Udayapur District
Udayapur District (उदयपुर जिल्ला, is one of 14 districts of Koshi Province of eastern Nepal. The district, with Triyuga as its district headquarters, covers an area of and in 2001 had a population of 287,689, in 2011 of 317,532, in 2021 of 342,773 The district border of Udayapur is drawn by Natural border with rivers and hills. Koshi river in the east of the district separates it from Sunsari District, Sun Kosi river in the north draw a borderline which separates it from Bhojpur and Khotang. Sindhuli District lies in the west across the Tawa khola and foothills of shiwalik in the south separates it from outer terai of Siraha and Saptari. Koshi Tappu Wildlife Reserve lies in the east occupying the area of Udayapur, Sunsari and Saptari District. According to the former administrative divisions of Nepal, Udayapur falls in Eastern Development Region in Sagarmatha Zone. Before the unification of modern Nepal by Shah kings. Udayapur District was under Sen dynasty. The Kingdom name was Chaudandi and capital of the Kingdom was chaudandigadhi. The last king of the Chaudandi was Karna Sen who fled to Bijayapur when Gorkha army evaded and captured the Sen Kingdom Chaudandi. Before 1972, Panchawati was Headquarter of Udayapur District, it moved to Gaighat in 1972. Udayapur district is surrounded by Mahabharat hills from north and Shiwalik from south, whereas both hills meet together by west which forms the region a valley Udayapur valley. Udayapur valley is about long and from wide, it is drained by the Triyuga river flowing east to join the Koshi river. Forest cover takes up 67% of the total land area of the district. 28% of the land is cultivated. Small and large river and ponds remain the main source of water in the district. Ponds like Rauta Pokhari, Suke Pokhari, Tapli Pokhari, Jogidaha Chure Forest Pond and Jhilke Pokhari are key water resources in the district. The district does not possess larger lakes. Triyuga is the largest river in this district. Other two major rivers are Tawa Khola from Western side and Vaidyanath River from mid-side unite with Tawa River.