Spatial evolution of irrigated areas using remote sensing – the Medium Paraíba do Sul Valley, Southeast of Brazil

Abstract

This study intends to evaluate the spatial analysis of the rice irrigation areas in the Medium Paraíba do Sul Valley for the period comprised between 1988 and 2003. Rice irrigation is a historical activity in Paraiba Valley being responsible for 51% of the water supply in this region. Supervised Classification was made for the multitemporal interpretation of remote sensing data (Landsat TM) using the software SPRING, ver 3.0. The analysis encompassed four regions (Guaratinguetá, Tremembé, Pindamonhagaba e Lorena-Canas), which represent 82% of the total irrigated area in the Paraiba Valley. The results show a significant decrease in irrigation area in Lorena-Canas (32.4%) and Pindamonhangaba (22.7%) and a smaller one in Tremebé region (6.4%). In contrast, Guaratinguetá region has presented an increase in irrigation area (14.2%). For the four regions analyzed, a reduction of 11.8% in irrigated area has been observed. Unlike other regions of São Paulo State, the irrigation activity in the Paraíba Valley is decreasing notably due to rapid urbanization and mineral extraction near, or on alluvial plan, contributing to the reduction of irrigated rice cultivation and elimination of wetlands ecosystems.