Trend Analysis of Reference Evapotranspiration in the São Francisco River Basin, Brazil

An important requisite in any water resources management program is the knowledge of the natural processes that regulate the hydrological cycle, especially for spatial and temporal analyses of these processes. This work aimed to explore spatial and temporal trends of reference evapotranspiration (ETo), evaluate ETo variation dynamics and quantify the contribution of each one of the meteorological variables in ETo calculation in the São Francisco River basin. Daily data of maximum and minimum air temperature, mean relative air humidity, wind speed and net radiation from 101 weather stations, for the period from 1961 to 2015, were used and are part of the network of the National Institute of Meteorology (INMET). Climate trend analysis was performed using the non-parametric Mann-Kendall statistical test and the sensitivity analysis for the Penman-Monteith equation was carried out based on partial derivatives as a function of the key meteorological variables of ETo (air temperature, net radiation, wind speed and actual water vapor pressure). A significant increase (p<0.01) in vapor pressure deficit (VPD) associated with the increase in mean air temperature contributed to increments in ETo along the studied period. The scenario in the entire São Francisco River basin is of increase in the values of the climatic variables, particularly evapotranspiration (85% of basin area with increments) and rainfall (52% of basin area with decrements). Results indicate an increase in ETo variation rates of approximately 2.424 mm year-2, on average, in the entire basin. The energy term represents higher weight in ETo calculation in 81% of the basin territory.

Experimental and Numerical Study of Hygrothermal Behaviour of a Washing Fines Hemp Test Wall

Bio-based materials are a promising tracks that offer thermal and environmental performances in order to reduce the consumption of energy and of non-renewable resources. For this purpose, in a previous study, the LGCGM worked on the development of Washing Fines Hemp composites (WFH) and characterized them on multiphysical points of view. Such materials show low thermal conductivity and high moisture buffer ability. In order to characterize their hygrothermal behavior at wall scale, a test wall is set up in an air-conditioned bi-climatic test room to simulate indoor and outdoor climates. This paper investigates the characterization of hygrothermal behavior of Washing Fines Hemp wall under typical Tunisian summer climate. It consists in an experimental study, supplemented by numerical simulation performed with WUFI Pro V6.5 software. The experimental hygrothermal response of the wall to such solicitations is analyzed from the temperature and relative humidity kinetics at several positions in the wall and from temperature and vapor pressure profiles. It shows that for daily cycles the two thirds of the thickness of the wall on the exterior side are active, as well regarding heat and moisture phenomena. More sorption-desorption phenomena are highlighted. The numerical results are consistent with experimental data for temperature and underestimate vapor pressure in the inner part of the wall.