Operação integrada dos reservatórios Engenheiro Ávidos e São Gonçalo.

Abstract

In this work, a study about the behavior of a two in series reservoirs system, Engenheiro Avidos and Sao Gongalo, with multiple water use such as urban water supply, irrigation, extensive fishing and downstream-regulated flow, was made. The reservoirs are located in the Alto Piranhas river basin, within the semiarid region of the Paraiba state. The aim was to study their performance with respect to the maximization of the net profit deriving from irrigated agriculture and of the extensive fishing when operating them in an individual or integrated way. In the optimization process, a monthly based nonlinear model, developed in ambient Matlab®, was applied. The solution tries to satisfy the physical, agronomic and operational constraints, including the reservoir water sustainability, in form of linear and nonlinear equations. Three different climatic situations, which were called of average, dry and rainy climatic scenarios, all for a period of twelve months, were considered. In fact, there were idealized and proposed twenty-six scenarios involving the reservoir system (individualized or integrated), climatic situations (dry, average or rainy), irrigation (proposed or existent), plantation scheduling (only perennial or perennial and seasonal), inflow (with reduction or with Sao Francisco river transposed flow) and types of cultures (real and hypothetical). The initial volumes of the reservoirs were defined through a series of historical data. The results showed that operating the system in an integrated way, they provide a greater net profit, with irrigated areas bigger than the ones attained with the optimization of the individualized reservoirs system. The extensive fishing is an economical activity that should to be developed because of its potential of income and employment generation. With the transposition of a flow of 3 m3/s from the Sao Francisco river, the same system, even when operating in a drought situation, was capable to irrigate areas three times larger than the one attained for a medium climatic scenario without transposition. Using water for irrigation, the evaporative losses were reduced in up to thirty one percent, which demonstrates the need to use the water for this purpose.