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Chapter 11 cc impact on water resources

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  • Climate change will lead to more precipitation - but also to more evaporation. In general, this acceleration of the hydrological cycle will result in a wetter world. The question is, how much of this wetness will end up where it is needed? Precipitation will probably increase in some areas and decline in others. Climate models are still unable to make precise regional predictions. In addition, the hydrological cycle is extremely complex: a change in precipitation may affect surface wetness, reflectivity, and vegetation, which then affect evapo-transpiration and cloud formation, which in turn affect precipitation. Meanwhile, the hydrological system is also responding to other human activities such as deforestation, urbanization, and the over-use of water supplies. Changing precipitation patterns will affect how much water can be captured. Several models suggest that downpours will become more intense. This would increase floods and runoff while reducing the ability of water to infiltrate the soil. Changes in seasonal patterns may affect the regional distribution of both ground and surface water supplies. The drier the climate, the more sensitive is the local hydrology. Relatively small changes in temperature and precipitation could cause relatively large changes in runoff. Arid and semi-arid regions will therefore be particularly sensitive to reduced rainfall and to increased evaporation and plant transpiration. High-latitude regions may see more runoff due to greater precipitation. Runoff would also be affected by a reduction in snowfall, deep snow, and glacier ice, particularly in the spring and summertime when it is traditionally used for hydroelectricity and agriculture. All climate change models show increased wintertime soil moisture in the high northern latitudes, with a reduction of moisture in some areas. Most models produce less soil moisture in summer in northern mid latitudes, including some important grain producing areas; these projections are more consistent for Europe than for North America. The effects on the tropics are harder to predict. Different climate models produce different results for the future intensity and distribution of tropical rainfall. Reservoirs and wells would be affected. Changes at the surface would influence the recharging of groundwater supplies and, in the longer term, aquifers. Water quality may also respond to changes in the amount and timing of precipitation. New patterns of runoff and evaporation will also affect natural ecosystems. Freshwater ecosystems will respond to altered flood regimes and water levels. Changes in water temperatures and in the thermal structure of fresh waters could affect the survival and growth of certain organisms, and the diversity and productivity of ecosystems. Changes in runoff, groundwater flows, and precipitation directly over lakes and streams would affect nutrients and dissolved organic oxygen, and therefore the quality and clarity of the water. Rising seas could invade coastal freshwater supplies. Coastal aquifers may be damaged by saline intrusion as salty groundwater rises. The movement of the salt-front up estuaries would affect freshwater pumping plants upriver. Reduced water supplies would place additional stress on people, agriculture, and the environment. Regional water supplies, particularly in developing countries, will come under many stresses in the 21st century. Climate change will exacerbate the stresses caused by pollution and by growing populations and economies. The most vulnerable regions are arid and semi-arid areas, some low-lying coasts, deltas, and small islands. Conflicts could be sparked by the additional pressures. The links among climate change, water availability, food production, population growth, and economic growth are many and complex. But climate change is likely to add to economic and political tensions, particularly in regions that already have scarce water resources. A number of important water systems are shared by two or more nations, and in several cases there have already been international conflicts. Improved water resource management can help to reduce vulnerabilities. New supplies must be developed and existing supplies used more efficiently. Long-term management strategies should include: regulations and technologies for directly controlling land and water use, incentives and taxes for indirectly affecting behavior, the construction of new reservoirs and pipelines to boost supplies, and improvements in water-management operations and institutions. Other adaptation measures can include removing levees to maintain flood plains, protecting waterside vegetation, restoring river channels to their natural form, and reducing water pollution.
  • Over 1 billion people don't have access to clean drinking water; more than 2 billion lack access to adequate sanitation; and millions die every year due to preventable water-related diseases. Water resources around the globe are threatened by climate change, misuse, and pollution. But there are solutions: we can provide for people's basic needs while protecting the environment by using innovative water efficiency and conservation strategies, community-scale projects, smart economics, and new technology. That 1.2 billion people lack access to clean water is surely one of the greatest development failures of the modern era. That as many as 5 million people – mainly children – die every year from preventable, water-related disease is surely one of the great tragedies of our time. Unfortunately, despite a growing recognition that more must be done to help those without clean water or adequate sanitation, a report by the Pacific Institute estimates that over 34 million people might perish in the next 20 years from water-related disease -- even if the United Nations “Millennium Development Goals,” which aim to cut the proportion of those without safe access by half, are met.The problem is not merely a lack of aid (although more money is needed) or a lack of technology. It is a failure of vision and will. According to many international water experts, hundreds of billions of dollars are needed to bring safe water to everyone who needs it. Since international water aid is so paltry, many of these experts claim that privatization of water services is the only way to help the poor.But many critics of this approach note that community-scale infrastructure and efficiency and conservation can bring basic water services to the millions who need it without breaking the bank. And many critics of the “gold-plated” approach argue that water privatization, although it can play some productive role, will never be able to bring water to the world’s poorest people.However, there are solutions to the global water crisis that don’t involve massive dams, large-scale infrastructure, and tens or hundreds of billions of dollars. First and foremost, we must use what the Pacific Institute calls “soft path” solutions to the global water crisis. Soft path solutions aim to improve the productivity of water rather than seek endless new supply; soft path solutions complement centrally-planned infrastructure with community scale projects; and soft path solutions involve stake-holders in key decisions so that water deals and projects protect the environment and the public interest.
  • Wigley (2004) has developed a statisticalsummary of the spatial distribution of precipitation change seen in scenarios generated byvarious climate models. Figure 21 displays these results in the form of normalized signalto-noise ratios, where noise represents scatter among model projections. In other words,at the red end of the spectrum, the models tend to agree on increased precipitation. Atthe opposite end, where the map is shaded in blue tones, they tend to agree on reducedprecipitation. However, in the middle of the color spectrum (corresponding to the greenand yellow-green tones), the various projections give differing results regarding whetherannual precipitation will increase or decrease. This suggests that mid-latitude areas suchas the continental U.S. and much of Europe and Asia face an especially uncertain futureregarding changes in average annual precipitation.Inter-model signal-to-noise ratios for annual-mean precipitation (mean precipitationchange per 1°C global-mean warming, averaged over 17 AOGCMs, divided by the inter-modelstandard deviation). This is a measure of both the sign and strength of the expected precipitationchange and the level of agreement between models. Values between –1 and +1 indicate considerableuncertainty in the expected change.
  • This means that the changes in rain rates, when it41Climate Change for Water Utilitiesrains, are at odds with the 1–2 percent per degree Celsius model estimates for totalrainfall amounts as discussed previously. The implication is that there must be a decreasein light and moderate rains, and/or a decrease in the frequency of rain events, as foundby Hennessey et al. (1997). Thus, the prospect may be for fewer but more intenserainfall – or snowfall – events.
  • A consistent prediction of climate models is that global warming will increase totalevaporation. Increases in surface temperature and higher wind speeds promote potentialevaporation, while the greatest change will likely result from an increase in the waterholdingcapacity of the atmosphereWhile potential evaporation will almost certainlyincrease with temperature, its impact on precipitation in specifi c regions remains uncertain.There are many balances and counter-balances in the atmosphere that aren’t fullyunderstood. For example, atmospheric moisture originating from actual evaporation overoceans may help offset, and possibly even lessen, potential evaporative pressures over land.Likewise, there are regional controls on evaporation. In humid regions where water is notlimiting and actual and potential evaporation are nearly equal, evaporation is constrainedby the water-holding capacity of air above the surface, so an increase in this capacity due towarming may have a large evaporative effect. In dry regions, other factors such as surfacewater availability, surface temperature and wind are more important determinants of actualevaporation. A reduction in summer soil water, for example, could lead to a reduction inthe rate of actual evaporative demands from a catchment despite an increase in potentialevaporation.While potential evaporation will almost certainlyincrease with temperature, its impact on precipitation in specifi c regions remains uncertain.There are many balances and counter-balances in the atmosphere that aren’t fullyunderstood. For example, atmospheric moisture originating from actual evaporation overoceans may help offset, and possibly even lessen, potential evaporative pressures over land.Likewise, there are regional controls on evaporation. In humid regions where water is notlimiting and actual and potential evaporation are nearly equal, evaporation is constrainedby the water-holding capacity of air above the surface, so an increase in this capacity due towarming may have a large evaporative effect. In dry regions, other factors such as surfacewater availability, surface temperature and wind are more important determinants of actualevaporation. A reduction in summer soil water, for example, could lead to a reduction inthe rate of actual evaporative demands from a catchment despite an increase in potentialevaporation.
  • A study by Arnell (2003) used several climate models to simulate futureclimate under differing emissions scenarios. The study linked these climate simulationsto a large-scale hydrological model to examine changes in annual average surface runoffby 2050 (Figure 23). The striking thing about this fi gure is the fact that all simulationsyield a global average increase in precipitation (not shown), but likewise exhibitsubstantial areas where there are large decreases in runoff. Thus, the global message ofincreased precipitation clearly does not readily translate into regional increases in wateravailability. In addition, the fact that these different simulations produce quite different regional impacts demonstrates the uncertainty related to climate projections. In NorthAmerica, for example, some models project much larger areas with reduced runoff thando other models.
  • It is very important to understand that natural variability will not go away. Anyprojected change in average annual runoff will occur “on top” of ongoing naturalvariability. In many cases, natural variability can be quite large compared to the changesprojected from global warming. Furthermore, relatively short instrumental records maynot provide an adequate picture of the full range of natural climatic variability. The workof several researchers who have developed proxy records for precipitation and streamfl owbased on tree rings and geological evidence provides a longer-term view.
  • The IPCC Working Group II (2001) Third Assessment Report identifi es sea level riseas one of the most important coastal impacts of global warming, and identifi es severalkey impacts. A number of these are particularly relevant for water utilities located incoastal areas, including: 1) lowland inundation and wetland displacement; 2) alteredtidal range in rivers and bays; 3) changes in sedimentation patterns; 4) severe stormsurgefl ooding; 5) saltwater intrusion into estuaries and freshwater aquifers; and 6)increased wind and rainfall damage in regions prone to tropical cyclones.These impacts are particularly likely to affect water utility infrastructure. Forexample, there could be impacts on water intakes located in transition areasbetween freshwater and saltwater interfaces of both surface and sub-surface systems.Sedimentation patterns in estuaries and deltas depend strongly on tidal patterns, stormsurges and fl ow conditions, whose changes could affect utility supplies.Saltwater intrusion into freshwater aquifers is already a problem in many coastalcommunities, primarily due to overdrafting of those groundwater supplies. Because ofthe higher density of saltwater, a rise in sea level could result in a disproportionate loss offreshwater aquifers in coastal zones due to the intrusion of the saltwater wedge.
  • At one extreme, heavy precipitation events may result in increased sediment andnon-point source pollutant loadings to watercourses. This may make water treatmentmore difficult. Floods, in particular, increase the risk of water source contamination fromsewage overflows, and runoff from agricultural land and urban areas. The location ofwater infrastructure, including both intakes and pipe distribution networks, could beincreasingly vulnerable to precipitation extremes. Physical damage to dams and wateroperations and treatment facilities is a possible consequence of severe floods. Regionswith combined sewage and storm runoff systems could have more frequent sanitarycontrol problems due to flooding.
  • It may become more diffi cult to meet delivery requirements duringprolonged periods between reservoir refi lling without also increasing the risk of fl ooding.Earlier spring runoff from snowmelt is a likely manifestation of global warming. Muchof Europe and the western United States depend on snowmelt as a water source for mostof the year, so earlier runoff clearly affects water storage on a broad scale. To the extentthat adequate reservoir space is available, changes in reservoir management practicescould mitigate some of these effects. Seasonal climate forecasts might provide someadaptation leverage for reservoir managers. For example, forecasts based on the currentstate of the El Niño-Southern Oscillation and other large-scale climatic indices correlatewell with precipitation patterns in some regions, and would be useful information forreservoir management decisions.
  • The impacts of climate change on freshwater systems andtheir management are mainly due to the observed andprojected increases in temperature, sea level andprecipitation variability (very high confidence).More than one-sixth of the world’s population live in glacier- orsnowmelt-fed river basins and will be affected by the seasonalshift in streamflow, an increase in the ratio of winter to annualflows, and possibly the reduction in low flows caused bydecreased glacier extent or snow water storage (high confidence)[3.4.1, 3.4.3]. Sea-level rise will extend areas of salinisation ofgroundwater and estuaries, resulting in a decrease in freshwateravailability for humans and ecosystems in coastal areas (veryhigh confidence) [3.2, 3.4.2]. Increased precipitation intensityand variability is projected to increase the risks of flooding anddrought in many areas (high confidence) [3.3.1].Semi-arid and arid areas are particularly exposed to theimpacts of climate change on freshwater (high confidence).Many of these areas (e.g., Mediterranean basin, western USA,southern Africa, and north-eastern Brazil) will suffer a decreasein water resources due to climate change (very high confidence)[3.4, 3.7]. Efforts to offset declining surface water availabilitydue to increasing precipitation variability will be hampered bythe fact that groundwater recharge will decrease considerably insome already water-stressed regions (high confidence) [3.2,3.4.2], where vulnerability is often exacerbated by the rapidincrease in population and water demand (very high confidence)[3.5.1].Higher water temperatures, increased precipitationintensity, and longer periods of low flows exacerbate manyforms of water pollution, with impacts on ecosystems,human health, water system reliability and operating costs(high confidence).These pollutants include sediments, nutrients, dissolved organiccarbon, pathogens, pesticides, salt, and thermal pollution [3.2,3.4.4, 3.4.5].Climate change affects the function and operation ofexisting water infrastructure as well as water managementpractices (very high confidence).Adverse effects of climate on freshwater systems aggravate theimpacts of other stresses, such as population growth, changingeconomic activity, land-use change, and urbanisation (very highconfidence) [3.3.2, 3.5]. Globally, water demand will grow inthe coming decades, primarily due to population growth andincreased affluence; regionally, large changes in irrigation waterdemand as a result of climate change are likely (high confidence)[3.5.1]. Current water management practices are very likely to beinadequate to reduce the negative impacts of climate change onwater supply reliability, flood risk, health, energy, and aquaticecosystems (very high confidence) [3.4, 3.5]. Improvedincorporation of current climate variability into water-relatedmanagement would make adaptation to future climate changeeasier (very high confidence) [3.6].The negative impacts of climate change on freshwatersystems outweigh its benefits (high confidence).All IPCC regions (see Chapters 3–16) show an overall netnegative impact of climate change on water resources andfreshwater ecosystems (high confidence).Areas in which runoffis projected to decline are likely to face a reduction in the valueof the services provided by water resources (very highconfidence) [3.4, 3.5]. The beneficial impacts of increasedannual runoff in other areas will be tempered by the negativeeffects of increased precipitation variability and seasonal runoffshifts on water supply, water quality, and flood risks (highconfidence) [3.4, 3.5].
  • There are apparent trends in streamflow volume, bothincreases and decreases, in many regions.• The effect of climate change on streamflow and groundwaterrecharge varies regionally and between scenarios, largelyfollowing projected changes in precipitation.• Peak streamflow is likely to move from spring to winter inmany areas due to early snowmelt, with lower flows insummer and autumn.• Glacier retreat is likely to continue, and many small glaciersmay disappear.• Generally, water quality is likely to be degraded by higherwater temperatures.• Flood magnitude and frequency are likely to increase in mostregions, and volumes of low flows are likely to decrease inmany regions.• Globally, demand for water is increasing as a result ofpopulation growth and economic development, but is fallingin some countries, due to greater water-use efficiency.• The impact of climate change on water resources alsodepends on system characteristics, changing pressures on thesystem, how the management of the system evolves, andwhat adaptations to climate change are implemented.• Unmanaged systems are likely to be most vulnerable toclimate change.• Climate change challenges existing water resourcemanagement practices by causing trends not previouslyexperienced and adding new uncertainty.• Adaptive capacity is distributed very unevenly across theworld
  • With higher temperatures, the water-holding capacity of theatmosphere and evaporation into the atmosphere increase, and thisfavours increased climate variability, with more intenseprecipitation and more droughts (Trenberth et al., 2003). Thehydrological cycle accelerates (Huntington, 2006). Whiletemperatures are expected to increase everywhere over land andduring all seasons of the year, although by different increments,precipitation is expected to increase globally and in many riverbasins, but to decrease inmany others. In addition, as shown in theWorking Group I FourthAssessment Report, Chapter 10, Section10.3.2.3 (Meehl et al., 2007), precipitation may increase in oneseason and decrease in another. These climatic changes lead tochanges in all components of the global freshwater systemKeep in mind – thoughexerted strongpressure on freshwater systems. This has resulted in waterpollution, damming of rivers, wetland drainage, reduction instreamflow, and lowering of the groundwater table (mainly dueto irrigation). In comparison, climate-related changes have beensmall, although this is likely to be different in the future as theclimate change signal becomes more evidentThesevulnerabilities are largest in semi-arid and arid low-incomecountries, where precipitation and streamflow are concentratedover a few months, and where year-to-year variations are high(Lenton, 2004). In such regions a lack of deep groundwater wellsor reservoirs (i.e., storage) leads to a high level of vulnerability toclimate variability, and to the climate changes that are likely tofurther increase climate variability in future. In addition, riverbasins that are stressed due to non-climatic drivers are likely tobe vulnerable to climate change.
  • http://environment.newscientist.com/channel/earth/dn12559-leaf-sweat-glands-to-worsen-future-flooding.html Tiny pores on the surface of plant leaves that are sensitive to carbon dioxide may contribute significantly to future flooding as a result of increasing atmospheric pollution , researchers say.The effect could help researchers predict which regions may be at greatest risk of flooding because of global warming. It may also help them predict which areas will receive some relief from drought.The tiny pores, known as stomata, are found on the surface of leaves and are each between a tenth and several hundredths of a millimetre across. The underside of black oak leaves can have as many as 60,000 stomata per square centimetre.The main function of stomata is to regulate the amount of carbon dioxide taken up by the plants during photosynthesis. Crucially, however, they also absorb and release moisture during transpiration. Furthermore, researchers have long known that stomata tend to shrink when CO2 levels in the atmosphere rise.Since the late 19th century, atmospheric CO2 has risen from 280 to 390 parts per million as a result of humans burning fossil fuels and chopping down forests. So it stands to reason that plants should be transpiring less now than they were before the industrial revolution, which triggered a sudden surge in fossil fuel consumption.The net effect of reduced transpiration is that plants consume less water, meaning more remains in the soil and can run off into rivers.Rushing riversA few years ago, a group led by Nicola Gedney of the UK Met Office analysed river flow during the 20th century to see how shrinking stomata might have affected this run-off. They found that river flow had increased by 3% worldwide during the 20th century and calculated that this must be due to increased soil moisture resulting from shrinking stomata (see Increased CO2 may cause plant life to raise rivers).Gedney, Richard Betts and others at the Met Office and the UK Centre for Ecology and Hydrology have now gone a step further, incorporating the effect of stomata into future predictions of flooding and drought.They first ran computer models to assess the effects of global warming on river run-off, through increased rainfall and other factors. They looked at what these effects will be if CO2 levels reach 560 ppm. This is double what levels were before the industrial revolution and is expected to happen sometime in the second half of the 21st century.The team then ran the same models again, this time switching on the "stomata effect". "Where climate change is predicted to increase river flow, the biological effect [of the stomata] will increase river flow further," says Betts.Less severe droughtsThe researchers also performed a regional analysis. They predict that there will be a positive impact on some regions, such as the Mediterranean and South America, which are expected to suffer from drought during the 20th century as a result of rising temperatures. These regions should suffer a little less because soil will contain more water than predicted by current climate change models, says Betts.But in Asia, Europe and North America, the stomata effect could mean worse flooding. Betts and colleagues warn that instead of expecting between 11% and 16% more water run-off as a result of climate change, governments should prepare for an increase of between 13% and 24%."We will have to consider these findings closely in order to assess their impact on floods in UK," says Christabel Mitchell of the UK Environment Agency.However, she says she is sceptical of the suggestion that the agency should take the effects of shrinking stomata into consideration when formulating flood policies. Several studies have indicated that the impact of soil moisture and transpiration on overland flow is "negligible", she says.Journal reference: Nature (DOI: 10.1038/nature06045)Climate Change - Want to know more about global warming - the science, impacts and political debate? Visit our continually updated special report.
  • Groundwater systems generally respond more slowly toclimate change than surface water systems. Groundwater levelscorrelate more strongly with precipitation than with temperature,but temperature becomes more important for shallow aquifersand in warm periods.
  • Disaster losses, mostly weather- and water-related, havegrown much more rapidly than population or economic growth,suggesting a negative impact of climate change (Mills, 2005).However, there is no clear evidence for a climate-related trendin floods during the last decades (Table 3.1; Kundzewicz et al.,2005; Schiermeier, 2006). However, the observed increase inprecipitation intensity (Table 3.1) and other observed climatechanges, e.g., an increase in westerly weather patterns duringwinter over Europe, leading to very rainy low-pressure systemsthat often trigger floods (Kron and Bertz, 2007), indicate thatclimate might already have had an impact on floods. Globally,
  • n the Sierra Nevada mountains of California, climate change is subtly eroding the health of pine and fir trees. The effect could be a portent of severe tree die-offs to come. Ecologists have been tracking the fate of more than 21,000 individual trees since 1983 as part of a project to study forest ecology at different elevations in the Californian mountains. When Phillip van Mantgem and Nathan Stephenson of the US Geological Survey in Three Rivers, California, looked at the first 22 years of this record, they noticed that mortality rates of both pine and fir trees had increased at an average of 3% a year, nearly doubling overall (Ecology Letters, DOI: 10.1111/j.1461-0248.2007.01080.x). The increased death rates were seen at all but the highest elevations. Meanwhile, the rate at which new trees established did not change.
  • From top left down:Multi-year droughts on US and Southern CanadaLand subsidence and land slides in mexico cityWater supply affected by shrinking glaciers in andesUp:Water supply reduced by erosion and sedimentation in reservoirs in north-east brazilMid left down:Damage to riparian ecosytems due to flood protection along Elbe riverRural water supply affected by extended dry season in BeninArea of Lake Chad decliningHealth problems due to arsenic and fluroride in groudnwater in IndiaFlood disasters in Bangladesh (more than 70% of the country inundated in 1998)In China: Huanghe river temporarily run dry due to precipitation decrease and irrigationAustralia: damage to aquatic ecosystems due to decreased streamflow and increased salinity in Murray-Darling basin
  • Increasing water temperature affectsthe self-purification capacity of rivers by reducing the amount ofoxygen that can be dissolved and used for biodegradation.Atrendhas been detected in water temperature in the Fraser River inBritish Columbia, Canada, for longer river sections reaching atemperature over 20°C, which is considered the threshold beyondwhich salmon habitats are degraded (Morrison et al., 2002).Furthermore, increases in intense rainfall result inmore nutrients,pathogens, and toxins being washed into water bodies. Chang etal. (2001) reported increased nitrogen loads from rivers of up to50% in the Chesapeake and Delaware Bay regions due toenhanced precipitationNumerous diseases linked to climate variations can betransmitted via water, either by drinking it or by consuming cropsirrigated with polluted water (Chapter 8, Section 8.2.5). Thepresence of pathogens in water supplies has been related toextreme rainfall eventsIn the USA, 20 to 40%of water-borne disease outbreaks can be related to extremeprecipitation (Rose et al., 2000). Effects of dry periods on waterquality have not been adequately studied (Takahashi et al., 2001),although lower water availability clearly reduces dilution.Water quality problems and their effects are different in typeand magnitude in developed and developing countries,particularly those stemming from microbial and pathogencontent (Lipp et al., 2001; Jiménez, 2003). In developedcountries, flood-related water-borne diseases are usuallycontained by well-maintained water and sanitation services(McMichael et al., 2003) but this does not apply in developingcountries (Wisner and Adams, 2002). Regretfully, with theexception of cholera and salmonella, studies of the relationshipbetween climate change and micro-organism content in waterand wastewater do not focus on pathogens of interest indeveloping countries, such as specific protozoa or parasiticworms (Yarze and Chase, 2000; Rose et al., 2000; Fayer et al.,2002; Cox et al., 2003; Scott et al., 2004). One-third of urbanwater supplies in Africa, Latin America and the Caribbean, andmore than half in Asia, are operating intermittently duringperiods of drought (WHO/UNICEF, 2000). This adverselyaffects water quality in the supply system.
  • Introduction:The Mediterranean region is one of the rare borders in the world that separates twoadjacent areas with opposite demographic characteristics and contrasted levels of development. Itincludes 25 countries or territories bordering the Mediterranean Sea. According to the United Nationsestimations the total population of the region will rise from 446 millions in 2000 to 508-579 million in2025. The region is subdivided into three sub-regions the North that includes all European countriesbordering the Mediterranean countries (Portugal, Spain, France, Monaco, Italy, Malta, Bosnia-Herzegovina, Croatia, Slovenia, F.R. of Yugoslavia, Albania and Greece), the East (Turkey, Cyprus, Syria,Lebanon, Israel, Palestinian Territories, and Jordan) and the South (Egypt, Libya, Tunisia, Algeria andMorocco).The Mediterranean water resources are limited, fragile and threatened, and intensely utilisedespecially in the South and East sub-regions. The renewable water resources are unequally sharedbetween countries and population with 72% percent in the North, 23% in the East and 5% in the Southsub-regions. The Mediterranean water is particularly sensitive to droughts, which occur approximatelyevery ten years with very low water input. Although the effects and extent of climate change are asyet uncertain and cannot be easily quantified or foreseen, a certain consensus exists regarding apresumed increase in climate contrast. In the South sub-region a drier climate is probable in the 21stCentury with the dual effect of decreasing water resources and increasing water demand, and in theNorth we can expect the climate to become more contrasted with more rainfall in winter and drier lessregular summers that could influence water production and increase water demand in summer.Climatic change combined with population growth will increase the pressure on the availablewater resources and may cause social instability in the area. The impacts on the water resourcesthemselves will affect surface and groundwater supplies for domestic, irrigation, industrial, waterbasedrecreation and other uses.http://www.iucn.org/places/medoffice/Documentos/climate-change-mediakit_EN2.pdf
  • http://www.terradaily.com/2007/070506030318.lefgd8pp.html Downing cited the impact of rising seas on land use the Egyptian city of Alexandria
  • Fresh water resources in the Mediterranean are under increasing pressure in terms of both quantity and quality.§ Northern Mediterranean countries with higher, more regular rainfall also face climate-induced natural hazards, flooding and water shortages in basins susceptible to periodic drought. As a consequence, human and natural systems sensitive to water availability and water quality are increasingly stressed, or coming under threat. Those countries will have to face water quality degradation and meet the increasing needs of environmental protection and restoration.§ In South and East Mediterranean counties where utilization is now approaching hydrological limits, and the combined effects of demographic growth, increased economic activity and improved standards of living have increased competition for remaining resources. Water resources are already overexploited or are becoming so with likely future aggravation where demographic growth is strong. The Eastern countries will be more sensitive to short term or structural shortages, in certain areas.
  • Many events associated to climate change threat the balance of the Mediterranean ecosystems. The projected impacts of climate change will create a greater variability and extreme weather events, wetter winters and drier summers and hotter summers and heat waves.The changes in temperatures and in precipitations levels and distribution will directly affect the water demand, quality and watershed. Pollution will be intensified by runoff in catchments and from urban areas. Rivers will have lower flows particularly in summer, and the sea temperature, salinity and concentration in CO2, nitrates and phosphates will also be affected. The most visible impact will be the floods which will be higher and more frequent.The changes in the frequency of extreme events might be the first and most important change registered in the Mediterranean. That will directly impact the vulnerability of the poorest countries.Floods are the most common type of natural hazard in the Mediterranean region, after the earthquakes: only in the last decades all the Mediterranean countries had to defend from some massive flood and its associated catastrophic effects.
  • Algeria is the largest country in the Maghreb region. In this country the significant exposure to recurring natural hazards (e.g., floods, earthquake, drought) emphasises the vulnerability of the poor population because of the recurring social, financial and economic losses.Algerian urban environment is characterised by rapid urbanisation and environmental degradation. Poor or non-existent drainage, water supply, sanitation, sewer and solid waste disposal systems, further enhance the deterioration and destabilisation of buildings and infrastructure. Deforestation, the elimination of vegetation cover, due to uncontrolled and often illegal development has contributed to further erosion, thus increasing hazard exposure. On November 2001, severe rains accompanied by floods and mud-flows affected 14 villages in the northern part of Algeria. The disaster caused the loss of about 900 lives, approximately 95 % of which occurred in the capital of Algiers (specifically in the Oued Koriche catchment area). Damage and loss of property were considerable across sectors, amounting to about US$300 million (according to the Government sources). Since this disaster, there is a new way of thinking about flood disaster management in Algeria, particularly in urban areas.
  • Kingdom Among Countries Most Affected by Climate ChangeM. Ghazanfar Ali Khan, Arab News   RIYADH, 6 June 2006 — Saudi Arabia is among a group of seven countries experiencing a depletion of water resources because of climate change, which is also threatening its vast arid lands and deserts.“The deserts, however, can be used as a key resource if urgent action is taken to protect them on regional and global levels,” said a report released by the United Nations Environment Program (UNEP).The report, released on World Environment Day yesterday, said that ground water levels in desert areas of the Kingdom and in similar regions around the world are dropping “very quickly as ancient underground aquifers are exhausted.” This year’s slogan of World Environment Day is: “Don’t Desert Dry Lands” whereas the theme is: “Deserts and Desertification.”The slogan emphasizes the importance of protecting dry lands, which cover more than 40 percent of the planet’s surface.Referring to the changes or threats faced by deserts because of climate change, the study said, “The world’s deserts are facing dramatic changes as a result of climate, high water demands, tourism and salt contamination of irrigated soils. There was also an overall temperature increase of 0.5 to two degrees Celsius in desert regions between 1976 and 2000. Many deserts will experience a decline of 5 to 10 percent in rainfall in the near future.”The report said that one possibility for improving water efficiency is to restrict irrigated agriculture. “Desalination plants, which turn sea water into drinking water, are used in some countries but they consume large amounts of energy in a world where energy prices are rising sharply,” said the study. 

Chapter 11 cc impact on water resources Chapter 11 cc impact on water resources Presentation Transcript

  • Chapter 11 Climate Change and Water Resources: Global and Local Impacts Prof. Dr. Ali El-Naqa Hashemite University June 2013
  • Module 2. Climate variability and climate change CLIMATE VARIABILITY AND CLIMATE CHANGE
  • Module 2. Climate variability and climate change Module structure Module 2. Climate variability and climate change Objectives The objective of this module is to summarise climate change concepts. Structure The module provides simple definitions of weather and climate; discusses climate variability and climate change; gives some evidence of climatic change; and briefly looks at projections of how climate may be for the rest of the century. Illustrations are linked to files with a larger view, expanding on the topics covered, or providing access to full text documents Caveat The information provided in this module provides comes from models which are currently believed to be the best available but they need to be looked out with caution as models are continuously refined.
  • Module 2. Climate variability and climate change Climate and weather • Climate and weather are different • Weather is what happens in a given time (e.g. days or hours), climate is the average weather over long periods • Factors that can affect climate are called ―climate forcing mechanisms‖ Weather and climate are different. Weather is the conditions, such as temperature, rain and wind that we see over short periods. These can change hour by hour, day by day. Climate can be thought of as the average weather over a long period. It results from the interactions between the atmosphere, oceans, ice sheets, land masses and vegetation. Scientists have defined characteristic climate zones around the world (see map). They give us an indication of the average climatic conditions of an area, i.e. arid, warm temperate, polar, etc. The factors that affect climate are called climate forcing mechanisms; they can include variations in solar radiation, deviations in the Earth's orbit, volcanic activity, continental drift, and greenhouse gas concentrations.Köppen-Geiger Climatic Classification.
  • Module 2. Climate variability and climate change Climate and weather Examples “Climate is what we expect, weather is what we get” See the difference between climate and weather in South America: South America's climate zones range from dry steppe to equatorial monsoon. It also includes tropical, as well as subtropical areas. Zones change with altitude, with each altitudinal zone displaying distinct local climate, soils, crops, domestic animals and modes of life (Figure A). The temperatures in South America on a given day - ―the weather‖ (Figure B). Figure A. Climate zones in South America. Note the classification differs slightly from Köppen-Geiger. Figure B. Weather in South America. Temperatures on 13 August, 2011. Source: The Weather Channel.
  • Module 2. Climate variability and climate change Climate variability • Climate varies naturally at different time and spatial scales • Climate variability can manifest periodically or suddenly The Earth's climate is dynamic and naturally varies at different time scales, e.g. within months, seasons, decades or larger scales. It also varies regionally or globally. Each "up and down" fluctuation can lead to conditions which are warmer or colder, wetter or drier, more stormy or quiescent. Some regions experience greater variability than others. More… El Niño (a variation in the Pacific oceanic temperatures) and the Southern Oscillation (a variation in surface air pressure over the western Pacific Ocean) are examples of climate variability. Climate variability is manifested in other ways as well. Decadal and seasonal shifts in wind patterns and sea surface temperatures in the Atlantic cause changes in hurricane frequency. Changes in volcanic activity can also change temperatures. Sometimes climate varies in ways that are random or not fully explainable. More… The Asian monsoon from space. Photo: NASA image STS51F-31-069.
  • Module 2. Climate variability and climate change Climate variability Examples Mount Pinatubo, in the Philippines, erupted in 1991. Gases and ash reached an altitude of about 34 km and covered over 400 km in a few hours. They were dispersed over the whole planet within a year. The ―cloud‖ over the Earth caused global temperatures to vary, temporarily reducing them by 0.5 C between 1992 and 1993. There is evidence that suggests the eruptions of the Laki craters in Iceland (1783–1784) affected the weather in Europe; weakened African and Indian monsoon circulations; and resulted in 1–3 millimetres less of daily precipitation than normal over the Sahel of Africa (Oman et al., 2006). Mount Pinatubo eruption. Source: U.S. Geological Survey Fact Sheet 113-97. Photo: Roderick Batalon.
  • Module 2. Climate variability and climate change Climate variability Examples In Central America climate variability translates into droughts and floods caused by tropical storms and hurricanes. According to the Comisión Centroamericana de Desarrollo y Medio Ambiente (CCDA /SICA), between 1930 and 2008, 248 severe weather events were recorded in the region, with 85% being floods, tropical storms and landslides, 9% droughts, 4% forest fires and 2% extremes in temperatures (mainly low temperatures). Honduras is the country which experienced the highest climate variability during this period. Aerial shots of damage by Hurricane Mitch to agricultural land: palm crops covered in mud. Photo: FAO/L. Dematteis.
  • Module 2. Climate variability and climate change Climate variability Reflections Ethiopia provides a good example of the influence of climate variability on a developing country’s economy. GDP in Ethiopia rises or falls about a year behind variations in average rainfall (see figure). With agriculture accounting for half of GDP and 80% of jobs, the Ethiopian economy is sensitive to climate variability, particularly variations in rainfall. Source: Adapting to climate variability and change, USAID and Ethiopia - Managing water resources to maximize sustainable growth: Water resources assistance strategy, The World Bank. Is your country sensitive to climate variations? You could consult your national statistics institute for rainfall records together with GDP data and find out if there is any relation.
  • Module 2. Climate variability and climate change Weather disasters and extreme events • Extreme weather events are rare • Weather disasters—not necessarily extremes in climatic statistical terms—result in ecological and economic losses • Weather disasters could reduce global GDP by up to 1% Although the term ―extreme weather event‖ was reserved for events that statistically were rare (occur with a frequency below 5%), the term is increasingly used to refer to weather events that result in disasters. Information on the few extreme weather events recorded in history can be found in the World weather/climate extremes archive maintained by The World Meteorological Organization and Arizona State University (USA). Weather disasters, which result from large departures from average weather conditions—but not necessarily climatic statistical extremes—result in ecological and economic losses. It is estimated that weather disasters could reduce global GDP by up to 1%. Weather disasters can include, for example, severe: heat and cold waves, tornadoes, dust storms, droughts, tropical cyclones, floods. Khulna in August 2010. A home still flooded by Cyclone Aila, which swept through Bangladesh in May 2009. Photo: FAO/M. Uz Zaman.
  • Module 2. Climate variability and climate change Weather disasters and extreme events Examples Weather disasters in the United States of America The United States of America, through its National Climatic Data Center (NCDC), keeps a record of weather disasters. The U.S.A. has sustained 108 weather-related disasters over the past 31+ years for which costs reached or exceeded US$1 billion. The total normalised losses for the 108 events exceed US$750 billion. Reports from the U.S. National Climatic Data Center on weather disasters costing more than US$1 billion during 1980–2010. Source: National Climatic Data Center.
  • Module 2. Climate variability and climate change Weather disasters and extreme events Examples Drought in East Africa By the end of August 2011, the worst drought in 60 years in the Horn of Africa had sparked a severe food crisis and high malnutrition rates, with parts of Kenya and Somalia experiencing pre-famine conditions. More than 10 million people were affected in drought-stricken areas of Djibouti, Ethiopia, Kenya, Somalia and Uganda and the situation continued deteriorating.. A pastoralist stands near a carcass in Sericho, Kenya. He used to walk 5 km with the herd to find pasture, but the distance is now 30–50 km. Photo: Tran Ngoc Huyen.
  • Module 2. Climate variability and climate change Weather disasters and extreme events Reflections The publication Weather extremes in a changing climate: Hindsight on foresight has a series of examples of weather disasters all over the world from 2000 to 2010. Heat waves, floods, droughts, bush fires, cold spells were prominent and all continents were affected. These events cost millions of dollars all over the world. Photos: Adapting to climate change and climate variability, USAID; Ethiopia - Managing Water Resources to Maximize Sustainable Growth: Water Resources Assistance Strategy, WB; Dimaberkut; FAO/Asim Hafeez. Have there been weather disasters associated with your area? Which type? Do they seem to show a pattern? How have they varied in the last decade? Do you know what are the costs of each event?
  • Module 2. Climate variability and climate change Climate change • Climate change implies sustained changes over decades • Changes have been more marked in the last 3 decades and are associated with human activities Climate change implies sustained changes (over several decades or longer) to the average values for climate variables such as temperature, precipitation, winds or atmospheric pressure. These changes are normally detected as trends, for example, a trend of global warming, sea level rise or reduction of snow cover (See figures and explanations via the links). Data gathered over the 30-year period from 1961 to 1990 define the latest Normals used for climate reference. Scientists have observed changes in the last decades compared to these values. There is evidence that these changes have been mainly caused by human activities, through an increased greenhouse effect, and that these changes are occurring at a faster rate than ever. Scientists have been monitoring these changes; reports of their findings can be found on the IPCC website. Observed changes in climate. Source: IPCC Climate Change 2007: Synthesis report .
  • Module 2. Climate variability and climate change What is the greenhouse effect • The atmosphere and greenhouse gases (GHGs) control the temperature of Earth; without them the Earth would be much cooler • Human activities are increasing GHG concentrations and the planet is warming faster than ever The planet and its atmosphere absorb and reflect the solar energy reaching it. The balance between absorbed and reflected energy determines the average temperature. The atmosphere and certain gases stop the heat from escaping into space. They allow the sun’s energy through, but stop it from escaping back into space, acting like a greenhouse. The gases producing this effect, such as water vapour, carbon dioxide and methane, are called Greenhouse Gases (GHGs). Without the greenhouse effect, the Earth would be 30 C cooler, making it uninhabitable for most forms of life. Unfortunately human activities are increasing the concentration of GHGs in the atmosphere and amplifying the greenhouse effect, trapping more and more heat and increasing global temperatures. A 1 or 2 C increase could drastically change the life on the planet. Emissions of long-lived GHGs from 1970 to 2004. Source: IPCC Climate Change 2007: Synthesis Report.
  • Module 2. Climate variability and climate change Observations on climate change • IPCC scientists are in agreement that climate change is unequivocal • Scientists have gathered evidence for changes in temperature, hydrosphere and extremes According to the IPCC, climate warming is unequivocal. Examples of evidence of the climate changing include (see also the figure): Temperature • Surface temperatures increased by about 0.74 C between 1906 and 2006. • Observations since 1961 show that the average temperature of the global ocean has increased to depths of at least 3,000 m. Hydrosphere • Satellite data since 1978 show the annual average ice cover in the Arctic sea has shrunk by an average 2.7% per decade, with larger decreases in summer of an average 7.4% per decade. • Global average sea level rose at an annual average of 1.8 mm (1961 to 2003) and 3.1 mm (1993 to 2003). Monthly Palmer Drought Severity Index (PDSI) for 1900 to 2002.
  • Module 2. Climate variability and climate change Observations on climate change Examples Changes in the Yellow River Basin. Obvious climate changes have been observed over the past decades in the Yellow River Basin. The mean annual temperature has risen continuously, especially since the 1990s, while precipitation and runoff have consistently decreased. The frequency and intensity of climate events has also changed in recent years . Mean annual temperature between 1961 and 2004 recorded in Menyuan station, one of the meteorological stations along the Yellow River Basin. Source: The China Climate Change Partnership Framework - Final Report. Menyuan station Temperature°C
  • Module 2. Climate variability and climate change Observations on climate change Reflections In 2009, the Mexican government reported in its 4th National Communication to the UNFCCC that from 1971 the country’s temperature increased by an average 0.6 C. With the last 10 years indicating an accelerated warming of 0.7 C. These data are in agreement with global findings. Temperature changes between 1971 and 2008 in Mexico. Source: Instituto Nacional de Ecología . Are you aware of observations for your country or region? How do they compare to global observations? You may be able to find data in the National Communications to the UNFCCC, your Environment Ministry, local universities or regional research centres.
  • Module 2. Climate variability and climate change Projecting future GHG emissions • Scientists use models and scenarios to study potential future greenhouse gas emissions and associated impacts on climate • If better policies are not introduced, the concentration of GHGs in the atmosphere will continue to increase Scientists use computer models and scenarios (or assumptions about the future) to study the way that emissions and climate would change under different development paths. The IPCC uses the Special Report on Emissions Scenarios (SRES), which groups scenarios into families A1, A2, B1 and B2. These explore ―story lines‖ or alternative development pathways, covering a wide range of demographic, economic and technological driving forces. The SRES scenarios do not include additional climate policies. Post-SRES scenarios have refined assumptions but this has only minor effects on overall emissions. At the moment there is high agreement that if better climate change mitigation policies and related development practices are not introduced, global GHG emissions will continue to grow over the next few decades (see graph). Global GHG emissions (in GtCO2- eq per year) in the absence of additional climate policies. Source: IPCC, SyR-3.
  • Module 2. Climate variability and climate change How will climate be in the future? • Continued GHG emissions can cause further warming, with larger changes than those observed for the 20th century • Temperature, precipitation, snow cover, sea level will change and weather events are expected to increase in frequency and magnitude Continued GHG emissions can cause further warming and induce many changes in the global climate during the 21st century. These changes could be larger than those observed during the 20th century, for example: • Temperatures will continue to increase. • Warming would be greatest over land, especially at northern latitudes, and least over the Southern Ocean (near Antarctica) and northern North Atlantic, continuing recent observed trends. • The area of snow cover will contract. • Sea ice is expected to shrink in both the Arctic and Antarctic under all SRES scenarios. • Sea level might rise 0.18–0.59 m (without considering ice melting). • Hot extremes, heat waves, cyclones and heavy precipitation events may become more frequent and intense. Relative changes in precipitation for the period 2090–2099, relative to 1980–1999. Source for both: IPCC Syr-3. Projections of global surface warming.
  • Module 2. Climate variability and climate change How will climate be in the future? Examples Using projections to know how countries could be affected Projections for sea level rise (SLR) are controversial, due to the contribution of many factors. Some countries are exploring what could happen under different SLR projections. According to the Arab Forum on Environment and Development, a SLR of only 1 m would flood much of the Nile Delta, inundating about one third of the land. Coastal cities such as Alexandria, Idku, Damietta and Port- Said would be at risk. In this case, it is estimated that about 8.5% of Egypt’s population will be displaced (see figure for other projections). Remote sensing and GIS analysis depict areas of the Nile Delta at risk of 1 m to 5 m sea level rise. Source: Impact of Climate Change on Arab Countries.
  • Module 2. Climate variability and climate change How will climate be in the future? Reflections Click here to find a summary of the most recent climate regional projections according to the Fourth Assessment Report of the IPCC. Temperature anomalies, observations and projections at continental level. Source: IPCC, Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, 2007. What are the IPCC projections for your region? Regional projections are very coarse (or low resolution); are you aware of downscaling models for your area? Areas to look for would be differences in temperature, precipitation, water availability, sea level rise, desertification, ice cover changes, weather events. If available, make a list of the projections for your area.
  • Module 2. Climate variability and climate change Resources References used in this module and further reading This list contains the references used in this module. You can access the full text of some of these references through this information package or through their respective websites, by clicking on references, hyperlinks or images. In the case of material for which we cannot include the full text due to special copyrights, we provide a link to its abstract in the Internet. Institutions dealing with the issues covered in the module In this list you will find resources to identify national and international institutions that might hold information on the topics covered through out this information package. Glossary, acronyms and abbreviations In this glossary you can find the most common terms as used in the context of climate change. In addition the FAOTERM portal contains agricultural terms in different languages. Acronyms of institutions and abbreviations used throughout the package are included here.
  • Module 2. Climate variability and climate change
  • Module 2. Climate variability and climate change Please select one of the following to continue: Part I - Agriculture, food security and ecosystems: current and future challenges Module 1. An introduction to current and future challenges Module 2. Climate variability and climate change Module 3. Impacts of climate change on agro-ecosystems and food production Module 4. Agriculture, environment and health Part II - Addressing challenges Module 5. C-RESAP/climate-smart agriculture: technical considerations and examples of production systems Module 6. C-RESAP/climate-smart agriculture: supporting tools and policies About the information package How to use Credits Contact us How to cite the information package C. Licona Manzur and Rhodri P. Thomas (2011). Climate resilient and environmentally sound agriculture or ―climate-smart‖ agriculture: An information package for government authorities. Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences and Food and Agriculture Organization of the United Nations.
  • Water and Climate Change Climate change will lead to more precipitation - but also to more evaporation  Precipitation will probably increase in some areas and decline in others.  Changing precipitation patterns will affect how much water can be captured.  The drier the climate, the more sensitive is the local hydrology.  High-latitude regions may see more runoff due to greater precipitation.  The effects on the tropics are harder to predict.  Reservoirs and wells would be affected.  New patterns of runoff and evaporation will also affect natural ecosystems.  Rising seas could invade coastal freshwater supplies.  Reduced water supplies would place additional stress on people, agriculture, and the environment.  Conflicts could be sparked by the additional pressures.  Improved water resource management can help to reduce vulnerabilities. 26
  • Situation now..  Global Water Crisis  Over 1 billion people don't have access to clean drinking water; more than 2 billion lack access to adequate sanitation; and millions die every year due to preventable water-related diseases.  5 million people – mainly children – die every year from preventable, water-related disease is surely one of the great tragedies of our time.  over 34 million people might perish in the next 20 years from water- related disease  hundreds of billions of dollars are needed to bring safe water to everyone who needs it. Since international water aid is so paltry, many of these experts claim that privatization of water services is the only way to help the poor.  are solutions to the global water crisis that don’t involve massive dams, large-scale infrastructure, and tens or hundreds of billions of dollars. … 27
  • Drivers of change Water resources stress Change in exposure Change in resources Change in vulnerability 28 Population demand for water River flows ; groundwater quality Wealth; equity access
  • Measures of stress  Indicators of exposure  Numbers affected by flood / drought  Indicators of access  Numbers with access to safe water  Indicators of availability  Resources per capita 29
  • Estimating the future  Future impacts depend on future climate and future exposed population  Simulate water availability using a macro-scale hydrological model  Construct climate change scenarios from global climate models  Construct consistent scenarios for change in exposed population 30
  • Effects of climate policy  Rescale changes in runoff to different global temperature changes  Calculate water stress indicators for different temperature increases  “2 degree C target”  ~0.8 degrees C above 1961-1990 mean by 2020  ~1.2 degrees C above 1961-1990 mean by 2050 31
  • What to look for specifically?  Precipitation amount  Precipitation frequency and intensity  Evaporation and transpiration  Changes in average annual runoff  Natural variability  Snowpack  Coastal zones  Water quality  Water storage  Water demand 32
  • Precipitation amount  Will increase as global temperatures rise  Evaporation potential will increase because warmer atmosphere can hold more moisture  For a one-degree Celsius increase in air temperature, the water- holding capacity of the atmosphere increases by 7 percent  What goes up – must come down  How much global average precipitation will increase? Not so certain  Models suggest: 1-2 percent per degree Celsius  Does not mean it will get wetter everywhere and year-round; some get less; some get more  More rain over high-latitude land areas; less over equatorial regions; 33
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  • Precipitation frequency and intensity  On average: less frequent; more intense  floods and droughts; consequences for water shortage  Why?  Local and regional rainfall rates greatly > evaporation rates and depend on the convergence of regional to continental scale moisture sources  Rainfall intensity should increase at same rate as increases in atmosphere moisture (7% / degree C) 35
  • Evaporation and transpiration evapotranspiration:  From open water, soil, shallow groundwater, water stored on vegetation  Transpiration through plants Consistent prediction: increase total evaporation One study: an increase/decrease in precipitation of 20%  runoff changing by ~ 20%; w/ no change in precipitation, a 2 degree C increase in temp -> reduce mean annual runoff by 4 to 12%. Thus – if temp increased by 4 degree, precipitation would need to increase by 20% to maintain runoff 36
  • Changes in average annual runoff  Importance?  Depend on changes in temp and precipitation  Global message of increased precipitation does not translate into regional increases in water availability 37
  • Natural variability?  Will not go away  Water supplies can change dramatically, and for extended periods, even without anthropogenic climate change 38
  • Temperature, snowpack, and runoff Very likely that a greater portion of winter precipitation will fall as rain rather than snow An increase in rain events would increase winter runoff But Result in smaller snowpack accumulations Warmer climate likely result in earlier melt season Increase in winter or spring flows May increase the risk of winter and spring floods 39
  • Coastal zones IPCC (2001): sea-level rise 1. Lowland inundation and wetland displacement 2. Altered tidal range in rivers and bays 3. Changes in sedimentation patterns 4. Severe storm surge flooding 5. Saltwater intrusion into estuaries and freshwater aquifers 6. Increased wind and rainfall damage in regions prone to tropical cyclones 40
  • Water quality  Flooding…  -> increased sediment and non-point source pollution loadings in watercourses  Decline in streamflows and lake levels …   nutrients and contaminants become more concentrated in reduced volumes with longer water residence times  -> reducing dissolved oxygen concentrations  -> Cold-water species (salmon, trout) susceptible to warm- water temp   increase salinity of surface water 41
  • Water storage  Tradeoff between storing water for dry-period use and evacuating reservoirs prior to the onset of the flood season to protect downstream communities 42
  • Water demand  Different rates of use in different climate zones  UK: a rise in temperature of ~ 1.1 d C by 2025 -> increase in average per capita domestic demand of ! 5% + larger % increase in peak demands  Still  rising water demands greatly outweigh greenhouse warming in defining the state of global water systems to 202 43
  • IPCC: Freshwater resources and their management. 2007  The impacts of climate change on freshwater systems and their management are mainly due to the observed and projected increases in temperature, sea level and precipitation variability (very high confidence)  Semi-arid and arid areas are particularly exposed to the impacts of climate change on freshwater (high confidence).  Higher water temperatures, increased precipitation intensity, and longer periods of low flows exacerbate many forms of water pollution, with impacts on ecosystems, human health, water system reliability and operating costs (high confidence).  Climate change affects the function and operation of existing water infrastructure as well as water management practices (very high confidence).  The negative impacts of climate change on freshwater systems outweigh its benefits (high confidence). 44
  • IPCC: Impacts on hydrology and water impacts (2001)  Variation in streamflow and groundwater recharge regionally and between scenarios  Early snowmelt – therefore…  Degraded water quality  Increase in flood magnitude and frequency  Increased demand for water (pop. growth & economic development) globally  High vulnerability in unmanaged systems 45
  •  Non-climatic drivers…  Current vulnerabilities correlated with climatic variability  Particularly: precipitation variability  Particularly where? 46
  • Surface waters and runoff generation Changes in river flows, lake and wetland levels depend on (climatic factors):  Changes in volume, timing and precipitation intensity  Changes in temperature, radiation, atmospheric humidity, and wind speed:  Potential evapotranspiration  offset small increases in precipitation  further effect of decreased precipitation on surface waters  Increased atmospheric carbon dioxide [ ]  Alters plant physiology  affecting evapotranspiration  Lake size  Decreased – due to human water use + climatic factors (Lake Chad) 47
  • Leaf 'sweat glands‘ (stomata) to worsen future flooding  Regulate the amount of carbon dioxide taken up by the plants during photosynthesis  Absorb and release moisture during transpiration  Tend to shrink when carbon dioxide levels rice  So – plants transpiring less  plants consume less water  more water remains in the soil  more water runs into the river  River flow increased by 3% worldwide  In the Med and South American: might ease the damage from drought; Not so in Asia, Europe, and North America 48
  • Groundwater  Respond slower than surface water systems  Correlate more strongly w/ precipitation than w/ temperature  Temperature more important for shallow aquifers  Temperature more important in warm periods 49
  • Floods and droughts  Climate may already have had an impact on floods  Droughts affect:  Rain-fed agriculture production  Water supply for:  Domestic  Industrial  Agricultural purposes 50
  • Other impacts  Climate change is killing US forests  Mortality rates increased at an average of 3% yearly 51
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  • Latest news Autumn rain down 90 percent in China rice belt BEIJING (Reuters) - Large areas of south China are suffering from serious drought, with water levels on two major rivers in rice-growing provinces dropping to historic lows, state media said on Tuesday. Bangladesh says reaches all cyclone-hit areas DHAKA (Reuters) - Relief workers and the Bangladesh military on Tuesday reached the last remaining pockets of the country devastated by a cyclone that killed nearly 3,500 people along the Bay of Bengal. 53
  • Water quality  Lakes and reservoirs: climate change effects primarily due to water temp. variations (climate change or thermal pollution)   oxygen regimes, redox potentials, lake stratification, mixing rates, biota development   diseases – via drinking water or via consuming crops irrigated with polluted water  ¼ of global pop lives in coastal regions: water-scarce + rapid pop growth   sea-level rise  increased saline intrusion  reduction in freshwater availability 54
  • Be sure to read…  http://www.ipcc.ch/pdf/assessment- report/ar4/wg2/ar4-wg2-chapter3.pdf 55
  • Status of Med  Fresh water resources in the Mediterranean are under increasing pressure in terms of both quantity and quality.  Northern Mediterranean countries with higher, more regular rainfall also face climate-induced natural hazards, flooding and water shortages in basins susceptible to periodic drought. As a consequence, human and natural systems sensitive to water availability and water quality are increasingly stressed, or coming under threat. Those countries will have to face water quality degradation and meet the increasing needs of environmental protection and restoration.  In South and East Mediterranean counties where use is now approaching hydrological limits, and the combined effects of demographic growth, increased economic activity and improved standards of living have increased competition for remaining resources. Water resources are already overexploited or are becoming so with likely future aggravation where demographic growth is strong. The Eastern countries will be more sensitive to short term or structural shortages, in certain areas. 56
  • IPCC: Mediterranean nations face up to threat of climate change Global warming threatens to wreak economic havoc across the Mediterranean basin IPCC 2007 reports issued in February and April: Mediterranean basin would be hit especially hard by mounting temperatures, which are predicted to rise globally by 1.8 to 4.0 C (3.2 to 7.2 F) by the end of the century Threatened by rising seas:  Nile River Delta  Venice  Tunisian island of Jerba 57
  • Climate change and water resources in the Mediterranean  http://www.iucn.org/places/medoffice/Documentos/clima te-change-mediakit_EN2.pdf  Status of fresh water resources in the Mediterranean  Fresh water resources in the Mediterranean are under increasing pressure in terms of both quantity and quality.  Northern Mediterranean countries susceptible to periodic drought.  In South and East Mediterranean counties –water resources already overexploited; more sensitive to short term or structural shortages. 58
  • Mediterranean vulnerability to climate change  greater variability and extreme weather events, wetter winters and drier summers and hotter summers and heat waves.  affect the water demand, quality and watershed.  Pollution will be intensified by runoff  floods which will be higher and more frequent.  The changes in the frequency of extreme events might be the first and most important change registered in the Mediterranean. 59
  • Algeria.. Significant exposure to recurring natural hazards (e.g., floods, earthquake, drought) emphasises the vulnerability of the poor population because of the recurring social, financial and economic losses. On November 2001, severe rains accompanied by floods and mud-flows affected 14 villages in the northern part of Algeria. Damage and loss of property were considerable across sectors, amounting to about US$300 million (according to the Government sources). 60
  • Saudi Arabia  Depletion of water resources due to climate change  Ground water levels dropping very quickly  Overall temperature increase of 0.5 to 2 degrees Celsius in desert regions between 1976 and 2000.  Many deserts will experience a decline of 5 to 10 percent in rainfall in the near future  Restrict irrigation agriculture 61