In this paper I am analyzing the societal effects caused by the water management of Lake Balaton in the last 150 years. The starting date of the research is 1863 when the first wooden Sió flood-gate was built at the joining point. During the decades the flood-gate went through several renovations and upgrades. The closing date of the research is 2013, when fishing, which has a tradition going back for several centuries, was first suspended, then permanently banned. In my research I used both primary and secondary sources. As secondary sources I used specialized literature concerning Lake Balaton, including demographic data of settlements, and time series of water management. As primary sources I interviewed regional leaders and professionals, and sociologists to get a clear picture about current events. As a result I found that in certain periods of its history the lake had been handled as an independent physical object, but by now the professionals involved in water management have mad attempts to set up a sustainable, harmonious relationship between the lake and the surrounding society.