Anthropogenic influence on addition of salts in the perennialized section of the Curu basin, Ceará State, Brazil.

Abstract

This research aims to analyze the variations of total salt along the perennialized section of the Basin of Curu River, Ceara state, Brazil, due to the anthropogenic influence. The indicators of ionic load used in this work were: electric conductivity (EC), sodium, chloride and Sodium Adsorption Ratio (SAR). Samples of water were collected monthly from October 2004 to September 2005, in nine points distributed along the river Curu and its main effluents, in a total of 102 samples. Analysis of variance and comparison of averages with the test of Tukey at 1% level were used in order to investigate water alterations along the studied section of the basin. The results indicate an increment of total salts along the basin. At point P1 (Serrota Dam, beginning of the perennialized section) average value of EC was 0,50 dS.m-1, while at P9 (Pedras Farm, near the basin outlet) it was 0,70 dS.m-1. The most significant differences among the parameters were observed at points P1, P2 and P3 (beginning of the perennialized section), and P8-P9 (down part of the Curu basin). The major alterations were registered at points situated in irrigated perimeters or urban areas, expressing the anthropogenic influence on the quality of the surface water of the Curu River basin. Sodium was the ion presenting the highest increment in concentration.