Degradation of water quality is the major health concern for lakes and reservoirs in the regions of north china as a result of highly diverse non-point source emissions caused by human activities.For describing the dynamic response between emission loads and receiving water conditions factually,model systems have became the typically decision support tools during the reservoir management strategy development,which is the vital key to estimate source loading inputs,evaluate receiving * water quality,and determine source loading allocations for meeting water quality standards.This study integrated GWLF ( Generalized Watershed Loading Functions) watershed and BATHTUB water-quality models to simulate actual reservoir water quality conditions of Yuqiao Reservoir,Tianjin,China and illustrated the use of this coupled model for simulating water quality response to changes in different watershed land use and management scenarios.Tbe Generalized Watershed Loading Functions (GWLF) indicated that livestock breeding and agricultural planting were the two leading contributions of non-point pollution sources to TN and TP loads.The Bathtub,designed to facilitate application of empirical eutrophication models to reservoirs,suggested that there were great relationships between land use type and water quality conditions.