Otimização e simulação plurianual conjunta de dois reservatórios interligados e dois perímetros irrigados no semiárido paraibano.

Abstract

In this work a operational study for the system consisting of two interconnected reservoirs, Coremas and Mae D'agua, which are, together, the largest water dam o f Paraiba state and the third largest one of the northwest region of Brazil, were performed. The use of its water includes urban demands, regulated release flow and irrigation. Two irrigation sites, which are located in the neighborhood of the dams and between the cities o f Souza and Aparecida-PB, with areas of 5084 ha and 2000 ha and subdivided into 3 and 2 production units according to the soil type, respectively, were taken into account. The reservoirs, which are part of the Pianco river basin, and the irrigated croplands are located within a semiarid region with low precipitation and high evaporation index. The operational rules were achieved by mathematically describing the system as a linear programming problem, whose objective was to maximize the net profit. It has been considered different hydro-climate and operational scenarios of sets of 6 years of monthly data as well as the guarantee of the sustainability of the system. The climate scenarios were characterized as dry, normal, medium and wet and the operational scenarios were related with the regulated release flow, which were taken as 4 m3/s and 5.5 m3/s, and the reservoirs initial volumes, which were taken as 40%, 60%, 80% and 100% of their capacities. Maximum areas for fifth types of crops were design for each production unit of the irrigated croplands according to soil type. The software CISDERGO 2.0 (Cropping and Irrigation System Design with Reservoir and Groundwater Optimal Operation), which is designed to work within MATLAB environment and whose solution is based on a recursive linear programming procedure, was used. The results have shown that an increase of the regulated flow implies in a reduction of irrigated areas and the net profit. This operational procedure, which limits the amount of water available for irrigation, along with the hydro-climate and initial conditions play an important role on the allocation of areas for irrigated crops.