Lake Ptuj is the largest Slovenian artificial lake. It was created in 1978 by putting a dam on the River Drava under Ptuj, and it serves as a reservoir for the Formin hydro power plant; at the same time it is becoming a place for recreational purposes as rowing, sailing and fishing. The lake is 7.3 km long and 1.2 km wide. It covers 420 hectares, the maximum depth reaches 12 metres and the water quantity in the lake is 20 for wintering of water birds in Slovenia. Around 10,000 birds spend every winter on this lake, which is around 20% of all wintering water birds in Slovenia. Owing to a huge importance of bird protection, Lake Ptuj was together with the River Drava pronounced as the Natura 2000 area in 2004. During the winter shortages, upsetting the water birds might be fatal. To pro-vide a necessary peaceful environment for wintering birds a part of the lake is prohibited for sailing. To this end the Municipalities Markovci and Ptuj adopt-ed a Decision which limits the sailing on most sensitive spots of the lake.