Groundwater Lecture Notes

What is the difference between a well and a piezometer?

A well is used to pump water, while a piezometer is used to determine water pressure at a specific depth.

What does Bernoulli's Law state?

Bernoulli's Law is expressed as E = Z + uwγw + vw^2/(2g), where Z is the Elevation Head, uwγw is the Pressure Head, and vw^2/(2g) is the Velocity Head.

What is a piezometric surface?

A conceptual surface representing the level to which water will rise in tightly cased wells/piezometers due to groundwater pressure in an aquifer.

Define Aquifer.

An aquifer is a layer in which water can flow easily, such as sand and gravel.

What is Darcy's Law?

Darcy's Law describes that the flow rate (Q) is proportional to the area (A) and the change in hydraulic head (∆h), and inversely proportional to the length (L).

What is a phreatic aquifer?

A phreatic aquifer, also known as a water table or unconfined aquifer, has its top of water at atmospheric pressure.

What characterizes a confined aquifer?

A confined aquifer is when groundwater is bounded by confining layers and the pressure is greater than zero.

How is hydraulic conductivity determined in the lab?

Hydraulic conductivity is often determined using constant head and falling head tests to measure water flow through soil.

What does the total head at a point represent?

The total head at a point is the sum of the elevation head and the pressure head at that location.

What is the effective stress at point A if the total stress is σv and water pressure is uw?

Effective stress at point A is calculated as σ' = σv - uw.

Will the water flow through the barrel?

WATER FLOWS DUE TO CHANGE IN TOTAL HEAD

Aquitard

A layer in which water flow is greatly restricted, such as silt or clay

Aquiclude

A layer in which water cannot flow, such as bedrock

Type of Aquifers

Phreatic, Water Table or Unconfined Aquifer

• Top of Water in Aquifer and at Atmospheric Pressure

• Phreatic Surface

Confined Aquifer or Artesian Condition

• Top of Water Against a Confining Layer and Water Pressure is greater than zero

• Piezometric Surface

Well vs. Piezometer

Well: Used to Pump Water

• Piezometer: Used to determine Water Pressure at a specific depth

Confined aquifer vs. Artesian Condition