Hydrologie : recherche actuelle

An important component of the water cycle in ecological systems, rainfall interception by virgin forests was here calculated from gross precipitation minus through fall and stem flow. The through fall measurement system was designed on the basis of a 3 m long trough mounted beneath the canopy and able to operate successfully under a range of rainfall conditions. Stem flow was measured using spiral collars consisting of a split plastic hose attached to sampled trees, with gross precipitation measured in an open area via a tipping-bucket rain gauge. This study was carried out to evaluate rainfall interception and distribution patterns of gross precipitation in two contrasting rainforest types (coniferous and broadleaved/coniferous mixed) in the Mount Gongga area on the eastern fringe of Tibet, China, from 2008 to 2009. Net precipitation was found to be primarily composed of through fall, while stem flow contributed less than 0.5% (0.1% and 0.4% in conifer and mixed forest, respectively) to total gross precipitation (GP) and was thus negligible in both forest types. The difference in the interception loss fraction between conifer and mixed forest was greater than 30%, with the interception loss of the former apparently more than that of the latter mainly due to the increased presence of small droplets produced by coniferous leaves. Additionally, interception loss in conifer forest was more dependent on rainfall than that in mixed forest. In contrast, through fall and stem flow exhibited the opposite pattern, likely attributable to a through fall lag of 8 to 10 h after rainfall in mixed forest but not in conifer forest.

Tunisia has mobilized the important amount of its conventional hydraulic resources (surface water and ground water). It is brought today, for considerations of saving of water but also in environmental ethics, to recycle its noconventional resources like municipal waste water and to applicant it for agriculture. The effect of treated wastewater (TWW), compared to the ordinary irrigation (with ground water (GW)) by means of tow irrigation methods (sprinkler (S) and integrated Gouttor (IG)) on the chemical properties of the sandy soil, and its organic composition, were investigated in 2004 at the experimental station of Oued-Souhil in Nabeul Governorate, NE Tunisia. Soil samples were collected from five depths (0–20, 20–40, 40–60, 60–80 and 80–100 cm) and were analyzed for electric conductivity (EC), pH, total nitrogen (TN), organic carbon (OC), potassium (K), phosphorus (P205) and nitrate (NO3 -). The results observed after a partner of irrigation show that the electric conductivity (EC) and pH of experimental soil decreased compared to his initial state. The irrigation has reduced the OC content in surface layer and has increased it in the deeper layer. The TN content varied in opposite direction. The P205, K and NO3 - concentrations decreased in the upper 40 cm at the end of the study for both TWW and GW irrigated soil; however the effect of TWW irrigation was significant only with potassium (K). The evolution of these elements in the soil during the study proves their important concentration in the GW.