Smolensk Oblast (Smolenskaya oblast), informally also called Smolenschina (Смоленщина), is a federal subject of Russia (an oblast). Its administrative centre is the city of Smolensk. As of the 2010 Census, its population was 985,537. The oblast was founded on 27 September 1937. It borders Pskov Oblast in the north, Tver Oblast in the northeast, Moscow Oblast in the east, Kaluga Oblast in south, Bryansk Oblast in the southwest, and Mogilev and Vitebsk Oblasts of Belarus, in the west and northwest, as part of the Belarus–Russia border. The main river of the region is the Dnieper River and its tributaries, Desna, Vop, Vyazma. By the rivers of the Volga basin and its tributary Vazuza Gzhat and tributary of the Oka river, Ugra. To the north-west flows a short section of the Western Dvina River and its tributary river Kasplya . Among the major reservoirs supplying water are Moscow Vazuzssky Yauza and reservoirs in the north-east, as well as cooling power plants, Smolensk reservoir in the north near the village of Lake and Desnogorsk Reservoir in the south area of the city near the Desnogorsk . The climate of Smolensk Oblast is humid continental, similar to the climate of Moscow Oblast, but slightly warmer in winter due to being located further west. Summers are short, warm and rainy, while winters are long, cold and snowy. Average temperatures range from in January to in July (although in the south it ranges from in January to in July). Annual precipitation varies from per year. During the Soviet period, the high authority in the oblast was shared between three persons: The first secretary of the Smolensk CPSU Committee (who in reality had the biggest authority), the chairman of the oblast Soviet (legislative power), and the Chairman of the oblast Executive Committee (executive power). Since 1991, CPSU lost all the power, and the head of the Oblast administration, and eventually the governor was appointed/elected alongside elected regional parliament. The Charter of Smolensk Oblast is the fundamental law of the region.