Groundwater Hydraulics: Groundwater head & flow Flashcards
True or False
Fluid potential in a fluid flow through porous media is defined as the mechanical energy per unit mass of fluid.
True
Fluid potential, denoted as ɸ, is calculated as gz + u^2/2 + ∫dP/ρ, where g represents _______, u is the velocity the fluid, and P is the pressure.
gravitational acceleration
What does the hydraulic head, h, represent in fluid dynamics?
A) The velocity of the fluid
B) The pressure head plus the elevation head
C) The temperature gradient of the fluid
B) The pressure head plus the elevation head
What does Darcy’s Law describe?
Darcy’s Law describes the flow of a fluid through a porous medium, quantifying the flow rate based on the hydraulic conductivity, the area perpendicular to flow, and the hydraulic gradient.
True or False
According to Darcy’s Law, the flow rate q is directly proportional to the hydraulic gradient Δh/Δz.
True
The hydraulic head in an observation well represents the average hydraulic head over the length of the _______ section of the well.
open
Which device is used to directly measure the hydraulic head at a specific point in a groundwater system?
A) Dipper
B) Piezometer
C) Thermometer
B) Piezometer
True or False
The water level in a piezometer always matches the water table level in unconfined conditions.
False
A dipper used to measure hydraulic head in a well has a graduated tape and makes a sound when it touches _______.
water
What is the purpose of the porous tip in a piezometer?
The porous tip allows water from the surrounding soil to enter the piezometer, enabling accurate measurement of the hydraulic head specific to that point.
True or False
The hydraulic head is calculated as h = z_m − d_w, where z_m is the elevation to the top of the casing and d_w is the depth of the water.
True
To measure the hydraulic head accurately, one must level in the casing to ensure the correct elevation of the top of _______.
casings
How many piezometers are required to determine the direction of groundwater flow?
A) 2
B) 3
C) 4
C) 4
What does the equation
h (t) = z_m − d_p + [P_p(t) − P_a(t)]/ρg describe?
It describes how the hydraulic head varies over time, accounting for the changes in pressure and elevation.
True or False
The gradient of the hydraulic head can be calculated without assuming constant hydraulic conductivity in the location and direction.
False (It assumes constant hydraulic conductivity)
The formula dh/ds = I = √(A^2 + B^2) is used to find the ______ gradient in an aquifer.
hydraulic head
In steady flow within a confined aquifer, what is significant about the product
HK?
A) It represents hydraulic conductivity.
B) It is referred to as the aquifer transmissivity.
C) It indicates hydraulic head.
B) It is referred to as the aquifer transmissivity.
True or False
In an unconfined aquifer under the Dupuit-Forchheimer assumption, there is a vertical head gradient.
False (The assumption is that there is no vertical head gradient, and flow is purely horizontal)
The equation h^2-h_0^2 =0 W/K(Lx - x^2) + (h_1^2 - h_0^2)x/L describes the water table profile under _______ conditions.
steady flow in an unconfined aquifer with recharge
What scenario does the model of two parallel ditches with vertical recharge illustrate in groundwater studies?
It models an unconfined aquifer with recharge and equal boundary conditions, showing the maximum water table height at the midpoint between the ditches.
What is A in the question?
A = ∂h/∂x
What is B in the equation?
B = ∂h/∂y
How do you find direction of flow?
θ = arctan(A/B)
What are the units of transmissivity?
L^2T^-1
