The reservoir of the Keban Dam in eastern Anatolia is a very deep and large water body subject to significant seasonal water level fluctuations within a given hydrological year. At the present time, different sections of the reservoir have different trophic status and the upper portion of the reservoir, in particular, is eutrophic. In this regard, there is a need for the assessment of alternative strategies to be implemented for phosphorus and thus eutrophication control in this segment of the reservoir. In this study, mathematical modeling techniques are used to compare various alternatives in terms of their relative effectiveness for phosphorus control. With this intention, a two dimensional depth-averaged hydrodynamic model and a three-dimensional compartmental water quality model are coupled to represent the complex water body dynamics prevailing in the reservoir, After calibration and verification, the coupled model was used to simulate dissolved oxygen and euphotic chlorophyll-a concentrations under different scenario conditions corresponding to various strategies proposed for phosphorus control. The modelling effort has yielded valuable information that can be used by decision makers for the evaluation of different management alternatives including reduction of the phosphorus load coming from point as well as diffuse sources within the catchment area, use of baffles and construction of pre-dam structures. (C) 1997 Elsevier Science B.V.