Unpaved roads may induce adverse effects on downstream water resources by increasing suspended sediment concentration (SSC). This study documents the localized impacts on stream SSC of six unpaved road–stream crossings in the rural Guabiroba River Catchment, in southern Brazil. Results demonstrated that SSC values downstream of road–stream crossings was between 3.5 and 10 times higher than upstream SSC at all third‐ and fourth‐order stream locations. However, downstream values were statistically undistinguishable from those collected upstream of road–stream crossings at fifth‐order sampling sites. These findings suggest that localized road effects on stream SSCs are scale‐dependent in that these are important for low‐order headwater streams yet undetectable for their higher order counterparts. Findings point to the importance of low‐order stream crossings in increasing SSC and the need to further explore the role of unpaved roads as agents of water quality degradation in agriculturally active rural settings.
O conhecimento da vazão ecológica é de suma importância para se determinar a disponibilidade hídrica, visando ao gerenciamento dos recursos hídricos. O presente estudo estimou a vazão ecológica e avaliou a disponibilidade hídrica em um trecho do rio das Pedras, manancial da cidade de Guarapuava, região Centro-Sul do Estado do Paraná. Para tal, aplicaram-se diferentes métodos empregados no Brasil para obtenção da vazão ecológica, uma vazão de referência à concessão de outorgas, e avaliou-se o regime fluvial. Os métodos utilizados foram média mínima de sete dias com período de retorno de dez anos, vazões associadas às permanências de 95% e 90%, vazões mínimas anuais de sete dias e vazão aquática de base. Os dados de vazão utilizados foram da estação fluviométrica localizada na ETA (Estação de Captação de Água de Guarapuava). Conclui-se que o débito fluvial anual, entre os anos de 1985 e 2009, apresentou uma média diária de 9,12 m³ s-1 e uma mediana de 9,16 m³ s-1. A vazão ecológica estimada pelos métodos utilizados para o trecho do rio das Pedras variou de 1,72 a 2,74 m³ s-1 , com uma média de 2,20 m³ s-1 , e coeficiente de variação de 19,5%. A vazão ecológica estimada para o trecho foi de 0,91 m³ s-1 , conforme os critérios adotados no Estado do Paraná. No trecho avaliado, a relação entre a vazão diária e o volume outorgado indica a ineficiência dos métodos avaliados na determinação da vazão ecológica, ou seja, eles não garantiram o volume de água mínimo necessário à conservação do ecossistema fluvial.
Fire is a key controlling factor in ecosystem dynamics worldwide, especially, in tropical areas under slash-and-burn agricultural systems. Farmers use fire as a tool to clean the land, and benefit from nutrient enrichment from ash-soil heating. However, fire can cause some detrimental effects on soil systems, such as organic carbon depletion, increased soil erodibility, and changes to aggregate stability. In this study, an experimental fire was applied to a plot of land following the local traditional practice of slash-and-burn. The fire temperature was monitored in the field, and its effect on soil aggregate stability was assessed. The fire temperature on soil surface was measured in four trenches, and it ranged from 355 to 660 °C (average 484 ± 142 °C). The fire temperature did not affect soil organic matter content. However, aggregate stability increased by 10 % in comparison to unburned soil. Moreover, the geometric mean diameter of burned soil was 20 % higher than that of unburned soil. In conclusion, high fire temperature changes soil aggregate stability in slash-and-burn agricultural systems.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.