Understanding the necessary relationship between the radar reflectivity factor Z and the rain rate R is still important today and constitutes an interesting challenge for the scientific community. Despite this interest and the advances already obtained in this field, understanding the variability of this Z-R law is not yet trivial. This work therefore consists of studying the implication of rain spectra at low intensities R≤1mm/h in this variability. Thus, from a large historical database of raindrop size distribution (DSD) acquired in tropical Africa, we have shown that rain spectra R≤1mm/h lead to high values ​​of the coefficients A and b of the Z-R power relationship. However, the variability of pre-factor A is pronounced in agreement with those of the NT and D0/NT parameters of the DSD; while the exponent b remains quasi-constant in such rainy samples, independently of their percentage. Establishing the link between the observation parameters D0, NT and D0/NT of the DSD and the pre-factor A of the Z-R relationship made it possible to arrive at close power relationships D0 – A, NT – A and D0/NT – A corresponding respectively to the microphysical modes «D0 constant, NT variable», «D0 variable, NT constant» and «D0 variable, NT variable». The last microphysical condition seems to be more suited to the power relationship A – α where α, is the pre-factor of the power relationship D0/NT – R found in the literature.

The aim of this study is to highlight the combined effects of climate change and anthropization on surface waters in the Agnéby watershed. The global hydrological balances produced by the SWAT model show that in the year 2050, precipitation will record a deficit of 1.87%, while actual evapotranspiration will be 2.80% higher. Groundwater recharge and runoff will be in deficit by 2.5% and 9.77% respectively, and stock variation will be in deficit by 36.62% compared with the reference period. For 2080, precipitation, groundwater recharge and runoff will be in deficit by 1.23%, 1.5% and 10.23% respectively. Actual evapotranspiration will show an excess of 3.37%, and the change in stock relative to the reference period will also show a deficit of 20.42%. The hydrological consequence of this state of affairs is the depletion of surface water resources over the years in the Agnéby watershed due to anthropogenic activities. The predominance of evapotranspiration can be explained by the fact that the area will be covered by large-scale farming operations. These could also be explained by the fact that the area will be less favorable to surface runoff than to infiltration.

This study was conducted to estimate the water requirement of the plant Lippia multiflora MOLDENKE. (Verbenaceae), also known as the bush tea or Gambia tea. Seeds initially germinated, are transplanted into pots of 14.5 cm high and 8.5 cm in diameter, completed soil indoors. The treatment consists of 5 parts water, I1, I2, I3, I4 and I5, respectively, for 15, 30, 50, 70 and 100 per cent of the usable reservation made by spraying the plants, for 3 months. Weighing pots with plants were made before and after watering, to calculate actual evapotranspiration (ETa).
The results show that actual evapotranspiration of Lippia multiflora, nursery ranges from 0.5 mm.d-1 to 2 mm.d-1. Plants with the irrigation dose, received I1, have a low ETR for the 3 months, followed by I2. Irrigation doses I3, I4 and I5 indicate ETR ranging from 1 mm to 2 mm per day. The crop coefficient in nursery phase is 0.32 for the month of May and 0.23 in July.
Regarding the vegetative growth, the results obtained show that, it is the I3 or I4 irrigation doses which allow a homogeneous development of the plants. These doses are thus, considered the maximum evapotranspiration of Lippia multiflora. And Culture of Lippia multiflora, it is necessary to go through the nursery phase by providing 50 or 70 per cent usable reserves of soil for optimal growth.