Assessment of Water Quality of Kodiat Rosfa Dam and Suitability For Consumption and Irrigation (Algeria)

The approach adopted for the assessment of Kodiat Rosfa dam water quality, through the respective indexes WQI and IWQI, allowed to highlight the quality of its waters for the intended uses. Indeed, the physicochemical analyzes of the months of February, March, July and December, corresponding to the monthly precipitation and regularized volumes of 2013, 2014, 2015 selected, revealed that 08 samples out of 12 have a WQI within 50 to 100, and 04 samples with WQI lower than 50. This classified the dam waters as good to excellent for consumption. Nevertheless, the results of IWQI index used to assess the quality of dam water Kodiat Rosfa for irrigation show that 7 samples out of 12 present an IWQI within 55 to 70 and 5 samples with IWQI lower than 55. These waters are characterized by moderate (MR) to high (HR) restriction.


 Calculation of water quality index for consumption (WQI)
The water quality index is a practical tool that makes it possible to synthesize the composite effects on water quality and to assess the influence of natural and anthropogenic factors on the basis of several parameters, the most important of which are (EC, pH, DO, SO4, BOD5, COD, TSS, N-NH4, N-NO3, Ca, Mg, Na, Cl, HCO3, and PO4). It is used in this study to classify the water quality of Kodiat Rosfa according to WHO and national standards. The WQI defines 5 quality classes [9], ( Table 2). It is calculated by the weighted arithmetic index method [5][6][7][8][9][10][11][12][13][14]. The specific relative weight of each physicochemical parameter (Wi) is calculated according to the following formula: With : k: Proportionality constant calculated using the following equation:  (Table I) Five water quality classes can be defined according to the values of the WQI water quality index (Table II).

 Calculation of index water quality for irrigation (IWQI)
Many researchers have developed several indices to measure the quality of water according to specific conditions and objective [2]. The IWQI model was developed by [8]. Simsek & Gunduz (2007) [20], Jerome1 and Pius (2010) [21] and Rokbani et al. (2011) [22], introduced irrigation water quality index (IWQI) as a management tool. In the first stage, the parameters identified for the model were considered more relevant to the irrigation use. In the second stage, a definition of quality measurement values (qi) and aggregation weights (wi) was established. Values of (qi) were estimated based on each parameter value, according to irrigation water quality parameters proposed by the University Of California Committee Of Consultants -UCCC and by the criteria established by Ayers and Westcot (1999) [23], as shown in Table 8. Water quality parameters were represented by a non-dimensional number; the higher value is the better water quality [24].
The irrigation water quality index (IWQI) was estimated using: ∑ Values of qi were calculated using the Equation 2, based on the tolerance limits shown in Table.3 below and water quality results determined in laboratory: Where qi max is the maximum value of qi for the class; xij is the observed value for the parameter; x inf is the corresponding value to the lower limit of the class to which the parameter belongs; x iamp is class amplitude; x amp is class amplitude to which the parameter belongs. In order to evaluate x amp , of the last class of each parameter, the upper limit was considered to be the highest value determined in the physical-chemical and chemical analysis of the water samples.
The parameters used to assess the suitability of irrigation water supply for agricultural purpose are given as follows (Table . 3): Electrical Conductivity, Sodium Absorption Ratio (SAR), Chlorine (Cl-), Total Hardness (TH), and Sodium (Na+). SAR* has been used by several researchers in assessing and classifying irrigation water quality.  (Table IV). In this study EC, SAR, Na+, Cl-and HCO3 were unified to obtain a particular number that indicates the irrigation water quality [9]. The parameter limiting values for quality measurement (q i ) and weights for IWQI parameter estimation according to [8], are shown in the Tables 1 and 2.

 Analyzes of Kodiat Rosfa dam waters
The analysis procedures are deduced from the standard methods [25].  pH, temperature, and conductivity of the water are measured in situ by portable devices HANNA (8014 Hi and Hi 8732)  Suspended matter (TSS) was filtered by a cellulosic filter and weighed after passage to the drying oven with 105˚C.  The biological demand of oxygen during five days (BOD 5 ) was measured by the apparatus BOD meter Oxi-Top.  Chemical demand of oxygen (COD), was measured by COD meter type photometer Hanna C214.  The determination of anions is performed by spectrophotometry kind DR2000 (HACH).  (Table V).    (Table 6 and Fig. 5), which makes it possible to qualify the waters of this dam as good to excellent for consumption according to the standards adopted (Table. 2). Should be avoided its use for irrigation under normal conditions. In special cases, may be used occasionally. Water with low salt levels and high SAR require gypsum application. In high saline content water soils must have high permeability, and excess water should be applied to avoid salt accumulation.
Only plants with high salt tolerance, except for waters with extremely low values of Na, Cl and HCO3.

IV. CONCLUSION
The approach adopted to assess the water quality of Kodiat Rosfa dam, through the respective indexes (WQI and IWQI), has made it possible to highlight the quality of this water and its use for consumption and for irrigation. Indeed, among 12 samples studied for consumption, 8 have WQIs within 50 to 100 and 04 WQIs lower than 50, which makes it possible to characterize the waters of this dam as good to excellent for consumption according to the WHO and national standards.
Moreover, the results of the second part of approach for the use of this water for irrigation showed that 7 out of 12 samples have an IWQI within 55 to 70, against 5 which have an IWQI lower than 55. This water quality is characterized by moderate (MR) to high (HR) restriction for irrigation use. In this case, a set of recommendations must be observed, especially in the choice of plants with moderate tolerance to salts and moderate to high permeability of soil.