This volume of Options Méditerranéennes collects the results of the research activities produced from 1998 to 1999 by the members of the CIS_Net, under the auspices of the European Commission DG.1 and the Ciheam - Iamb. Taking into account the limited availability of water, particularly severe in many countries of the Mediterranean basin, the main objective of the investigations was to contribute in better understanding the performance of collective irrigation systems in order to improve the sound use of this limited resource.

In particular the studies aimed at :

- improving the knowledge and understanding of the behavior of collective irrigation systems, mainly referring to the factors that influence the performance of irrigation ;

- providing updated methodologies for analysis and design of collective irrigation systems ;

- developing tools to estimate the demand in collective irrigation systems aiming at improving both management and design (design for management) ;

- studying the interaction between on-farm and collective irrigation systems, with consequent development of simulation models ;

- improving on-farm irrigation systems, mainly under the perspective of the overall betterment of irrigation and environmental performances.

A short presentation of the CIS_Net introduces this volume.

These proceedings are dedicated to the memory of the late Yves Labye. He was partner and founder member of the CIS_Net, Grand Master in Irrigation Engineer, teacher and friend of all the participants.

Yves Labye greatly contributed to the scientific background of the approaches presented in the meeting, and his works still remain an outstanding intellectual reference.