The Groundwater Project

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Graphical Construction of Groundwater Flow Nets

Eileen Poeter and Paul Hsieh

Cover of the bok Graphical Construction of Groundwater Flow Nets

Publication year: 2020
Number of pages: 67
ISBN: 978-1-7770541-3-7

Authors:
Eileen Poeter – Colorado School of Mines, USA
Paul Hsieh – California, USA

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Book Description

A groundwater flow net consists of two families of intersecting lines: equipotential lines, which connect locations of equal hydraulic head, and flow lines, which show paths of groundwater flow. Together, these two sets of lines provide a visual, two-dimensional representation of the groundwater conditions under steady state (that is, neither set of lines change with time).

Although flow nets can be readily constructed using computer software, graphical construction using pencil and paper remains an essential skill that every groundwater hydrologist should possess. This book explains graphical construction of groundwater flow nets and provides exercises and videos links to help readers gain a deeper and intuitive understanding of groundwater flow.

The construction of a groundwater flow net begins with the definition of the flow domain and the boundary conditions along the domain boundary. Two common boundary conditions are (1) constant hydraulic head along the boundary and (2) no flow across the boundary. After the boundary conditions are specified, the flow net is constructed by following an iterative, step-by-step procedure.

If the hydraulic conductivity of the material is known, the volumetric flow rate through the flow domain can be calculated. This book also covers more advanced topics, including treat of a flow domain having a water-table boundary or anisotropic hydraulic conductivity.

A groundwater flow net is, in effect, a graphical solution of the groundwater flow equation. Although the mathematical requirement for this book is no more than basic algebra, the practice of flow net construction will lead to an intuitive understanding that enhances the learning of more advanced and quantitative aspects of groundwater theory.

To provide additional practice in visualizing flow nets, this book uses the online computer software, TopoDrive, which simulates groundwater flow in a topographically-driven flow system.

Contents

1 INTRODUCTION

1.1 What is Graphical Construction Of a Flow Net?

2 FLOW NET CONSTRUCTION

2.1 Approaches to Constructing Flow Nets

2.2 Drawing a Flow Net For a Homogeneous Isotropic System

Basic Criteria for Drawing Graphical Flow Nets
Steps for Drawing a Flow Net Using Pencil and Paper

2.3 Drawing a Flow Net for Flow Beneath an Impermeable Dam

2.4 calculating volumetric discharge

2.5 Drawing a Flow Net for an Unconfined System With a Water Table Boundary

2.6 The "Hear See Do" Of Flow Nets

2.7 Flow Nets Provide Insight Into Groundwater Flow

2.8 Drawing a Flow Net For a System With Anisotropic Hydraulic Conductivity

2.9 Create and Investigate Topographically Driven Flow Systems

2.10 Summary

Note on Transient Groundwater Flow Systems

3 EXERCISES

Exercise 1

Exercise 2

Exercise 3

Exercise 4

4 REFERENCES

5 BOXES

BOX 1 – Review of Hydraulic Head

BOX 2 – Review of Darcy’S Law

BOX 3 – Derivation: Formula for Volumetric Flow Rate Through a Flow Net

BOX 4 - Drawing a Flow Net For an Unconfined System With a Water Table Boundary

BOX 5 - Drawing Flow Nets for Anisotropic Systems

BOX 6 - Create and Investigate Topographically-Driven Flow Systems

Introduction
Governing Equation
Boundary Conditions
Running the Model
Example 1
Example 2

6 EXERCISE SOLUTIONS

Exercise 1 - Solution

Exercise 2 - Solution

Exercise 3 – Solution

Exercise 4 - Solution

7 ABOUT THE AUTHORS

Interview with Authors