Climate Change and Water Resources

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The user has requested enhancement of the downloaded file. Chapter 12 Climate Change and Water Resources José A. Marengo, Javier Tomasella, and Carlos A. Nobre Abstract This report presents a general vision of the availability of water in Brazil within the context of climate variability and change. Despite Brazil having great water availability, its distribution among the regions is very uneven. The current situation, in terms of scarcity, is mainly due to inadequate planning of land and water use associated to economic growth: as an example, the Southeast area of Brazil, which has great water availability, is affected by lack of water due to uncontrolled urbanization growth. Water availability in Brazil is directly related to the climate, especially during the months of summer. Delays in the start of rainy seasons can affect agriculture and the hydroelectric power generation; and the occurrence of severe floods and droughts have caused great impacts in the economy and to the population. This can be seen, for example, in the case of the drought in Amazonia in 2005 and the floods of 2009 in Amazonia. Brazil is vulnerable to these climatic anomalies and will be vulnerable to the changes projected on rainfall patterns and on extremes weather patterns due to climatic change. Changes in patterns and in precipitation regimes could also affect river flows; current studies indicate that the most affected river will be the São Francisco River, where the reduction in rainfall will result in a drastic decrease of discharge and consequently will severely impact irrigation and the hydroelectric power generation. Without a doubt, the uncertainties of the future projected scenarios always need to be taken into consideration. Actions focused on adaptation and mitigation is urgent, as are monitoring plans for water resources in order to assess climatic risks. Comprehensive research on climatic change and its impacts on water resources is extremely necessary. Water resources management should also consider the climate change projections and uncertainties in the implementation of water policies and regulations. Keywords Agriculture • Governance • Irrigation • Public policies • Scarcity • Water resources J.A. Marengo (*) • J. Tomasella • C.A. Nobre Centro de Ciência do Sistema Terrestre, Instituto Nacional de Pesquisas Espaciais, Rodovia Presidente Dutra, km 40, 12630-000 Cachoeira Paulista, SP, Brazil e-mail: jose.marengo@inpe.br © Springer International Publishing Switzerland 2017 C.E. de Mattos Bicudo et al. (eds.), Waters of Brazil, DOI 10.1007/978-3-319-41372-3_12 171 172 J.A. Marengo et al. Introduction Brazil occupies a privileged position in the world with regards to availability of water resources, with about 12 % of the world’s water, which corresponds to 1.5 million m3 s−1 (Shiklomanov et al. 2000). Yet, part of the Brazilian population lives without the benefit of this resource. Brazilian freshwater reserves are not evenly distributed throughout the country, since 80 % of them are found in the Amazonian region. The Northeastern semi-arid region, even with the inclusion of part of the São Francisco river basin, possesses only 4 % of the country’s water resources but is home to 35 % of the Brazilian population, mostly composed by low income families. The humid regions of the South and the Southeast, where 60 % of the population lives, had in the past ample reserves of water resources. Currently these areas run the risk of local or generalized water scarcity due to economic growth and accelerated urbanization. This situation will only be tackled with the improvement of management of water quantity and quality. Water availability in Brazil greatly depends upon the climate and the climatic variations over time. Heavy rainfall, especially during summer can be associated to floods and have direct impacts on the population, yet in seasonal time scales, a delay in the start of the rainy season can cause tremendous impacts to agriculture and to hydroelectric power generation. The presence of droughts in several different basins in Brazil, on annual level, are examples of the inter-annual variability of the climate associated to the El Niño or La Niña in the Tropical Atlantic to the North and South of the equatorial line, that can generate climatic anomalies that lead to great droughts such as the ones of 1877, 1983 and 1998 in the Northeast, 2004–2006 in the South of Brazil, 2001 in West Central and Southeastern Brazil, and in 1926, 1983, 1998 and 2005 in Amazonia (Marengo et al. 2008a, b; Cox et al. 2008). Additionally, the risk deriving from climate change, whether natural or of anthropogenic origin has caused great concern within the scientific community and the government, with the water resource sector being one of the most affected areas, both with regards to quantity as with regards to quality of water. The Fourth Scientific Report by IPCC AR4 (Trenberth et al. 2007; Meehl et al. 2007) and the Climate Report by INPE (Marengo et al. 2007; Ambrizzi et al. 2007) present evidences of climate changes, that can significantly affect water availability in several regions, with severe impacts to total rainfall and on the hydrometereological extremes by the end of the twenty-first century. Brazil is vulnerable to the current climate variability, as can be seen by the recent intense rainfall during the Summer of 2008/2009 in the states of the South and Southeast of Brazil and the historical flood in Amazonia and in the North of the Northeast, that have caused significant financial losses of hundreds of millions of reais, more than 200 deaths and millions homeless. Analysis of rainfall databases over the last 50 years indicate that extreme events of rainfall are more and more frequent and intense and that the projections from global and regional models for the future, indicate that this trend will probably continue and become even more intensified. Therefore, Brazil is also vulnerable to climate changes projected for the future, especially with regards to 12 Climate Change and Water Resources 173 climate extremes. The knowledge on possible future climatic-hydrological scenarios and their uncertainties can assist us in estimating water demands for the future and define environmental policies for use and management of water. In this study, we assess the state-of-the-art in knowledge on climate change and the impacts of the availability of water in the future, taking into consideration studies on long-term tendencies of the last 50 years and the projections made by climatic models up until the end of the twenty-first century. For further information, we recommend the reader to refer to the Reports of the Work Groups 1 and 2 of IPCC AR4 (www.ipcc.ch), the Climate Report by INPE (www.cptec.inpe.br/mudancas_ climaticas) and IPCC’s Report on Climate Changes and Water (Bates et al. 2008). Current Problems In Brazil, the most vulnerable region to the risk of climate variability and change and to an increase in aridity and subsequent desertification due to climate changes is the Northeast (Salazar et al. 2007). Over 70 % of the cities of the northeastern semi-arid region, with a population of more than 5000 inhabitants, may suffer a crisis by 2025 with regards to water supply for human consumption. Supply problems will most likely affect about 41 million inhabitants of the semi-arid region and its surroundings, as per projections from researchers of the National Water Agency (ANA), who estimated population growth and water demand in approximately 1300 cities that belong to nine states of the Northeast and the northern part of Minas Gerais (ANA 2005). The situation in Amazonia is worrisome. In 2005, a severe drought—the worst in the last 103 years, only comparable to the drought of 1962–1963—hit the west and the southwest of Amazonia. Some large rivers from the Amazon basin decreased their tidal level up to about 6 cm per day. Millions of fish died and rotted in the beds of the tributaries of the Amazon River that served as a source of water, food and transport to riverside communities (Marengo et al. 2008a, b). The possibilities of periods of intense droughts occurring in the Amazonian region can surpass the current 5 % (which represents one severe drought in every 20 years), to 50 % by 2030 and even 90 % by 2100 (Cox et al. 2008). On the other side of the pendulum of climatic extremes, Amazonia has been facing a flood of historical dimensions, greater than the historical maximums registered in the port of Manaus in the last 100 years, greater than the Record levels ever registered of 1953. According to the Geological Service of Brazil, 1953 marked Manaus’ history as the period of the worse flood of the capital. At the time, the level of the Negro River reached 29.68 m and it is anticipated that within the next months, this level will surpass 30 m. These extremes are repeated in the North of the Northeast region, causing considerable economic damages and a strong social impact. In the South and Southeast regions of Brazil, the systematic increases of rain can also be seen through hydrological data and via rainfall extremes (Marengo et al. 2009). The intense rainfall that hit parts of Santa Catarina, especially in the 174 J.A. Marengo et al. Valley of the Itajaí-açu River during November 22–25 of 2008, was caused by an atmospheric blocking in the Atlantic Ocean. The rains affect the coastal strip of the State of Santa Catarina. In several cities on the coast of this state, daily rainfalls exceeding 200 mm were registered in Blumenau, Balneário Camboriú, São Francisco do Sul, Itapoá and Biguaçu. Official data from EPAGRI/CIRAM indicated that the rains in November were historical records in the cities of Itajaí, Blumenau, Joinville, Indaial and Florianópolis. The volumes of the rain mentioned, are equivalent to 50–70 % of the total expected for the entire year and registered over a period of only 1 month. The intense rainfall and floods and subsequent avalanches affect 1.5 million people, with 123 deaths and more than 69,000 people who lost their homes (INPE 2008). The majority of the anomalous rains in the Southeastern South America, including those from Santa Catarina are being associated to the simultaneous occurrence of intense weather events related to the El Niño phenomena such as those from 1911, 1957, 1983, 1987, 1998, among several others. However, intense rainfall, even if in a smaller special scale, can occur regardless of the large scale influence of El Niño, as occurred in 1984 and in 2008. The floods from 1983, which caused damages of about US$ 1.1 billion in the entire state of Santa Catarina, reached a peak level of the Itajaí-açu River of 15.34 m. These were immediately followed by the floods of 1984, with a peak level of 15.46 m. In February of 1987 the phenomenon El Niño caused floods in 15 municipalities of Santa Catarina and in 1997 caused additional floods of great proportions also in Santa Catarina during the months of January and October. During the floods of January, 35 municipalities were affected and in October the floods hit 37 cities. Water Resources in the Context of Climate Change For several specialists, the water crises is the result of a set of environmental problems, made worse by economic issues and by lack of development (Gleick 2000). With this vision in mind, it is a mistake to deal with the issues related to water resources, exclusively as if it were an issue of lack of availability in the face of an increase of demand. It is crucial to view the problem as an issue related to management of resources. There are several causes that explain water resources scarcity (Tundisi 2008): 1. Intense urbanization, increasing the demand for water supply and water for economic and social development, increasing discharge of contaminated water resources. 2. Water stress and scarcity in several regions of the planet due to alteration in availability and increase in demand. 3. Poor, and in critical stage of infrastructure in several urban areas with losses of up to 30 % in the networks following water treatment. 4. Problems of stress and scarcity due to global warming and climate change, with extreme hydrological events increasing human population vulnerability and compromising food security (intense rainfall and periods of intense droughts). 12 Climate Change and Water Resources 175 5. Problems in the lack of coordination and lack of consistent actions in the management of water resources and in environmental sustainability. In addition to these problems, we can add the inadequate use of land in suburban and rural areas. The floods that hit Santa Catarina in 2008 resulted in dramatic characteristics in terms of economic damages and loss of human life caused by landslides from slopes, whose outbreak is strongly accelerated by the removal of natural vegetation. The advancement of desertification in several areas of the semiarid of the country, as well as in Rio Grande do Sul are clear examples of how the inadequate management of the land increases the impacts associated to water deficiency. Amazonia, which is the region of the country that presents the highest level of preservation of water resources, is dramatically being affected by the increase of livestock ranching and agriculture along the so called “deforestation arc”. Taking into account that these affected areas form the headwaters of rivers such as Tocantins, Xingu and Tapajós, the occupation of this region without any concern for the environment will result in consequences in large areas downstream of the headwaters of these rivers due to the transfer of the impacts. Very little is known about how these actions today will affect the sediment load of these rivers or their hydrological regime, which can severely affect activities such as navigation, fishing and the generation of electricity. Therefore, the impact of climate change on water resources cannot be dealt with without considering all the current uses of the resources; and inevitably these changes will increase all the problems preciously identified. The solution to these problems requires an institutional approach, not only locally, but also regionally and globally. Therefore, the greatest challenge when facing the issue of water resources, with regards to climate change, relates to the need of have one unique institutional framework which allows for an integrated management of the water resources. The provisions introduced in the Water Act of 1995 represent a tremendous breakthrough in the integrated management of water resources. However, many of these principles have not been properly incorporated in the planning of water resources and many of the provision of this Law have still not rendered a practical result. A typical example of this is the implementation of basin committees in several hydrographic basins of the country, which is still very incipient. At the same time, it is necessary to analyze whether the legal framework is adequate considering the global nature of water security, especially faced by climate change, and should be dealt with on a global scale which surpasses all the political boundaries. Up until recently, the biggest problems with regards to the issue of climate change, referred to the lack of assessment of the impacts, possible actions for its mitigation and adaptation to these impacts. The lack of a coordinated action at an institutional level resulted in a majority of studies being carried out in a sector manner, without the necessary systematic approach required by the water problem. 176 J.A. Marengo et al. Present and Future Climate The continent has already experienced a series of radical occurrences in the last years such as: torrential rains in Venezuela and in the southeast of South America, floods in the pampas of Argentina, droughts in Amazonia and in the South of Brazil, floods in Amazonia and in the North of the Northeast, hailstorms in Bolivia, a record season of hurricanes in the Caribbean and, recently in 2009, drought in the North of Argentina and in the South of Brazil and the great floods in Amazonia and in the Northeast. At the same time, the rains decreased in Chile, in the South of Peru and in the Southeast of Argentina. With the increase of temperatures already registered (1 °C in Central America and in South America in a century, with a world average of 0.74 °C), the Andean Glaciers are receding and can compromise water availability destined for consumption and for the generation of electricity, worsening the problem for the future, which could become chronic if measures are not taken, states the report of IPCC GT2 for Latina America (Magrin et al. 2007). Global warming is drying out lakes in mountains and swamps in the Andes and compromising water supply to great Latin American countries such as La Paz, Bogotá and Quito (Vergara et al. 2007). The melting of glaciers, also caused by global warming can jeopardize water supply to Quito and the generation of hydroelectric energy to Peru. The glacier from Chacaltaya in Bolivia can disappear completely within the next 20–30 years and several other Andean glaciers can disappear in the twenty-first century, resulting in important consequences to the availability of water, to the generation of energy and to the integrity of the ecosystems (Francou et al. 2003). With regards to rainfall, one can observe a trend already detected in previous studies of IPCC AR4 (Trenberth et al. 2007), of an increase of rainfall of up to 30 % per decade in the Prata Basin and in some isolated areas of the Northeast of the country. In Amazonia, a specific trend of increase or decrease of rainfall due to deforestation cannot be determined, showing instead a trend of more contrasting inter-decadal variations between the North and the South of Brazil. In the Northeast, the observed trends also suggest an inter-annual variability associated to El Niño and to the sea surface temperature (SST) in the Tropical Atlantic, as well as a decadal scale trend associated to the changes in the meridional position of the Intertropical Convergence Zone (ITCZ). Regionally, since 1950 an increase of the total and of the extremes of rain in the South and in parts of the Southeast of Brazil, in the Paraná-Prata basin, have been observed, consistent to the similar trends of other countries of the Southeast of South America. In the Southeast, the total annual rainfall does not seem to have suffered any noticeable modifications in the last 50 years. The projections of changes in the regimes and distribution of rains, obtained from global models of IPCC AR4 for warmer climates in the future, are not conclusive and the uncertainties are still many because they depend upon the 12 Climate Change and Water Resources 177 models and the regions being considered. In Amazonia and in the Northeast, even though some global climate models of IPCCC AR4 present drastic reductions of rainfall, other models indicate an increase of rainfall. On the other hand, the averages of all models indicate a greater probability of reduction of rainfall in regions such as eastern Amazonia and Northeast Brazil, as a result of global warming (Fig. 12.1a). The IPCC AR4 (Meehl et al. 2007) indicated a reduction of rainfall in the North and the Northeast of Brazil during the months of winter (JJA), which can affect the rainfall in the eastern Amazonia and Northeast, Brazil that has its peak rainy season during this time of the year. According to reports from IPCC for Latin America (Magrin et al. 2007) and from INPE (Marengo et al. 2007; Ambrizzi et al. 2007), the semiarid region will tend to become more arid. The frequency and intensity of droughts will increase and water resource availability will be reduced. The projections for the future of climate models also suggest an increase of rainfall for the Southern Brazil and in the Prata basin and for the west of Amazonia by the end of the twenty-first century. This increase might possibly present itself in the form of extreme rains occurring more intensely and frequently (Fig. 12.1b), which is already being observed since (Marengo et al. 2008a, b). Fig. 12.1 (a) Changes in annual rainfall (%) and (b) R10 index or number of days with rainfall above 10 mm (by means of standard deviations) (average of 15 IPCC AR4 global models) for the period of 2080–2099 of the scenario of greenhouse gas emission A1B for the average of 1900– 1998. Areas with dots show regions where at least 60 % of the models showed the same sign (Bates et al. 2008) 178 J.A. Marengo et al. Current Hydrology and Future Projections With regard to river flows, the observed trends of rainfall clearly reflected the trend of rain, with an evident increase of flows in the Paraná River and in other rivers of the Southeast of South America. In Amazonia, in the Pantanal and in the Northeast Brazil, long term systematic trends were not observed with regards to dry spells or rainy conditions; most importantly however, were the inter-annual and inter-decadal variations associated to the natural variability of the climate in the same time scale of the variability of inter-decadal phenomena of the Pacific Ocean and the Tropical Atlantic ocean. River flow analysis in South America and in Brazil (Milly et al. 2005) indicated increases between 2 and 30 % in the Paraná basin and in the neighboring regions of the Southeast of South America, consistent to the analysis of the trends of rain in the region. Important trends were not observed in the flows of the rivers of Amazonia or in the São Francisco River basin. In the west coast of Peru, the positive trends of rainfall can be explained due to the extremely high quantity of rains and flows during the years of El Niño in 1972, 1983, 1986 and 1998 that clearly affect these trends. Milly et al. (2005) analyzed the components of the flows of the rivers of several IPCC AR4 models for the future, compared to the present. Figure 12.2a,b shows that the IPCC AR4 (Fig. 12.2a) models adequately represent the growing trends observed in the Paraná-Prata basin. By the end of the twenty-first century, the IPCC AR4 models indicate reductions in the flows of the São Francisco, Parnaíba, Tocantins and Xingu Rivers, and in other rivers in the East of Amazonia, as well as in Central Chile. On the other hand, the models also indicate increases of flows in rivers in the West Fig. 12.2 (a) Relative change (%) of flows of rivers in South America (average of 9 IPCC AR4 global models) for the period of 1971–2000 for the average of 1900–1970 of the climate simulation of the twentieth century (20C3M) from IPCC; (b) Relative change (%) of the flows of rivers in South America (average of 9 IPCC AR4 global models) for the period of 2041–2060 of the scenario A1B of the average of 1900–1988 (turn 20C3M) (Milly et al. 2005) 12 Climate Change and Water Resources 179 Coast of South America, near Peru-Ecuador and in the Paraná-Prata basin. These projections are very important, because the alterations of flows can change the frequency of floods and this can cause damages to the ecosystems and affect the production of food, transportation and the generation of energy. The increases in flows are consistent to the increases of rainfall in the future (Meehl et al. 2007). Hydrometeorological Climatic Extremes In the Southeast and in the South of Brazil, and intense increase in rainfall has been observed in the last 50 years, as shown in Fig. 12.2a (Marengo et al. 2009). They were identified positive trends of systematic increases of rain and of other rainfall extremes in the subtropical region in the South and in the Northeast of Brazil. These authors indicated that Southeastern South America has shown, since 1940, systematic increases in the frequency of intense rains of up to almost 58 % every 100 years. There was indication that in São Paulo, more occurrences of extreme rains are see during the El Niño, which indicates that these States are sensitive to the intensity of the South-Atlantic Convergence Zone (SACZ). Some authors investigated the trends of extreme rains in the southeast of South America for the period of 1960–2000 and encountered trends for more humid conditions in the South of Brazil, Paraguay, Uruguay and in the North and Central Argentina. They also noticed that the Southeastern South America experienced an increase in the intensity and in the frequency of days with intense rains, which coincides with the works of Groissman et al. (2005) for the same region. Intense occurrences of rains in autumn can be the cause of the great flows of the Paraná River, in the Argentinean Pampas. It was showed that in São Paulo, on an inter-annual scale, the number of occurrences of extreme rains shows a correlation with anomalies of SST in the Tropical Atlantic and in the Southeast of the Atlantic, near the coast of São Paulo. The control performed by the South Atlantic Convergence Zone (SACZ) and by the South American Low-Level Jet (SALLJ), on and inter-annual and intra-seasonal scale, can be observed in the frequency of occurrences of intense rainfalls associated to the presence of the SACZ and the SALLJ, that on average, indicate a greater frequency of intense rains in the southeast of Brazil, when the SALLJ is intense and the SACZ is weaker and relocated to the south of the Northeast region. Different authors defined extreme occurrence of rain following different methodologies and using similar of superior values of percentages (95° C), which makes comparison of results difficult. In the South of Brazil, It was identified a slight trend of increase in the number of occurrences of extreme rains, with a greater frequency in years such as 1993–1994 e 1997–1998, which were the years of the El Niño. Trends were analyzed in annual extremes of rain and concluded that they appear to be similar to those of total accumulated rain, in other words, positive in the South of Brazil, Paraguay and Uruguay, and in the central north of Argentina. These extremes identified positive trends in the number of days with intense and very intense rains (R20 mm) concentrated in short periods of time and in quantities of J.A. Marengo et al. 180 rain found in occurrences which are indicators of rains that cause floods during the period of 1961–2000. These trends suggest an increase in the frequency and intensity of occurrences of rain in the southeast of South America, while the lack of data in the tropical region does not allow for a more comprehensive analysis of the extremes in this part of the continent. The projections of extremes, according to IPCC AR4 (Meehl et al. 2007, Bates et al. 2008), indicate increases in the frequency of extreme rain for all of Brazil, mainly in the west of Amazonia, south and southeastern of Brazil. For the period of 2080–2099, in comparison to the previous period (1980–1999), within the scenario of greenhouse gas emission A1B, extreme occurrences of intense rain show an increase in the frequency and in the contribution of very rainy days in the west of Amazonia, while in the Eastern Amazonia and in Northeast Brazil the probability is of an increase in the frequency of consecutive dry days, which can also be observed for Southeastern Brazil. Recent studies (Marengo et al. 2009) suggest in fact, that the possible scenario of increase of rain in the South of Brazil, projected for the end of the twenty-first century, can occur in the form of more intense and frequent extremes of rains (Fig. 12.3). The west of Amazonia may experience an increase in the frequency of extreme rains by 2100, which may lead to problems of erosion and floods in this region. However, the lack of trustworthy hydrological information in this region, does not allow us to ensure the certainty of the simulated trends for this current projection. Observations R 10mm PRECIS R 10mm - Scenario A2 10N 5N DAYS 5N EQ EQ 16 5S 12 10S 8 15S 5S 10S 4 20S 15S 25S −4 30S −8 35S −12 40S −16 45S −20 50S −24 20S 25S 30S 35S W 70 W 65 W 60 W 55 W 50 W 45 W 40 W 35 W W 75 W 80 85 W W 35 W 40 45 50 W 55 W 60 W 65 W 70 W 75 W 80 W 55S DAYS /30 YR −24 −20 −16 −12 −8 −4 4 8 12 16 Fig. 12.3 Trends of extreme rains represented by the R10 index (number of days with rain above 10 mm), (a) based on information for the period of 1951–2000; and (b) projected by the regional model HadRM3P for the period of 2071–2100 relating to 1961–1990, scenario A2 of high emissions (Source: Marengo et al. 2009) 12 Climate Change and Water Resources 181 Impact and Vulnerability Studies in Brazil The majority of studies in Brazil have been focused on the impacts on surface water resources, with emphasis on the issues related to hydroelectricity and agriculture. As an example, we can highlight three studies that generally summarize the existing studies in terms of impacts of climate changes on water resources. They are: 1) Recent studies of the Sustainable Development Foundation (Salati et al. 2009) indicate that the climate scenario will cause a reduction of the water surplus in all the large Brazilian basins (Table 12.1). This study utilized the average of 15 climatic models from IPCC for the scenarios B1 and A2 and the HadRM3P regional model for the same scenarios. The study used the Thornthwaite-Mather Water Balance model for eight hydrographic regions of Brazil together with calibrated water balance, so that the water surplus generated in the period of 1960–1990 would be compatible to the flow values measured by the ANA network station. Table 12.1 shows that the reduction of water surplus is not significant in the Northeast region of Brazil and in particular in the São Francisco River basin. The study also foresees reductions in the Tocantins River basin. Taking into consideration the enormous vulnerability to water scarcity of the Northeast region, it becomes evident that, in the agricultural point of view, one can expect severe impacts of climate change in this region. Table 12.1 Reduction of water surplus the Northeast region of Brazil, particularly in the São Francisco River basin Hydrographic basin Tocantins Amazonas Paraguay Parnaíba São Francisco Occidental NE Atlantic South region Paraná 1961– 1990 (%) 100 100 Average models 2° × 2° lat/long Period 2011–2100 B1 A1 11– 41– 71– 11– 41– 40 70 100 40 70 (%) (%) (%) (%) (%) 83 77 73 84 73 88 82 80 89 80 100 100 100 68 69 73 60 59 57 59 56 43 73 70 72 100 88 87 86 100 95 93 100 80 74 71– 100 (%) 63 73 HadRM3P 50 km × 50 km B2 A2 11– 41– 71– 11– 41– 40 70 100 40 70 (%) (%) (%) (%) (%) 72 67 54 73 55 93 84 75 93 73 71– 100 (%) 47 70 54 54 46 40 47 30 81 32 38 91 19 42 92 14 47 90 34 43 85 13 45 147 10 53 92 85 80 72 62 59 71 52 47 92 95 90 86 111 109 116 109 101 107 67 83 67 47 84 84 93 94 88 110 182 J.A. Marengo et al. 2) In the area of agriculture, recent studies from EMBRAPA (2008) estimated that global warming shall cause losses of about R$ 7.4 billion in 2020, which could reach R$ 14 billion in 2070. EMBRAPA’s study indicated that the cultivation of soybeans will be the most affected. In the worse scenario, losses could reach 40 % by 2070, leading to a loss of up to R$ 7.6 billion. In EMBRAPA’s study, the coffee produced in Southeastern Brazil will be severely affected due to the increases of risks, but may present an increase in production in the south of the country. Corn, rice, beans, cotton and sunflower will suffer a considerable reduction in the low risk area of the Northeast, with a significant decrease in production. The cassava will have an overall gain of area of low risk, but should suffer serious losses in the Northeast. The cultivation of sugar cane could double in the next decades. 3) One of COPPE’s studies should be mentioned (Schaeffer et al. 2008), that focused on the issue of hydroelectricity. This study predicted falls in the production of energy which varied between 1 % and 2.2 % (average of the national electric park) in the A2 and B2 scenario respectively, with, once again, the São Francisco River basin being the most affected, with losses between 4.3 and 7.7 %. 4) In a more detailed research, however, with a regional coverage, Tomasella et al. (2009) presented an analysis of the impacts of climate changes for the Tocantins River basin and all of its main sub-basins, for scenery A1B, using model ETA (resolution 40 km) with boundary conditions from the global model HasCM3. The study concluded that, in terms of monthly averages, the reduction for the scenario 2080–2090 is of about 30 %, but that these reductions could reach up to 60 % in drought seasons. In general, this study showed a displacement of the duration curves for the minimums, which indicates that there is a probability of a reduction of flows for almost all the probability scales. In addition, the impacts are greater in the Araguaia River basin, whose draining area is located in crystalline soils. One important aspect of this study is that it indicates that the occurrence of water deficiency is not the same all year long and that the impact can vary according to the characteristics of the hydrographic basin. Although these studies are concentrated in areas and activities of great economic impact for the country, they often lack the level of details necessary for planners to have the technical support needed for the elaboration of regional plans for mitigation. This occurs due to technical and scientific constraints which pervade the lack of detailing within the climate scenario, within the specification of uncertainties and within the limitation of the mathematical models used in the assessment of the impact. Another problem about the existing studies on impact is its sectorial nature. The different uses of water, whether or not consultants, are strongly interdependent. For example, the expansion of an irrigated area affects the generation of energy downstream. Therefore, the lack of an integration of the focus on the use of water resources does not allow for an assessment, in terms of climate changes, of whether the route of changes, summed to the increase in water demand due to population growth, will or will not have a synergetic effect among the possible future uses of the resource. And lastly, there are considerable limitation of scientific knowledge with regards to establishing functional relationships between hydrology, land, climate and vegetation (ecohydrology) in the main ecosystems of the country. This knowledge is crucial not 12 Climate Change and Water Resources 183 only to determine spatial distribution of ecological communities and their physical structure as well as their species structure, in a way of better quantifying the natural resources of the country, but also in order to provide theoretical and experimental support to the future scenarios such as the “savannization” of Amazonia (Oyama and Nobre 2003) or of “aridization” of the Northeast (Salazar et al. 2007). These functional relationships between the vegetation and the water regime are completely unknown in the seasonal flooded ecosystems of the country, such as the extensive areas of the Pantanal or of the Amazonian Plain. It is therefore necessary to improve these studies not only with regards to uncertainties, but also with regards the approach towards different studies. Ground Water The increase in temperature due to climate changes have direct effects on the hydrological cycle, altering the total amount of rainfall, its temporal and spatial distribution (frequency of droughts and floods), affecting therefore the hydrological processes such as flows and infiltration. These changes will affect water storage in the ground and consequently, the recharge of aquifers. Therefore, within this context, it is obvious that climate change is affecting temporal and spatial levels of aquifers, with consequences not only to human supply, but also affecting the capacity of regularization of large rivers (with consequences to all water uses, consultative or not) or even indirectly, affecting activities like construction and mining. As per ANA’s report (2005), the flow of recharge of renewable ground water reserves in the country are of about 42,000 m3 s−1 or 24 % of the mean flow of the rivers of national territory and 49 % of the flow in dry seasons. Considering the usable reserves as being equal to 20 % of the renewable resources, one has about 8400 m3 s−1 of ground water resource availability (usable reserve) total, in the country. This estimate corresponds to all aquifer systems of the country, including those of a smaller hydro geological potential as for example, those found in crystalline grounds. The country possesses important aquifer systems with good distribution in hydrographic regions and with good water potential. The majority of these aquifers is of the porous type and is found in sedimentary basins, which occupy approximately 48 % of the national territory. The main aquifer systems of the country, totals a renewable reserve of 20,000 m3 s−1, with about 4100 m3 s−1, estimated as ground water availability (usable reserve). One can argue that in a country with such an abundance of surface water, the ground water reserves have a relatively limited reach. However, in several regions and urban centers of the country, ground water represents the main source of water, being used for several purposes such as human supply, irrigation, industry and leisure. Aquifers constitute, due to their large spatial extent (which eliminates the need for complex supply and distribution systems like in the cases of fountains located in rivers and lakes) together with their natural capacity of debugging, the main source of water supply in many regions of Brazil. 184 J.A. Marengo et al. This deficiency arises, partly due to the lack of hydro geological studies. The existing studies, usually limited to the sedimentary areas of the country, are of a limited regional scale and are usually outdated articles (ANA 2005). Conclusions As was previously discussed, one still does not possess a clear picture of the possible impacts of climate change on spatial and temporal distribution of the water resources in the continent. The uncertainties still represent obstacles for the operational planning and the management of the water resources, but, even so, this cannot be used to avoid immediate actions focused on adaptation. One of the first actions would to establish research programs and monitoring to assess the risks related to climate change. Regions like the Northeast and the southeast central west are highly vulnerable, due to their dependency on electric energy. In these regions, climate change (especially in the form of an increase of air temperature) can increase to the risk already imposed by the growing population, urbanization, industrialization, and the changes to the use of land associated to agriculture and cattle farming. In Amazonia, however, the problems are associated to the possible loss of biodiversity and to the impacts to the hydrological cycle. Scientific evidence indicates the fact that climate changes represent a serious risk to water resources in Brazil. Not only do the future climate changes represent risks, but also the climate variability. As examples, we have the droughts in Amazonia, Northeast, South and Southeast in Brazil in the last 10 years, the extremes of rains in the South and Southeast of Brazil during the recent summer seasons and the floods in Amazonia 2009, of which all have affected the regional and national economy, causing great social impacts. The appropriate management of water resources, in view of the climate change, will depend upon the knowledge about its availability and on how this availability will be affected by the different scenarios. Thus, it is necessary to improve the existing studies, reduce the uncertainties and increase the amount of details about the information. Despite there being several studies on surface water availability, one has noticed that studies on ground water availability are scarce. There is very little experimental evidence on the level of resilience of Brazilian ecosystems, which is crucial to determine the survival of the ecosystems in the scenario of climate changes. Some adaptations actions of the water resources, to the climate changes could be: 1) Improvement of the infrastructure of the sewage and water supply systems. 2) Reduction of leaks. 3) Implementation and encouragement of conservation measures of water use, by the industries and by the population. 4) A demand for measures that avoid water waste for the approval of new construction projects. 5) Recovery of natural ecosystems in watershed areas. 12 Climate Change and Water Resources 185 6) With regards to the risks of floods and landslides, it is necessary to improve identification of the areas of risk. 7) Alert systems of weather forecasts and a preparation for natural disasters. 8) Avoid new ventures in high risk areas and relocation in areas of extreme risks. 9) Improvement or creation or warning systems for floods and landslides. 10) Promotion of design and anti-flood materials for buildings. Due to its important social function as a source for human supply, it is necessary to improve the assessment of the potential of aquifers in the country and how this potential will be affected in the future. This study will be important to determine how the ground water reserves can contribute towards the mitigation of these changes. Acknowledgements This document is generated mainly from the results of the following projects: Characteristics of the current climate and definition of the climate alteration for the Brazilian territory throughout the twenty-first century, supported by CNPq through the National Institute of Science and Technology (INCT) for Climate Changes, Conservation and Sustainable Use of Brazilian Biological Diversity Project, PROBIO, with the support MMA/BIRD/GEF/CNPq and by Global Opportunity Fund-GOF from the United Kingdom, through the project Using Regional Climate Change Scenarios for Studies on Vulnerability and Adaptation in Brazil and South America. 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