Banca de DEFESA: SARA SILVA ALVES

INTEGRATION OF MULTI-CRITERIA ANALYSIS AND GIS AS A SUBSIDY TO THE CONTAMINATION RISK

 MODELING IN THE MUNICIPALITY OF ALAGOINHAS - BA

Groundwater; Contamination Risk; Multiple criteria analysis.

Groundwater plays an essential role in the aquatic ecosystems, keeping rivers and lakes perennial. Due to its resilience and storage capacity, this resource is considered to be an important alternative during water crises. Despite its global importance, the impacts caused by human actions are increasingly affecting this ecosystem service. Thus, the present proposition is focused on the integration of geo-environmental parameters, as a subsidy for assessing the risk of contamination. Alagoinhas is one of the cities in Brazil that has most of its population supplied by groundwater (85%). It is located in the eastern region of the state of Bahia with an area of approximately 761km², situated 107 km north of Salvador. The population is currently estimated at 152,327 inhabitants, resulting in a population density of 188.7 inhabitants/km. It is inserted in the tectonic setting of the Recôncavo-Tucano-Jatobá Basin. Around 80% of the mapped area is made up of lithotypes that constitute the Marizal and São Sebastião formations. Besides these ones, the Barreiras formations in the region, occupying less than 10% of the area, the Aliança formations, The Grupo Ilhas and the Candeias, Itaparica and Sergi formations, besides rocks of the crystalline basement are found. Factors such as terrain slope, soil types, drainage, land use and occupation, and the number of tube wells are directly associated with the risk of groundwater contamination. These parameters have been integrated to perform a modeling of the risk of groundwater contamination in the city. Therefore, the objective was to ally the Geographic Information System to the Analytic Hierarchy Process as a methodology, aiming at the confection of the groundwater contamination risk map. In this model, the zones were classified according to the risk of groundwater contamination. The final model proposed four classified zones, these being: low risk (13.5%), medium risk (44%), high risk (40%), and very high risk (1.8%). Through this model, a more detailed planning and organized prevention, and mitigation measures according to the region's degree of risk can be organized, which can favor public managers.