of the prefecture (the Hoh Xil plateau), and along its northern borders, there are some endorheic basins as well. A significant portion of the prefecture's territory is incorporated into the Sanjiangyuan National Nature Reserve, intended to protect the headwaters of the three great rivers. Most of the prefecture's population lives in its southeastern part: primarily in the valley of the upper Yangtze (whose section within the prefecture is known in Chinese as the Tongtian River, in Tibetan as Drichu ), and some also in the valley of the Mekong (the Dzachu () River). The highlands away from these two rivers, as well as the western part of the prefecture, have very little population. Climate With elevations above , the prefecture has a harsh climate, with long, cold winters, and short, rainy, and cool to warm summers. Specifically, in the Köppen system, the prefecture ranges from the alpine variation of the subarctic climate (Köppen Dwc), to a full alpine climate (Köppen EH), to a semi-arid climate (Köppen BSk). Most of the annual precipitation occurs from June to September, when on average, a majority of the days each month has some rainfall. The annual mean temperature in Yushu County, at an elevation of , is and in Qumarlêb, in the northeast of the prefecture at elevation, . Sunshine is generous, ranging from around 2500 hours in the prefecture seat to 2780 hours in Qumarlêb. Subdivisions The prefecture is subdivided into six county-level divisions, composing 5 counties and 1 County-level city: Economy Agricultural produce of Yushu includes trees, wheat and millet including black Highland barley. Transportation The eastern part of the prefecture, where most of its population lives, is served by the China National Highway 214 and the recently constructed (opened 2009) Yushu Batang Airport. In 2017 the G0613 Xining–Lijiang Expressway was completed, connecting the region to Hainan Tibetan Autonomous Prefecture and Xining. The far western part of the prefecture, which is hundreds of kilometers away from the prefecture's eastern "core", and has very little population, is crossed by China National Highway 109 and the Qinghai-Tibet Railway. Population Ethnic groups in Yushu, according to 2005 Yushu Statistical Yearbook: This statistics only includes the registered population, not the floating population which is estimated at 50–60,000 for the entire prefecture. References Citations External links Yushu: A Tibetan Town Rebuilt in Beijing's Image The East Tibet Website Nangchen historic area Yushu Tibet Autonomous Prefecture Official Website