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Groundwater resources in southwestern Tunisia are facing serious quantity and quality degradation. Given that they are the only source used for oasis irrigation, serious impacts on the soil of the region are expected. Accordingly, the main objective of this study is to evaluate the suitability of the sampled water from the Complex Terminal aquifer for irrigation purposes and to determine the potential impacts of their long-term use within the present agricultural practices on soil properties. The calculated ionic ratios indicate different classes ranging from permissible to unsuitable waters with respect to alkalinity standards (sodium adsorption ratio from 3.68 to 9.34, %Na from 36.7 to 61.2, and rill erodibility from 0.48 to 1.43). Water samples present high values of electrical conductivity, total dissolved solids, and potential salinity, about 54.5, 29.4, and 32.2%, respectively, which indicates serious salinity hazard. All the sampled waters may induce corrosion and clogging problems as deduced from the calculated light dynamic penetrometer and total hardness indices. The weighted water quality indices results (Canadian Water Quality Index and the irrigation water quality index) confirm the poor quality of the used irrigation water. The results of this study coupled with field investigations indicate that the cumulative impacts of low water quality and poor agricultural practices have damaged the total oasean ecosystem. K E Y W O R D S agricultural development, Complex Terminal, groundwater quality, land degradation, southern Tunisia oasis Résumé Les ressources en eau souterraine du sud-ouest de la Tunisie sont confrontées à une grave dégradation de la quantité et de la qualité. Étant donné qu'ils sont la seule source utilisée pour l'irrigation des oasis, de graves impacts sur le sol * Durabilité de l'agriculture dans les terres arides du sud de la Tunisie: impacts écologiques de la qualité de l'eau d'irrigation et des pratiques humaines

Given the aesthetic, cultural, ecological, and economic value of the date agro-system in Southwestern Tunisia, different management and conservation strategies have been warrantee to optimize land productivity sustainably. However, the inefficiency of the adopted management actions resulted in a continuous loss of soil fertility and decreasing fruit quality. Thus, the present paper attempts to evaluate accurately the evolution of the principal factors influencing date palm production and agricultural activities sustainability in the region. Integrated approaches of various irrigation water quality indices and geostatistical analysis coupled with field investigation and farming survey were applied to evaluate the evolution of key parameters influencing the development of date palm sustainably. The obtained results of the research indicate that the progressive land degradation is due to the effects of poorquality of water used for irrigation (EC between 674.4 and 5450 µs/cm, SAR exceeding locally 20 and about 80% of all the samples waters are of undoubtful quality according to the calculated indices), inappropriate irrigation scheduling (physiologic drought that might reach 3 months), traditional basin irrigation technique (decreasing of yield productivity, locally of 0.23, 0.23 and 0.25 kg m−3), an indigenous knowledge (sandy amendment, biologic compost, gravity improved irrigation…..). Also climate variability has leaded to furthermore degradation of crop quality. The degradation of date palm culture will be a great challenge for environmental conservation, food security and socio-economic values of the region unless a reasonable management take place, a flexible strategy based on indigenous knowledge of landowner, and scientific-based outlines with climate risks evaluation. The present paper might be useful to policy makers as a multi-disciplinary research covering most of the important aspects of date palm production.

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