Environ Monit Assess (2008) 142:149–152 DOI 10.1007/s10661-007-9916-7 Assessment of irrigation water quality. A proposal of a quality profile César Almeida & Silvya Quintar & Patricia González & Miguel Mallea Received: 9 February 2007 / Accepted: 27 August 2007 / Published online: 14 September 2007 # Springer Science + Business Media B.V. 2007 Abstract Water quality indices provide a simple and understandable tool for managers on the quality and possible uses for irrigation water, however an individual quality factor alone is not enough to evaluate the irrigation water quality because it could be restrictive and sometime it could give an unfavorable qualification. The aim of this paper was propose a quality profile of irrigation water using the preexisting water quality indices to be applied to arid and semiarid regions. As a case studied, the water of the Del Molle River (Nogolí, San Luis, Argentina) was researched. Samples were collected during the period October 2005–May 2006. Conductivity, pH, total hardness, sulphate, nitrate, nitrite, alkalinity, chloride, sodium, potassium, TDS, DO and phosphate were analyzed. The irrigation water quality, according to Riverside Norm, belongs to C2–S1 class, according to Wilcox Norm as excellent to good, according to Scott quality factor it is good and according to SAR<10 and according to RCS it is recommendable. From the obtained data, it can be concluded that the water quality profile was good, so it is useful for normal irrigation agriculture. C. Almeida (*) : S. Quintar : P. González : M. Mallea Área de Química Analítica, Facultad de Química, Bioquímica y Farmacia, Universidad Nacional de San Luis, Chacabuco y Pedernera, 5700 San Luis, Argentina e-mail: almeida@unsl.edu.ar Keywords Environmental . Irrigation water quality . Quality indices . Irrigation water quality profile Introduction The kind of water used for irrigation has effects in the quality, production and type of culture as well as in the soil since it can turn it useless if the water is of a bad quality. Whatever the origin of the water, it should be evaluated and must fulfills some quality empiric indices required for irrigation water. Therefore, its quality should be verified before establishing the culture. The quality indices studied are second grade indices and they depend on the cations and anions concentrations present in water and could be influenced by the type of soil or water (Hernández et al. 2003). The use of these indices is very important to evaluate the quality water, because they relate, at least, two variables such as electrical conductivity, sodium adsorption ratio, total dissolved solids, etc., given a more extended and wide point of view (Orihuela 1992). The use of an unique variable is not appropriated. Irrigation water quality criteria developed by US Salinity Laboratory (Richards 1954) has received with acceptance in many countries. Total salt concentration and probable sodium hazard of the irrigation water are two major constituents of the criteria. Four classes of 150 salinity risk and another four class of sodium hazard were proposed to assess irrigation water quality. Salinity hazard is based on electrical conductivity measurements. A concept called sodium adsorption ratio (SAR) is used for possible sodium hazard. To determine how the interaction of the various ions affect the suitability of the water for crop irrigation, the SAR has been plotted versus the conductivity measurement, (riverside norms) given a classical diagram to classificate irrigation water quality (Wilcox 1955). The norm of H. Greene is one of less restrictive that exists when we want to qualificate irrigation water samples because it does not offer many guarantees. If this norm qualificate the water sample as bad, the water is definitively bad, but in the case that it is good we must take certain precaution. L.V. Wilcox considers the percentage of sodium to develop a quality factor for the water qualification with regard to the whole of cations and the electrical conductivity. The estimate of residual sodium carbonate (RSC) is another way to examine the irrigation water quality as was suggested by Eaton (Eaton 1950). A negative RSC is the best situation since the total concentration of CO23 and HCO3 is lower than the combined Ca2+and Mg2+ concentrations. This means that there is no residual carbonate to react with Na+ to increase the sodium hazard in the soil. Scott quality factor (alkalimetric coefficient) classifies irrigation water according to the relation between sodium concentration and the chlorides and sulphates concentrations. The quality indices are intended to provide a simple and understandable tool for managers on the quality and possible uses for irrigation water, but the use of an unique quality factor is not appropriated. The aim of this paper was to propose a quality profile of irrigation water that expresses the results of several parameters in order to assess the water quality. Methods Site description San Luis is a province located in the center-west region of Argentina with a predominantly moderate Environ Monit Assess (2008) 142:149–152 semi-arid climate, with summer rains. The Del Molle River is located in the northwest of the province and its confluence with the Chico River gives origin to the Nogolí River. This zone is located in the homonymous town about 50 km north of San Luis city. The soil is sandy, calcareous, with gravel and, sometimes, tuff (Peña Zubiate et al. 1988). Methodology A systematic and monthly sampling was carried out in eight opportunities, doing the respective physicochemical analysis of the water. To evaluate water quality and its suitability for irrigation, in situ measures such as pH, electrical conductivity and nitrite, and laboratory analyses such as total hardness, calcium, magnesium, alkalinity, nitrate, sulphate, chloride, sodium and potassium were carried out. Determinations were performed using procedures recommended in the Standard Methods for Examination of Water and Wastewater (APHA 1992). Calcium and magnesium (Ca2+and Mg2+) cations were analyzed by complexation volumetry with ethylene diamine tetra acetic acid (EDTA). Sodium and potassium (Na+ and K+) were analyzed using flame photometry. Carbonate and bicarbonate (CO23 and HCO3 ) were analyzed by acid-base volumetry using sulfuric acid (H2SO4) and the chlorides ions (Cl−) were analyzed by argentometric volumetry using silver nitrate (AgNO3). The determination of sulphate (SO24 ) was carried out by the turbidimetric method. Nitrites and nitrates (NO2 and NO3 ) were measured using molecular spectrometry. Electrical conductivity and pH were measured using conductimetric and potentiometric techniques, respectively. Results and discussion Table 1 summarizes the values of the various parameters of the river monitored during October 2005–May 2006. Excessive salinity retards crop yields by restricting the availability of soil water to the crop and, although many crops can tolerate different degrees of salinity, an EC mean value of 509 μmohs cm−1 is much below the threshold salinity for even many sensitive crops (Hoffman et al. 1981). Environ Monit Assess (2008) 142:149–152 151 Table 1 Physicochemical parameters obtained for the Del Molle River 2005 pH Conductivity (μmoh cm−1) Total hardness (mg l−1 CaCO3) Calcium hardness (mg l−1 CaCO3) Magnesium hardness (mg l−1 CaCO3) Sulphate (mg l 1 SO24 ) Nitrate (mg l 1 NO3 ) Nitrite (mg l 1 NO2 ) Alkalinity (mg l−1 CaCO3) Chloride (mg l−1 Cl−) Sodium (mg l−1 Na+) Potassium (mg l−1 K+) TDS (mg L−1) Dissolved oxygen (mg l−1) Phosphate (mg l 1 PO34 mg L−1 PO43−) 2006 October November December January February March April May 8.78 526.44 217.28 136.15 81.13 210.76 0.30 0.21 150.84 19.13 27.27 6.89 336.76 7.81 0.01 8.59 514.97 212.55 133.18 79.36 206.17 0.29 0.20 147.55 18.71 26.68 6.74 329.42 7.64 0.01 8.59 514.72 212.44 133.12 79.33 206.07 0.29 0.20 147.48 18.71 26.66 6.74 329.26 7.64 0.01 8.37 504.27 208.19 130.46 77.75 201.89 0.29 0.20 144.49 18.24 26.08 6.57 322.61 7.45 0.01 8.32 498.92 205.92 129.03 76.89 199.75 0.28 0.20 142.95 18.13 25.85 6.53 319.15 7.40 0.01 8.22 492.80 203.40 127.45 75.95 197.30 0.28 0.19 141.20 17.91 25.53 6.45 315.24 7.31 0.01 8.42 504.52 208.24 130.48 77.75 201.99 0.29 0.20 144.56 18.33 26.14 6.60 322.74 7.48 0.01 8.68 520.32 214.76 134.57 80.19 208.31 0.30 0.20 149.09 18.91 26.95 6.81 332.85 7.72 0.01 Sodium adsorption ratio (SAR) is used for possible sodium hazard. This value was calculated by the following equation: SAR ¼  Naþ Ca2þ þMg2þ 2 1=2 The obtained value is 0.78 (>10), so the water has little sodification power. According to Riverside Norms, all water samples analyzed belong to the C2–S1 class (medium salinity and low sodium content class); however, water that belongs to this class is also useful for almost all plants provided moderate amount of leaching takes place or for plants with reasonable salinity tolerance without large practices for salinity control (Ayers and Westcot 1985). However, Riverside Norms should not be used for a complete evaluation because: It can be obtained the same EC in a water where predominate SO24 and Ca2+ (at the same concentration) as well as where predominate Cl− and Na+. These norms do not have in account the influence of Cl− and SO24 . If the ratio Mg2+ and Ca2+ is high it should not be included in the same quality factor. Another objection to this norm is that it is very restrictive and sometime it could give an unfavorable qualification. Greene Norms relate the total concentration of ions in the water and the percentage of sodium in relation to the total content of the majority cations (Ayers and Westcot 1985). According to this norm, the analyzed water is of good quality. Wilcox norm is another quality factor that related Electrical conductivity versus % Na to evaluate irrigation waters given five qualification zones. In our case the water is classificated as excellent to good. To evaluate Residual Sodium Carbonate (RSC) the concentrations of Ca2+, Mg2+, CO23 and HCO3 expressed in mequiv l−1 are needed for its calculation. The value of the CSR quality factor, in our case, is −2.74 mequiv l−1, so this water is recommendable because the CSR quality factor is lower than 1.25. A low Residual Sodium Carbonate implicates a minimum risk to the sodium hazard in the soil. To calculate Scott quality factor (alkalimetric coefficient), we must applied the following equation þ þ K ¼ 6620=½Na  Š2þ2:6½Cl Š when 0 < ½Na Š 0:65 ½Cl Š < 0:48 SO4 . The value obtained in this study was K=88.79 (K>18), so the water is good (no need to take precautions; Cánovas Cuenca 1986). 152 Conclusions An irrigation water quality factor alone is not enough to evaluate potential salinity and sodification hazards which may be confronted under irrigated agriculture. The concept of quality is not unique but multiple and they can be so different that they could be incompatible among they, so it makes no sense to talk about an unique quality factor. It is more correct to talk about a quality profile. This means that instead of bring an unique value we can bring many values to reach a better understanding about the kind of water. A quality profile is not unique; it will depend on the problem severity, too. A widest understanding of the water under study is reaching by the use of many indices that take into account different dissolved ions. For this reason, in this paper the use of, at least, three indices such as CSR, Riverside and Scott Indices to overcome potential salinity hazard, is proposed. From the analysis of the different parameters measured and the application of indices and quality norms, we can conclude that the quality profile for water from the Del Molle River is good and fulfills all the requirements for the intended use. This water does not have any use restriction. The cultures with moderate tolerance to salts are developed without any special control practices, and the vegetal growth is not affected. The permeability of the substrate notably affects the quality of the irrigation water, which makes it necessary to know the soil composition in order to determine the salinity and sodification risk. Besides, Environ Monit Assess (2008) 142:149–152 one must not only evaluate the water quality profile but consider plant, soil, climatic conditions and irrigation practices in a given region. Acknowledgements The authors wish to thank to Ciencia y Técnica de la Universidad Nacional de San Luis for financial support of this research. References APHA (1992). Standard methods for the examination of water and wastewater (18th ed.). Washington, DC, USA: American Public Health Association. Ayers, R. S., & Westcot, D. W. (1985). Water quality agriculture. FAO Irrigation and Drainage Paper 29 Rev. 1, Roma, 174. Cánovas Cuenca, J. (1986). Calidad agronómica de las aguas de riego (2da ed.). Ed, Madrid: SEA. Eaton, F. M. (1950). Significance of carbonate in irrigation waters. Soil Science, 69, 123–133. Hernández, J. C., Orihuela, D. L., Marijuan, I., Pérez, S., & Furnet, N. R. (2003). Efecto de la modificación de cationes en columna de suelos calizos. Estudio de la zona saturada del suelo. Ed. Javier Álvarez-Benedí y Pilar Marinero (pp. 99–104). Hoffman, G. J., Ayers, R. S., Doering, E. J., & McNeal, B. L. (1981). Salinity in irrigated agriculture. In M. E. Jensen (Eds.), Design and operation of farm irrigation systems. ASAE Monograph 3. Orihuela, D. L. (1992). Salinización de las aguas de uso agrícola en el sector III del plan Almonte-Marisma. AIQB. 233. Peña Zubiate, C. A, Anderson, D. L., Demmi, M. A., Saenz, J. L., & D’Hiriart, A. (1988). Carta de suelos de la provincia de San Luis, 76. Richards, L. A. (1954). Diagnosis and improvement of saline and alkali soils. U.S. Salinity Laboratory Staff. USDA Handbook, 60, 160. Wilcox, L. V. (1955). Classification and use of irrigation waters. US Department of Agric Circ., 969, 19.