Avaliação dos impactos decorrentes do uso das águas do baixo rio Bodocongó (PB), em áreas irrigadas.

Abstract

Bodocongo river basin is located in the Southwest area of the State of Paraiba and is part of watershed of Paraiba river. The river passes through the municipalities of Campina Grande, Queimadas, Caturite and Barra de Santana in the north-south direction. When the river crosses the city of Campina Grande it receives several diffuse sewage contributions and the final effluent of the Wastewater Treatment Plant (WTP). The interval between the WTP and the river end, called the "Baixo Bodocongo", has about 50 km of extension. It is used for unrestricted irrigation of fodder and vegetables (lettuce, cabbage, tomatoes, etc), washing of clothes and primary contact recreation. Due to the importance of this water resource for the area, evaluation of the sanitary and physical-chemical quality, the impacts of its use on the sanitary quality of the irrigated products and the soil salinization process is a necessity. In 6 (six) samples collection campaigns at 7 (seven) different locations it was observed that the water of the "Baixo Bodocongo" was inappropriate for unrestricted irrigation. None of these points conform simultaneously to two recommended standards of WHO for unrestricted irrigation: fecal coliforms < 1000 CFU/lOOml and helmints eggs < 1 egg/1. The cabbages irrigated with water presented a concentration of 1000 MPN/g, 17 times higher than the maximum allowed by the Brazilian legislation for the raw vegetable consumption. These waters presented high salinity, with electrical conductivity varying from 2,421 to 3,510 uS/cm, classified as "moderate to severe restriction for irrigation". The evaluation of the sal content of these irrigated soils demonstrated that these areas already present high salinization level compared to the same soils in adjacent non irrigated areas, perhaps due to high salt content of water and inadequate management of the irrigation (absence of drainage system, non uniform water distribution),. In agreement with the legislation CONAMA 20/86 the water of "Baixo Bodocongo" was classified as Class 4, destined to navigation, landscape harmony and other less demanding uses. This situation demonstrates the urgency for collection and treatment sewage of Campina Grande in order to minimise the impacts in the "Baixo Bodocongo" and to guide farmers to adopt appropriate management practices for the irrigation system.