Inajá Francisco de Sousa

Evapotranspiração de referência nos perímetros irrigados do estado de Sergipe

The knowledge of reference evapotranspiration (ETo) is essential for the irrigation scheduling of crops throughout the world. This work used daily meteorological data of Class A pan evaporation, maximum and minimum air temperatures, insolation, wind speed at 2 m above surface and relative humidity from 1989 to 1993 for four irrigated perimeters of Sergipe. These data were used for estimating ETo based on the following methods: Class A pan evaporation, Solar Radiation, Hargreaves & Samani, Linacre and Penman-Monteith (FAO/56). The daily values of ETo were compared to those obtained by FAO Penman-Monteith method in order to choose the best method of estimating ETo for the region. The best performance was obtained for those models which used the solar radiation as the data input. The Class A pan evaporation method did not show favorable performance in any irrigated perimeter.

Análise da pluviometria e dias chuvosos na região Nordeste do Brasil

Rainfall daily data of 600 meteorological stations were analyzed to assess the changes in precipitation in northeastern Brazil. Maps of rainy day numbers and the coefficient of variation (CV) for rainfall and rainy days are presented. Autocorrelation function was obtained for the annual rainfall in northeastern Brazil. Results showed that the semiarid regions have a high coefficient of variation for both rainfall and rainy days than those located in northeastern coast and ´agreste´ of Brazil. The highest values of coefficient of variation are associated to the lowest values of rainfall and rainy days. The rainfall change in northeastern Brazil is smaller in rainy regions than in dry regions. The high changes in rainfall and rainy days are limiting features to the rainfed agriculture in semiarid environments. The correlograms of rainfall indicated significant trend for the limits of 95% confidence levels on some stations.

Evapotranspiração e coeficientes de cultivo simples e dual do coentro

The study was carried out in a vegetable production unit in Itabaiana, Sergipe state, Brazil, with coriander crop from August 2nd to October 12th, 2011. The objective of this study was to determine the evapotranspiration and single and dual crop coefficients of coriander grown in tropical environment. The dual coefficient was obtained following FAO nomenclature. The crop evapotranspiration was obtained based on soil water balance and reference evapotranspiration by Penman-Monteith method (FAO-56), using the data of air temperature, relative humidity, wind speed and solar radiation from automatic weather station next to the experimental site. The coriander crop coefficient values for the growth stages: initial, development, mid-season and late season are, respectively, 0.82; 1.03; 1.07 and 0.93. Results also indicated that the dual crop coefficient approach can provide accurate estimates of water requirements for coriander growth in tropical environment. The water requirements of coriander based on soil water balance and the dual crop coefficient method are, respectively, 332 and 348.7 mm.

Entropy theory for analysing water resources in northeastern region of Brazil

ABSTRACT Using the Shannon entropy, the space–time variability of rainfall and streamflow was assessed for daily rainfall and streamflow data for a 10-year period from 189 stations in the northeastern region of Brazil. Mean values of marginal entropy were computed for all observation stations and entropy maps were then constructed for delineating annual and seasonal characteristics of rainfall and streamflow. The Mann-Kendall test was used to evaluate the long-term trend in marginal entropy as well as relative entropy for two sample stations. The marginal entropy values of rainfall and streamflow were higher for locations and periods with the highest amounts of rainfall. The entropy values were higher where rainfall was higher. This was because the probability distributions of rainfall and the resulting streamflow were more uniform and less skewed. The Shannon entropy produced spatial patterns which led to a better understanding of rainfall and streamflow characteristics throughout the northeastern region of Brazil. The total relative entropy indicated that rainfall and streamflow carried the same information content at annual and rainy season time scales.

Lisímetro de pesagem de grande porte.: desenvolvimento e calibração

The objectives of present study were to develop and to calibrate a large-scale weighing lysimeter in order to estimate evapotranspiration of fruit plants. The equipment consisted of a metallic bucket (steel carbon) of circular design with total area of 5.72 m2 and total mass of 10.5 t. A seedling of dwarf-green coconut palm was transplanted in lysimeter and maintained under same fertilization conditions of experimental field. For automation of the process, a mechanism of load relief based on systems of levers and counterbalances was used, leaning in a load cell with capacity of 200 kg and precision of 0.02% of its capacity. The output data of load cell were stored in an automatic data acquisition system. The relationship between mass variation (mm) and voltage (mV) of the load-cell lysimeter described a linear model with minimum hysterisis. Also, it can be concluded that the methodology used for the calibration of the weighing lysimeter was appropriate, showing a coefficient of determination of 0.99 for the calibration equation. Results also indicated that the large-scale weighing lysimeter can be used with success in the determination of evapotranspiration of fruit plants.

Lisímetro de pesagem de grande porte. Parte II: consumo hídrico do coqueiro anão verde irrigado

This paper, as Part II of a research carried out in Sergipe state, aims to determine evapotranspiration and crop coefficient of dwarf-green coconut (Cocos nucifera L.) based on lysimeter measurements and Bowen ratio-energy balance method. The reference evapotranspiration was obtained by the Penman-Monteith approach on daily-scale during the experimental period. The data acquisition system was used to obtain all data from the sensors necessary to determine the energy balance components. The water requirements of coconut palm during the phenological growth stage is 1263.30 mm, with daily average of 3.90 mm d-1. The crop coefficient during this phenological growth stage varies between 0.50 and 1.80, with daily mean of 0.96.

Time and space evaluation of features physical and chemical of surface water in the river Catumbela, Angola.

O presente trabalho foi realizado na provincia de Benguela em Angola na regiao do baixo Rio Catumbela, tendo como objeto de estudo a caracterizacao fisico-quimica da qualidade da agua. Para a realizacao dessa pesquisa foram utilizados como procedimentos metodologicos coleta de amostras, avaliacao e selecao de parâmetros da qualidade da agua de forma a realizar amostragem em 9 pontos com padroes distintos de analise no Rio Catumbela em duas epocas distintas do ano (chuvosa e seca). Fundamentando-se nos parâmetros estudados e nos dados coletados durante a pesquisa de campo, ficou demonstrada uma nitida variacao na qualidade da agua de acordo com as sazonalidades anuais. Os resultados demonstraram que as variacoes na composicao e na qualidade da agua estao relacionadas com a litologia da area de estudo e com a atividade antropica, atraves de lancamento direto e/ou indireto de efluentes domesticos e industriais, disposicao inadequada dos residuos solidos, assoreamento do rio gerado pela urbanizacao, desmatamento e producao agricola intensiva ao longo de seu percurso.