Bojonegoro Regency (, older spelling is Kabupaten Bodjanegara, ) is a regency in East Java, Indonesia, about 110 km west of Surabaya. It is located in the inland part of northern Java plain, on the banks of the Solo River, the longest river in Java. It had a population of 1,209,973 at the 2010 Census and 1,301,635 at the 2020 Census, comprising 653,686 males and 647,949 females. The administrative centre of the regency is the town of Bojonegoro District. Previously known as a major producer of teak and tobacco, Bojonegoro is a focus of attention in Indonesia as a new oil field has been found in this area. This oil find is the biggest oil discovery in Indonesia in three decades and one of the biggest reserve in Indonesia. Geography Across the eastern border of Bojonegoro is the Lamongan Regency, to the north is Tuban while to the south is Ngawi, Madiun, Nganjuk and Jombang. Blora is located to the west, in Central Java. Bojonegoro occupies an area of 2,307.06 km2. Much of it consists of low plains along the Solo River, with hilly areas in southern part of the Regency. As with most of Java, the Bojonegoro landscape is dominated with rice paddy fields. In the Bojonegoro area, the Solo River changes its course from northward to eastward. Climate in Bojonegoro is tropical with six months of rainy and dry seasons. Seasonal conditions are often very contrasting. In the rainy season, rain will fall almost daily while in the dry season, rain will not come for months, causing widespread drought and water shortages. These problems have been compounded with the loss of forest and other green areas. Teak forest once covered much of Bojonegoro, but has since considerably reduced due to over exploitation. Floods in the rainy season of 2007 were bigger than in previous years. The water level of Solo River rose due to heavy rain, especially in the upper valley in Central Java, forcing the Gajah Mungkur Dam to be opened. The resulting flood submerged 15 districts, with water as high as 1.5 m, and displaced 2,700 families. A further 2.5 hectares of rice fields were damaged. No casualties were reported. Climate Bojonegoro has 42-100% of humidity. Maximum humidity is 100% and average humidity is 81%. Bojonegoro has 0–35 km/hr of wind velocity. Maximum wind velocity is at 35 km/h (18.9 knot). Average wind velocity is 30