Respostas hidrológicas em pequenas bacias na região semiárida em função do uso do solo

Abstract

RESUMOPropôs-se, neste estudo, avaliar e comparar o comportamento hidrológico em pequenas bacias investigando a influência da ação antrópica sobre as respostas hidrológicas. O estudo foi conduzido em duas microbacias adjacentes e com distintos usos da terra, denominadas B1 e B2, no semiárido do nordeste do Brasil. Na microbacia B1 foi aplicado o manejo de raleamento eliminando-se as espécies vegetais com diâmetro inferior a 10 cm; na segunda (B2) se manteve a cobertura vegetal original, a qual não é explorada há mais de 30 anos. Nesta investigação foram considerados 24 eventos chuva-deflúvio, correspondendo a toda estação chuvosa de 2009, cujos resultados revelaram que a prática de raleamento da caatinga apresentou modificações no escoamento mas apenas nos eventos inicias e que o rápido crescimento da vegetação herbácea reduziu o escoamento superficial direto na microbacia raleada, que apresentou valores de lâminas escoadas inferiores aos da microbacia preservada; verificou-se, contudo, que as descargas máximas na microbacia raleada foram superiores às da bacia preservada. Palavras-chave: microbacias, escoamento superficial, raleamento, picos de descargaHydrological responses in small watersheds in the semiarid region according to land use ABSTRACT The main goal of this study was to evaluate and to compare the hydrological behavior of small watersheds investigating the influence of the anthropogenic activities and the hydrologic responses due to these activities. The experimental area was composed of two small watersheds denominated B1 and B2. In watershed B1, a treatment (thinning) was applied, eliminating the species with diameters less than 10 cm. The experimental watershed B2 was not submitted to any treatment maintaing the original vegetation. In this investigation a total of 24 rainfall-runoff events were considered, corresponding to the 2009 rainy season as a whole. The results revealed that the thinning of the caatinga generated modifications in the runoff only in the initial rainy season. The growing of herbaceous vegetation attenuated the water flow and reduced the runoff in B1, promoting small changes in response to the applied treatment. There were, however, higher peak discharges in watershed B1 compared with the preserved watershed.

Belowground Carbon and Nitrogen on a Thinned and Un-Thinned Seasonally Dry Tropical Forest

“…Another factor that may have contributed to maintaining greater levels of carbon in the subsurface layers of the TC 5 is based on the fact that herbaceous vegetation reduced surface runoff and increased the chances of infiltration [17].…”

“…Studies show that thinning promotes the emergence of an herbaceous layer [14], enables water content in the soil [15] [16] [17] and can add biomass to the soil [18] [19].…”

Effective Preciptation, Soil Loss and Plant Cover Systems in the Caatinga Biome, Brazil

“…The influence of vegetation removal and the use of fire on soil loss was evident, since this was the first year of management after the burning procedure in the area (ARAUJO WESTER et al, 2014). The TC area had less soil loss, with loss 4-fold smaller than the FC, proving to be an efficient soil protection management for the region (RODRIGUES et al, 2013b).…”

“…The sensors were calibrated, since they measure the frequency by an equation (potential frequency / height of the water column) (Figure 2a), to measure the surface runoff height, with data acquired every five minutes (RODRIGUES et al, 2013a). The surface runoff was determined by Equation 1, following the procedure used by Fang et al (2012), Rodrigues et al (2013b) and Zhou et al (2016). (1 Where: Q is the Parshall flume flow (L s -1 ); W is the width of the flume bottleneck (cm), with value of 47.5 for FC and TC and 30 for the DBP flume; and h is the height of the water in the flume (cm).…”

“…The intensification of anthropic interference on natural resources in the Brazilian semiarid region has caused degradation of soil and water resources and vegetation and biodiversity loss, which, under the influence of the regional climatic factors, may result in significant changes in hydrological processes, especially rain and overland flow (ALMEIDA et al, 2012;ARAÚJO NETO et al, 2013;RODRIGUES et al, 2013b). Water erosion and sediment production have been a subject of growing concern to all situations related to the soil management and water use (PARANHOS;PAIVA, 2008).…”