquifer thickness and S_S is the specific storage coefficient.
True
Mass continuity in an aquifer can be described as the change in storage equaling mass _______ minus mass _______.
in, out
Explain why changes in mass occur in groundwater systems according to the principles of mass continuity.
Changes in mass occur due to alterations in fluid density from compression and changes in porosity due to matrix expansion or contraction, which are influenced by variations in effective stress.
If a fluid slight compressible, can be assumed ρ to be ______.
a constant
Formula for c_F?
dρ/ρdP
Formula for c_R?
dn/ndP
What causes the lowering of the water table in specific yield?
The yield (i.e. loss) of water that causes the lowering of the water table is from some pores that were full becoming partially saturated and others about the capillary fringe become less saturated.
Formula for S_y?
S_y = ∆V\∆Az
