O presente trabalho consistiu na caracterização hidrológica de duas microbacias visando identificar critérios e indicadores hidrológicos que possam contribuir para a implementação de melhores práticas de manejo nas plantações de eucalipto e para o esclarecimento de possíveis impactos dessa atividade sobre a produção de água em quantidade e qualidade, na escala da microbacia hidrográfica. As microbacias experimentais monitoradas localizam-se na Fazenda Santa Terezinha, município de Bofete (SP). A microbacia E possui Eucalyptus grandis, usado para fins de serraria pela Eucatex S.A. Situada na mesma vertente da Bacia do Rio do Peixe, a microbacia P é destinada à pecuária extensiva, uso tradicional da terra na região. A caracterização hidrológica quantitativa baseou-se na análise dos dados pluviométricos e fluviométricos obtidos no decorrer de 2 anos de monitoramento contínuo (novembro de 2000 a outubro de 2002). A precipitação média anual registrada no ano hídrico de nov/00 a out/01 foi de 1.893,80 mm e 1.407,90 para nov/01 a out/02. O deflúvio anual para a microbacia E no primeiro ano hídrico foi de 148,76 mm e de 125,62 mm, para o segundo. As perdas médias ocasionadas por evapotranspiração no período monitorado somaram 1.513,66 mm. Para a microbacia P, o deflúvio observado para o ano hídrico de nov/00 a out/01 correspondeu a 383,35 mm e para nov/01 a out/02, 365,67 mm. As perdas médias por evapotranspiração nessa microbacia corresponderam a 1276,34 mm. A temperatura média observa entre set/01 a ago/02 foi de 21,38 ºC e a umidade relativa média, de 69,67 %. A microbacia P apresentou uma maior variação para todos os parâmetros físico-químicos usados para avaliar a qualidade da água do deflúvio e uma resiliência menor. As reduzidas concentrações de nutrientes no deflúvio da microbacia E e seu padrão estável de comportamento indicam melhor estabilidade hidrológica equilíbrio da floresta. Na microbacia E verificou-se que a resistência do solo à penetração para a linha de plantio, entre árvores foi inferior àquela observada fora da linha de plantio. Para a microbacia P, a avaliação foi feita na trilha de pisoteio do gado e fora da trilha, sendo que na trilha os valores de densidade do solo e índice de compactação foram mais expressivos. Os indicadores visuais sugeridos mostraram correspondência com os demais resultados observados. As microbacias hidrográficas monitoradas fazem parte do programa mais abrangente de Monitoramento e Modelagem de Bacias Hidrográficas desenvolvido pelo Instituto de Pesquisa e Estudos Florestais, através do Laboratório de Hidrologia Florestal do Departamento de Ciências Florestais da Escola Superior de Agricultura "Luiz de Queiroz", Universidade de São Paulo (ESALQ/USP). / The present work consisted of the hydrological characterization of two catchments aiming to identify hydrologic criteria and indicators that can contribute for the implementation of better management practices of Eucalyptus plantations, as well as the evaluation of possible impacts of these activities on catchment yield and quality. The experimental catchments are located at Fazenda Santa Terezinha, Bofete (SP). The catchment E is covered with Eucalyptus grandis, management for sawmill situated at Eucatex S.A. Catchment P is covered with pasture, traditional land use in the region. The quantitative hydrological characterization was based on the analysis of rainfall and streamflow data during two consecutive years (November of 2000 the October of 2002). The average annual precipitation for the water year of nov/00 out/01 was 1.893,80 mm and 1,407.90 mm for nov/01 out/02. The annual streamflow for the same water years were 148,76 mm and 125,62 mm, respectively. The average losses caused by evapotranspiration in the monitored period amounted to 1,513.66 mm. For catchment P, the streamflow observed for the water year of nov/00 out/01 corresponded to 383,35 mm and for nov/01 out/02, to 365,67 mm. The average losses for evapotranspiration in this catchment corresponded to 1276,34 mm. The average temperature observed between set/01 ago/02 was 21,38 ºC and the average relative humidity, 69,67 %. Catchment P presented a higher variation for all the studied parameters used physicist-chemistries to evaluate the quality of the water of the emanation and a lesser resilience. The reduced concentrations of nutrients losses in streamflow of catchment E, coupled with a more stable hydrological responses, reflect better protection from Eucalyptus forest. In the catchment, it was verified that the soil resistance to penetration in the plantation line, between trees, was lower than that observed outside of the plantation line. For catchment P, the evaluation it was made in the cattle track, where the values of soil bulk density and resistance to penetration were higher than those observed outside the cattle track. The suggest visual indicators of catchment health shown correspondence with the observed results. The monitored catchments are part of a broader of catchment environmental and monitoring developed by the Institute of Forest Research and Studies, through the Laboratory of Forest Hydrology of the Department of Forest Sciences of the Escola Superior de Agricultura "Luiz de Queiroz", University of São Paulo (ESALQ/USP).

This dissertation integrates a process-based hydrological investigation with an ongoing paired-catchment study to better understand how forest harvest impacts catchment function at multiple scales. We do this by addressing fundamental questions related to the stocks, flows and transit times of water. Isotope tracers are used within a top-down catchment intercomparison framework to investigate the role of geology in controlling streamwater mean transit time and their scaling relationships with the surrounding landscape. We found that streams draining catchments with permeable bedrock geology at the Drift Creek watershed in the Oregon Coast Range had longer mean transit times than catchments with poorly permeable bedrock at the HJ Andrews Experimental Forest in the Oregon Cascades. We also found that differences in permeability contrasts within the subsurface controlled whether mean transit time scaled with indices of catchment topography (for the poorly permeable bedrock) or with catchment area (for the permeable bedrock). We then investigated the process-reasons for the observed differences in mean transit time ranges and scaling behavior using a detailed, bottom-up approach to characterize subsurface water stores and fluxes. We found that the mean transit times in catchments underlain by permeable bedrock were influenced by multiple subsurface storage pools with different groundwater ages, whereas storage in the poorly permeable catchments was limited to the soil profile and that resulted in quick routing of excess water to the stream at the soil bedrock interface, leading to mean transit times that were closely related to flowpath lengths and gradients. Finally, we examined how and where forest trees interacted with subsurface storage during the growing season using a forest manipulation experiment, where we tested the null hypothesis that near-stream trees alone influenced daily fluctuations in streamflow. We felled trees within this zone for two 2.5 ha basins and combined this with isotopic tracing of tree xylem water to test if water sources utilized by trees actively contributed to summer streamflow. We rejected our null hypotheses and found that diel fluctuations in streamflow were not generated exclusively in the near-stream zone. We were unable to link, isotopically, the water sources trees were utilizing to water that was contributing to streamflow. Our results provide new process-insights to how water is stored, extracted, and discharged from our forested catchments in Western Oregon that will help better explain how forest removal influences streamflow across multiple scales and geological conditions. / Graduation date: 2012