The Seyhan river has a total catchment area of 20,731 km(2) with major pollution sources located downstream of the Seyhan Dam in Adana. The so-called Lower Seyhan, is under the threat of nor only domestic and industrial wastewater discharges originating from the metropolitan area of Adana, but also agricultural wastes of the fertile Cukurova Plain. In this study, the present and future water qualify characteristics of the Lower Seyhan have been investigated by means of a mathematical modelling study based on actual field data as well as in-situ water quality measurements. The model of choice was the QUAL2EU. The behaviour of the Lower Seyhan was studied under different pollution control scenarios in order to develop plausible water quality management strategies for the target year of 2010. As a result of these studies, two alternative systems were proposed for the management of the wastewater sources within the Lower Seyhan catchment. Alternative wastewater treatment plant designs and their cost implications were evaluated by means of the CAPDET-PC software package. A user-charging scheme and an optimisation model that can be used for demonstrating the economic viability of the proposed systems were also developed for obtaining a cost-optimum management policy for both municipalities and industrial establishments of the area. (C) 1999 Published by Elsevier Science Ltd on behalf of the IAWQ. All rights reserved.