Study area
The experiment was conducted in five streams at the Pirancajuba River basin, within and near the Silvânia National Forest (FLONA Silvânia). FLONA Silvânia is an environmental conservation unit, located in the eastern region of the state of Goiás, with 486.37 hectares that preserves most of the natural characteristics of the Cerrado (ICMBio 2015). The region has a warm and semi-humid tropical climate, strongly characterized by a rainy season in the summer (November to March), and a dry winter season with an average duration of four months (May to September) (Nimer 1972). The experiment was conducted July to September 2010, because the dry season maximizes sampling of aquatic insects in Cerrado streams (Bispo et al. 2004, Bispo and Oliveira 2007).
The five streams have similar water velocity, average depth, and streambed composition, and a prevalence of sand, silt, and small-sized stones. Waterflow was the hydrologic measure with the greatest variation (Coefficient of Variation: 108%), followed by the width of the channel (CV: 67%). Average depth and water velocity presented more constant values (Table S1).