Modeling the Evolution of Nitrate Pollution of Groundwater in the Plain of Western Middle Cheliff

Abstract

Groundwater constitute a potential source of drinking water supply and should, consequently, benefit from the necessary protection against the various forms of pollutions, particularly those diffuse of agricultural origin. The plain of Western Middle Cheliff which contains an important resource in groundwater supplying the whole population of the province of Chlef and contributing to the satisfaction of the need for irrigation because of the inaccessibility of most crops surface water distributed in the collective network, is confronted with risks of contamination resulting mainly from agricultural practices that generate high levels of nitrates in these waters. The part of the domestic effluents rejected often without purification and of the industrial activity is not to be neglected. Nitrate leaching to groundwater is influenced, among others, soil type, crop type and fertilization. To see the spatial evolution of nitrate pollution in groundwater of the plain, a map was established by ordinary kriging for the results of the campaign carried out in May of 2012. It appears clearly that the lowest nitrate levels cover the central part, the north and the east of the ground-water sheet under fine-textured soils. Conversely, the most affected grounds are concentrated around the edges, especially in the west, in more permeable soils receiving intensive nitrogenous fertilization. The annual contributions of nitrogen on the soils of the plain are estimated at 1958,83 T among which 95% are attributed to nitrogen fertilizers and the rest in the irrigation water.