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Groundwater Resource Development

Effects and Sustainability

Book cover for Groundwater Resource Management

Publication year: 2020
Number of pages: 96
ISBN: 978-1-7770541-4-4

Authors:
Leonard F. Konikow – Emeritus Scientist, U.S. Geological Survey, USA
John D. Bredehoeft – Principal, the Hydrodynamics Group, LLC., USA

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Book Description

Groundwater withdrawals expanded dramatically during the last half of the 20th century. Approximately half the population of the world depends upon groundwater for its drinking water supply, and groundwater supplies almost half of the water used for irrigation in agricultural areas. This large and expanding use of groundwater is the primary driving force for concerns about groundwater (aquifer) depletion and sustainability of groundwater pumping.

When a water-supply well is drilled, it is usually with the hope that the well will reliably provide water for a long time (that is, its use will be sustainable for future generations). This book presents the principles associated with development of groundwater at the macro scale. These ideas date back to a classic paper by C.V. Theis in 1940 on the source of water derived from wells, in which he noted that all pumpage is balanced by a loss of water somewhere, with the loss during early times coming largely from aquifer storage and at later times increasingly from capture, which includes increases in recharge and decreases in discharge (such as base flow to streams and evapotranspiration).

Groundwater is often characterized as a “renewable resource.” Yet data now accumulating indicate that much of the current development of groundwater is depleting the resource at rates that cannot be sustained — in many places groundwater is being “mined” at high rates — contradicting its renewability over human timeframes. This poses a challenge to groundwater scientists and managers — can the resource be developed in a sustainable manner, and if so, how can that goal be accomplished?

The desirability and value of sustainable development of groundwater is clear. If the groundwater storage depletion over time becomes negligible, then groundwater withdrawals are maintainable indefinitely (as long as other factors do not affect the aquifer’s water balance). But “sustainability” should be assessed in a larger perspective than just whether pumping can continue indefinitely — the assessment should include impacts on surface-water flows, other environmental consequences (e.g., land subsidence and water-quality changes), as well as other linkages, such as socio-economics.

Hydrogeologists have the knowledge and tools to understand and predict the magnitude and timing of these effects. The most effective tool is a well-calibrated numerical simulation model, through which hydrogeologists can develop understanding and quantitative assessments of complex aquifer systems. Thereby, hydrogeologists can provide predictive understanding, which offers a long-view scientific basis for policy makers and water managers to make sound and defensible policy decisions.

Contents

1 INTRODUCTION

2 GROUNDWATER USE

3 SUSTAINABILITY OF GROUNDWATER DEVELOPMENT

3.1 Basic Assumptions

3.2 Water Balance

3.3 The System Prior to Development

3.4 Pumping

3.5 Long-Term Pumping Equilibrium (Development)

3.6 A New Perspective

4 STORAGE DEPLETION

4.1 Some Effects of Storage Depletion

Economic and Societal Benefits
Water Level Declines
Land Subsidence
Sea Level Rise

4.2 Methods to Estimate Depletion

Head Changes
Models
Water Budgets
Gravity Measurements
GRACE Remote Sensing
Subsidence
Confining Layers

4.3 Magnitude of Storage Depletion

5 CAPTURE

5.1 Streamflow Depletion

5.2 Capture of Evapotranspiration

5.3 Capture of Spring Discharge

5.4 Estimating the Magnitude and Timing of Streamflow Depletion

5.5 Methods to Estimate Capture

6 CASE STUDIES ILLUSTRATING GROUNDWATER DEVELOPMENT DYNAMICS

6.1 Case Study 1: Hypothetical Stream-Aquifer System

Description of Problem
Simulation Model
Base Case: No Recharge and No ET (No Phreatophytes)
Low ET Case (Phreatophytes)
ET and Recharge Case (Phreatophytes and Rainfall)
Running the Model
Summary

6.2 Case Study 2: Paradise Valley, Nevada

Description of Study Area
Paradise Valley Simulation Model
An Initial Steady State
Transient Historical Simulation
Simulated Future Development
The Lesson of the Paradise Valley Example

7 SUMMARY AND CONCLUDING REMARKS

8 EXERCISES

Exercise 1) Effects of Well Location (Distance from Well to River)
Exercise 2) Lower Ratio of Streamflow to Pumping
Exercise 3) Analytical Solution for Streamflow Depletion

9 REFERENCES

10 BOXES

Box 1 - Regional Unconfined Aquifer System: The High Plains Aquifer

Box 2 - Storage Depletion in a Thick Confining Layer: Dakota Aquifer System

Box 3 – Running and Post-Processing the Model For Case Study 1

11 EXERCISE SOLUTIONS

Exercise 1 Solution: Effects of Well Location (Distance from Well to River)
Exercise 2 Solution: Lower Ratio of Streamflow to Pumping
Exercise 3 Solution: Analytical Solution for Streamflow Depletion

ABOUT THE AUTHORS

Interview with Authors