Moss, Richard H

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6WATER AND THE CHALLENGE OF LINKEDENVIRONMENTAL CHANGESRichard H. MossBattelle Pacific Northwest National LaboratoryHead, IPCC WorkGroup II, Technical Support UnitINTRODUCTIONWater is essential and precious, yet often undervaluedand wasted.  Its abundance and our long experience withmanaging its fluctuations can make us complacent aboutour ability to meet demands for this critical resource inthe future.  Do current and potential future conditionssupport the conclusion that water will be available in thequantities and quality needed for human development?This introduction raises some questions about currentconditions and future projections for water resourcesmanagement.  It lays down a challenge to those currentlyengaged in managing water resources:  to explore thecombinations of conditions and changes that would leadto potential problems for water supply systems in thefuture.  The point of such an exploration is not to dreamup problems where none may exist.  Rather it is toprepare for potential surprises resulting from theinteraction of population growth, increasing water use percapita, and environmental changes including climatechange, land-use change (including deforestation and lossof wetlands), land degradation, introduction of persistentorganic pollutants, and loss of biodiversity.  Given thestakes - continued adequate water supplies in someregions, and improvement to minimum standards inothers - there is value in the mental exercise ofchallenging our assumptions that incremental changes incurrent practices will enable us to cope with the range ofdemand and supply changes that we may encounter in thefuture.THE CHALLENGES OF TODAYFreshwater supplies are limited by the rate of thehydrological cycle, since they are created when sea waterevaporates and falls onto the Earth’s terrestrial surface asprecipitation.  This precipitation is absorbed into theground, where it provides moisture for plants andrecharges aquifers;  runs off into surface bodies of water,including rivers, lakes, streams, and wetlands;  or isstored as ice in glaciers and snow.  Fresh water can bereused many times - for drinking, cooking, cleaning,growing food, recreation, and disposal of wastes -depending on how it is managed.In places where poverty is not a major problem, water ismade available to human populations on a reliable basisby controlling and channeling water supplies.  Elaborateinter-connected systems of dikes, levees, canals, andreservoirs can store water when and where it is abundantand move it to other locations, to ensure availability intimes and places that it is in short supply.  This does notmean that relatively wealthy populations do not facewater resources-related challenges.  Even in thesecountries, migration and population growth are strainingwater resources in some regions.  In the United States, forexample, a number of locations (e.g., California andregions drawing on the Ogalala aquifer) are facing supplyshortages due to continued agricultural uses andincreasing demands for household and industrial use.Water quality problems abound even in regions wheresupply is not a problem.  The U.S. Army Corps ofEngineers reports that there are multiple indicators ofpoor water quality in many reservoirs and other waterbodies in the United States.  In some areas (e.g., LowerMississippi Valley Division), nearly all reservoirs showcontaminants in fish flesh (it is not uncommon for onesample to show traces of three or four differentpesticides), indicating significant concentrations ofmetals and other toxics in the water.  Urbanization clearlyis resulting in serious impacts to reservoir systems,especially sedimentation associated with constructionactivities.Unfortunately, the situation in regions where most peoplelive in poverty is much worse.  It has been estimated thatmore than one billion people do not have access toreliable supplies of safe water for domestic uses.7Although  these people  are dispersed throughout theglobe - reflecting sub-national variations in wateravailability and quality - the most severe water supplyand quality problems often are found in developingcountries.  Examples of unsustainable water uses in theseregions include over-pumping of aquifers (e.g., NorthAfrica, the Middle East, India, and Southeast Asia), anddiversion of river water leading to depletion of wetlandsand lakes (e.g., Aral Sea) and intrusion of sea water intodeltas and coastal aquifers (e.g., China, Vietnam,Bangladesh).  Because of the lack of adequate sanitationfacilities in many of these same locations, people oftenwithdraw water for consumption from the same waterbodies into which human, agricultural, and industrialwastes flow, leading to a widespread incidence of water-borne illnesses such as diarrhea.LINKED DEMOGRAPHIC, ECONOMIC, ANDENVIRONMENTAL TRENDS: SCENARIOS FORTHE FUTURENo one can say with any certainty whether waterresources will be available in adequate quantity andquality in the future.  It is within our influence, however,to help steer the situation in a positive direction.Certainly broad forces such as population growth - anissue with ramifications far broader than its impact onwater supply - will affect the availability of waterresources in a number of ways, such as increasingdemand and increasing population density in majorwatersheds.  These factors are important to consider but,in the context of water resources management, they aredifficult to steer.  Other factors, however, such as water-use policies and the design and maintenance ofinfrastructures, are more directly under the control ofwater resource managers and planners; it is thus helpfulto examine the sensitivity of water supply and demand tosuch factors under potential future conditions.  Due to the imprecision of quantitative predictions aboutfuture conditions, it is useful to examine potential futurechallenges for the water resources sector through theanalysis of several different scenarios.  These scenariosshould not attempt to constitute a single, “best guess”forecast of future conditions, but rather should exploredifferent trajectories and sets of choices that could lead tovarying conditions, reflecting the divergent startingpoints for water resources management in differentsectors and regions around the globe. Scenarios are animportant tool because they can help us to conceive ofsome of the choices that may shape future conditions, andto explore the implications of different strategies formanaging water resources.These scenarios should be based on an assessment of thecritical trends that will matter most in shaping futuresupply and demand for water resources.  The remainderof this introduction will review an initial list of the trendsthat could most affect water resources management andthat should thus be factored into the scenarios.PopulationPopulation growth could affect water resources byincreasing demands for water as well as by alteringconditions that influence the quantity and quality of watersupplies;  for example, land clearance practices, intensityof agriculture, and density of settlement in watersheds allaffect sedimentation and reservoir capacity.  A number ofstudies have calculated the effects of population growthon water resources, holding water resources constant - apotentially questionable assumption.  Based on UnitedNations population projections, the number of peopleliving in “water-scarce” countries (those where wateravailability falls below 1,000 cubic meters per capita peryear) could rise from 132 million in 1990 to between 650million and 900 million  in  2025, and  to approximately1-2.5 billion (roughly 13-20 percent of the projectedglobal population) by 2050.  A challenge for futureanalysts will be to develop improved projections of theeffects of population growth not only on water demands,but also on those factors that will affect water supply andquality.Land-Use Change, Including Deforestation and Loss ofWetlandsEcosystems, particularly forests, are being cleared anddegraded at rapid rates in many parts of the world,resulting in changes dramatic enough to be seen easily insatellite images.  One recent study estimates that only onefifth of the world’s original forests remain in a naturalstate.  Conversion of forests to agricultural systems orsuburban or urban environments reduces the land’sability to absorb and hold precipitation.  Converted areascan become more prone to flooding during rainy seasonsbecause of increased rates of runoff, and more vulnerableto water scarcity during dry periods.  Deforestation andother types of land conversion also increase rates of soilerosion, which contributes to sedimentation of reservoirsand leads to decreased water storage capacity.  Wetlands,which serve several important hydrological functions -including absorbing pollutants and wastes from runoff,stabilizing soils, and preventing massive runoff during8floods - also are undergoing rapid conversion.  It has beenestimated that more than half of the world’s wetlandshave disappeared since 1900, and that this trend willincrease, especially in developing countries, due toagricultural development.  The overall effect on waterresources will depend on how land-use patterns change inthe future, and how these changes affect the ability ofhuman management regimes to work in harmony withnatural processes to provide adequate supplies of highquality water for human uses.Land Degradation Roughly one fourth of the Earth’s land surface is used forproduction of food.  As use of these lands has intensifiedin order to increase production per unit of land, landdegradation has become an increasingly serious problem,particularly where poor land management practices havebeen followed.  It is estimated that erosion, salinization,compaction, and other forms of degradation affect 30percent of irrigated lands and an even higher percentageof rainfed agricultural lands.  These problems often areaccompanied by reduced water infiltration and increasedsoil erosion.  These conditions not only reduceagricultural productivity, but also lead to increasedpollution of surface waters as a result of both increasedrunoff of fertilizers and sediment loading of streams,rivers, lakes, and reservoirs.  A key question for thefuture is the extent to which land degradation willaccelerate or abate, and how it will affect water qualityand the condition of water management systems.Climate ChangeMuch has been written recently about changes in theEarth’s climate resulting from human activities,particularly the burning of fossil fuels.  The climatealready has warmed by about half a degree Centigradethis century, and is projected to warm another 1.0-3.5degrees C over the next century, assuming continuedincreases in atmospheric concentrations of greenhousegases.  These changes are projected to result in changesin the overall amount, frequency, intensity, and perhapsvariability of precipitation around the world.  Whileprojections of regional effects are uncertain, all globalclimate models show a tendency to mid-continentalwarming and drying resulting from increasedtemperatures and evapotranspiration.  Changes in thehydrological cycle would likely affect both water supplyand demand as well as water quality, presenting waterresources managers with a need to reexamine designcriteria, operating rules, and water allocation policies.  Afurther challenge will be to anticipate the potentialinteractions of climate change with other environmentaltrends, such as increased water pollutant loads resultingfrom urbanization and industrial development.Urbanization and Industrial DevelopmentSince 1950, the number of people living in cities hastripled - by 1990, it was estimated that nearly 43 percentof the world’s population lived in cities, and this numbercould rise to 60 percent by 2025.  Much of this growthhas occurred in very large cities in developing countries,where infrastructure for handling human and industrialwastes is lacking.  Indeed, water pollution fromindustrial, municipal, and agricultural sources presentsan extremely serious hazard to future water quality.Progress in controlling these pollution sources has beenmade in many developed nations over the past threedecades, but pollution problems are intensifying in mostdeveloping nations and remain high in the transitioneconomies of Russia and central Europe.  Pollutioncontrol in many human settlements in these regions isstill rudimentary or nonexistent: domestic sewage andindustrial effluents often are left to drain into urban riversand groundwater sources, making it more difficult toprovide clean water and basic sanitation services.  Someof the pollutants (e.g., dioxins, PCBs, and others)released from industries in these burgeoning cities, orused as pesticides in applications both within and outsideurban areas, have chemical structures that allow them topersist in the environment, resisting natural degradation.These can be carried in wastewater into lakes andreservoirs, where their concentrations increase -eventually accumulating in the fatty tissues of a widerange of organisms, including humans.  Some of thesecompounds have been shown to cause cancers and birthdefects.  It is unknown to what extent pollution problemswill worsen and increase the technical challenges andeconomic costs of purifying fresh water for humanconsumption.Ecosystem PreservationBecause humans appropriate only a fraction of globally-available water resources for their own direct use, itfrequently is assumed that the remaining water will bemore than adequate to maintain natural ecosystems,including aquatic systems.  In many regions, however,this is no longer the case, as increasing percentages ofsurface waters are diverted for human uses.  In someregions, such as south Florida, ecosystem maintenancecompetes directly for water with other uses such as9agriculture.  Even in areas where quantity of water is nota problem for maintenance of ecosystems, water qualityis being seriously affected.  Runoff from the applicationof agricultural chemicals and increasing concentrationsof untreated sewage and other pollutants are causing die-off of aquatic organisms, due to reduced dissolved oxygencontent and/or the spread of bacteria or other pathogensthat attack the endemic species.  Biodiversity infreshwater systems is particularly threatened by thesetrends because freshwater habitats are discontinuous andseparated by land barriers that make migration to newhabitats difficult.  A key issue for water resourcesmanagement is the extent to which it will be possible toanticipate “ecosystem needs” for fresh water and makethe tradeoffs with human consumption without disruptingeither ecological or social/economic systems.Policies and MeasuresIn many countries, the policies (e.g., taxes, subsidies, andregulations) that shape private decision making,development strategies, and resource-use patterns (andhence environmental conditions) hinder improvedmanagement of water resources.  Although increases inwater-use efficiency have been demonstrated in bothagriculture and industry, the failure to adopt andimplement more efficient water management practicesoften can be traced back to water management policies,particularly the underpricing of water.  Direct andindirect subsidies, especially for agricultural use,encourage the overuse of water and its diversion awayfrom higher value domestic or industrial uses.Administrative or market mechanisms can provideincentives for efficient use and can help finance theneeded infrastructure to expand services to new users.Important questions include the extent to which thepolicy and regulatory context of water resourcesmanagement has been improved, and how theseimprovements will affect the condition of infrastructureand management capability in the next 10-20 years.CONCLUSIONSMeeting the challenges of the next century will requirewater managers to think more creatively about thepotential to manage water demands and supplies, and tolook for opportunities for improving water managementsystems that also have benefits in other economic sectorsor to the environment.  In light of both environmentaland fiscal/technical constraints, water managers will needto think beyond traditional instruments (e.g., changes tomanagement of existing infrastructure, newinfrastructure, and promoting changes in water usepatterns), although these will be important tools.  Theywill need to design ways to integrate their work with thatof resources managers in other sectors, includingagriculture, forestry, ecological conservation, industry,and energy.  Developing approaches that build on theselinks and minimize the inherent tradeoffs among theseissues is a growing challenge for water management andpolicy development.Richard Moss currently heads the Technical SupportUnit for the Intergovernmental Panel on Climate Change(IPCC), Working Group II.  In this capacity, he serves aslead author or coordinator of a number of IPCC technicalpapers and special reports on subjects related toassessment of potential climate-change impacts ormitigation strategies.  He co-edited Climate Change1995: Impacts, Adaptation, and Mitigation, one of thethree volumes of the IPCC’s Second Assessment Report,which was published by Cambridge University Press, andhas written a number of other articles and scholarlypublications on global change.  Before taking up hiscurrent position, Richard served as programme officer ofthe International Geosphere-Biosphere Programme(IGBP) and Human Dimensions Programme (HDP) inStockholm, Sweden, where he edited an IGBP-HDPresearch report on land use and land-cover change andworked toward establishment of an IGBP-HDP coreresearch project on this topic.  He was also on the facultyof Princeton University from 1989-1991, where he servedas lecturer at the Woodrow Wilson School of Public andInternational Affairs.  In 1991, he received a two-yearCouncil on Foreign Relations (NY) International AffairsFellowship for work on international aspects of globalchange.  Richard received his B.A. in 1977 from CarletonCollege, Northfield, MN (Magna cum Laude, Phi BetaKappa); he earned his MPA in 1983 from PrincetonUniversity, (University Fellowship), and he received hisPh.D. from Princeton University, Woodrow WilsonSchool of Public and International Affairs (UniversityFellowship) in 1987.

Water and the Challenge of Linked Environmental Changes

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Water and the Challenge of Linked Environmental Changes

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