Rutinéia Tassi

Telhado verde: uma alternativa sustentável para a gestão das águas pluviais

O crescimento da populacao urbana tem gerado impactos negativos muito mais significativos sobre o meio ambiente, tais como as enchentes, que se mostram cada vez mais severas em decorrencia da impermeabilizacao do solo com a falta de um plano de manejo das aguas pluviais, e o emprego excessivo de canalizacoes. Diante da necessidade de uma mudanca de paradigma na concepcao das obras de drenagem pluvial, surgiu o conceito de Desenvolvimento de Baixo Impacto (DBI), cujo principio e a gestao das aguas pluviais proximo a sua origem, buscando a utilizacao de tecnicas que permitam mimetizar funcoes naturais que sao perdidas com a urbanizacao. Nesse contexto, os telhados verdes vem sendo empregados, pois, alem de outros beneficios, contribuem para o controle quali-quantitativo das aguas pluviais. Neste trabalho sao apresentados os resultados de um estudo de longo prazo sobre a eficiencia de um telhado verde no controle quantitativo das aguas pluviais. Foi possivel reduzir, em media, 62% do escoamento superficial, promovendo um retardo no escoamento e reduzindo as vazoes de pico, o que gerou o controle desejado. No entanto, sua eficiencia e altamente influenciada pelas condicoes climaticas e de umidade do solo que antecedem cada evento chuvoso.

Estimativa da infiltração de água no solo na escala de bacia hidrográfica

The spatial variability of soil characteristics makes the estimation of water infiltration highly dependent on the scale of analysis. Many studies require information on the dynamics of infiltration to describe the dynamics of other processes associated with water, sediment and solutes. This study aims to use two methodological strategies to estimate water infiltration at the catchment scale. The parameters of two infiltration models were fitted to a data set collected over two years of monitoring (77 rainfall-runoff events) occurring under different land use and management conditions in a rural catchment of 1.2 km2. The results of fitting to the two infiltration models at the catchment scale were compared with those obtained from two site-specific methods for estimating infiltration. With the set of monitoring data, it was possible to establish an infiltration model for the monitored catchment area. Furthermore, the results indicate that the comparison between values from the models and site-specific values are strongly dependent on the scale of analysis. That is, the site-specific measures showed mean values of high infiltration rates for this catchment, but field observations indicate low infiltration, especially in saturated areas, which affect runoff in this catchment area. This is in contrast with the results obtained by the estimation models, which present a lower order of magnitude for the estimated values of infiltration, due to the greater incorporation of factors controlling the process in their methodology, among other aspects.

Projeções de Vazão Afluente à Lagoa Mangueira com Base em Cenários de Mudanças Climáticas

This manuscript presents the assessment of climate change impacts on the streamflow at the Mangueira lake watershed, located in Southern Brazil, based on precipitation predictions of twenty Atmospheric/Ocean General Circulation Models (AOGCMs) that feed a hydrologic model named IPH II. The projections were based on two emission scenarios of the IPCC that set the forcing conditions for the AOGCMs to estimate future climate: A2, characterized by higher emissions and B2, characterized by lower emissions. The MAGICC/ScenGen was used to obtain the projected monthly anomalies of precipitation for the scenarios A2/B2 at two future time intervals centered at 2030 and 2070. Time series of projected precipitation were estimated using the delta change approach. The results in terms of average annual flow shows that mean value of the anomalies on the near horizon resulted very similar, equal to +2.86%(A2) and +2.48%(B2). This statistic increased on the long horizon, with a mean value of the anomalies of +16.94%(A2) and +11.83%(B2). The dispersion among results of the AOGCMs showed anomalies that may reach [+10%,−7%] in the near future and [+30%,−20%], in the long horizon. Thus, although there was higher agreement between AOGCMs in increasing flows, it is important to highlight the dispersion of results.