Vulnerability analysis to contamination of the water aquifer and soil infiltration rate of Almada basin of the river and the adjacent coastal area

Abstract

Esta pesquisa teve como objetivo a identificacao de areas vulneraveis a contaminacao do aquifero freatico da Bacia do Rio Almada e area costeira adjacente, Bahia - Brasil. Para tanto, foi realizada a caracterizacao da area de estudo, com base em dados primarios e pre-existentes; bem como da taxa de infiltracao e da caracteristica fisica do solo. O mapa de vulnerabilidade a contaminacao do aquifero freatico foi obtido a partir da integracao das caracteristicas climatica, declividade, profundidade do nivel freatico, solo e uso e ocupacao do solo, por meio de algebra de mapas em ambiente de Sistema de Informacao Geografica (SIG) na escala de 1:100.000, classificado em cinco graus de vulnerabilidade, assim identificados: muito baixo, baixo, medio, alto e muito alto. Os resultados apontaram que as areas com maior vulnerabilidade a contaminacao do aquifero freatico situam-se, principalmente, na regiao costeira, nos locais relacionados aos solos arenosos, baixa declividade e nivel freatico raso. Os 15 pontos de amostragem de solo permitiram caracteriza-lo como de textura arenosa com elevados teores de areia (fina + grossa) - acima de 90% da composicao granulometrica e valores de taxa de infiltracao entre 0,00005 e 0,00075 cm/s. As informacoes levantadas e analisadas constituem produtos que poderao subsidiar tomadas de decisoes, priorizando acoes que venham a minimizar os danos ambientais como forma de resguardar a qualidade ambiental, orientar o manejo do solo e a recuperacao ambiental. ABSTRACT Analysis of vulnerability to phreatic aquifer contamination and infiltration rate of the soil of Almada River Watershed and adjacent coast – BA . This research aimed to identify areas vulnerable to phreatic aquifer contamination Almada River Watershed and adjacent coastal area, Bahia - Brazil. Therefore, it was performed to characterize the study area, based on the primary and preexisting; well as the permeation rate and physical characteristics of the soil. The map of vulnerability to phreatic aquifer contamination was obtained from the integration of climate characteristics, slope, water table depth, and soil use and occupation of land by means of map algebra environment in Geographic Information System (GIS) on the scale of 1:100,000, classified into five degrees of vulnerability, thus identified: very low, low, medium, high and very high. The results showed that areas with greater vulnerability to phreatic aquifer contamination are located mainly in the coastal region, in areas related to sandy soils, low slopes and shallow groundwater. The 15 points allowed soil sampling characterize it as sandy with large amounts of sand (fine + coarse) - over 90% of the particle size distribution and infiltration rate values between 0.00005 and 0.00075 cm/s. The information gathered and analyzed are products that can support decision making, prioritizing actions that will minimize environmental damage as a way of protecting environmental quality, direct soil management and environmental remediation. Keywords: land use and occupation ; geographic information system; environmental planning.