Water use optimization through alternative water depths in the Formoso Irrigation District/Otimizacao do uso da agua no Perimetro Irrigado Formoso aplicando laminas alternativas de agua

This study aimed to propose an optimal cultivation plan using a separable linear programming model, with alternative water depths, that allows maximizing the net revenue of the Formoso Irrigation District (FID), specifically with respect to the area of family plots. The model used in this study was based on data from the 2010 Annual Agricultural Report of the 2nd Regional Superintendency of CODEVASF (Sao Francisco and Parnaiba Valley Development Company), the 2011 Service and Extension Plan for the Formoso Irrigation District and further information provided by this government department. Based on the studied crops and their respective water response functions, on the constraints of cultivated area, prices and production costs, the maximization of the net revenue in the FID was equal to R$ 68,384,956.53, using the following cultivation pattern: 30 ha of pumpkin, 30 ha of Phaseolus beans, 977 ha of watermelon, 1868 ha of banana, 1200 ha of papaya and 300 ha of Tahiti lime. The optimal solution found by the model indicated that the monthly water availability in the FID did not constitute an effective restriction to crop production, since in all months the water volume needed was lower than the maximum volume that the FID can provide (10,833,500 [m.sup.3]). For the monthly volumes used in the solution, the available annual volume will not be restrictive if the annual pumping capacity is higher than 79,649,000 [m.sup.3]. Key words: irrigation planning economic efficiency O objetivo do presente trabalho consistiu em propor um plano otimo de cultivo utilizando um modelo de programacao linear separavel, com laminas alternativas de agua, que proporcione a maximizacao do retorno liquido do Perimetro Irrigado Formoso (PIF), especificamente quanto a area de lotes familiares. O modelo utilizado neste estudo foi baseado em dados do Relatorio Anual Agricola da 2a Superintendencia Regional da CODEVASF em 2010, no Plano de Servico e extensao para o PIF para 2011 e informacoes adicionais apresentadas por este departamento governamental. Com base nas culturas consideradas e suas respectivas funcoes de resposta a agua, nas restricoes de area cultivada, nos precos e nos custos de producao, a maximizacao da receita liquida no Perimetro Irrigado Formoso foi de R$ 68.384.956,53, utilizando o seguinte padrao de cultivo: 30 ha de abobora, 30 ha de feijao Phaseolus, 977 ha de melancia, 1868 ha de banana, 1200 ha de mamao e 300 ha de limao Tahiti. A solucao otima encontrada pelo mod