Proposal for an index to classify irrigation water quality: a case study in northeastern Brazil

Abstract

suMMary one way of classifying water quality is by means of indices, in which a series of parameters analyzed are joined a single value, facilitating the interpretation of extensive lists of variables or indicators, underlying the classification of water quality. the objective of this study was to develop a statistically based index to classify water according to the Irrigation Water Quality Index (IWQI), to evaluate the ionic composition of water for use in irrigation and classify it by its source. for this purpose, the database generated during the technology generation and adaptation (gat) program was used, in which, as of 1988, water samples were collected monthly from water sources in the states of Paraíba, rio grande do norte and Ceará. to evaluate water quality, the electrical conductivity (eC) of irrigation water was taken as a reference, with values corresponding to 0.7 ds m -1 . the chemical variables used in this study were: ph, eC, Ca, Mg, na, K, Cl, hCo 3 , Co 3 , and so 4 . the data of all characteristics evaluated were standardized and data normality was confirmed by lilliefors test. then the irrigation water quality index was determined by an equation that relates the standardized value of the variable with the number of characteristics evaluated. thus, the IWQI was classified based on indices, considering normal distribution. finally, these indices were subjected to regression analysis. the method proposed for the IWQI allowed a satisfactory classification of the irrigation water quality, being able to estimate it as a function of eC for the three water sources. Variation in the ionic composition was observed among the three sources and within a single source. although the water quality differed, it was good in most cases, with the classification IWQI II.Index terms: salinity, electrical conductivity, ionic composition.(1) received for publication in august 8, 2011 and approved in March 7, 2012. (2) agronomist, doctor in natural resources. Professor of the environmental and technological sciences department of the universidade federal rural do semiárido (rural federal university of the semiarid region) -ufersa. fellowship holder from the CnPq. e-mail: celsemy@ufersa.edu.br (3) agronomist, Master's degree in Irrigation and drainage, ufersa, Br 110, km 47, Costa e silva, CeP 59625-900 Mossoró (rn).

A proposed index to assess quality of waters from desalination plants

“…In addition, crop yield seems to be lower in soils with high contents of Mg, or when irrigation is conducted using waters with high levels of this element, even when infiltration is adequate. Maia & Rodrigues (2012), proposing a water quality index, reported that yield loss is due to Ca deficiency induced by the excess of exchangeable Mg in the soil. P 1 -First sampling period; P 2 -Second sampling period; P 3 -Third sampling period; P 4 -Fourth sampling period For brackish well water, the indices of the deviations in the indicators remained between 0.05 for Na in P 3 in Jacu and 3.98 for SAR in P 3 in EMA.…”

Assessment of Water Quality and Trophic Status of Duhok Lake Dam

“…[27] record the highest chlorophyll a content in Marzanaland shallow wetland in Iran during warm periods. Depending on irrigated water quality index (IWQI) values for Duhok lake dam in different seasons, water quality is regarded as excellent types for irrigation purpose based on [21] classification (Table 4). Site 3 is characterized by higher values with maximum value 1.72 observed during winter.…”

“…Where, WQIi is Water Quality Index for the characteristic and IWQI is Irrigation Water Quality Index. The results, are classified according to [21] Table (1).…”

Hydrochemical Characterization of Water Resources From Reverse Osmosis Desalination Plants

“…Ayers and Westcott (1999) point out that the productivity of most crops is lower in soils with high magnesium contents, or when irrigation water contains high levels of this element, even when the infiltration is adequate. According to Maia and Rodrigues (2012) this is due to calcium deficiency induced by the excess of exchangeable magnesium in the soil. In this situation, the effects of sodium are slightly higher when it is present in the irrigation water, or in the soil solution, since, due to the lower attraction force presented by magnesium, there may be dispersion of the clays, generating problems of infiltration.…”