It is bordered by the Inner Mongolia Autonomous Region to the north, Shanxi province to the east, Henan and Hubei provinces to the southeast, Chongqing municipality and Sichuan province to the south, Gansu province to the west, and the Hui Autonomous Region of Ningxia to the northwest. Han River, which is a northern tributary of the Yangtze River (Chang Jiang).The Huang He (Yellow River) constitutes Shaanxi’s entire eastern border with Shanxi. The Han flows between two mountain complexes that structurally form part of a great, single fold zone.Farther downstream the valley again narrows, after which the river flows between mountains and through deep gorges, only emerging into the plain once more in Hubei province.
In this area agriculture depends on techniques for minimizing evaporation losses and in conserving moisture in the soils.Structurally this is a basin of largely undisturbed sedimentary rocks of immense thickness. On the eastern border of the basin the Huang He flows from north to south through a narrow, gorgelike trough.In this section it falls some 2,000 feet (600 metres) in less than 500 miles (800 km), and it is mostly unnavigable, with frequent rapids, culminating in a very deep, narrow gorge and falls at Longmen Gorge.The capital is Xi’an, in the south-central part of the province. These complexes are the Qin (Tsinling) Mountains—the major environmental divide between northern and central China—to the north.The Daba Mountains range from 5,000 to 6,500 feet (1,500 to 2,000 metres) in height, with individual peaks reaching elevations of up to some 8,000 feet (2,450 metres).Its northern flank in Shaanxi is heavily dissected by the complex pattern of the Han River’s southern tributaries.The only major break in this mountain chain occurs in the far southwest of the province where the Jialing River, which rises to the north in the Qin Mountains, cuts through the Daba chain to flow into Sichuan on its way to join the Yangtze at Chongqing.The northern border of the Wei River trench is less abrupt, and the large northern tributaries of the Wei, Jing, and Luo rivers have themselves formed in their lower courses quite extensive alluvial plains that are continuations of the Wei River plain.The plain consists largely of loess (the wind-borne silty deposits that also mantle parts of the northern face of the Qin Mountains), as well as redeposited loess washed off the plateau to the north. The third region, to the north, is the great upland plateau of northern Shaanxi.Mean temperatures in January are from 37 to 39 °F (3 to 4 °C), and the annual frost-free growing season is from 260 to 280 days, although the summer and autumn are not so hot as in the middle Yangtze region.Total precipitation is between 20 and 40 inches (500 and 1,000 mm), falling mostly between May and October.