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Introduction
In Algeria, where climatic conditions are characterized by low and poorly distributed precipitation, irrigation is of the utmost importance in ensuring a regular and a sufficient agricultural production (Guemraoui and Chabaca, 2005).
Guelma's plain in located in the North-East of Algeria. It is a part of the mid-Seybouse wadi catchment (Figure 1). This basin is characterized by the presence of one of the largest wadis in Algeria, namely, the Seybouse, which flows from west to east and reacts with the alluvial aquifer throughout its path. The lands of the plain are most essentially devoted to agriculture. Consequently, surface waters are an undeniable factor for the socio-economic development of the area. However, water resources in the region are subject to a qualitative degradation. Extensive irrigation by potentially polluted water cannot only leach down the soil but also deteriorate groundwater quality (Ibrahim and Salmon, 1992). Traditionally, water resources management has focused on surface water or groundwater as if they were separate entities. As the development of land and water resources increases, it is apparent that the development of either of these resources affects the quantity and quality of each other (Thomas et al. , 1998). For this reason, since the startup in 1996 of the Guelma-Bouchegouf irrigated perimeter, Seybouse irrigation water quality has arisen as a serious and worrying issue. The current question that one needs to answer is, if these wadi waters could still be used for irrigation being aware that industrial wastewater, domestic sewage as well as oils and other garbage are discharged directly into the wadi without any prior treatment (Hajar, 1999). Because environmental pollution and food safety are two of the most important challenges of our time (Lu et al. , 2015), the purpose of this study is to assess the degree of pollution of these waters and to determine their suitability for irrigation. This would contribute to the protection of agricultural products' consumers as well groundwaters and the environment by the same way.
The climate of the region is considered as temperate to semi-arid. The average annual precipitation is 599 mm; actual evapotranspiration is 427 mm/year which is 71 percent of the precipitation. The region reveals an agricultural deficit of 542 mm/year which should be covered by irrigation. Guelma alluvial...