Andrea Sousa Fontes

Cost-benefit analysis of reservoir operation scenarios considering environmental flows for the lower stretch of the São Francisco River (Brazil)

A alocacao ambiental da agua consiste em considerar o meio ambiente como licito usuario da agua. A importância em determinar as necessidades hidricas da agua para protecao do ecossistema, e reconhecida mundialmente, entretanto as implementacoes praticas de vazoes ambientais sao restritas, necessitando da avaliacao dos impactos dessa implementacao nos demais usuarios da agua. Nesse contexto, o artigo objetiva avaliar o impacto economico no setor eletrico considerando as vazoes ambientais como restricao de escoamento a jusante dos reservatorios. O estudo de caso e o baixo curso do rio Sao Francisco, uma regiao que presenta uma degradacao social e ambiental acentuada com extrema relevância para o sistema energetico do Brasil. A metodologia adotada compreendeu a construcao de cenarios de operacao de reservatorios, modelagem matematica do sistema hidrico e analise custo-beneficio para o setor energetico. A simulacao aponta a possiveis conflitos entre os usos nao consuntivos. Avaliando a analise custo-beneficio para periodos normais e secos, os primeiros resultam em perdas financeiras totais para o setor eletrico, enquanto os segundos em ganhos totais, permitindo acordos entre a geracao de energia e a implementacao de vazoes ambientais no baixo curso do rio Sao Francisco.

Identification of the degree of impact of dams on the hydrologic regime of semi-arid rivers: an evaluation of the DHRAM method

The flow regulation that results from the implantation of dams causes consequences to the river ecosystems due to the modification on the characteristics of the hydrologic regime. The investigation of these changes become relevant, mainly in semi-arid regions where there is a great amount of these hydraulic structures and lack of such analyzes. Considering the above, this paper aims to evaluate the Dundee Hydrological Regime Alteration Method (DHRAM) through the classification of the degree of impact of dams located on rivers Itapicuru, Paraguacu and their tributaries, verifying the adequacy of its use to represent the semi-arid hydrologic regime. Thereby, the DHRAM was applied in three versions: considering the thresholds that define the scores to classify the degree of impact in its original set (accordingly to Black et al. (2005)); with the adjustment of those thresholds to local conditions; and, with the regrouping of variables and adjustment of thresholds. The results showed that the method in its original set is applicable to semi-arid rivers, however it tends to be very restrictive against the high natural hydrologic variability characteristic of these rivers, and it ends up pointing to a high degree of alteration for dams that are known for not causing a very siginifcant flow regulation. The DHRAM with the regrouping of variables and the adjustment of thresholds presented the classification that approached the most to the known characteristics of the studied dams, being useful for the evaluation of the impact of dams still in project, and also to guide the adoption of operating rules that minimize the most significant hydrologic alterations that are identified.

Water permit integration in the Paraguaçu River Watershed (Bahia)

In Brazil, water regulatory agencies adopt two different methodologies of equating water balance for the purposes of water permits: one that considers the uses for surface water withdrawal and waste water discharge in an integrated way, and one that analyses these two uses as demands that do not relate with each other. In the state of Bahia, this analysis disregards the integration of quantitative and qualitative uses. Furthermore, at the moment, there are not internal procedures that enable the integration of the water permit with other water resources management instruments. In this context, the aim of this work consists of analysing the advantages and limitations of the implementation of the equating methodology that integrates the quali-quantitative analysis of the water balance for purposes of water permit, compared with current procedures in the state of Bahia. For this analysis, a diagnosis of use of the Paraguaçu River Watershed (BHRP) was developed through the Water Balance Control System (SCBH), simulating the two methodologies and comparing potential water use index. The results reinforce that the methodology of equating the quali-quantitative water balance does not represent an advance for water resources management when the other instruments, present in the State Water Resources Policy, are not integrated with the water permit.

MODELAGEM HIDROLÓGICA DE SISTEMA HÍDRICO COMPLEXO DO SEMIÁRIDO BAIANO

A gestao dos recursos hidricos depende da caracterizacao da dinâmica do escoamento na bacia hidrografica, a qual pode ser fundamentada atraves do conhecimento de variaveis hidrologicas, adquirido com o monitoramento continuo dessas variaveis. No entanto, esse monitoramento e, muitas vezes, escasso, especialmente em bacias que apresentam vazoes de menores magnitudes, tal como ocorre em regioes semiaridas. Tal problema tem sido atenuado com adocao de ferramentas matematicas de modelagem hidrologica, que gera informacao a partir da simplificacao da representacao e compreensao do comportamento hidrologico da bacia. O presente trabalho teve como objetivo propor ajuste metodologico de calibracao para modelar o comportamento hidrologico da bacia hidrografica do rio Salitre, sub-bacia do rio Sao Francisco, localizada em regiao semiarida, que configura um sistema hidrico complexo devido as caracteristicas climatica e geologicas, utilizando o modelo hidrologico SMAP. Foram contempladas as etapas de calibracao e validacao do modelo em sua versao diaria, sendo proposta a aplicacao da tecnica de multicalibracao, que consiste na calibracao de diferentes conjuntos de parâmetros de acordo com condicoes hidrologicas distintas e criterios de calibracao. Os resultados obtidos com a multicalibracao foram comparados ao resultado da calibracao convencional do modelo, sendo verificada melhoria na representacao das vazoes com a adocao da tecnica de multicalibracao.