Keywords

Introduction

Brazil went through the worst drought in recorded history in the Southeast and Northeast regions during the years of 2014 and 2015 (Barifouse 2014). The drought has a great impact especially because Brazil generates around 80% of its electricity with through hydropower. The Brazilian climate seems to be changing over recent years, either due to global climatic changes or due to changes in regional climate resulting from deforestation. This in turn is affecting the reliability of hydropower generation in Brazil (Hunt et al. 2014). The expansion of the electricity sector has focused on hydroelectric plants in the Amazon, without storage, that will further enhance the electricity sector vulnerability.

Over the next 10 years, the hydroelectric energy storage capacity will not increase as the new hydropower generation (33% increase in 10 years) will be in the Amazon Basin with no storage and generating most of its electricity generated during the wet period (Empresa de Pesquisa Energética 2015). Other alternatives such as wind and solar will partially complement electricity generation in Brazil. The Brazilian wind potential has started to be explored and is foreseen to reach 22 GW of wind power by 2024. This is convenient because it generates more electricity during the dry period, when hydropower generation is reduced. Solar power has less seasonal variations and is set to increase by 7 GW capacity by 2024 (Empresa de Pesquisa Energética 2015).

A promising power generation alternative, with great potential in Brazil, is biomass (Hunt et al. 2016). However, it should be noted that a biomass plantation directly affects the hydrology of the water basin where it is located by consuming large amounts of water which will affect the multiple uses of water (environmental requirements, irrigation, industrial, commercial and residential uses) and hydropower generation on the dams downstream. For example, if there is a eucalyptus plantation near the Nova Ponte Reservoir in Minas Gerais, the water consumed by the plantation turns into moisture in the atmosphere, which eventually precipitate in another place with a different hydroelectric generation potential. In this case, water used for growth of biomass would be removed from the reservoir of a hydroelectric cascade with a maximum generation head of 642 m. If this moisture precipitates near the Ilha Solteira Reservoir with a generation head of 199 m, there will be a potential loss of hydroelectric generation of 442 m as the water is consumed by the biomass plantation. This hydroelectricity generation loss in this example is around 10% of the electricity that would be generated when burning the biomass planted near Nova Ponte Reservoir (Hunt et al. 2016). However, there is the possibility of planted biomass in a low-altitude locations, with low potential for hydroelectricity generation, where the moisture generated by biomass transpiration may result in an overall increase in hydropower potential in Brazil. This is detailed in the next section.

The objective of this paper is to create a strategy to provide water for irrigated biomass and agricultural plantations with the intention that the transpired water might result in an increase in water availability in Brazil and result in overall benefits to the hydroelectric generation of the country. This paper presents a possibility of creating an artificial hydrological cycle resulting from the transposition of water from the basins of the Tocantins and Paraná Rivers to São Francisco River and the use of this water for irrigated biomass plantation. The resulting moisture transpired by the irrigated biomass may then return to the Tocantins and Paraná Basins carried by the strong trade winds. This mechanism was called “Watershed Transposition Cycle with Irrigated Biomass” or “Transposition Cycle”.

The transposition projects could be implemented with Seasonal-Pumped-Storage plants (Hunt et al. 2014a). Thus, if feasible, it is possible to pump water from the Tocantins and Paraná Rivers during the wet season, when there is excess electricity in the system, and excess of water in the basins where the water is extracted. During the dry season, the stored water will then be used to generate electricity and enhance agriculture in the São Francisco Basin.

In addition to increasing the overall hydroelectric generation in Brazil, Transposition cycle is able to assist adaptation to climate change, with the control of atmospheric humidity according to the amount of water transposed into the São Francisco Basin and transpired by the irrigated biomass. The agricultural sector, which is also vulnerable to climate change and has great importance in the Brazilian gross domestic product, would also benefit from a mechanism for climate control.

Biomass Irrigation in Northeast Brazil

Focusing on the São Francisco Basin, according to Fig. 11.1, considering the section of the São Francisco River mouth, it can be seen that the direction of the trade winds and the São Francisco River flow are in the opposite directions.

Fig. 11.1
figure 1

Diagram demonstrating the transposition cycle for the São Francisco River

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The Transposition Cycle intends to increase hydroelectric generation with biomass irrigated plantation. For this to occur, biomass may be planted in locations with low hydropower potential thereby not reducing the hydropower generation and increasing the probability of precipitation in high hydropower potential locations.

Biomass, especially eucalyptus, requires large quantities of water to grow. If the plantation is located at the São Francisco River mouth, the water will be removed from the river through irrigation and will be released into the atmosphere as moisture in the air. The strong trade winds, carry the moisture back inland from the mouth of the São Francisco River, in the opposite direction of the São Francisco River flow. This moisture may increase rainfall in the São Francisco Basin and, thus, it may create a partially closed artificial water cycle, as described in Fig. 11.1, increasing the amount of hydroelectric generation in the basin. The hydropower generation head from Sobradinho dam to Xingó dam is 307 m.

The area downstream the Xingó dam near the São Francisco River has an area of approximately 40,000 km2. Downstream of the Paulo Afonso plant is an area of about 50,000 km2. It should be noted that the mouth of the São Francisco River has a humid coastal climate. The plantation, would not require intensive irrigation. However, plant biomass would decrease the amount of water that flows towards the river.

However, the water transpired near the mouth of the São Francisco River would probably not only precipitate in the São Francisco Basin. It may also precipitate in the Tocantins, Amazon, Paraná and other basins. It is important to study climatic and hydrological models to establish where the water removed from the plantation might precipitate. This article uses the estimated data from the Winds Atlas developed by CEPEL (Amarante et al. 2001).

Figure 11.2 shows the probability distribution of the wind direction in Brazil at ground height. As can be observed moisture generated by transpiration of biomass at the São Francisco River Mouth and in Sobradinho Reservoir (number 1 on the map) is directed predominantly to the east and northeast directions. This pattern continues predominant up to 4,000 m in the atmosphere (https://www.windyty.com). The wind patterns close to the Três Marias Reservoir (number 2 on the map) are mainly directed to the east.

Fig. 11.2
figure 2

Probabilistic wind direction over the Northeast of Brazil (Amarante et al. 2001)

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Figure 11.3 shows the inflow and outflow of the Sobradinho Reservoir. The difference between the inflow and outflow consists of the reservoir storage capacity. As it can be seen, the average inflow has been considerably reduced during the last 10 years. This is because there is a reduction in rainfall and because of the rapid increase of irrigated agriculture in the São Francisco Basin (Valdes et al. 2004; Nys et al. 2015; Comitê da Bacia Hidrográfica do Rio São Francisco 2004). The transposition of water to the São Francisco Basin is an important climate change adaptation measure to reduce its vulnerability to climatic variations and climate change.

Fig. 11.3
figure 3

Inflow and outflow of the Sobradinho Reservoir

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The next section presents a preliminary case study of a Transposition Cycle in Brazil.

Water Transposition: Removing Water from Flood Areas to Use It Where There Is Low Water Availability

The Araguaia River Basin is marked by periods of extreme drought and flood throughout the year. It has a very flat geology and suffers from intense silting of the river on the border between the states of Pará, Mato Grosso and Tocantins. This sedimentation restricts the flow of water, increasing the level of the Araguaia River from 6 to 11 m during the flood period (http://www.snirh.gov.br/hidroweb/), which can cause severe floods in the Mid Araguaia Basin. In addition, there is a 10-year period of large scale floods with severe floods in the years 2013, 2002, 1990 and 1980 (http://www.snirh.gov.br/hidroweb/; Dias 2014). In February 2002, the flooded area in the Mid Araguaia region reached around 60,000 km2 (https://www.ufrgs.br/hge/modelos-e-outros-produtos/mgb-iph-propagacao-inercial/).

In addition, in Fig. 11.4, there is a reliable supply of water in most location of the Xingú, Araguaia and Tocantins Basins. On the other hand, the Northeast river basins suffers from critical or very critical water availability. A water transposition system would reduce the incidence of floods in the Araguaia Basin and reduce the impact of droughts in the São Francisco basin, functioning as a climate change adaptation measure.

Fig. 11.4
figure 4

Water demand versus availability in Brazilian river basins (http://arquivos.ana.gov.br/planejamento/estudos/sprtew/2/2-ANA.swf, http://portal1.snirh.gov.br/ana/apps/webappviewer/index.html?id=ac0a9666e1f340b387e8032f64b2b85a)

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Transposition Cycle Between the Xingú, Tocantins and Paraná Basins, and the São Francisco Basin

Expanding the concept of a Transposition Cycle between different river basins in Brazil further increases its potential. Figure 11.5 shows the water balance and the average flow of the main basins of Brazil. The blue arrows represent the yearly average water flow to the Atlantic Ocean. It shows that the Amazon average water flow is around 130,000 m3/s, Tocantins flow is 8000 m3/s, Paraná flow is 12,000 m3/s, São Francisco flow used to be 2000 m3/s but has reduced to 800 m3/s in 2016 (http://www.snirh.gov.br/hidroweb/). The transparent blue arrows represents the predominant trade wind direction bringing humid air into the continent. The trade winds direction is predominant up to a height of 4000 m (https://www.windyty.com).

Fig. 11.5
figure 5

Hydrological and climatic characteristics of major Brazil basins (numbers represent m3/s) (Operador do Sistema Nacional 2015)

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It should be noted that if water is transposed by artificial channels from the Paraná and Tocantins Rivers into the São Francisco Basin and from there it is used for plantation irrigation, a share of the water transposed may return as humidity to the Tocantins, Amazon and Paraná Basins carried by the trade winds, with wind speeds of yearly average of 11 m/s at 1400 m absolute height in some locations on Northeast Brazil (Centro de Referência para Energia Solar e Eólica 2013; http://pt-br.topographic-map.com/places/Brasil-3559915/). This climate change adaptation methodology is suggested because, apart from removing water, from where it causes problems and putting in a region with lack of water availability, the water consumed would return to where it was taken and increase the overall water availability of Brazil. This solution has not been proposed before and is limited to locations with strong and constant trade winds and locations where these trade winds returns the water to where it originally taken from.

An ambitious Transposition Cycle developed by the author is presented in Fig. 11.6. This project involves the basins of Rivers Xingú, Tocantins, Paraná, and the São Francisco River. The transposition of water of the Paraná Basin to the São Francisco Basin is not very complicated. According to Fig. 11.6, nine hydropower plants in the Grande River should be upgraded with reversible turbines to capture the rainfall in the region in purple and pump to Furnas Reservoir. The pumping capacity should guarantee a 1500 m3/s flow at the Furnas reservoir so that it can be transposed to the São Francisco Basin. The average flow at the Furnas Reservoir is around 1200 m3/s. However, during the drought in 2015 the flow was reduced to 250 m3/s.

Fig. 11.6
figure 6

Transposition of the Xingu, Araguaia, Tocantins and Paraná to São Francisco River

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To connect the Furnas Reservoir, at the Paraná Basin, with the São Francisco River, a pipeline of 15 km is required. In addition, this pipeline has a 100 m head difference, which could be used for hydroelectricity generation. Two more run-of-the-river dams should be built upstream of Três Marias Dam and increase the hydropower generation head in the São Francisco River by 100 m.

Figure 11.6 also shows water transposition of the Xingu River to the Araguaia River, Araguaia to Tocantins and Tocantins to São Francisco River. This implementation is not simple, but provides several benefits.

Transposition of the Xingú River to the Araguaia River captures water from the green area in Fig. 11.6. A 120 km canal with an average depth of 15 m, takes water from Xingu River to a conventional storage reservoir in the Araguaia Basin. This reservoir will fill only during the wet season, when there is excess water in the Xingu River and generate electricity during the dry period with a maximum head of 210 m. This water will be transposed into the Tocantins River and then to the São Francisco River.

To facilitate the transposition of water from the Araguaia River to the Tocantins River it is important to control the flow of the Araguaia River in its head to reduce its seasonal flow and allow the transposition system to operate during the wet and dry periods. In order to achieve this, water from the Mortos River will be stored in a Seasonal-Pumped-Storage plant during the wet period and transposed to the Araguaia River during the dry period. The Araguaia River Basin has little investment in agriculture and other activities because it suffers annual flooding during the wet season due to its flat geological formation (Santos 2006; Costa 2012). In addition to Seasonal-Pumped-Storage, a channel will be created to remove sediments and stop the flooding in the Araguaia River. A Sedimentary Basin Storage Dam will control the amount of water stored in the Mid-Araguaia Sedimentary Basin. Sedimentary Basin Storage intends to store water in the sandy ground and control the level of the groundwater with the dam. Flood control in the Araguaia Basin will enable the economic development of the region and the increase in water storage will enable the transposition of water from the Araguaia River to Tocantins River throughout the whole year.

The Southern Transposition Project from the Araguaia River to the Tocantins River will require with the Crixás-Acu River at an altitude of 230 m with a 140 km canal with an average depth of 10 m, followed by a tube with 50 km and pumping facility, a 40 km canal with an average depth 10 m and a run-of-river dam at 490 m absolute height. The Southern Transposition Project will have a 500 m3/s capacity flow and will make use of the underutilized Serra da Mesa Reservoir storage potential.

The Southern Transposition Project from the Tocantins River to the São Francisco River will require a 20 km tube with pumping facility and a 120 km channel at 1050 m absolute height with an average depth of 10 m. Then a 60 km long tube will connect the channel to the São Francisco Basin. Part of the electricity used to pump the water will be generated at the other end of the transposition. New dams will be built to generate electricity in the São Francisco Basin.

The Northern Transposition Project from the Araguaia River to the Tocantins River will take place after the Araguaia National Park at an altitude of 170 m, where the Araguaia and Javaés Rivers converge. The transposition will require a 140 km canal with an average depth of 15 m with a tube 80 km long with pumping facility to Lajeado Reservoir at an absolute height of 210 m.

The Northern Transposition Project from the Tocantins River (210 m) to the São Francisco River requires a 60 km canal with an average depth of 20 m, tubes with 20 km and pumping facility to a run-of the-river dam at an absolute height of 390 m. Following, another tube 60 km long with pumping facility to a Seasonal-Pumped-Storage reservoir, with its level varying between 750 and 650 m to store water and energy. In addition, two dams at the São Francisco Basin will recover some of the energy used for pumping. The Northern Transposition Project has a 1.500 m3/s flow capacity.

Additionally, this article suggests the operation of the Sobradinho Reservoir at its lowest level. The Sobradinho Reservoir has a maximum flooded area of around 4200 km2, which results in an evaporation of around 14% of the São Francisco River flow (Operadora Nacional do Sistema Elétrico 2004). The Seasonal-Pumped-Storage sites proposed will be able to regulate the flow of the São Francisco River. The Sobradinho Dam will not be required and will operate at its minimum level to reduce evaporation.

Figure 11.7 shows the amount of water transposed to the São Francisco Basin, the area where the water can be used for irrigation and a preliminary suggestion of how the moisture might return to the other inland basins. In order to estimate the amount of moisture that would stay in the São Francisco Basin and the amount of moisture that would be carried to the inland basins, a climate and hydrological model should be developed with the intention to estimate the moisture dispersion and how it might affect the Brazilian climate and its rain patterns.

Fig. 11.7
figure 7

Transposition cycle in Brazil and wind direction probability distribution

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Due to its environmental flexibility, eucalyptus is the most widely used tree for biomass based electricity generation. It has a high productivity (more than 60 m3/ha/year have been reported (Couto et al. 2011)) and energy characteristics (wood density and heat capacity (Chen et al. 2014)). The tree genus has been acclaimed as one of the best options for energy production due mainly to the large number of species, which enables wide ecological distribution, favouring its introduction in various regions with different soil and climatic conditions (Couto and Müller 2008). Data used to estimate the water transpiration and biomass production assumed the Eucalyptus Grandis species planted with a spacing of 3 m × 3 m at the Três Lagoas Municipality (Sartorio 2014).

Assuming that the annual average precipitation in the São Francisco Basin is 1,200 mm and an water for irrigation of 12,000 m3/ha year (Confederação da Agricultura e Pecuária do Brasil 2011), and an average growth rate of 60 m3/ha year (Sartório 2014) (due to high solar radiation and water availability with irrigation). Thus, an approximately 100,000 km2 of irrigated plantation area would be required to remove 4000 m3/s of water from the São Francisco River for irrigation.

If all this area was used for the cultivation of eucalyptus, it would result in a production of 63 billion m3 of eucalyptus per year. If this eucalyptus were used for electricity generation, it would be able to generate around 90 GW of electricity at a 90% capacity factor. The planted biomass could be transported by waterway to the mouth of the São Francisco River and exported to other countries. In addition, the irrigated areas could produce sugarcane, corn, cotton and other crops (giving preference to crops that consume a lot of water).

It should be noted however that this transposition cycle might have a negative net hydroelectric generation. This means that the amount of energy required to pump will be higher than the amount of hydropower generation. This is because there is a great need for pumping and because the hydropower potential of most of the São Francisco Basin (up-river of the Sobradinho reservoir) is high at 307 m and few areas surrounding the São Francisco, where the moisture might precipitate, have a higher hydropower potential.

Discussion

The transfer of water between river basins is a very debatable issue because of the high costs involved and the multiple interests and uses of water. This study presents a new approach to transposition with positive and negative aspects. These aspects are mentioned below:

Positive:

  1. (1)

    Increase the availability of water in the São Francisco River Basin for irrigated crops.

  2. (2)

    Increase the energy storage in Brazil with Seasonal-Pumped-Storage (Hunt et al. 2014b).

  3. (3)

    Facilitate the construction of flood control systems in the Araguaia River Basin, which prevents the development of the region (Santos 2006; Costa 2012).

  4. (4)

    Create mechanisms to control the climate in the country. When there is a drought, an increase in transposition and biomass irrigation, might increase the humidity of the country.

Negative:

  1. (1)

    High implementation costs.

  2. (2)

    Reduction of overall hydroelectricity generation.

  3. (3)

    Environmental impacts with the construction and operation of the transposition projects and the intense irrigated plantations.

  4. (4)

    Indirect environmental impact resulted from the changes in climate. For example, it could be the case that the increase of transpiration in the São Francisco Basin creates a climatic condition that pushes the trade winds higher into the atmosphere that will possibly increase the precipitation in the São Francisco Basin.

  5. (5)

    Ecological consequences of planting many square kilometres of non-native species.

The limitations of this work is the need to develop a climatic and hydrological model to estimate to where the moisture transpired might be carried and where it might precipitate. The constraints which have not been quantified are the construction and operation costs of the transposition systems and the irrigated plantations. In addition, the environmental impacts involved should be quantified.

Conclusion

Climate change and climate adaptation has not been intensively studied and included in the strategic planning of Brazil. Climate change alters the climate behaviour patterns and the frequency of extreme events, which may result in substantial socio-economic and environmental impacts.

This article introduced a new mechanism named Watershed Transposition Cycle with Irrigated Biomass aiming to take water from where it may cause flooding problems and transport it where there is low water availability. The Transposition Cycle is an artificial water cycle generated by the transposition of water to another basin. This water is used for irrigation and then returned by the strong trade winds to the location from where it was removed.

An example of this mechanism is the transposition of the Xingú, Araguaia, Tocantins and Paraná Basins to the São Francisco Basin. The direction of the wind along the São Francisco River Basin carries moisture into Brazil, in the opposite direction of the transposition. This might increase the residence time of the water in the continent, which would increase the availability of water in Brazil.

It was found that an approximately 100,000 km2 of irrigated plantation area would be required to remove 4000 m3/s of water from the São Francisco River for irrigation. In eucalyptus plantation, this amount of land would be able to generate around 90 GW of electricity at a 90% capacity factor. In addition to increasing irrigation in Brazil, this mechanism can be used to assist adaptation to climate change, as it would include an artificial variable that would increase the humidity of Brazil’s countryside and have a direct impact on the country’s climate.

For future work, it is necessary to create a climate and hydrological models in order to estimate the amount of water that can be withdrawn from the São Francisco River with the transpiration of irrigated plantations and to estimate the moisture dispersion and where it might precipitate.

Eventually, it might be shown that Watershed Transposition Cycle with Irrigated Biomass is not a viable endeavour. However, it is important to understand that changes in land use and water use have an impact on the regional climate. It is important to understand the effects of these changes to better plan for future projects and for climate variations.