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- Herausgeber: John Wiley & Sons
- Kategorie: Wissenschaft und neue Technologien
- Serie: Challenges in Water Management Series
- Sprache: Englisch
In the 21st Century, the world will see an unprecedented migration of people moving from rural to urban areas. With global demand for water projected to outstrip supply in the coming decades, cities will likely face water insecurity as a result of climate change and the various impacts of urbanisation. Traditionally, urban water managers have relied on large-scale, supply-side infrastructural projects to meet increased demands for water; however, these projects are environmentally, economically and politically costly. Urban Water Security argues that cities need to transition from supply-side to demand-side management to achieve urban water security. This book provides readers with a series of in-depth case studies of leading developed cities, of differing climates, incomes and lifestyles from around the world, that have used demand management tools to modify the attitudes and behaviour of water users in an attempt to achieve urban water security.
Urban Water Security will be of particular interest to town and regional planners, water conservation managers and policymakers, international companies and organisations with large water footprints, environmental and water NGOs, researchers, graduate and undergraduate students.
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Seitenzahl: 607
Veröffentlichungsjahr: 2017
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Table of Contents
Cover
Title Page
Series Editor Foreword – Challenges in Water Management
Acknowledgements
Introduction
1 Water 101
Introduction
1.1 What is water?
1.2 Hydrological cycle
1.3 Natural variations to water quantity
1.4 Natural variations to water quality
1.5 Impacts of urbanisation on water resources
1.6 Water and wastewater treatment processes
2 What is urban water security?
Introduction
2.1 Non-climatic challenges to achieving urban water security
2.2 Climatic challenges to achieving urban water security
2.3 Reducing non-climatic and climatic risks to urban water security
3 Managing water sustainably to achieve urban water security
Introduction
3.1 What is sustainability?
3.2 What does sustainability mean in urban watermanagement?
3.3 Sustainable water resources management frameworks
3.4 Framework for managing urban water sustainably: Integrated urban water management
3.5 Other frameworks for managing urban water sustainably
4 Demand management to achieve urban water security
Introduction
4.1 Purpose of demand management
4.2 Regulatory and technological demand management instruments
4.3 Communication and information demand management instruments
4.4 Portfolio of demand management tools
5 Transitions
Introduction
5.1 What is a transition?
5.2 Operationalisation of transitions
5.3 Diffusion mechanisms
5.4 Transition management
6 Transitions towards managing natural resources and water
Introduction
6.1 Transitions in natural resource management
6.2 What is a transition in urban water management?
6.3 Operationalising transitions in third-order scarcity
6.4 Barriers to transitions towards urban water security
7 Amsterdam transitioning towards urban water security
Introduction
7.1 Brief company background
7.2 Water supply and water consumption
7.3 Strategic vision: Amsterdam’s Definitely Sustainable 2011–2014
7.4 Drivers of water security
7.5 Regulatory and technological demand management tools to achieve urban water security
7.6 Communication and information demand management tools to achieve urban water security
7.7 Case study SWOT analysis
7.8 Transitioning towards urban water security summary
8 Berlin transitioning towards urban water security
Introduction
8.1 Brief company background
8.2 Water supply and water consumption
8.3 Strategic vision: using water wisely
8.4 Drivers of water security
8.5 Regulatory and technological demand management tools to achieve urban water security
8.6 Communication and information demand management tools to achieve urban water security
8.7 Case study SWOT analysis
8.8 Transitioning towards urban water security summary
9 Copenhagen transitioning towards urban water security
Introduction
9.1 Brief company background
9.2 Water supply and water consumption
9.3 Strategic vision: water supply plan (2012–2016)
9.4 Drivers of water security
9.5 Regulatory and technological demand management tools to achieve urban water security
9.6 Communication and information demand management tools to achieve urban water security
9.7 Case study SWOT analysis
9.8 Transitioning towards urban water security summary
10 Denver transitioning towards urban water security
Introduction
10.1 Brief company background
10.2 Water supply and water consumption
10.3 Strategic vision: Denver Water’s 22 percent water target
10.4 Drivers of water security
10.5 Regulatory and technological demand management tools to achieve urban water security
10.6 Communication and information demand management tools to achieve urban water security
10.7 Case study SWOT analysis
10.8 Transitioning towards urban water security summary
11 Hamburg transitioning towards urban water security
Introduction
11.1 Brief company background
11.2 Water supply and water consumption
11.3 Strategic vision: the HAMBURG WATER Cycle
11.4 Drivers of water security
11.5 Regulatory and technological demand management tools to achieve urban water security
11.6 Communication and information demand management tools to achieve urban water security
11.7 Case study SWOT analysis
11.8 Transitioning towards urban water security summary
12 London transitioning towards urban water security
Introduction
12.1 Brief company background
12.2 Water supply and water consumption
12.3 Strategic vision: reducing consumption
12.4 Drivers of water security
12.5 Regulatory and technological demand management tools to achieve urban water security
12.6 Communication and information demand management tools to achieve urban water security
12.7 Case study SWOT analysis
12.8 Transitioning towards urban water security summary
13 Singapore transitioning towards urban water security
Introduction
13.1 Brief company background
13.2 Water supply and water consumption
13.3 Strategic vision: balancing supply with rising demand
13.4 Drivers of water security
13.5 Regulatory and technological demand management tools to achieve urban water security
13.6 Communication and information demand management tools to achieve urban water security
13.7 Case study SWOT analysis
13.8 Transitioning towards urban water security summary
14 Toronto transitioning towards urban water security
Introduction
14.1 Brief company background
14.2 Water supply and water consumption
14.3 Strategic vision: Toronto’s Water Efficiency Plan
14.4 Drivers of water security
14.5 Regulatory and technological demand management tools to achieve urban water security
14.6 Communication and information demand management tools to achieve urban water security
14.7 Case study SWOT analysis
14.8 Transitioning towards urban water security summary
15 Vancouver transitioning towards urban water security
Introduction
15.1 Brief company background
15.2 Water supply and water consumption
15.3 Strategic vision: clean water and lower consumption
15.4 Drivers of water security
15.5 Regulatory and technological demand management tools to achieve urban water security
15.6 Communication and information demand management tools to achieve urban water security
15.7 Case study SWOT analysis
15.8 Transitioning towards urban water security summary
16 Sharing the journey: Best practices and lessons learnt
Introduction
16.1 Best practices
16.2 Lessons learnt
16.3 Moving forwards
Conclusions
Best practices
Lessons learnt
Moving forwards
Index
End User License Agreement
List of Tables
Chapter 01
Table 1.1 Principal residence times of the global water stores
Table 1.2 Drought severity classification
Table 1.3 Palmer Drought Severity Index
Chapter 03
Table 3.1 Differing values placed on ecosystems
Table 3.2 Ecosystem services
Table 3.3 Ecosystem service value
Table 3.4 Management instruments in IWRM
Chapter 04
Table 4.1 Water Corporation’s pricing structure of water
Table 4.2 Sydney Water’s pricing structure
Table 4.3 Seattle’s seasonal pricing structure
Table 4.4 Objectives of pricing
Chapter 05
Table 5.1 Components of a sociotechnical system
Table 5.2 STEEP drivers of transitions
Table 5.3 Transition management actions at multiple levels
Chapter 06
Table 6.1 Managing the impacts of climate change and resource scarcity
Table 6.2 Components of a water system
Table 6.3 External drivers of transitions in IUWM
Table 6.4 Direct demand management tools
Table 6.5 Indirect demand management tools
Chapter 07
Table 7.1 Water consumption in Amsterdam
Table 7.2 Water tax for metered customers
Table 7.3 Waternet education programmes
Table 7.4 Demand management tools to achieve urban water security
Table 7.5 Barriers to further urban water security
Chapter 08
Table 8.1 Fixed tariff for domestic customers
Table 8.2 Demand management tools to achieve urban water security
Table 8.3 Barriers to further urban water security
Chapter 09
Table 9.1 Distribution of water consumption types
Table 9.2 Water tariffs for domestic and non-domestic customers
Table 9.3 Wastewater tariffs for domestic and non-domestic customers
Table 9.4 Additional wastewater tariffs for non-domestic with high pollution content
Table 9.5 Demand management tools to achieve urban water security
Table 9.6 Barriers to further urban water security
Chapter 10
Table 10.1 Denver Water’s infrastructure
Table 10.2 Total retail treated water use by category
Table 10.3 Fixed water charges
Table 10.4 Single-family treated water charges
Table 10.5 Multifamily treated water charges
Table 10.6 All other (non-residential) treated water charges
Table 10.7 Demand management tools to achieve urban water security
Table 10.8 Barriers to further urban water security
Chapter 11
Table 11.1 Tariff for water flow
Table 11.2 Demand management tools to achieve urban water security
Table 11.3 Barriers to further urban water security
Chapter 12
Table 12.1 Fixed charges per annum
Table 12.2 Demand management tools to achieve urban water security
Table 12.3 Barriers to further urban water security
Chapter 13
Table 13.1 Demand and supply for water resources
Table 13.2 Pricing of water
Table 13.3 Demand management tools to achieve urban water security
Table 13.4 Barriers to further urban water security
Chapter 14
Table 14.1 Demand for water per customer category
Table 14.2 Metric water rates
Table 14.3 Progress towards universal metering
Table 14.4 Water main breaks per 100 kilometres of water distribution
Table 14.5 Demand management tools to achieve urban water security
Table 14.6 Barriers to further urban water security
Chapter 15
Table 15.1 Vancouver water use by sector
Table 15.2 Projected changes in climate for Vancouver
Table 15.3 Metered seasonal rates
Table 15.4 Metered sewer rates
Table 15.5 Flat utility rates: water and sewer annual flat rates
Table 15.6 Water loss reduction programmes
Table 15.7 Demand management tools to achieve urban water security
Table 15.8 Barriers to further urban water security
List of Illustrations
Chapter 02
Figure 2.1 Elements of water security.
Figure 2.2 Risk management framework to create or enhance resiliency of the water system.
Chapter 04
Figure 4.1 Benefits of demand management (ECONOMIC AND SOCIAL RESEARCH COUNCIL. 2008.
Behavioural change and water efficiency
. Available: http://webarchive.nationalarchives.gov.uk/20080821115857/http://esrc.ac.uk/ESRCInfoCentre/about/CI/events/esrcseminar/BehaviouralChangeandWaterEfficiency.aspx?ComponentId=25751&SourcePageId=6066 (accessed 9 May 2016)).
Chapter 05
Figure 5.1 The transition ‘s’ curve.
Figure 5.2 Transition management cycle.
Chapter 07
Figure 7.1 Drivers of water security in Amsterdam.
Chapter 08
Figure 8.1 Drivers of water security in Berlin.
Figure 8.2 Source protection of groundwater supplies.
Chapter 09
Figure 9.1 Evolving drivers of water security in Copenhagen.
Chapter 10
Figure 10.1 Residential rebates for water-efficient devices.
Chapter 13
Figure 13.1 Singapore’s four national taps.
Guide
Cover
Table of Contents
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Challenges in Water Management Series
Editor:
Justin TaberhamIndependent Consultant and Environmental Advisor, London, UK
Other titles in the series:
Water Resources: A New Management Architecture
Michael Norton, Sandra Ryan and Alexander Lane2017ISBN: 978-1-118-79390-9
URBAN WATER SECURITY
ROBERT C. BREARS
This edition first published 2017 © 2017 by John Wiley & Sons, Ltd
Registered OfficeJohn Wiley & Sons, Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK
Editorial Offices9600 Garsington Road, Oxford, OX4 2DQ, UKThe Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK111 River Street, Hoboken, NJ 07030-5774, USA
For details of our global editorial offices, for customer services and for information about how to apply for permission to reuse the copyright material in this book please see our website at www.wiley.com/wiley-blackwell.
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All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by the UK Copyright, Designs and Patents Act 1988, without the prior permission of the publisher.
Designations used by companies to distinguish their products are often claimed as trademarks. All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners. The publisher is not associated with any product or vendor mentioned in this book.
Limit of Liability/Disclaimer of Warranty: While the publisher and author(s) have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. It is sold on the understanding that the publisher is not engaged in rendering professional services and neither the publisher nor the author shall be liable for damages arising herefrom. If professional advice or other expert assistance is required, the services of a competent professional should be sought.
Library of Congress Cataloging-in-Publication data applied for
ISBN: 9781119131724
A catalogue record for this book is available from the British Library.
Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books.
Cover image: © Peter Zelei images/Gettyimages
Series Editor Foreword – Challenges in Water Management
The World Bank in 2014 noted:
Water is one of the most basic human needs. With impacts on agriculture, education, energy, health, gender equity, and livelihood, water management underlies the most basic development challenges. Water is under unprecedented pressures as growing populations and economies demand more of it. Practically every development challenge of the 21st century – food security, managing rapid urbanization, energy security, environmental protection, adapting to climate change – requires urgent attention to water resources management.
Yet already, groundwater is being depleted faster than it is being replenished and worsening water quality degrades the environment and adds to costs. The pressures on water resources are expected to worsen because of climate change. There is ample evidence that climate change will increase hydrologic variability, resulting in extreme weather events such as droughts, floods, and major storms. It will continue to have a profound impact on economies, health, lives, and livelihoods. The poorest people will suffer the most.
It is clear that there are numerous challenges in water management in the twenty-first century. In the twentieth century, most elements of water management had their own distinct set of organisations, skill sets, preferred approaches and professionals. The overlying issue of industrial pollution of water resources was managed from a ‘point source’ perspective.
However, it has become accepted that water management has to be seen from a holistic viewpoint and managed in an integrated manner. Our current key challenges include the following:
The impact of climate change on water management, its many facets and challenges – extreme weather, developing resilience, storm water management, future development and risks to infrastructure
Implementing river basin/watershed/catchment management in a way that is effective and deliverable
Water management and food and energy security
The policy, legislation and regulatory framework that is required to rise to these challenges
Social aspects of water management – equitable use and allocation of water resources, the potential for ‘water wars’, stakeholder engagement, valuing water and the ecosystems that depend upon it
This series highlights cutting-edge material in the global water management sector from a practitioner as well as an academic viewpoint. The issues covered in the series are of critical interest to advanced-level undergraduates and masters students as well as industry, investors and the media.
Justin Taberham, CEnvSeries Editorwww.justintaberham.com
Acknowledgements
I wish to say a big thank you to all the people who took time out of their busy schedules to sit down for an interview as well as provide any supplementary material. Without your help this book would not have been possible. Specifically I wish to thank Jan Peter van der Hoek (Waternet); Jens Feddern and Joachim Jeske (Berliner Wasserbetriebe); Allan Broløs and Charlotte Storm (HOFOR); Marc Waage, Greg Fisher and Melissa Elliot (Denver Water); Christian Guenner (Hamburg Wasser); David Grantham, Karen Simpson, Paul Rutter and Rosie Rand (Thames Water); Wai Cheng Wong and Gayathri Kalyanaraman (PUB); Lisa Botticella (Toronto Water) and Jennifer Bailey (Waterworks Utility). Finally, I wish to thank mum who has a great interest in the environment and water and has supported me in this journey of writing the book.
Introduction
In the twenty-first century, the world will see an unprecedented migration of people moving from rural to urban areas: In 2012, human civilisation reached a milestone with 50 percent of the world’s population living in urban settings. This is projected to reach 70 percent by 2050. With global demand for water projected to outstrip supply by 40 percent in 2030, cities will likely face water insecurity as a result of climate change and the various impacts of urbanisation.
Traditionally, urban water managers facing increased demand alongside varying levels of supplies have relied on large-scale, supply-side infrastructural projects, such as dams and reservoirs, to meet increased demands for water; however, these projects are environmentally, economically and politically costly. Environmental costs include disruptions of waterways that support aquatic ecosystems, while economic costs stem primarily from a reliance on more distant water supplies often of inferior quality. This not only increases the costs of transportation but also the cost of treatment. Furthermore, with the vast majority of water resources being transboundary, supply-side projects can create political tensions due to water crossing intra- and interstate administrative and political boundaries. As such, cities need to transition from supply-side to demand-side management to achieve urban water security.
Integrated urban water management (IUWM) recognises actions that achieve urban water security extend beyond improving water quality and managing quantity. In particular, IUWM integrates the elements of the urban water cycle (water supply, sanitation, stormwater management and waste management) into both the city’s urban development process and the management of the river basin in which the city is located for the purpose of maximising water’s many environmental, economic and social benefits equitably. IUWM activities to maximise these benefits include: improving water supply and consumption efficiency; ensuring adequate drinking water quality and wastewater treatment; improving economic efficiency of services to sustain operations and investments for water, wastewater and stormwater management; utilising alternative water sources; engaging communities in the decision-making process of water resources management; establishing and promoting water conservation programmes; and supporting capacity development of personnel and institutions that engage in IUWM.
In IUWM, demand management is the process by which improved provisions of existing water supplies are developed. In particular, demand management promotes water conservation during times of both normal and atypical conditions through changes in practices, culture and people’s attitudes towards water resources. Demand management involves communicating ideas, norms and innovative methods for water conservation across individuals and society; the purpose of demand management is to positively adapt society to reduce water consumption patterns and achieve urban water security. Demand management instruments can be divided into regulatory and technological instruments or communication and information instruments. Regulatory and technological instruments include the pricing of water, waste and stormwater to encourage water conservation as well as ensuring the efficient distribution of water. Communication and information instruments include education of young people, public awareness campaigns to encourage water conservation as well as encouraging the installation of water-efficient technologies, such as tap inserts, to reduce water consumption. The book is case study led and provides new research on the human dimensions of IUWM. In particular, it contains nine in-depth case studies of leading developed cities of differing climates, incomes and lifestyles from around the world that have used demand management tools to modify the attitudes and behaviour of water users in an attempt to achieve urban water security. Data for each case study is collected from interviews conducted with each city’s respective water utility along with primary documents. The nine cities are Amsterdam, Berlin, Copenhagen, Denver, Hamburg, London, Singapore, Toronto and Vancouver. Each city scores highly on the Siemens Green City Index for water management. The Green City Index is a research project conducted by the Economist Intelligence Unit (EIU) and sponsored by Siemens. Each city is selected as a case study for the following reasons. Amsterdam is a city attracting sustainability-related companies and investments and so is attempting to manage its resources wisely while Berlin has a history of managing its water in a closed system. Copenhagen uses a variety of demand management tools to promote water conservation due to scarcity of good quality water: the majority of the city’s groundwater is contaminated from agricultural and industrial production. Denver, since facing a drought in 2002, has been using demand management tools to reduce average per capita water consumption in order to increase the city’s resilience to future droughts. Hamburg has a history of relying on imported water but faces population growth challenges. Similarly, London has implemented demand management efforts in response to demand outstripping supply due to rapid population growth, along with a changing climate. Singapore has a limited surface area to collect surface water and has no groundwater supplies; hence, the city state imports nearly all of its water from neighbouring Malaysia. To reduce the country’s dependency on imported water, the city has implemented aggressive water conservation campaigns in an attempt to achieve urban water security. Toronto, despite being located by the Great Lakes, has implemented water conservation efforts in response to the city government requiring its utilities to be sustainable, both environmentally and financially. Finally, Vancouver is implementing demand management strategies to ensure the city does not have to expand its storage capacity to meet rising demand.
This book will introduce readers to the transition management framework that guides cities and their transitions towards urban water security through the use of demand management strategies. A transition in IUWM is a well-planned, coordinated transformative shift from one water system to another, over a long period of time, where a water system comprises physical and technological infrastructure, cultural/political meanings and societal users. In a water system, society is both a component of the water system and a significant agent of change in the system, both physically (change in processes of the hydrological cycle) and biologically (change in the sum of all aquatic and riparian organisms and their associated ecosystems). In IUWM, transitions to new water systems are triggered by changes in the external environment of the system, leading to it being inefficient, ineffective or inadequate in fulfilling its societal function: the main drivers of water insecurity are rapid population and economic growth, increased demand for food and energy and climate change. In transitions towards urban water security, cities set a target water consumption level to achieve (per capita litres/day, for example) with the baseline for comparison being current levels of water consumption and select a portfolio of demand management tools to promote the better use of existing water supplies before plans are made to further increase supply. Overall, transitions in IUWM involve an iterative, long-term and continuous process of influencing people’s beliefs and practices to achieve urban water security.
The importance of this book is that in IUWM our understanding of the social, economic and political dimensions of demand for water lags significantly behind engineering and physical science knowledge on the supply of urban water resources. As such, little has been written on the actual processes that enable the application of IUWM; therefore, it is difficult to demonstrate or compare successes across cities in managing urban water sustainably. This is despite the fact it is human attitudes and behaviour that determines the actual amount of water that needs supplying. More specifically, the emphasis on engineering, scientific and technological solutions is no longer sufficient to deal with the numerous problems and uncertainties of increasing demand and climate change on water resources. Therefore, it is critical that human dimensions are incorporated into the managing of urban water, as the perspective of society is crucial for the success or failure of any water management strategy. Nevertheless, the concept of IUWM for addressing water scarcity is changing only slowly from an emphasis on science and technology towards solutions that incorporate cultural and behavioural change. This book presents new research on the human dimensions of IUWM. In particular, the book is case study led containing nine case studies on how leading developed cities from around the world have used demand management strategies (involving regulatory and technological and information and communication instruments) to modify the attitudes and behaviour of water users in an attempt to achieve urban water security. Each case study is written from the perspective of the water utility with input from each city’s respective water utility representative.
The book’s chapter synopsis is as follows:
Chapter 1
provides a ‘Water 101’ for readers to understand what exactly constitutes water and how the quality and quantity of water can vary naturally. The chapter will then describe the impacts of urbanisation on water quality and quantity.
Chapter 2
defines what water security is and the challenges to achieving urban water security. These challenges include rapid economic and population growth, urbanisation and rising demand for energy and food as well as climate change.
Chapter 3
defines what sustainability and sustainable development is before discussing the differing approaches to sustainability. The chapter introduces sustainable water management frameworks to achieve water security and then discusses how IUWM can achieve urban water security by balancing demand for water with supply.
Chapter 4
first discusses the purpose of demand management strategies before discussing the types of demand management strategies available to urban water managers. The chapter then discusses demand management tools available to water managers in transitions towards urban water security.
Chapter 5
provides readers with a definition of a transition before discussing types of transitions, how they occur over and the various drivers and forces of transitions. The chapter then discusses how transitions can be managed.
Chapter 6
discusses transitions in the context of managing natural resources sustainably. In particular, the chapter discusses transitions in the context of climate change and natural resource scarcity before introducing readers to transitions towards the sustainable management of water to achieve urban water security.
Chapter 7
provides readers with a case study on Amsterdam transitioning towards urban water security through demand management.
Chapter 8
provides readers with a case study on Berlin transitioning towards urban water security through demand management.
Chapter 9
provides readers with a case study on Copenhagen transitioning towards urban water security through demand management.
Chapter 10
provides readers with a case study on Denver transitioning towards urban water security through demand management.
Chapter 11
provides readers with a case study on Hamburg transitioning towards urban water security through demand management.
Chapter 12
provides readers with a case study on London transitioning towards urban water security through demand management.
Chapter 13
provides readers with a case study on Singapore transitioning towards urban water security through demand management.
Chapter 14
provides readers with a case study on Toronto transitioning towards urban water security through demand management.
Chapter 15
provides readers with a case study on Vancouver transitioning towards urban water security through demand management.
Chapter 16
provides readers with a series of best practices and lessons learnt from the selected case studies of water utilities implementing demand management strategies in an attempt to achieve urban water security. The chapter then provides readers with a range of recommendations to achieve further urban water security.
1Water 101
Introduction
Before we can manage water sustainably to achieve water security – in the face of global challenges including rapid economic and population growth, rising demand for energy and food and climate change impacting the availability of water resources – we need to understand what is water and its natural variations in terms of quantity and quality. This chapter will first describe the physical properties of water, before discussing the Earth’s hydrological cycle. The chapter will then discuss natural variations to water quantity and water quality before finally providing readers with an overview of the impacts of urbanisation on water resources.
1.1 What is water?
On Earth, 97.5 percent of all water is saltwater with only 2.5 percent in the form of freshwater. Of this 2.5 percent, 70 percent is locked up in ice or permanent snow cover in mountainous regions and the Antarctic and Arctic regions, while 29.7 percent is stored below the ground (groundwater). Surface water, including rivers and lakes, comprise the remaining 0.3 percent of freshwater resources available.1
A water molecule is made up of two hydrogen atoms bonded to a single oxygen atom. The connection between atoms is through covalent bonding: the sharing of an electron from each atom to give a stable pair. In the water molecule structure, the hydrogen atoms are not arranged around the oxygen atom in a straight line; instead there is an angle of approximately 105° between the hydrogen atoms.2 The hydrogen atoms are positive and so do not attract one another, while the oxygen atom has two non-bonding electron pairs that repulse the two hydrogen atoms.
Water molecules are described as bipolar because there is a positive and negative side of the molecule. This enables water molecules to bond with one another; this is known as hydrogen bonding. In hydrogen bonding, the positive side of the water molecule (the hydrogen side) is attracted to the negative side (the oxygen side) of another water molecule, and a weak hydrogen bond is formed.3 The hydrogen bonding of water molecules is responsible for a number of water’s properties. For instance, based on water’s molecular weight (MW = 20), water should evaporate and become a gas at room temperature, given that CO2(MW = 44), O2(MW = 32), CO(MW = 28), N2(MW = 28), CH4(MW = 18) and H2(MW = 2) are all gases at room temperature. The reason why water does not evaporate at room temperature is due to water’s high specific heat capacity (a temperature increase is effectively an increase in the motion of molecules and atoms comprising the substance). When water is heated, it causes a movement of water molecules – breaking of the hydrogen bonds. However, due to water’s cohesiveness, water molecules have a high resistance to increasing their motion. Therefore, it requires a lot of energy to break the hydrogen bonds. As such, water does not evaporate easily. This high heat capacity means water is resistant to radical swings in temperature which is taken advantage of by organisms. Other properties of water include adhesiveness – water molecules are attracted to other substances such as chemicals, minerals and nutrients; solvency – water is a universal solvent as it can dissolve more substances than any other liquid on Earth and uniqueness – water is unique as its solid form (ice) is less dense than liquid water, and it can change from ice to water vapour without first becoming a liquid.4
1.2 Hydrological cycle
The hydrological cycle is the continuous movement of water in all its phases: liquid (precipitation), solid (ice) and gaseous (evaporation) forms. Because water is indestructible, the total quantity of water in the cycle does not diminish as water changes from vapour to liquid or solid and back again. In this cycle, evaporation from oceans (505 000 cubic kilometres) exceeds the 458 000 cubic kilometres of precipitation that falls on them. Meanwhile, 119 000 cubic kilometres of precipitation falls on land, which comprises one third of the Earth’s surface, and 72 000 cubic kilometres returns through evaporation to the atmosphere. The difference (47 000 cubic kilometres) is either ground or surface water that eventually returns to the ocean.5 The average amount of time a water molecule remains in a particular part of the hydrological cycle is known as its residence time. Streams and rivers usually have residence times of only days or months, while lakes and inland seas have residence times of years to decades. In comparison, oceans and groundwater systems have residence times of 3000–5000 years (Table 1.1).6
Table 1.1 Principal residence times of the global water stores
Compartment
Volume (1000 cubic kilometres)
Percent
Mean residence time (years)
Oceans
1 370 000
93.943
3000
Groundwater
60 000
4.114
5000
Actively exchanging groundwater
4 000
0.274
300
Glaciers and ice caps
24 000
1.646
8600
Lakes/inland seas
230
0.016
10
Soil water
82
0.006
1
Atmospheric vapour
14
0.001
0.027
Rivers
1.2
0.0001
0.032
CLOSS, G., DOWNES, B. J. & BOULTON, A. J. 2004. Freshwater Ecology: A Scientific Introduction. Malden, MA: Wiley-Blackwell
The hydrological cycle contains four key components: precipitation, runoff, evaporation and groundwater storage.
1.2.1 Precipitation
Atmospheric vapour, which results in precipitation in both liquid (rainfall) and solid (snow) forms, accounts for less than 0.001 percent of the world’s total water; however, due to its low residence times in the atmosphere, it is one of the main drivers of the hydrological cycle.7
Precipitation occurs when a body of moist air is cooled sufficiently for it to become saturated. Air can be cooled by a meeting of air masses of differing temperatures or by coming into contact with cold objects such as land surfaces. However, the most important cooling mechanism is the uplifting of air: as warm air rises, its pressure decreases while it expands and cools.8 This cooling reduces the air’s ability to hold water vapour and condensation forms. Condensation is composed of minute particles floating in the atmosphere, providing a surface for water vapour to condense into liquid water. Water or ice droplets formed around condensation particles are usually too small to fall directly to the ground as precipitation due to the upwards draught within the cloud being greater than the gravitational forces pulling the droplets down. In order to have a large enough mass to fall, raindrops grow through collision and coalescence. In this process, raindrops collide and join together (coalesce) to form larger droplets that collide with many other raindrops before falling towards the surface as precipitation. Whether precipitation is rain or snow depends on the warmth of the clouds. In warm clouds temperatures are above freezing point, and water droplets grow through collision (the coalescence process) to form rain. In cold clouds temperatures are below freezing point. These clouds contain ice crystals and supercooled water that is liquid water chilled below its freezing point without it becoming solid. In these clouds precipitation is in the form of snow.9
There are three types of precipitation: frontal and cyclonic, convectional and orographic precipitation. Frontal precipitation occurs in the narrow boundaries or fronts between air masses of large-scale weather systems. In this system, warm moist air is forced to rise up and over a wedge of colder, dense air. There are both warm and cold fronts each distinguished by the resulting precipitation: cold fronts have steep frontal surface slopes causing rapid lifting of warm air, resulting in heavy rain over a short duration, while warm frontal surfaces are much less steep, causing gradual lifting and cooling of air, leading to less intense rainfall but over a longer duration.10 In cyclonic systems, there is a convergence and rotation of uplifting air. In the northern hemisphere, cyclonic systems rotate anticlockwise and in the southern hemisphere clockwise. Above and below the tropics in the northern and southern hemispheres, cyclonic systems usually have a weak vertical motion, resulting in moderate rain intensities for long durations, while in the tropics, because of greater heating of the air, there is more intense precipitation but of a shorter duration.11 Convectional precipitation happens when the ground surface of a landmass causes warming of the air: as the warm air rises, it cools down and condenses, leading to localised, intense precipitation of a short duration. As this type of precipitation is dependent on the heat of the landmass, it is most common over warm continental interiors such as Australia and the United States. However, this type of precipitation does occur over tropical oceans with slow-moving convective systems producing significant amounts of rainfall. It is common for clusters of thunderstorm cells to be embedded inside convective systems, which commonly leads to flooding events.12 Orographic precipitation is the result of moist air passing over land barriers such as mountain ranges or islands in the ocean. The South Island of New Zealand is an example of orographic precipitation: the warm moist air off the Tasman Sea reaches the West Coast of the South Island, and as it starts to lift over the Southern Alps, the warm moist air cools and condenses, producing significant rainfall on the West Coast, while on the leeward side the air descends and warms up resulting in low levels of cloud and rainfall.13
1.2.2 Runoff
Runoff, or streamflow, is the gravitational movement of water in channels. A channel can be of any size ranging from small channels in soils with widths in the millimetres to channels of rivers. The unit of measurement for runoff is the cumec, with one cumec being one cubic metre of water per second. Streamflows react to rainfall events immediately indicating that part of the rainfall takes a rapid route to the stream channel. This is known as quick flow, while base flow is the continuity of flow even during periods of dry weather.14 Precipitation can arrive in stream channels through four ways: direct precipitation, overland flow, throughflow and groundwater flow. Direct precipitation comprises only a small amount of streamflow as channels usually occupy only a small percentage of the surrounding area; therefore, it is only during prolonged storms or precipitation events that direct precipitation contributes significantly to streamflow. Overland flow is water that instead of infiltrating soil flows over the ground surface into stream channels during periods of high-intensity rainfall. Overland flows usually occur on moderate to steep slopes in arid and semi-arid areas as these areas lack vegetation and so have dry, compact soil.15 Throughflow is all the water that infiltrates the soil surface and moves laterally towards a stream channel. This type of flow occurs during periods of prolonged or heavy rainfall when water enters the upper part of the soil profile more rapidly than it can drain vertically. Finally, groundwater flow is water that has percolated through the soil layer to the underlying groundwater and from there into the stream channel.16
1.2.3 Evaporation
Evaporation is the transferral of liquid water into a gaseous state followed by its diffusion into the atmosphere. The presence or lack of water at the surface provides the distinctions in definitions for evaporation.17 For instance, open water evaporation (E) occurs above a body of water such as a lake, stream or ocean. Potential evaporation (PE) is evaporation that would occur if the water supply was unrestricted, while actual evaporation (AE) is the quantity of water that is actually removed from a surface due to evaporation.
Evaporation over a land surface occurs two ways, either as actual evaporation from the soil or transpiration from plants. Transpiration occurs as part of photosynthesis and respiration and is controlled by the plant leaf’s stomata opening and closing.18 The main source of energy for evaporation is the sun. The term used to describe the amount of energy received from the sun at the surface is net radiation (Q*), and its calculation is
where QS is sensible heat, the heat we feel as warmth; QL is latent heat and is the heat absorbed or released during water’s phase change from ice to liquid water or liquid water to water vapour (there is a negative flux (when energy is absorbed) when water moves from liquid to gas and a positive flux when gas is converted to liquid) and QG is solid heat flux and is the heat released from the soil that has previously been stored within the soil.19
1.2.4 Groundwater
Below the Earth’s surface, water can be divided into two zones – unsaturated and saturated. In the unsaturated zone, water is referred to as soil water and occurs above the water table, while the saturated zone is referred to as groundwater and occurs beneath the water table. In the unsaturated zone, the majority of water is held in soil that is composed of solid particles (minerals and organic matter) and air. The infiltration rate is used to determine how much water enters the soil over a specific period of time. The rate is dependent on the current water content of the soil and the soil’s ability to transmit water. For instance, soil that has high moisture content will have a low infiltration rate because water has already filled voids between the soil’s solid particles.20
Once water has infiltrated the unsaturated zone, it percolates down through the water table to become groundwater. Groundwater can be found at depths of 750 metres below the surface. It is estimated that the volume stored as groundwater is equivalent to a layer of water approximately 55 metres deep spread over the entire Earth’s landmass.21 Most groundwater is in motion; however, unlike stream and river flows, groundwater moves extremely slow at rates of centimetres per day or metres per year with the actual rate dependent on the nature of the rock and sediment it passes through. Porosity is the percentage of the total volume of a body of rock that contains open spaces (pores). Therefore, porosity determines the amount of water rocks can contain, while porosity in sediments is dependent on the size and shape of the rock particles it contains and the compactness of their arrangement.22 Meanwhile, permeability is the measure of how easily a solid allows fluid to pass through. Rocks with a very low porosity are likely to have low permeability; however, rocks with high porosity does not mean they have high permeability. Instead, it is the size of the pores, how well they are connected and how straight the path is for water to flow through the porous material that determines the permeability of a rock or sediment.23
An aquifer is a body of highly permeable rock, typically gravel and sand, that can store water and yield sufficient quantities to supply wells, while an aquitard is a geological formation that transmits water at a much slower rate (aquitards are usually defined as a formation that confines the flow over an aquifer, while the term aquifuge is sometimes used to define a completely impermeable rock formation).24 There are two types of aquifers: confined and unconfined. A confined aquifer has a boundary (aquitard) above and below it that constricts the water into a confined area. Geological formations are usually the most common form of confined aquifers because they often occur as layers, and so the flow of water is restricted vertically but not horizontally.25 Water in confined aquifers is normally under pressure: when it is intersected by a borehole, it will rise up higher than the restrictive boundary. If the water rises to the surface, then it is known as an artesian well. Unconfined aquifers have no boundaries above, and so the water table is free to rise and fall depending on the amount of water in the aquifer.
The movement of groundwater can be described by Darcy’s law: Henry Darcy was a nineteenth-century French engineer who conducted observations on the characteristics of water flowing through sand. Darcy observed that the rate of flow through a porous medium was proportional to the hydraulic gradient. The most common formula for Darcy’s law is
The discharge (Q) from an aquifer equals the saturated hydraulic conductivity (ksat) multiplied by the cross-sectional area (A) multiplied by the hydraulic gradient (dh/dx). The negative sign is based on the fact that a fall in gradient is negative.26 The h term in the hydraulic gradient includes both the elevation and pressure head.
1.2.5 How old is water?
Determining the age of water is important for managing water resources as the age provides an indication of how quickly contaminated water can move towards an extraction zone and how long ago the contamination occurred. Because Darcy’s law cannot be used to determine the time it takes for water to reach a certain position, scientists instead conduct chemical analyses of dissolved substances in water to estimate its age. Carbon dating is common for testing the age of groundwater; however, it is problematic for young groundwater because it is only accurate if the sample is more than thousand years old.27 When testing old groundwater, carbon dating involves the analysis of the rate of decay of 14C in dissolved organic carbon. For younger groundwater, chemical dating of water involves determining the concentrations of material that humans have polluted the atmosphere with as these substances are dissolved in precipitation. The concentrations of these substances provide an estimate on the average age of the groundwater tested. Tritium is a radioactive isotope of hydrogen and was added to the atmosphere in large quantities as a result of hydrogen bomb tests in the 1960s and 1970s. Tritium concentrations in the atmosphere peaked in 1963 and have since declined to background levels.28 This particular radioactive isotope has a half-life of 12.3 years. Chlorofluorocarbon (CFC) compounds were commonly used in aerosols and refrigeration from the 1940s until they were banned in the 1990s. There are two CFC compounds: CFC-11 which has slowly declined since 1993 and CFC-12 which is still increasing but at a slower rate than before 1990. Sulphur hexafluoride is used for cooling and insulation mainly in electronics.
Another method for dating groundwater is analysing the ratio of the two isotopes of oxygen and/or the two isotopes of hydrogen found in water molecules. When water in the atmosphere condenses to form rain, there is a preferential concentration of heavy isotopes of hydrogen and oxygen in the water molecules.29 The heavy isotope of hydrogen is known as deuterium, and the heavy isotope of oxygen is 18O, and the colder the temperature at the time of condensation, the more enriched in deuterium and 18O the water sample is. Therefore, in climates with distinct seasons, the amount of deuterium and 18O will vary with each season, and so if the groundwater shows variations in deuterium and/or 18O, then it comprises relatively new rainfall. If there is little variation in deuterium and/or 18O, it indicates that there has been mixing of rainfall from both past summers and winters and therefore it is older.30
1.3 Natural variations to water quantity
There are two types of natural variations to water quantity: floods and droughts.
1.3.1 Floods
Floods occur when precipitation and runoff exceed the capacity of the river channel to carry the increased discharge. Flood frequencies are used when planning land use and infrastructure design and are calculated based on the history of a river, that is, how often it has flooded in the past and what the historical extremes of high precipitation are. Flood frequencies are expressed as a recurrence interval – the probability a particular flood will occur in a given year, for example, a hundred-year flood means there is a one in a hundred chance of it occurring in that particular year.31 Recurrence intervals are calculated using models that incorporate probable maximum precipitation (PMP) and probable maximum flood (PMF) calculations. The PMP is the finite limit for precipitation from a single storm event – the maximum depth (amount) of precipitation that is reasonably possible during a single storm event. Flood events have maximum extremes, and the PMF is the maximum surface water flow in a drainage area that could be expected from a PMP event.32 Floods can cause significant damage to buildings and properties with water washing away soils and crops, depositing sediments on land and property and be potentially fatal to humans and animals. Services are usually designed to resist floods or be serviceable against the following probabilities: important roads are designed to withstand a hundred-year floods, that is, a 1 percent chance of being overtopped in any given year; general roads and buildings are designed to withstand 50-year floods and less important roads, 20-year floods and storm water drains and pipes can be designed to withstand anything from a 2- to 20-year recurrence interval depending on the consequences over overtopping.33
1.3.2 Droughts
A drought is a period of unusually dry weather that persists over a long enough period of time to cause crop damage and/or water supply shortages. There are four different ways a drought can be defined. Meteorological droughts are a measured departure of precipitation from normal levels. Agricultural droughts refer to situations in which the amount of moisture in the soil no longer meets the needs of a particular crop. Hydrological droughts occur when surface and groundwater supplies are below normal levels. Socioeconomic droughts occur when physical water shortages begin to affect people.34,35 Droughts have varying levels of severity and return periods ranging from minor droughts that have a return period of 3–4 years, with slowing of growth in crops and pastures, to exceptional droughts with a return period of over 50 years with widespread crop and pasture loss and shortages of water in reservoirs (Table 1.2).
Table 1.2 Drought severity classification
Drought severity
Return period (years)
Description of possible impacts
Minor
3–4
Going into drought: short-term dryness slowing growth of crops or pastures
Coming out of drought: some lingering water deficits, pastures and crops not fully recovered
Moderate
5–9
Some damage to crops or pastures, streams, reservoirs or wells low, some water shortages, developing or imminent voluntary water restrictions requested
Severe
10–17
Crop or pasture losses likely, water shortages common, water restrictions imposed
Extreme
18–43
Major crop and pasture losses, widespread water shortages or restrictions
Exceptional
44+
Exceptional and widespread crop and pasture losses, shortages of water in reservoirs, streams and wells, creating water emergencies
SMITH, K. 2013. Environmental Hazards: Assessing Risk and Reducing Disaster. Hoboken, NJ: Taylor & Francis
Both the onset and end of droughts can be predicted by meteorologists observing precipitation patterns, soil moisture and streamflow data. To do this, meteorologists use a variety of indices that show deficits in precipitation over a period of time. One common tool is the Standardised Precipitation Index (SPI), which is a drought index based on the probability of an observed precipitation deficit occurring over a period of time ranging from 1 to 36 months. This variable timescale allows the index to describe drought conditions important for a range of meteorological, agricultural and hydrological applications. For example, soil moisture responds to a precipitation deficit immediately, while groundwater recharge and reservoir levels respond to precipitation deficits over many months. When describing the severity of droughts, the common index used is the Palmer Drought Severity Index. This index is a soil moisture algorithm that includes water storage and evapotranspiration levels with a scale ranging from ≥4.0 (extremely wet) to ≤ −4.0 (extreme drought) (Table 1.3).
Table 1.3 Palmer Drought Severity Index
Index
Description
4.0 or more
Extremely wet
3.0 to 3.99
Very wet
2.0 to 2.99
Moderately wet
1.0 to 1.99
Slightly wet
0.5 to 0.99
Incipient wet spell
0.49 to −0.49
Near normal
−0.5 to −0.99
Incipient dry spell
−1.0 to −1.99
Mild drought
−2.0 to −2.99
Moderate drought
−3.0 to −3.99
Severe drought
−4.0 or less
Extreme drought
CENTER, N. D. M. 2011. Comparison of major drought indices: Palmer Drought Severity Index [Online]. Available: http://www.drought.unl.edu/Planning/Monitoring/ComparisonofIndicesIntro/PDSI.aspx (accessed 10 May 2016)
1.4 Natural variations to water quality
Natural processes, including temperature, dissolved oxygen, pH, dissolved and suspended solids, turbidity, minerals, salinity, inorganic and organic chemicals and nutrients, affect the quality of water resources, specifically those discussed in the following text.
1.4.1 Temperature
Numerous physical, biological and chemical characteristics of water bodies are dependent on temperature. For instance, temperature is an important signal for spawning and migration. Sudden changes in temperature can be deadly for many species, and this usually occurs when deep, cold reservoir water is released into warm waterways.36,37 Temperature and dissolved oxygen are interdependent with warmer water holding less dissolved oxygen than colder water.
1.4.2 Dissolved oxygen
The presence or absence of dissolved oxygen in an aquatic ecosystem is one of the main determinants of whether organisms can live in that environment or not. Habitats that have a presence of oxygen are aerobic, while environments lacking dissolved oxygen are anaerobic.38 Dissolved oxygen levels are an indicator of water quality, with high concentration levels indicating high water quality. Oxygen however is only slightly soluble in water, and so there is high competition among aquatic organisms including bacteria for it. Dissolved oxygen is important for aquatic plants and animals as it allows species to breathe.39 When dissolved oxygen levels decrease below 5 milligram per litre, most sensitive organisms such as fish become stressed. If dissolved oxygen levels reach 1 milligram per litre, most species will not survive for more than a few hours.40
1.4.3 pH
The pH (p, power; H, hydrogen) level of a solution indicates its basicity or acidity, and it is defined as the negative logarithm of the hydrogen proton. Solutions with a pH less than 7 are said to be acidic, and those with a pH greater than 7 are basic or alkaline. Because the scale used to measure pH is logarithmic, each number represents a 10-fold change in the proton activity in a solution. Therefore, water with a pH of 4 is 10 times more acidic than that with a pH of 5.41 Different water bodies have differing pH levels, for instance, bogs and wetlands have acidic conditions with pH levels between 4 and 7, while water in rivers and lakes usually have pH levels between 4 and 9. Fish in water bodies usually have a narrow range of pH preference which varies greatly with specie. If the pH level of a water body changes to a level outside a fish’s preferred level, it can cause physical damage to skin, gills and eyes and eventually be fatal.42
1.4.4 Dissolved and suspended solids
As water passes through the soil column or over a surface, it dissolves substances attached to the soil particles. Water also dissolves particles in the air as it passes through the atmosphere in the form of rain. The amount of dissolved substances in a water sample is known as the total dissolved solids (TDS), and the higher the TDS, the more contaminated the water body is.43 TDS can also be used to estimate the conductivity of water. Conductivity is the amount of electricity that can be conducted by water, and the more the ions present, the higher the conductivity. Conductivity is correlated roughly to productivity because high-nutrient water has high conductivity.44
The measuring of total suspended solids (TSS) is another key measure of water quality. Rivers and streams carry suspended sediment as part of the natural erosion and sediment transport process in which sediment is deposited/picked up whenever river velocity decreases/increases. Soil particles are usually naturally carried as suspended load in water bodies. However, events such as landslides remove natural vegetation exposing bare soils. This can lead to excessive suspended loads in water bodies, increasing turbidity and decreasing water clarity.45 When sediment enters waterways and becomes suspended in the water body, it can severely damage the wildlife inhabiting the waterway. For instance, suspended sediment abrades and damages fish gills, increasing the risk of infection, disease and death. This leads to the loss of sediment-sensitive fish species. Suspended sediment also reduces sight distance for fish, reducing feeding efficiency. It also blocks light from entering the water, reducing photosynthesis in plants, leading to a reduction in aquatic food for many species. Deposited sediments also affect aquatic wildlife in waterways. For instance, it physically smothers benthic aquatic insect communities, which in turn reduces the amount of food available for species higher up the food chain. Deposited sediments also cover and destroy spawning grounds reducing fish populations. It also smothers fish eggs reducing their survival rates.46
1.4.5 Turbidity
Turbidity is the measure of clarity in water and is dependent on the amount of suspended matter in the water that reduces transmission of light. It is caused by suspended matter, including clay, silt and organic material, in the water creating cloudiness. High turbidity levels indicate that there are problems in the water body as turbidity blocks out sunlight needed for aquatic vegetation, impacting on the health of the aquatic ecosystem. Turbidity can also create water quality problems with toxic chemicals attaching themselves to suspended particles in water bodies.47 Because turbidity is a measure of the cloudiness of water, TSS and turbidity are directly related.48
1.4.6 Minerals
As water moves through the terrestrial system, materials containing minerals are dissolved or weathered from the land. Chemical weathering involves the dissolving of materials, while mechanical weathering reduces particles of matter to sizes that may be dissolved at a later stage. The total concentration of dissolved solids carrying minerals is inversely dependent on the amount of runoff – the greater the runoff, the less the time taken for water to dissolve the ions.49 The minerals that enter water bodies through chemical and mechanical weathering are important for plant and animal life as minerals are needed to control chemical reactions. The main minerals required in human diets include calcium, magnesium, phosphorus and potassium.
