No abstract

Seven catchments of diverse size in Mediterranean Europe were investigated in order to understand the main aspects of their hydrological functioning. The methods included the analysis of daily and monthly precipitation, monthly potential evapotranspiration rates, flow duration curves, rainfall-runoff relationships and catchment internal data for the smaller and more instrumented catchments. The results showed that the catchments were less "dry" than initially considered. Only one of them was really semi-arid throughout the year. All the remaining catchments showed wet seasons when precipitation exceeded potential evapotranspiration, allowing aquifer recharge, "wet" runoff generation mechanisms and relevant baseflow contribution. Nevertheless, local infiltration excess (Hortonian) overland flow was inferred during summer storms in some catchments and urban overland flow in some others. The roles of karstic groundwater, human disturbance and low winter temperatures were identified as having an important impact on the hydrological regime in some of the catchments. Key words flow regimes; runoff generation; baseflow; Mediterranean Étude des régimes et processus hydrologiques dans un ensemble de bassins versants aux eaux temporaires dans l'Europe MéditerranéenneRésumé Sept bassins versants de tailles variables, situés en Europe Méditerranéenne, ont été étudies pour appréhender les principaux aspects de leur fonctionnement hydrologique. L'analyse est conduite sur la base de données de précipitations mensuelle et journalière, d'évapotranspiration potentielle mensuelle, de courbes de débits classés, de coefficients d'écoulement et, pour les bassins les plus petits et les plus instrumentés, de données internes aux bassins. Les résultats montrent que les bassins versants considérés sont moins "arides" que prévu. Seul l'un d'entre eux est vraiment semi-aride toute l'année. Les autres bassins présentent des saisons humides, avec des précipitations qui dépassent l'évapotranspiration potentielle, permettant la recharge des nappes, l'apparition de processus de génération de l'écoulement typiques de zones "humides" et une contribution significative du débit de base. Toutefois, des phénomènes de ruissellement liés, localement, au dépassement de la capacité d'infiltration (processus Hortonien) sont observés durant les événements orageux estivaux sur quelques uns des bassins et des phénomènes de ruissellement urbain sur quelques autres. Les rôles des aquifères karstiques, des perturbations anthropiques et des faibles températures hivernales ont été identifiés comme ayant un impact important sur le régime hydrologique de certains des bassins versants.Mots clefs régimes hydrologiques; génération de l'écoulement; débit de base; Méditerranée

This article aims mainly to verify the consequences of urban wastewater reuse in irrigation practices on hydrological behavior of soils. Herein the effects on both the hydraulic and dispersive properties of characteristic soils in South Sardinia are illustrated. The study was carried out at the Ente Autonomo del Flumendosa (EAF) laboratory. Ten undisturbed soil monoliths, 120 cm height and 40 cm diameter, were collected from plots, the locations of which were preliminarily individuated through a prior pedological study. An experimental facility was set up and sensors for monitoring both soil water and solute concentrations were inserted horizontally in each column at different depths. A disturbed layer at the soil surface, which expands in depth with time, was observed, characterized by reduced soil porosity, translation of pore size distribution towards narrower pores and consequent drastic decrease of permeability. It will be shown that these changes occurring in the disturbed soil layer, although local by nature, affect the mean hydrological behavior of the whole soil profile.

In Sardinia, as in many other Mediterranean regions, recurrent droughts and climate change have dramatically reduced available water resources. As a result of this critical situation, in 1995 the Italian Government declared a state of emergency and drew up a program for financial support by the State and local authorities with the aim of reducing this serious deficit. One of the actions focused on reclaiming and reusing the effluent from the sewage treatment plant of Cagliari. This article reports on the multidisciplinary preliminary study performed by the Ente Acque della Sardegna (ENAS) to evaluate the suitability of reusing Is Arenas effluent for irrigation and on the operation of the tertiary treatment plant.