# Thiem Equation for Steady-State Flow in a Confined Aquifer (2 monitoring wells)

Application: Geotechnics

## Summary

### Notes on Thiem Equation for Steady-State Flow in a Confined Aquifer (2 monitoring wells)

- Select the required output, then set the other parameters to the required values.
- Transmissivity (T) = K * D

For equations, assumptions and references see equations below.

For determination of steady state conditions see procedures below.

### Tool Parameters

Values displayed with a may be changed ... click on a value to display an entry form ... or use the arrows right of a value to select from a list.

### Tool Behaviour

This tool exhibits spreadsheet-like behaviour ... change a value and related values are re-calculated automatically.

### Thiem Equation for Steady-State Flow in a Confined Aquifer^{1}

^{1}Thiem, G., Hydrologische Methoden; Gebhardt, Leipzig, 1906.

### Two piezometers:

where:

*Q* = well discharge rate (m^{3}/d)

*KD* = transmissivity of aquifer (m^{2}/d)

*r _{1}, r_{2}* = respective distances of the piezometers from the pumping well (m)

*s*= respective steady-state drawdowns in the piezometers (m)

_{1}, s_{2}

### Assumptions^{2}:

- The aquifer is confined.
- The aquifer has an infinite areal extent.
- The aquifer is homogeneous, isotropic and of uniform thickness over the area influenced by the test.
- Prior to pumping, the piezometric surface is horizontal over the area that will be influenced by the test.
- The aquifer is pumped at a constant discharge rate.
- The well is screened over the entire thickness of the aquifer ensuring entirely horizontal flow.
- The hydraulic gradient between the pumping well and monitoring wells is at steady-state.
- The water removed from storage is discharged instantaneously with decline of head.
- Storage in the well can be neglected (the diameter of the well is small).

### References:

^{1}Thiem, G., Hydrologische Methoden; Gebhardt, Leipzig, 1906.

^{2}Kruseman, G.P. and N.A. de Ridder, Analysis and Evaluation of Pumping Test Data (Second Edition), Publication 47; International Institute for Land Reclamation and Improvement, Wageningen, 1994.

### Procedure to Determine if Flow to a Pumping Well is Steady-State^{1}

^{1}Kruseman, G.P. and N.A. de Ridder, Analysis and Evaluation of Pumping Test Data (Second Edition), Publication 47; International Institute for Land Reclamation and Improvement, Wageningen, 1994.

In practice, flow to a pumping well is considered steady-state when the difference in drawdown between piezometers becomes negligible, i.e., when the *gradient* between the piezometers becomes constant. The following procedures can be used to determine whether flow to a well is steady-state.

### Procedure 1:

- Create a semi-log plot of drawdown (s) vs. time (t) for all piezometers (Fig. 1). Drawdown is plotted on the vertical, linear axis, while time is plotted on the horizontal, logarithmic axis.
- Draw a best-fit curve through the data for each piezometer. The curves for the piezometers may become parallel for the data collected late in the pump test. If this is the case, then the gradients are constant and the system has reached steady-state.
- Where two curves are parallel, read the steady-state drawdown (s) for each piezometer at the end of the test and substitute these values with the corresponding radii into the Thiem equation or tool.
- Repeat 3 for any combination of piezometers with parallel time-drawdown curves. If the aquifer is truly homogeneous, then the different combinations of piezometers should yield a similar transmissivity (K x D). Different values of transmissivity suggest that the aquifer is heterogeneous, in which case, the mean of the values is used as a final result.

Figure 1: Sample time-drawdown graph produced in Procedure 1. Note that the gradient between piezometer H215 and the other piezometers is not constant (curves are not parallel) and therefore this piezometer would not be used to calculated transmissivity by the Thiem method.

### Procedure 2:

- Create a semi-log plot of observed drawdown (s) for each piezometer vs. the distance of the piezometer from the well (Fig. 2).
- Draw a best-fit line through the plotted points.
- Pick two colinear points (not necessarily observed data points) and substitute values of
*r*_{1,2}and*s*_{1,2}into the tool*or*

Determine the difference of drawdown (Ds) per log cycle of r (note log (*r*_{1}/*r*_{2}) = 1) and substitute into a simplified version of the Thiem equation:

Figure 2: Sample distance-drawdown graph used in Procedure 2.

- Principles and Practice of Ethics for Professionals in Mining
- Rock Mass Characterization for Mine Design
- Advanced Tailings Facility Design, Construction, Operation, and Closure
- Responsible Tailings Management 101
- Fundamentals of Mine Water Management
- Open Pit Slope Design and Implementation
- Risk Assessment and Decision Making for Mine Geowaste Facility Management
- Advanced Mine Water Management and Treatment
- Groundwater Modelling for Mining
- Geosynthetics for Geowaste Facilities
- Geosynthetics in Mining - Practice and Developments
- Open Pit Slope Design
- Tailings Management 101
- Covers for Mine Geowaste Facilities - 1: Principles, Practice, and Selection
- Covers for Mine Geowaste Facilities - 2: Design and Performance Analysis
- Design for Underground Metal Mines 1 - Design Parameters
- Design for Underground Metal Mines 2 - Design Guidelines
- Risk Assessment, Decision-Making, and Engineering Management for Mine Geowaste Facilities
- Geosynthetics in Mining
- Geotechnical Engineering for Mine Geowaste Facilities
- Groundwater in Mining
- Groundwater Modelling for Mining 1 - Model Conceptualization
- Groundwater Modelling for Mining 2 - Numerical Modelling
- Rock Mass Classification for Mine Design
- Introduction to Groundwater Modeling for Mines and Mining
- Guidelines for Open Pit Slope Design 1 - Fundamentals and Data Collection
- Guidelines for Open Pit Slope Design 2 - Modelling
- Guidelines for Open Pit Slope Design 3 - Design
- Guidelines for Open Pit Slope Design 4 - Operation
- A Rock Engineering Primer for Non-Engineers in Mining
- Design and Operation of Large Waste Dumps
- Practical Rock Engineering 1 - Introduction
- Practical Rock Engineering 2 - Structural Analysis
- Practical Rock Engineering 3 - Slope Stability and Rockfalls
- Practical Rock Engineering 4 - Stress Analysis
- Practical Rock Engineering 5 - Excavation and Support
- Stereographic Projections
- Surface Water Management at Mines
- Tailings Facility Design, Operation, and Closure
- Tailings Management
- Mine Water and Chemical Balance Analysis
- Groundwater Modelling for Mining
- Open Pit Slope Design
- Rock Mass Characterization for Mine Design
- Rock Mass Classification for Mine Design
- Advanced Tailings and Mine Waste Facility Design, Construction, Operation, and Closure
- Advanced Topics in Mine Water Management
- Mine Water Management: Surface and Groundwater
- Stereographic Projections
- Stereographic Projections
- Tailings Management 101

- Unit Conversions for the Geosciences
- Darcy Equation for Flow in a Confined Aquifer
- Dictionary of Mining, Mineral and Related Terms
- Dupuit Equation for Steady-State Flow to a Trench in an Unconfined Aquifer (No Recharge)
- Dupuit Equation for Steady-State Flow to a Trench in an Unconfined Aquifer (With Recharge)
- Jacob Method for Transient Flow in a Confined Aquifer
- Periodic Table with Minerals, Isotopes and Water Quality
- Spatial Analysis - Area of an Irregular Polygon
- Principle Stress Calculations
- Rock Mass Rating (RMR) Calculations
- Rock Mass Rating (RMR) Design Tables
- Rock Tunneling Quality Index Design Tables
- Rock Property Tables for Specific Gravity, Density and Porosity
- Geometric Properties of Circle Components
- Geometric Properties of Parabolic Components
- Tool for Slurry Conversions
- Phase Relationships for Soils
- Thiem Equation for Steady-State Flow in a Confined Aquifer (2 monitoring wells)
- Thiem Equation for Steady-State Flow in a Confined Aquifer (1 monitoring well)
- Dupuit Equation for Steady-State Flow in an Unconfined Aquifer (2 monitoring wells)
- Dupuit Equation for Steady-State Flow in an Unconfined Aquifer (1 monitoring well)