assessment of type and usage of thermal water in mahalat, markazi province, iran

in this study, water samples were collected from 10 thermal and non-thermal springs of mahalat setting during four periods in 2011. the discharge rates of these springs vary from 2 l/s to 45 l/s and their temperature range from an average minimum of 18oc to maximum 47oc. spring water is high in so4-cl and this is related to gypsum dissolution. correlation coefficient, principal component analysis, and isotopic data of samples showed there was mixing of young and old water and meteoric water in springs. the quality of water for irrigation was assessed by parameters such as sar, ssp, rsc, pi, mar and kelly’s index for major elements (so42-, hco3-, cl-, ca2+, na+, mg2+ and k+). all water quality indices have shown that the water is suitable for irrigation. the metal index of heavy metals (hg, zn, co, as, b, cu, mn, mo and ni) was compared to the standard iranian guideline values for irrigation and was also used to determine the contamination index. the calculated values have shown that almost all samples are above the threshold of warning and most of the water samples are contaminated.