Vajapeyam S. Srinivasan

Manejo da cobertura do solo e de práticas conservacionistas nas perdas de solo e água em Sumé, PB

The effect of the soil cover management and conservation practice on soil and water losses caused by the erosivity of rainfall in Haplargid soil have been analyzed in this paper. The field data corresponding to the years 1983-1990 were collected at the Experimental Basin of Sume, PB operated by the Federal University of Paraiba (UFPB). The experimental data resulting from one erosion plot cleared bare of vegetation and continuously ploughed in, two cleared bare runoff plots, one runoff plot with native semiarid vegetation, two mulched runoff plots, one plot with cactus planted down the slope and one plot with cactus planted along contour lines were used in the analysis. The bare ploughed plot contributed with annual soil and water losses of 23.1 t ha-1 and 201 mm respectively. In the cleared runoff plots, the soil losses were of 35.7 and 58.5 t ha-1 and the water losses of 224.2 and 241.0 mm, respectively. The runoff plot with native semiarid vegetation when compared with the bare runoff plots, showed a reduction in the soil losses of about 99% and the water losses of around 89%, while in mulched runoff plots there was a reduction of approximately 99% of soil losses and 74% of water losses when compared with the bare plots. The contour planted cactus plot reduced the soil losses by about 53.4% compared with the down the slope planted cactus plot.

Influência das atividades antrópicas na qualidade das águas da bacia hidrográfica do Rio Salitre

Avaliar os impactos das atividades agricolas sobre a qualidade das aguas da bacia hidrografica do Rio Salitre, foi o objetivo deste estudo. Para isto, 92 fontes hidricas localizadas em areas irrigadas ou nao, foram analisadas nos periodos de chuva e sem chuva de 2001, avaliando-se os principais indicadores para consumo humano e irrigacao. A partir dos resultados, observou-se a influencia da irrigacao sobre a qualidade das aguas, ocorrendo aumentos significativos na condutividade eletrica da agua e no extrato de saturacao dos solos; esses aumentos indicam baixa eficiencia dos sistemas de producao, constatando-se que, em media, 35 e 77% das fontes hidricas foram classificadas como C3 e C4, respectivamente; tambem, que 78% dessas fontes estao localizadas sob formacoes calcarias, cuja influencia sobre a qualidade das aguas pode ser notada pelos elevados teores de solidos dissolvidos totais (SDT = 7.940,0; 5.060,0 mg L-1), relacao de adsorcao de sodio (RAS = 25,27; 6,71 mmol L-1)1/2), dureza total (DT = 2.999,6; 2.940,0 mg L-1) e percentual de cloretos (ClP = 97,51; 94,59%), entre outros, limitando sua utilizacao; tais resultados apontam para a necessidade de medidas de preservacao e de conservacao dos recursos hidricos e dos solos desta bacia hidrografica para permitir a sustentabilidade ambiental.

Influência do tipo da cobertura vegetal sobre a erosão no semi-árido Paraibano

The type of vegetation cover present in an area, greatly influences the surface runoff as well as the sediment yield. The objective of this paper is to establish a relationship between the type of vegetal cover and erosion by means of an empirical equation for soil loss. The proposed equation was calibrated using synthetic data obtained from a physically-based runoff-erosion model in which the erosion parameter values are representative of a cleared bare-land surface in the semiarid area of Paraiba State. A comparison between the values obtained from the equation and the observed data collected from several erosion plots in the Sume Experimental Watershed with different conditions of vegetal cover and slope is presented as an evaluation of the influence of the vegetation cover on soil erosion.

Uso de análise multivariada na classificação das fontes hídricas subterrâneas da bacia hidrográfica do Salitre

Este estudo teve por objetivo identificar as variaveis responsaveis pela maior variabilidade da qualidade das aguas subterrâneas da bacia hidrografica do Rio Salitre - BA, e detectar as fontes que apresentam caracteristicas semelhantes, visando a subsidiar medidas de monitoramento e gestao da qualidade das aguas da bacia. Para isso, foram utilizadas tecnicas de analise multivariada referente a analise fatorial em componentes principais e de agrupamento. A analise fatorial permitiu agrupar as variaveis em tres fatores principais que explicaram 86,99%; 72,08% e 68,33% da variância total acumulada em 1984 e 2001, nos periodos de chuvas e sem chuvas, respectivamente. As variaveis priorizadas estao relacionadas com a salinidade das aguas. Assim, medidas de melhoria da qualidade das aguas nessa bacia devem necessariamente priorizar a salinidade das aguas, a qual esta associada a sua geologia. As fontes hidricas foram classificadas em tres classes, de forma que C1 agrupou as fontes de melhor qualidade das aguas, totalizando 25,0%; 74,3% e 61,7% das fontes hidricas, cujos valores medios dos solidos dissolvidos totais variaram de 199,00 mg L-1, em 1984, para 724,86 e 650,34 mg L-1, em 2001, respectivamente. A maioria das fontes enquadradas como C1, em 1984, permaneceu em 2001, decorridos 16 anos.

Chuvas intensas para o estado de Sergipe com base em dados desagregados de chuva diária

Floods have frequently been observed worldwide, particularly in urban and rural areas of Brazil as a consequence of antropic impacts and climate change. To cope with the problem hydraulic structures are designed based on the observed maximum flood, or statistically predicted through the rainfall-duration relationship established with recorded data, which are generally scarce. Due to the lack of such data, disaggregation of daily rainfall is generally utilized. In the State of Sergipe-Brazil, the rainfall-duration relationships were established utilizing disaggregated daily rainfalls, observed in 48 stations, and the probability distributions of Weibull and Gumbel. The best results were obtained with the Weibull distribution. The spatial distributions of the parameters of the rainfall-duration relationships demonstrated the high rainfall variability in the region.

Mapeamento do potencial de erosão laminar na bacia do rio Japaratuba, SE, via SIG

Soil erosion is a natural phenomenon that reduces soil fertility and causes a great impact on agricultural areas. Laminar erosion is characterized by the removal of the top soil fairly uniformly as well as its nutrients, which is accelerated by human activities. To minimize the impacts it is necessary to adopt an adequate soil management that takes into account the type of the soil, relief, and vegetation cover. The soil management can be aided by mapping the erosive potential of a region using GIS tools. In this work, the technique that was used for mapping the erosive potential in the Japaratuba River Basin (1685 km2) located in the State of Sergipe is presented. The results show that 48.71% of the basin area lie within medium and high erosive potentials zones, suggesting the inadequate land use for the soil types and relief within the basin.

PERDAS DE ÁGUA E SEDIMENTO EM DIFERENTES SISTEMAS DE MANEJO NO SEMIÁRIDO DA PARAÍBA

Resumen pt: O presente trabalho busca descrever as perdas de agua e sedimentos na Bacia Experimental de Sao Joao do Cariri - BESJC. A BESJC esta nas coordenadas -7o ...

Parâmetros erosividade da chuva, da enxurrada e da chuva-enxurrada correlacionados com as perdas de solo de um luvissolo

Simple linear, multiple linear and nonlinear correlations between rainfall, runoff and rainfall-runoff erosivity parameters were studied, as well as soil losses caused by erosive rainfall on a Haplargids. Data were obtained in the period from 1986 to 1990 at the Experimental Station in Sume, which belongs to the Universidade Federal da Paraiba - UFPB, Paraiba State, Brazil. Individual rainfalls registered in 136 rain gauges were analyzed for the determination of rainfall, runoff and rainfall-runoff erosivity parameters. The runoff volume, single or combined with rainfall characteristics improved the estimated soil losses of individual rainfall significantly. The erosivity parameters for rainfall-runoff a(Vu α I30)b; a(Vu α I5)b; a(EIA)b and runoff a(Vu)b were best fit to estimate soil losses caused by individual storms. The rainfall erosivity parameters that included the product of rainfall volume at a maximum intensity for thirty minutes (VrI30) were the ones that correlated best with soil losses.