GIS-based evaluation of groundwater quality and estimation of soil salinization and land degradation risks in an arid Mediterranean site (SW Tunisia)

• Published in: Arabian journal of geosciences 2017-08, Vol.10 (16), p.1-20, Article 350
• Main Authors: Besser, Houda, Mokadem, Naziha, Redhouania, Belgacem, Rhimi, Nacira, Khlifi, Faten, Ayadi, Yosra, Omar, Zohra, Bouajila, Abdelhakim, Hamed, Younes
• Format: Article
• Language: English
• Subjects: Agricultural practices; Agrochemicals; Agronomy; Aquifers; Aridity; Classification; Composition; Contamination; Copper; Desertification; Distribution; Drought; Durability; Earth and Environmental Science; Earth science; Earth Sciences; Environmental monitoring; Evaluation; Fertility; Geographic information systems; Geographical information systems; Graphical methods; Groundwater; Heavy metals; Information systems; Irrigation; Irrigation water; Land degradation; Land management; Land use; Metal concentrations; Metals; Nickel; Oases; Organic chemistry; Original Paper; Overexploitation; Petroleum; Physiochemistry; Ratios; Risk; Risk factors; Salinization; Satellite navigation systems; Soil; Soil degradation; Soil fertility; Soil profiles; Soil salinity; Soil salinization; Soils; Surface water; Vertical distribution; Water availability; Water chemistry; Water crises; Water quality; Zinc
• ISSN: 1866-7511; 1866-7538
• DOI: 10.1007/s12517-017-3148-0

Southwestern Tunisia is known for its high-quality date palm production. The agricultural activity supports the social and economic pressure. Considering prolonged drought conditions and surface water insufficiency, increasing supplies rely on deep aquifers in spite of the critical status of the water quality used. Intense agriculture development has placed oases durability and crop quality to high risks of soil fertility loss, land degradation, and water availability issues, due to severe climate conditions, overexploitation of groundwater resources, intense desertification, overuse of soil, and poor land management. The recent contamination of the largest aquifer in southern Tunisia (Continental Intercalaire) by petroleum flows adds another dimension to the problem of water crisis and soil salinization in the region of interest. In this study, 41 water samples from CI wells were correspondingly collected for hydrochemical analyses. Major and minor element concentrations were evaluated by different standard methods. The obtained dataset indicates that the western side possesses low salinity hazard, whereas Nefzaoua and El Fedjej areas reveal highly mineralized water unsuitable for irrigation purposes. A number of assessment ratios (KR, TH, SAR, ESP, PS, etc.) and graphical methods (Riverside and Wilcox) confirm this classification. The combination of geochemical indicators with geographic information system permits the assessment of water quality on the basis of two different indexes. The resulted maps show, in turn, scattered classification between the western field with acceptable water quality and El Fedjej-Nefzaoua areas where the CI water is unsuitable for agricultural activities. Besides water chemistry evaluation, the assessment of soil composition, particularly toxic element concentrations, constitutes reliable criteria for monitoring the effectiveness of agricultural practices and the suitability of irrigation water. Hence, the concentrations of four heavy metals have been monitored along three soil profiles ranging from the surface to 80 cm of depth. The results are within permissible limits. The vertical distribution of Ni, Pb, Cu, and Zn is related mainly to physiochemical soil parameters, difference in moisture, and fine fraction distribution.