Eutrophication poses a threat to lakes worldwide, driven by factors such as cyanotoxins, fish kills, reduced water treatability, and diminished tourism appeal. In developed countries, where point source pollution and watershed nutrient loading have been largely addressed, internal nutrient loading has emerged as a critical driver of eutrophication. In these regions, sediment phosphorus management has become a priority for restoration. In contrast, wastewater treatment in developing countries is often inadequate and leads to higher external nutrient inputs. Therefore, addressing external nutrient loading may yield a higher return on investment in these regions. Traditional lake restoration is frequently portrayed as a long-term challenge requiring decades of research. However, this perspective can sometimes result in disproportionate funding allocation to problem diagnosis rather than actionable solutions. An alternative approach is adaptive lake management, which involves establishing baseline parameters, rapidly implementing management strategies, and then refining these strategies based on post-management data. This approach involves the creation of conceptual systems context diagrams and mass balances based on pre-existing data, while working to refine these relationships after management strategies have been implemented. This lake management strategy utilizes a learn by doing approach and prioritizes a systems thinking approach to lake restoration. Adaptive lake management is also quick to highlight management deficiencies by embracing a “fail forward” mindset when management targets are not achieved. This iterative process allows for more timely and cost-effective interventions, accommodating the diverse challenges faced in both developed and developing contexts. This presentation will explore several adaptive lake management case studies and demonstrate methodologies for swiftly and economically identifying the root causes of eutrophication. It will also review various management options for restoring toxin-rich, eutrophic lakes and reservoirs, highlighting the importance of a systems thinking approach and the consideration of environmental, social, and economic factors.