Subsurface drip irrigation (SDI) is one of the most promising irrigation systems. It is based on small and frequent water supplies. Because SDI emitters are buried, their discharges are dependent on the water status at the vicinity of the outlets. This paper was targeted to design the SDI laterals accounting for the soil water-retention characteristics and the roots water extraction. The proposed approach provides systematic triggering and cut-off of irrigation events based on fixed water suctions in the vadose zone. In doing so, the soil water content is maintained at an optimal threshold ascertaining the best plant growth. Knowing the soil water-retention curve, the appropriate water suction for the plant growth, and the emitter discharge-pressure head relationship, the developed method allows the computation of the required hydraulics of the lateral (e.g., inlet pressure head, inside diameter, etc.). The proposed approach is a helpful tool for best SDI systems design and appropriate water management. An illustrative example is presented for SDI laterals’ design on tomato crop.

During 2005-2010 the annual water balance was calculated within Kalaat El Andalous irrigation district and recorded values ranged from À0.77 million m 3 (À257 m 3 ha À1 ) to +3.64 million m 3 (+1210 m 3 ha À1 ). Monthly analysis of the water balance revealed two distinct phases. Through the first phase (September-May), the water balance showed a highly variable tendency due to erratic rainfall and irrigation water inflows. However, during the second phase (June-August) the water balance remained positive, reflecting farmers' tendency to over-irrigate. Analysis of water productivity confirmed this result mainly during the full irrigation period (June-August). Therefore, the average annual drainage fraction was 26%. The assessment of salt balances during 2005-2010 indicated a general tendency for soil desalination (average annual salt balance: À25 600 t (À8.5 t ha À1 )). Monthly analysis revealed the succession of three distinct phases. The first phase occurring during September-November is characterized mainly by salts leaching and secondly by salts accumulating. The second phase spanning December-April is characterized by salts leaching, while the third phase spanning May-August is characterized by salts accumulating. Thus, 95% of accumulated salts were recorded RÉSUMÉ Au cours de la période 2005-2010, le bilan hydrique annuel a été calculé dans le district irrigué de Kalaat El Andalous et les valeurs enregistrées allaient de À0.77 million de m 3 (À257 m 3 ha À1 ) à +3.64 millions de m 3 (+1210 m 3 ha À1 ). L'analyse mensuelle du bilan hydrique a révélé deux phases distinctes. Au cours de la première phase (septembre-mai), le bilan hydrique a montré une tendance très variable due aux pluies erratiques et aux apports d'eau d'irrigation. Cependant, durant la deuxième phase (juin-août), le bilan hydrique est resté positif, reflétant la tendance des agriculteurs à la sur-irrigation. L'analyse de la productivité de l'eau a confirmé ce résultat principalement pendant la période d'irrigation complète (juin-août). Par conséquent, la fraction de drainage annuelle moyenne était de 26%. L'évaluation des bilans salins au cours de la période 2005-2010 a révélé une tendance générale au dessalement du sol (bilan annuel moyen des sels: À25 600 t (À8.5 t ha À1 )). L'analyse mensuelle a révélé la succession de trois phases distinctes. La première phase de septembre à novembre se caractérise principalement par la lixiviation des sels puis par l'accumulation de sels. La deuxième phase, qui s'étend de décembre à avril, est caractérisée par la lixiviation des sels, tandis que la troisième phase, qui s'étend de mai à août, se caractérise par l'accumulation de sels. Ainsi, 95% des sels accumulés ont été enregistrés en maiÀaoût et 5% en septembreÀnovembre alors que 91% des sels lessivés ont été enregistrés de décembre à avril et 9% de septembre à novembre.

The oases of the South of Kébili are subjected to serious problems related to climate change and water scarcity resulting from the rise in temperature and the decrease in rainfall. Thus, the region suffers from a significant shortage of irrigation water due to long periods of drought affecting this already fragile area, but also due to human behavior. Our study aims to discuss and analyze the issue related to the impacts of climate change and social changes on water scarcity in the oases the South of Kébili, as well as to contribute to the assessment of the impact of these changes on palm productivity and groundwater quality. The results obtained during the spatiotemporal monitoring of climate indicators and hydrogeological data showed an increase in the vulnerabilities of the oases. In particular, the fragility of the water sector through the excessive exploitation of groundwater has led to the deterioration of the quality of irrigation water and the loss of biodiversity. On the other hand, the high rates of degradation that have been observed in the study area indicate another source of vulnerability in addition to pollution, which is agricultural activity. Water scarcity, due to various factors, both climatic and anthropogenic, requires defining a strategy for managing water resources in the oases of this region. Some of the results of research and development activities in the study area which mainly aim to support the preservation and sustainable development of the oases of the Kébili region will be presented.