using fuzzy comprehensive assessment method for rivers water quality zoning

water quality zoning have been recognized as a useful tool, which gives managers a sweeping view for taking environmental conservative actionsin oeder of priority. ordinary methods, which have been used in iran, involve some defections such as disregard water usage, uncertainty due to sampling error and classification, and changing the class number due to a bit change in water quality parameters. the main idea of this paper is to use fuzzy comprehensive assessment (fca) technique in gezel ozan river, which overcomes mentioned disadvantages. according to this method, at first four water quality classes have been extracted based on available standatdes for agriculture. three water quality parameters, including total hardness, electrical conductivity, and sodium absorption ratio, have been used. then, degree of membership matrix has been built based on this method. for calculating the weight factor, information antropy method has been used. finally the water quality class has been defined by multiplying the weight matrix by membership matrix. accordig to the results, the river water is unsuitable for agriculture porpuses. because of its high tds water.