Hydrogeochemical assessment to characterize the water quality for agricultural use in Mexanna and Bougous dams in the province of El Tarf, Algeria

The Mexa and Bougous dams were built to control river floods and supply crop-irrigation and drinking water. This study aimed to characterize the hydrogeochemical state in the region containing the dams, which influences the quality of the waters and thus their suitability for agricultural use, given the extent of the river networks that naturally transport sediments and pollutants into the reservoirs via streams. Thus, some physicochemical and organic parameters, including electrical conductivity, calcium, magnesium, sodium, potassium, chloride, bicarbonate, sulfate, biological oxygen demand, nitrite, ammonium, and phosphate, were used as benchmarks to examine the stiffness of the water pollution. Sampling was carried out during May and September of 2011 and 2012. The obtained results showed that, according to the Stiff diagram, the dominant hydrogeochemical facies is calcium bicarbonate in waters that do not have calcium levels in excess of 3 meq/l and bicarbonate levels in excess of 2.4 meq/l. The organic pollution index disclosed that the waters have evolved from a moderate to a high degree of organic pollution due to the accumulation of pollutants and nutrients from waste disposal and fertilizers. The samples fell into the C2-S1 class in the Richards diagram; this implies that the waters are suitable for plants that are salt tolerant, but that the use of these waters can cause problems for clay soils. However, in the long term, irrigation with the dam waters may pose difficulties for agriculture due to the resulting increase in the electrical conductivity of the soil. This study concludes that water salinity and alkalinity affect crop suitability, meaning that the temporal monitoring of water quality is needed to avoid adverse consequences for crop production.