The purpose of research was to get overview about melioration history and practices in Estonia and to document hydrological changes in Pususoo bog and in its watershed. Pususoo is one of the biggest bogs in Harju district and it influences environment in three neighbouring counties. In 1981 Pususoo bog got national reserve status under name Laukesoo, what is round and extra bog pond rich part of this wetland. Since 2004 the reserve is part of the Natura 2000 protected areas network. During 2010—2020 took place the renewal and reconstruction of land improvement systems in Pususoo region, during what environmental changes occurred in its watershed. Environmental changes in this wetland influence roughly 1/3 of Estonian population because it regulates availability of their drinking water.