A B S T R A C TSoil moisture estimation is very important in decision making regarding agricultural practices and investigations in hydrology. The aim of the study was to evaluate surface soil moisture temporal stability under two cover crop conditions in an experimental watershed in the Brazilian semi-arid region, aiming to identify stable points, thus reducing monitoring costs and highlighting the importance of temporal stability in a watershed. Fourty five soil moisture monitoring campaigns in the layers of 0-0.10 and 0.10-0.20 m were conducted using a capacitance probe (Diviner -2000®) during the period from 10/07/2010 to 03/25/2014, with soil cover under native bushy vegetation and degraded pasture, predominantly Brachiaria decumbens. Temporal stability was evaluated through the mean relative difference technique. The point located at the middle of a slope under pasture and bushes was the most stable, with determination coefficient of 90 and 92% for both layers.Estabilidade temporal da umidade do solo em bacia experimental do semiárido pernambucano R E S U M O A estimativa da umidade no solo é de grande relevância na tomada de decisão de práticas agrícolas e pesquisas na área da hidrologia. Objetivou-se, neste estudo, avaliar a estabilidade temporal da umidade do solo nas camadas superficiais em duas condições de cobertura vegetal em uma bacia hidrográfica experimental, no semiárido brasileiro, buscando-se identificar pontos com maior estabilidade da umidade desonerando, assim, custos de monitoramento e ressaltando a importância da estabilidade temporal em uma bacia hidrográfica. Realizaram-se 45 campanhas de monitoramento de umidade do solo nas camadas de 0-0,10 e 0,10-0,20 m utilizando a sonda capacitiva/Diviner -2000® no período de 07/10/2010 a 25/03/2014, com cobertura do solo e presença de vegetação arbustiva natural, além de pastagem degradada com predominância de capim Braquiária (Brachiaria decumbens). A estabilidade temporal foi avaliada por meio da diferença relativa média. O ponto localizado em meia-encosta da bacia em presença de pastagem foi o mais estável, com coeficientes de determinação de 90 e 92% para ambas as camadas.

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R ESU M OA erosão hídrica é um dos principais processos responsáveis pela degradação física dos solos, em particular em áreas semiáridas, susceptíveis a chuvas de alta intensidade e com limitada cobertura vegetal, principalmente nos períodos secos. O presente trabalho teve como objetivo avaliar experimentalmente as características hidrossedimentológicas da bacia hidrográfica do Riacho Mimoso, no semiárido pernambucano, no município de Pesqueira, PE. A bacia representativa do Riacho Mimoso apresentou respostas hidrológicas com altos picos de vazão, em seção de controle com regime hidrológico intermitente. A produção de descarga sólida em suspensão do Riacho Mimoso é elevada, tendo-se registrado concentrações de sedimentos de 10,91 e 0,91 t ha -1 ano -1, para os anos de 2009 e 2010, respectivamente. Palavras-chave: descarga líquida, sedimentologia, descarga sólidaProduction of water and sediments in a semiarid basin representative of Pernambuco A B ST R A C T Water erosion is a major physical process responsible for soil degradation, particularly in semiarid areas, susceptible to high intensity rainfall and limited vegetation cover, especially during dry periods. This study aimed to experimentally evaluate the hydrossedimentological characteristics of Mimoso watershed, in the semiarid region of Pernambuco, in Pesqueira-PE. The representative Mimoso watershed presented high peak flows in a control section with intermittent hydrological regime. The suspended solid discharge production in the Mimoso Rivulet is high and the observed sediment concentrations was of 10.91 and 0.91 t ha -1 yr -1, for the years 2009 and 2010, respectively.

Macropores and water flow in soils and substrates are complex and are related to topics like preferential flow, nonequilibrium flow, and dual-continuum. Hence, the quantification of the number of macropores and the determination of their geometry are expected to provide a better understanding on the effects of pores on the soil's physical and hydraulic properties. This exploratory study aimed at evaluating the potential of using infrared thermography for mapping macroporosity at the soil surface and estimating the number and size of such macropores. The presented technique was applied to a small scale study (laboratory soil flume).

Abstract:The infrared thermography has been successfully applied as a tool for high resolution imaging in different hydrological studies. This exploratory experimental study aimed at evaluating the possibility of using infrared thermography to determine the diameter of raindrops. Rain samples are collected on a pre-heated acrylic board, which is exposed to rain during an instant, and thermograms are recorded. The area of the thermal stains ("signatures" of the raindrops) emerging on the board is measured and converted to drop diameters, applying a calibration equation. Diameters of natural raindrops estimated using this technique were compared with laser disdrometer measurements; the Nash-Sutcliffe efficiency coefficient was used for evaluating the match between the resulting histograms of drop size distribution. Results confirm the usefulness of this simple technique for sizing and counting raindrops, although it is unsatisfactory in light rain or drizzle.

Summary Understanding the temporal and spatial dynamic of soil temperature is crucial for agriculture, since it affects soil evaporation and soil biological activity, influencing seed germination, root growth and absorption of water and nutrients by crops, and ultimately the runoff process. Mulching is one of the most applied soil and water conservation method for soil moisture and soil temperature variations control. This study aimed to investigate the influence of three different mulch types (dried elephant grass straw, dried cashew tree leaves and coconut powder or coir dust), applied with three area densities (2, 4 and 8 t ha−1), on the soil surface temperature, under field conditions in the Brazilian semiarid region. Soil temperature monitoring was carried out using thermocouple sensors and an infrared camera in the Brazilian semiarid region. Results show that mulching provided a buffer zone, dampened soil temperature fluctuations over time, mainly for the 8 t ha−1 density. Mulching reduced soil temperature during the hotter period of the day and increased soil temperature during the night period.