Estimativa dos benefícios econômicos do uso da água do sistema Coremas/Mãe d'Água para irrigação nas várzeas de Sousa.

Abstract

A system o f two interconnected reservoirs, Coremas and Mae D'Agua, is located at south-western part of the Paraiba state. They are fed by three rivers: Pianco, Emas and Aguiar. Togheter they, are the largest reservoir of the Paraiba state and the third largest one in the northeast of Brazil. Their waters are used for human supply, hydroelectric power generation, irrigation and fishing activities and to meet downstream water demand required from the Rio Grande do Norte state. Recently, an open channel, which is connected to the Mae D'Agua reservoir and has a capacity of 4 m3/s and a length of 37 Km, has been built to supply an irrigation site, of nearly 5000 ha, in the neighborhood of the city of Sousa-PB. The aim of this work is to study the behavior of the system and ways to maximize the economical benefits through the choice of irrigation areas for 13 selected types of fruits and the irrigation systems while attending all water demands for the reservoirs. The mathematical model uses a recursive linear programming method, in order to couple with the nonlinearities o f the problem. The system is modeled using 85 decision variables and 1479 constraints that represent the physical and operational behavior of the system, including the sustainability of the reservoirs. The analyses were performed using sets o f 6 years of hydro-climate data series, as well as their monthly mean values, which represent dry, normal, wet and average scenarios. Sensitivity analyses were also performed taking into account the variability of the crop's production costs, selling prices, scheduling, requirement of minimum production area and with scenarios of orchads in settlement or with full yield production, choice o f irrigation systems and capacity of the open channel.