Understand the effects of climate change on urban water and wastewater utilities with this collection of international scientific papers. Case studies and practical planning, mitigating and adapting information provided on greenhouse gases, energy use, and water supply and quality issues.
This title is co-published with the American Water Works Association.
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No Doubt About Climate Change and Its Implications for Water Suppliers
John E. Cromwell III, Joel B. Smith, and Robert S. Raucher
With the release of its Fourth Assessment Report: "Climate Change 2007," the Intergovernmental Panel on Climate Change (IPCC) has removed many doubts that previously shrouded both scientific and policy discussions of climate change. Mounting evidence about climate change and its effects made the situation much clearer to the scientists and government policy analysts from around the world who participated in a six-year process and arrived at the consensus presented in the report.
The World Meteorological Organization and the United Nations Environment Program (UNEP) established the IPCC in 1988. IPCC's role is to assess on a comprehensive, objective, open, and transparent basis the scientific, technical, and socioeconomic information relevant to understanding the scientific basis for the risk of human-induced climate change, its potential effects, and the options for adaptation and mitigation. The IPCC does not carry out research nor does it monitor climate-related data or other relevant parameters. Its assessment is based primarily on peer-reviewed and published scientific/technical literature.
A main activity of the IPCC is to provide at regular intervals an assessment of the state of knowledge on climate change. The First Assessment Report was completed in 1990, the second in 1995, and the third in 2001. Background reports are written by hundreds of scientists from around the world and are subject to extensive peer review. The "Summary for Policy Makers," typically a 20-page summary of the entire report that usually receives extensive attention in the press, is drafted by scientists but subject to approval by governments. In approving, adopting, and accepting reports, the IPCC makes every effort to reach consensus. If consensus cannot be reached, differing views are explained, and scientific and policy differences are distinguished. The IPCC's conclusions are not official until they have been accepted in a plenary meeting by the governments. Thus governments cannot ignore the conclusions of the IPCC because they have endorsed them.
The IPCC's adherence to scientific rigor and openness, coupled with the objective of articulating the best possible consensus views, might result in a slower and more cautious process of deliberation than some would prefer, but it also gives tremendous weight to IPCC findings when they are finally put forward as consensus statements.
During the six years since the release of the Third Assessment Report, the scientific evidence regarding climate change has become much more compelling. Accordingly, the Fourth Assessment Report (IPCC 2007a–c), released in 2007, contains consensus statements that are much more profound than those in previous reports. This article provides a brief review of some of the statements that pertain to water resources. These statements serve as a foundation from which to examine the implications of climate change for water suppliers.
IPCC REPORT REMOVES DOUBTS ABOUT CLIMATE CHANGE
The Fourth Assessment Report made headlines because the IPCC made very strong statements that left no room for doubt that global warming is producing long-term effects on natural systems and that anthropogenic sources are a likely cause. The summary statements that captured attention were:
Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level.
Most of the observed increase in global average temperatures since the mid-twentieth century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.
Observational evidence from all continents and most oceans shows that many natural systems are being affected by regional climate changes, particularly temperature increases.
A global assessment of data since 1970 has shown it is likely that anthropogenic warming has had a discernable influence on many physical and biological systems.
Anthropogenic warming and sea level rise would continue for centuries due to the time scales associated with climate processes and feedbacks, even if greenhouse gas concentrations were stabilized.
The first three of the preceding conclusions had been made in previous IPCC assessments, although with less confidence. This time the authors felt there was much stronger evidence. In addition, the conclusions tying human emissions to these impacts are new.
This IPCC assessment made it clear that continued warming is inevitable. Six scenarios of greenhouse gas emissions were considered. All would result in an acceleration of the rate at which global temperatures and sea levels are rising.
CONSEQUENCES FOR WATER RESOURCES
The Fourth Assessment Report states with "high confidence" that among the effects of global warming on hydrologic systems the following are presently occurring:
Increased run-off and earlier spring peak discharge in many glacier- and snow-fed rivers.
Warming of lakes and rivers in many regions, with affects (sic) on thermal structure and water quality.
Turning to the future, the Fourth Assessment Report makes the following predictions regarding water resources:
By mid-century, annual average river runoff and water availability are projected to increase by 10–40% at high latitudes and in some wet tropical areas, and to decrease by 10–30% over some dry regions at mid-latitudes and in the dry tropics, some of which are presently water stressed areas. In some places and in particular seasons, the changes differ from these annual figures.
Drought-affected areas will likely increase in extent. Heavy precipitation events, which are very likely to increase in frequency, will augment flood risk.
In the course of the century, water supplies stored in glaciers and snow cover are projected to decline, reducing water availability in regions supplied by meltwater from major mountain ranges, where more than one-sixth of the world population currently lives.
Coasts are projected to be exposed to increasing risks, including coastal erosion, due to climate change and sea level rise (0.2–0.6 m by 2100, and probably more).
The IPCC's more specific projections regarding future effects of global warming in North America include the following statements:
Warming in western mountains is projected to cause decreased snowpack, more winter flooding, and reduced summer flows, exacerbating competition for over-allocated water resources.
Disturbances from pests, diseases, and fire are projected to have increasing impacts on forests, with an extended period of high fire risk and large increases in area burned.
Moderate climate change in the early decades of the century is projected to increase aggregate yields of rain-fed agriculture by 5–20% (in mid- and high latitudes), but with important variability among regions. Major challenges are projected for crops that are near the warm end of their suitable range or depend on highly utilized water resources.
Cities that currently experience heat waves are expected to be further challenged by an increased number, intensity, and duration of heat waves during the course of the century, with potential for adverse health effects.
Coastal communities and habitats will be increasingly stressed by climate change impacts interacting with development and pollution. Population growth and the rising value of infrastructure in coastal areas increase vulnerability to climate variability and future climate change, with losses projected to increase if the intensity of tropical storms increases.
BOTTOM LINE IMPLICATIONS FOR WATER SUPPLIERS: ADAPTATION
The IPCC concludes adaptation will be necessary to address the effects of warming that are already unavoidable because of past emissions. A further 0.6°C (1°F) increase in global mean temperature — relative to temperatures during the period from 1980 to 1999 — is projected to occur by the end of the twenty-first century even if greenhouse gas concentrations remained at 2000 levels. The IPCC projects that the average rise in global temperatures could range from 1.1 to 6.4°C (about 2 to 12°F) by 2100 when examining a range of greenhouse gas emissions scenarios. Temperatures in the lower 48 states are expected to rise about a third more than the global average (Wigley 1999).
One of the simplest ways to envision many of the implications of global warming for water resources is to follow the logic of what happens when water is heated; global warming will basically accelerate the pace of the hydrologic cycle. Consistent with this, forecasters predict effects for water resources in the arid western regions of North America that are different from those in the humid eastern regions. Recent trends indicate that many of these effects are already happening.
In the West, warming effects may be seen most prominently in reduced water supply capacity. Snowpack will be smaller and melt earlier, altering the recharge of surface water and groundwater sources. In addition to less rainfall in this region, droughts are expected to be more extensive, with more heat waves and dry days, accompanied by increases in evaporation and greater irrigation demands. When precipitation does come, it is likely to be more intense. The combination of earlier snowmelt and more intense precipitation will likely increase turbidity, sedimentation, and the risk of flooding in many areas.
In the East, evidence of warming will primarily come in the form of increased rainfall frequency and intensity. The increased rainfall intensity will likely produce increased runoff and erosion with resulting increases in turbidity and sedimentation. Related effects include direct flood damage to water and wastewater facilities, loss of reservoir storage capacity for flood control and water supply, and increased sewage overflows during wet weather events.
In both the East and the West, the changes in temperature and hydrology will produce changes in watershed vegetation and aquatic ecosystems, which in turn will have implications for water suppliers. One result will be changes in watershed conditions because of wildfires and pest infestations, both of which are likely to increase. With increased water temperatures and shallower reservoirs (because of lower base flows and sedimentation), eutrophic conditions will be more prevalent. Rising sea levels will pose the risk of flood damage to coastal water and wastewater facilities in both the East and the West, especially as a result of more intense coastal storms. Rising sea level, coupled with lower base flows in freshwater sources because of altered recharge, will also increase the salinity of both coastal aquifers and brackish surface water sources.
The individual effects of climate change are staggering enough, but they will also have compound effects on water resources because of the interactions of natural and human systems. The bottom line in water supply planning has always been a matter of coping with variability. With the coming changes in climate, there will be a heightened need to respond to increased variability. Global warming will change the variability of many key parameters affecting the quantity and quality of water that would normally be available at specific times and places. In addition, the capability to store water in various forms and the demand for water will be changed.
Portfolio Approach to Planning Encouraged
Given the difficulty of predicting the magnitude of individual effects, let alone compound effects, IPCC and others have recommended that adaptation planning should employ a portfolio approach. This approach would maintain a maximum degree of flexibility within the portfolio by devising coping strategies to address an array of possible climate change scenarios that may affect the quantity and quality of supply sources, and the demands placed on them. Reevaluating the entire portfolio from source to tap with respect to adaptation strategies may seem like a daunting task; however, there are several guiding philosophies that can offer a pragmatic way to start.
A first practical step in evaluating the adaptation strategies is to conduct a "bottom-up" vulnerability assessment. Rather than starting with complex climate modeling, it is more tractable to begin with what a utility already knows about its own systems and water sources to determine the points at which water quality or water quantity changes would present a major challenge. This type of "threshold analysis" — based on a utility's current models and knowledge — can identify key climate-related tipping points (e.g., what reduction of instream flows would be most problematic given current supply strategies). Where possible, these thresholds could be verified through simulation modeling of altered operating regimes or through actual system tests. Once these thresholds are identified, climate expertise can be brought to bear in a focused manner to examine the potential process changes that could lead to these key tipping points being exceeded.
Once a water utility is equipped with a sense of its vulnerabilities, the IPCC and others recommend development of adaptation strategies by focusing first on ways to improve system flexibility and resiliency across the entire portfolio. In concert with this emphasis on flexibility, it may be prudent to adopt a step-wise approach that recognizes that irreversible choices or capital commitments might be easier to optimize within a portfolio as information improves over time.
TRIPLE BOTTOM LINE IMPLICATIONS: MITIGATION
In addressing water supply planning in the context of portfolio optimization, it is necessary to consider all of what should go into a sustainable solution. As has already happened in many water-short areas in both the East and West, it is possible to conceive of many ways to enhance the reliability of water resource management outcomes by essentially investing more energy to produce more water. But in evaluating these options, it must also be acknowledged that water utilities account for a significant share of total electric consumption and that power plant emissions account for a significant share of greenhouse gases. There is no doubt, therefore, that water utilities need to apply a broader "triple bottom line" discipline to the design of adaptation strategies in order to balance the cost and reliability of water supply against social and environmental consequences. The key to implementing this approach in practice will be to apply it to overall portfolio outcomes and not just to the individual project elements. There are several areas in which the need for this broader thinking arises most visibly.
As urban and suburban areas continue to grow, water resource managers have already devised elaborate portfolio strategies to tap into multiple sources of supply and to make strategic investments in capabilities to move and store water. To wring every last drop from available supplies, flexibility in transmission and storage operations has been taken to great extremes in some water-short areas in order to stay within complex constraints imposed by environmental withdrawal limits and seasonal and annual swings in water availability. Although flexibility in transmission and storage will be valuable in re-optimizing current schemes to meet future challenges, some system features designed for the current understanding of climatic variability may not be reversible or easily adaptable under altered operating regimes that were never envisioned. Operating flexibility needs to be an even more important design consideration for future system improvements.
Excerpted from "Climate Change and Water"
Copyright © 2010 American Water Works Association, IWA Publishing.
Excerpted by permission of IWA Publishing.
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Table of Contents
UNDERSTANDING THE IMPACT, 3,
1. No Doubt About Climate Change and Its Implications for Water suppliers, 5,
2. HOW should Water Utilities Prepare for Climate Change?, 13,
3. Mountain Water and Climate Change, 21,
4. Prevailing Water Demand Forecasting Practices and Implications for Evaluating the Effects of Climate Change, 41,
5. Impacts of Climate Change and Variability on source Water Quality of Lake Cachuma, California, 47,
6. The Climate Footprint and the Practical Application at Water Companies in the Netherlands, 55,
7. Climate Footprint and Mitigation Measures in the Dutch Water Sector, 73,
8. The Water Footprint of Bio-Energy, 81,
9. The Water — Energy — Climate Nexus — Systems Thinking and Virtuous Circles, 99,
10. Energy Use in Urban Water, 111,
11. WATERGY: Energy and Water Efficiency in Municipal Water Supply and Wastewater Treatment, 123,
12. Station Efficiency Reduces Greenhouse Gas Emissions, 137,
13. Climate Change — Mitigation Policy Issues, 145,
14. Climate Change Mitigation Strategies in the Water Sector in Developing Countries, 157,
15. Incorporating Climate Change in Water Planning, 173,
16. Climate Change and Water Utilities, 183,
17. Half Full or Half Empty? Either Way It's Time to Plan, 193,
18. Climate Change Is Real: How Can Utilities Cope with Potential Risks?, 199,
19. Planning Strategy in a Changing Climate, 205,
20. Climate Change: Charting a Water Course in an Uncertain Future, 215,
21. Implementation of Climate Adaptation and Mitigation Strategies for Drinking Water Production in the Netherlands, 227,
22. Meeting the Challenges of Climate Change: Singapore, 241,
23. Climate Change and Adaptation in southern California, 251,
24. Melbourne Water Climate Change study, 263,
25. Climate Change Impacts on Urban Drainage systems in Scandinavia, 277,