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River Flows In Estuarine Regions In Brazil: A Downscaled Analysis On Long Term Climate Scenarios (2011-2040-2070-2100)

Congress: 2015
Author(s): Bruno Castro de Carvalho (Brasilia, Brazil), Priscilla Santos, Geraldo Goes

Secretaria de Assuntos Estratégicos da Presidência da República do Brasil1, Ministerio do Meio Ambiente do Brasil2



Keyword(s): Sub-theme 17: Climate change, impacts and adaptation,
Abstract

The Intergovernmental Panel on Climate Change reports show that climate change, particularly in South America, represents a major threat to sustainable development, by affecting directly and indirectly significant portion of the population and their health, as well as water resources, urban and rural infrastructure beyond their respective value chains and estuarine zones. According to Defant (1960), the estuary is a coastal environment of transition between the continent and the adjacent ocean, where seawater is diluted by freshwater from continental drainage. This specific ecosystem is forced by local and remote agents generated by the action of climatic, oceanographic, geological, hydrological, biological and chemical events, which occur in the drainage basin and in the adjacent ocean. This work consists in a novel and unprecedented attempt to approximate the climate and hydrologic modeling in estuarine areas, considering a time horizon of 30 years (2011-2040). To address this challenge, this article unfolds in four steps. The first one is based on the study of Alcantara (2004), which consists of the characterization of the drainage basin of the Rio Anil, located in São Luiz in the state of Maranhão, Brazil, which consists in our methodological context to conduct this work and was chosen on the basis of preliminary tropical location, socioeconomic vulnerability and dependence on water resources. These particular conditions enable the replication of this methodological approach in other regions. The second step consists of the calculation of the baseline scenario, the flow of the Rio Anil through the Schreiber Equation (1904) and according to Holand (1978), given as Eq. I: ln P / Δƒ = E0 / P where P / Δƒ is the inverse of the runoff and E0 is the maximum amount of water that can be evaporated annually. The evaporation, according to Holand (1978) can be calculated by the equation Eq. II: E0 = 1,2x109. E(-4,62x10^3)/(T) with T in degrees Kelvin. Thus, once the calculated rate of runoff Δƒ/P, the discharge (Qf) can be obtained by knowing the total area of the drainage area (At), and the time interval analysis, representative for calculating the average values of E0 and P, through the following equation, Eq. III: Qf = Δƒ / Dt x At (m2). The third stage consists of the future calculation of river discharges of the Anil River, considering the previous equations through regionalized climate scenarios, acquired by the Secretariat of Strategic Affairs of the Presidency of Brazil (SAE/PR in Portuguese) in a partnership with the National Institute for Space Research (INPE in Portuguese). For that, the results of regionalized climate scenarios of temperature and precipitation will be used, considering the summer season, taking into account the larger amplitudes, with a spatial resolution of 20 x 20 km of the EtaHadgen and EtaMiroc5 models for the Representative Concentration Pathways (RCPs) in 4.5 and 8.5 variations, according to the 5th IPCC report in 2013. This unprecedented future calculation, since it takes ownership of data generated by a climate model regionalized to Brazil, considers 3 periods of 30 years for each one of the RCPs of 4.5 and 8.5 - 2011-2040, 2041-2070 and 2071 -2100 - with combinations of maximum rainfall and maximum temperature and minimum temperature and minimum precipitation. That said, the following combinations will be generated through the Eta Hadgen: 1) EtaHadgen (4.5) - summer - minimum temperature and minimum rainfall - 2011-2040, 2041-2070 and 2071-2100; 2): EtaHadgen (4.5) - Summer - maximum temperature and maximum precipitation - 2011-2040, 2041-2070 and 2071-2100; 3) EtaHadgen (8.5) - summer - minimum temperature and minimum rainfall - 2011-2040, 2041-2070 and 2071-2100; 4): EtaHadgen (8.5) - Summer - maximum temperature and maximum precipitation - 2011-2040, 2041-2070 and 2071-2100. EtaHadgen (8.5) -- summer. Additionally, through the EtaMiroc5 model the following scenarios will be generated: 5) EtaMiroc5 (4.5) -- verão - temperatura mínima e precipitação mínima - 2011-2040, 2041-2070; 6) EtaMiroc5 (4.5) -- verão - temperatura máxima e precipitação máxima - 2011-2040, 2041-2070e 2071-2100; 7) EtaMiroc5 (8.5) -- verão - temperatura mínima e precipitação mínima - 2011-2040, 2041-2070; 8) EtaMiroc5 (8.5) -- verão - temperatura máxima e precipitação máxima - 2011-2040, 2041-2070 e 2071-2100. Finally, the last step consists of evaluating the behavior of the flow of the Rio Anil facing the different projected scenarios, as well as flagging some measures of adaptation to climate change, particularly for users upstream and downstream of the given watercourse, considering also the peculiarity of its occurrence in an estuarine zone. ALCÂNTARA, E.H. (2004). Mudanças Climáticas, incertezas hidrológicas e vazão fluvial: o caso do Rio Anil. ALEXANDRE, A. M. B. 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