Wells Hydraulics

Groundwater is the water beneath the ground surface. It is a vast freshwater reservoir often overlooked because invisible, yet 1000 times greater than all lakes and rivers. The Earth is blue for its oceans, but green for the freshwater under our feet. Half of the world’s population rely on groundwater for drinking and almost half of the irrigated land now depends on groundwater, a ten-fold increase in the past 50 years. In order to use the water from the ground, we first have to extract it! This course introduces wells hydraulics. Wells are used to provide groundwater for domestic, agricultural or industrial uses. Wells are also used in applications to control groundwater flow and contamination. Pump and treat systems are designed to extract contaminated water before it can be treated. The treated water is released to the environment, sometimes using recharge wells that can replenish aquifers. Wells can also control salt intrusions in coastal environments or the water table level at a construction site.

This course addresses questions such as:

How exactly do we extract groundwater?

How do we know if an aquifer can provide enough water?

How do we model underground flow to wells?

How can we use wells to remove water from construction sites or water-logged fields?

This wells hydraulics course starts with a description of steady flow to wells. We introduce the notion of radial coordinates and steady flow to wells in confined and unconfined aquifers. We also introduce finite difference methods to model flow to wells. We introduce transient flows in confined, semiconfined and unconfined aquifers. We use graphic methods and semi-automated methods to calculate aquifer properties from well tests. We also introduce slug tests and their analysis.

After the well and slug tests, we introduce well fields and issues of dewatering. We review the superposition principle and problems of domain boundaries before focusing on dewatering examples. We continue to explore the topic of well fields in the context of extraction and injection wells, with an example of pump and treat design and an in-situ remediation design. We also show an example of a well model in MODFLOW.

What you'll learn

• Describe the steady-state flow to wells in confined and unconfined aquifers
• Explain the correspondence between linear and radial coordinates
• Derive the flow equations for steady flow to wells
• Build simple aquifer models
• Apply the flow equations to estimate aquifer parameters
• Design wells for steady water supply
• Describe the unsteady flow to wells in confined, semi-confined and unconfined aquifers
• Explain what well functions are
• Use graphical methods to calculate transmissivity
• Compare the (transient) flow behavior in (semi)confined and unconfined aquifers
• Explain slug tests
• Contrast slug tests and well tests
• Choose the appropriate analysis to calculate aquifer properties from slug tests
• Model aquifers and wells
• Apply analytical methods to steady state flows
• Use finite difference methods to model aquifers and wells
• Use computer models to automate calculations
• Relate mathematical models to numerical models such as MODFLOW
• Explain how well fields work
• Apply flow equations for multiple wells
• Explain how boundaries can be modeled with multiple (imaginary) wells
• Plan dewatering systems
• Interpret pump and treat systems from a hydraulics perspective