Recent Changes in Hydroclimatic Patterns over Medium Niger River Basins at the Origin of the 2020 Flood in Niamey (Niger)

Niamey, the capital of Niger, is particularly prone to floods, since it is on the banks of the Niger River, which in its middle basin has two flood peaks: one in summer (the red flood) and one in winter (the black flood). In 2020, the Niger River in Niamey reached its all-time highest levels following an abundant rainy season. On the other hand, the floods in Niamey have been particularly frequent in the last decade, a symptom of a change in hydroclimatic behaviour already observed since the end of the great droughts of the 1970s and 1980s and which is identified with the name of Sahelian Paradox. This study, starting from the analysis of the 2020 flood and from the update of the rating curve of the Niamey hydrometric station, analyses the rainfall–runoff relationship on the Sahelian basins of the Medium Niger River Basin (MNRB) that are at the origin of the local flood. The comparative analysis of runoffs, annual maximum flows (AMAX) and runoff coefficients with various rainfall indices calculated on gridded datasets allowed to hydroclimatically characterise the last decade as a different period from the wet one before the drought, the dry one and the postdrought one. Compared to the last one, the current period is characterised by a sustained increase in hydrological indicators (AMAX +27%) consistent with the increase in both the accumulation of precipitation (+11%) and the number (+51%) and magnitude (+54%) of extreme events in the MNRB. Furthermore, a greater concentration of rainfall and extremes (+78%) in August contributes to reinforcing the red flood’s positive anomalies (+2.23 st.dev in 2020). The study indicates that under these conditions the frequency of extreme hydrological events in Niamey will tend to increase further also because of the concurrence of drivers such as river-bed silting and levee effects. Consequently, the study concludes with the need for a comprehensive flood-risk assessment on the Niamey city that considers both recent hydroclimatic trends and urbanisation dynamics in flood zones hence defining the most appropriate risk-reduction strategies

Il paesaggio vegetale delle ANPIL del Fiume Magra

Nell'ambito di studi sul paesaggio vegetale di aree pedemontane della Toscana Nord occidentale, sono state censite, interpretate e cartografate le fitocenosi igrofilo-riparie di due aree proteete del fiume Magra in Lunigiana ed è stata censita la flora dell'are

Maxwell's color box: Retracing the path of color matching experiments

In his 1860 paper On the theory of compound colours, James Clerk Maxwell described an instrument used to obtain a direct comparison between daylight and a mixture of three selected spectral colors. This investigation was part of Maxwell’s study of human color vision, color perception, and color representation, and it encompasses his main achievements in the field. The working principle underlying this device provided the basis from which color diagrams have been derived, beginning with the standard chromaticity diagram proposed by the International Commission on Illumination in 1931. We describe a reconstruction of Maxwell’s original version of the color box. Constructing and analyzing data obtained with such a replica could serve as a semester project for advanced optics students

NATURAL AGING - POLY(A) POLYMERASE IN GERMINATING EMBRYOS OF TRITICUM-DURUM WHEAT

The viability of seeds is associated with ageing and storage conditions. A loss of viability is accompanied by slow germination, reduced growth, and a decline in protein and poly(A)(+)RNA synthesis. This paper reports on the activity of poly(A) polymerase in dry and germinating embryos of Triticum durum Desf. cv. Cappelli caryopses of different ages and viability. The enzyme was present as a single form during ageing and germination. The poly(A) polymerase was active at decreasing levels in all aged dry embryos, in parallel with loss of viability. Its activity strongly increased during the germination only in viable embryos. The observed increase was due to de novo synthesis of the enzyme. Poly(A) polymerase synthesis was low during germination of less viable embryos and absent in older ones. Reduced poly(A) polymerase activity in dry or germinated wheat embryos may cause a shortening of poly(A) chains in vitro and a decline in poly(A)(+)RNA synthesis. (C) 1995 Annals of Botany Compan