Sustaining freshwater systems in the face of rapid changes in land use continue to be a major challenge in lake watersheds. Lake Egirdir is a major freshwater lake in Turkey and is significant in supporting several ecosystem services of the region. The nutrient loading from both point and nonpoint sources has reduced the quality of the tributaries and the lake ecosystem. There is a need for comprehensive modeling of strategies to protect the lake and watershed ecosystems. This study uses a watershed systems modeling to assess hydrologic flows and nutrient loads in order to quantify effectiveness of management practices in reducing runoff and nonpoint source pollution. The study uses GIS to process spatial data and simulation modeling to assess hydrologic and contaminant processes at a watershed scale. Management strategies are evaluated by quantifying the effect of targeted best management practices (BMPs) in urban, forest and agricultural land uses. The results show that urban and forest loss can affect the watershed and lake ecosystems. There is a need for spatially targeted policies to sustain the lake watershed. Land use management through education and incentives through conservation practices can be used to reduce nutrient and sediment loads in sensitive areas of the watershed. (C) 2013 Elsevier B.V. All rights reserved.