A new method to evaluate the vulnerability of watersheds facing several stressors: A case study in mediterranean Chile.

Freshwater systems are subjected to multiple anthropogenic stressors and natural disturbances that act as debilitating agents and modifiers of river systems, causing cumulative and synergistic effects that deteriorate their health and result in watershed vulnerability. This study proposes an easy-to-apply spatial method of watershed vulnerability evaluation using Geographic Information Systems (GIS) in the Andalién River watershed, located in the Chilean mediterranean. A watershed vulnerability index (WVI) based on three sub-indices - anthropogenic stressors, environmental fragility and natural disturbances - was developed. To determine the index grouping weights, expert surveys were carried out using the Delphi method. We subsequently normalized and integrated the factors of each sub-index with relative weights. The ranges of each thematic layer were re-classified to establish vulnerability scores. The watershed was divided into three sections: headwaters zone, transfer zone and depositional zone. The watershed vulnerability index showed that 41% of the watershed had very low vulnerability and 42% had medium vulnerability, while only 1% - in the depositional zone - had high vulnerability. A one-way ANOVA was carried out to analyze the vulnerability differences among the three sections of the watershed; it showed significant differences (F (2, 16) = 8.15: p < 0.05). The a posteriori test showed differences between the headwaters and depositional zones (Tukey test, p = 0.005) and between the transfer and depositional zones (Tukey test, p = 0.014). To validate the WVI, water quality was measured at 16 stations in the watershed; there was a significant correlation between vulnerability level and NO2- levels (r = 0.8; p = 0.87; α = 0.05) and pH (r = 0.8; p = 0.80; α = 0.05). The WVI showed the cumulative effects of multiple stressors in the depositional zone of the watershed. This is the first study to evaluate and validate non-regulated watershed vulnerability with GIS using multiple anthropogenic and natural stressors.

Elaboração de Carta de Adequabilidade Ambiental de uma pequena propriedade rural no município de São Miguel Arcanjo, São Paulo, utilizando técnicas de geoprocessamento / Preparation of environmental statement of fitness for a small rural property in the municipality of São Miguel Arcanjo, São Paulo, Brazil, using geoprocessing techniques

RESUMO Utilizando técnicas de geoprocessamento, cartas de declividades, de solos, de uso e cobertura vegetal, a Lei Federal nº 12.651/2012 e as recomendações do Forest Stewardship Council (FSC) para áreas ripárias, este trabalho teve por objetivo elaborar uma Carta de Adequabilidade Ambiental que indica os níveis de adequação ambiental e legal da área de estudo. A Carta de Uso do Solo e Cobertura Vegetal mostrou que o uso agrícola ocupa 44% da área de estudo, seguido pela vegetação nativa (29,1%). A Carta de Declividaderevela que 62,1% da área de estudo possui classe de declividade entre 6 e 12% e 23,3% entre classe de 12 a 20%. Na área de estudo foi identificado somente o Latossolo Vermelho Distrófico, de baixa vulnerabilidade à erosão. Baseado na lei já citada e recomendações do FSC (2005) para gerenciamento de áreas ripárias, foi elaborada a Carta de Usos Restritosna qual a área de preservação permanente (APP) existente ocupa 22,4% da área, a APP a recompor 0,3%, a reserva legal 18,3% e a área de gestão ripária 9,9%. Essas três últimas cartas temáticas foram sobrepostas, considerando sua importância na conservação dos recursos hídricos e atendimento legal, para gerar a Carta de Uso Conservacionista, que demonstra que as áreas com alta e muito alta prioridade são as APP e as de declividade entre 12 e 20% e representam 45,5% da área de estudo. Essa carta foi sobreposta pela Carta de Uso do Solo e Cobertura Vegetale por meio de uma soma ponderada foi produzida a Carta de Adequação Ambientalque indica os níveis de adequação da área de estudo. A integração de variáveis ambientais com os requisitos legais se mostrou eficaz para avaliar as áreas potenciais para adequação ambiental, indicando que aproximadamente 44% da área de estudo necessita de algum tipo de adequação.

ABSTRACT According geoprocessing techniques, slope maps, soil, land use and land cover, the Federal Law number 12.651/2012 and the recommendations of the Forest Stewardship Council (FSC) for riparian areas, this study aimed to develop a Map of Environmental Suitability that indicates levels of environmental and lawful adequacy of the study area. The Map of Land Use and Vegetation Cover showed that agricultural uses occupy 44% of the study area, followed by native vegetation (29.1%). Meanwhile, the Map of Slope reveals that 64.8% of the study area has slope class between 6 and 12%, and 22.6% between 12 and 20%. In the study area, only Dystrophic Red Oxisols was identified, with very low vulnerability to erosion. Based on the abovementioned law and recommendations of the FSC (2005) for management of riparian areas, the Map of Restricted Uses was produced, in which 22.4% of the area is composed of permanent preservation areas (APP), 0.3% of APP to recompose, 18.3% of legal reserve (LR) and 9.9% of riparian management areas. The three last thematic maps were overlaid, considering the importance in the conservation of water resources and the legal attendance to generate the Conservationist Use Map, which shows that the areas with high and very high vulnerability are the APP; those with slope between 12 and 20% represent 45.5% of the study area. This map was overlaid by the Land Use and Land Cover maps, and an Environmental Adaptation Map was produced using a weighted sum, indicating adequacy levels of the study area. The integration of environmental variables with legal requirements proved to be effective to assess potential areas for environmental compliance, indicating that approximately 44% of the study area needs some sort of adjustment.