Abstract

CTo assess the quality of ground water and its suitability for irrigation, a study was carried out during pre and post monsoon seasons of 2006-2007. In the present study, the ground water samples from open wells, bore wells and dug cum bore wells were collected in the Noyyal river basin that encompasses the urban and industrial stretch of Tirupur. The values of EC ranged from 0.41 to 15.95 dSm-1 and pH ranged from 7.61 to 8.61. Sodium dominated among the cations and chloride among the anions. The sequence of cations found to be Na + >Mg 2+ >Ca 2+ >K + and anions followed the sequence of Cl - > SO 4 2- >HCO 3 - >CO 3 2- . Salinity and sodicity classes were assessed as per Richards (1969). Very high salinity category (C4) dominated (56.90 per cent) and low sodium (S 1 class) (74.14 per cent) category recorded the major classes of salinity and sodicity respectively. Residual sodium carbonate and Residual Sodium Bicarbonate content classified under satisfactory with 68.9 per cent (<1.25 m.e L -1 ) and 87.93 per cent (<5 m.e L-1 ) respectively. Classification of the samples based on salinity and SAR indicated that 68.97 per cent of samples did not pose infiltration problem to the soils and 31.03 per cent will result in slight to moderate infiltration due to irrigation. It was found that 50 per cent of samples having slight to moderate (0.7 t0 3.0 dSm -1 ) salinity problem followed by 43.01 per cent under severe salinity (>3.0 dSm-1 ). Sodium and chloride toxicity were found in majority of the samples. Slight to moderate toxicity of sodium (SAR>9) was recorded by 67.24 per cent of samples which may cause accumulation of sodium over a long period.

Keywords: Irrigation water quality, Noyyal river basin, Tamil Nadu