EVALUATION OF THE QUALITY AND SELF PURIFICATION POTENTIAL OF TAJAN RIVER USING QUAL2E MODEL

Tajan river is among significant rivers of caspian sea water basin. pollution sources that threaten thequality of water in tajan river may be classified in to two categories namely point and non-pointsources. major pollutants of latter category are mazandaran wood and pulp, paksar dairy products andsari antibiotic production factories, as well as 600-dastgah residential area. on the other hand, non-pointsources whose waste is considered as a distributed load consist of sari municipal wastewater andagriculture-related pollutants that are drained towards the river. in order to model the quality of riverflow, qual2e model is taken in to consideration. considering tds, the river quality is completelyacceptable in cold seasons. however, in spring and summer the value of this parameter is increased andthis causes some restrictions in the use of this water for irrigation of specific sensitive crops. agriculturalactivities and consequent irrigated waters are the major causes of higher reported tds values in warmseasons. current status of do is completely acceptable and this is highly related to the relative highvalue of width on depth ratio along the river. bod and cod locate in a fairly poor condition. qualitydeterioration is more noticeable in cold seasons. higher rate of precipitation and consequent greater runoffgeneration towards the river basin justify the relative increase of mentioned parameters in fall andwinter. generally, non-point pollution sources are more contributed in deterioration of tajan river waterquality.