Groundwater and Wells Flashcards
(28 cards)
What is an aquifer?
A geological formation that can store and transmit water.
What are the two main types of aquifers?
Confined and unconfined aquifers.
What is a confined aquifer?
An aquifer trapped between two impermeable layers under pressure.
What is an unconfined aquifer?
An aquifer where the water table is exposed to the atmosphere through permeable material.
What is porosity?
The ratio of void space to total volume in a rock or soil.
What is permeability?
The ability of a material to transmit water.
What is the difference between porosity and specific yield?
Specific yield is the portion of water that drains by gravity; porosity includes all voids.
What type of soil typically makes a good aquifer?
Gravel and coarse sand due to high porosity and permeability.
What law governs groundwater flow?
Darcy’s Law.
Write Darcy’s Law.
Q = K × A × (dh/dl), where Q is flow rate, K is hydraulic conductivity, A is area, and dh/dl is the hydraulic gradient.
What is hydraulic conductivity?
A measure of how easily water moves through a material.
What is the hydraulic gradient?
The change in hydraulic head per unit distance.
What is a potentiometric surface?
An imaginary surface representing hydraulic head in a confined aquifer.
How does water move in an aquifer?
From areas of high hydraulic head to low hydraulic head.
What is an aquitard?
A layer with low permeability that restricts groundwater flow.
What is an artesian well?
A well where water rises above the top of the aquifer due to pressure.
What is drawdown?
The lowering of the water level in a well due to pumping.
What is the cone of depression?
A conical lowering of the water table around a pumped well.
What is well yield?
The volume of water a well can produce per unit time.
What factors affect well yield?
Aquifer properties, well design, and pumping rate.
What is the Theis equation used for?
To model drawdown in a confined aquifer over time.
What is transmissivity?
The rate at which groundwater is transmitted through a unit width of the aquifer.
What is storativity?
The amount of water a confined aquifer releases per unit decline in head per area.
What does a step-drawdown test determine?
The efficiency and performance of a well under different pumping rates.
