The Hexi Corridor, also known as the Gansu Corridor, is an important historical region located in the modern western Gansu province of China. It refers to a narrow stretch of traversable and relatively arable plain west of the Yellow River's Ordos Loop (hence the name Hexi, meaning 'west of the river'), flanked between the much more elevated and inhospitable terrains of the Mongolian and Tibetan Plateaus. The Hexi Corridor enabled cultural and agricultural exchange between China and Eurasia for several milennia, in both prehistory and as part of the Northern Silk Road after the Han Dynasty.
As part of the Northern Silk Road, running northwest from the western section of the Ordos Loop between Yinchuan and Lanzhou, the Hexi Corridor was the most important trade route in Northwest China. It linked China proper to the historic Western Regions for traders and military incursions into Central Asia. It is a string of oases along the northern edges of the Qilian Mountains and Altyn-Tagh, with the high and desolate Tibetan Plateau further to the south. To the north are the Longshou, Heli and Mazong Mountains separating it from the arid Badain Jaran Desert, Gobi Desert and the cold steppes of the Mongolian Plateau. At the western end, the route splits into three, going either north of the Tianshan Mountains or south on either side of the Tarim Basin. At the eastern end, the mountains around Lanzhou grants access to the Longxi Basin, which leads east through Mount Long along the Wei River valley into the populous Guanzhong Plain, and then into the Central Plain.
Geography The Hexi Corridor encompasses much of northwestern Gansu province, and is located on the west side of the Yellow River as it runs north around the Ordos Loop (hence the name Hexi, meaning 'west of the river'). The corridor stretches roughly from the Wushao Mountains in the east to Yumen Pass in the west, from north to south, ranges from in width, and covers an area of approximately or around 60% of the area of Gansu Province. Its population was 4.82 million people in 2011, representing around 19% of the province's total population. As of 2024, the corridor contains 20 administrative divisions and five prefecture-level cities, which are, from east to west: Wuwei, Jinchang, Zhangye, Jiuquan, and Jiayuguan.
The elevation of the Hexi Corridor descends from around above sea level in the southeast to in the northwest. It is bordered by the Qilian Mountains in the south and southeast, the Kumtag Desert to the west, the Mazong, Helan, and Longshou Mountains to the north, the Badain Jaran Desert to the northeast, and the Tengger Desert to the southeast. The Qilian Mountains run south of the Hexi Corridor for and contain several peaks exceeding above sea level, while the mountains to the north generally range from in height. The location of the Hexi Corridor between these landforms as a relatively arable and low-lying valley makes it the most convenient route between China and Central Asia.
The three largest rivers in the Hexi Corridor are the Shiyang, Heihe, and Shule rivers. Like most rivers in the region, much of their discharge is derived from the melting of glaciers and snow in the Qilian Mountains; they form extensive alluvial fans and inland drainage basins as they flow through the Hexi Corridor, beyond which lie deserts and large sand-dune fields. Arid landscapes such as deserts comprise roughly 70% of the Hexi Corridor, while fertile land and vegetation are largely confined to oases along the major rivers, which have sustained both nomadic groups and settled societies for thousands of years.
Geology The Hexi Corridor is a Cenozoic foreland basin formed over millions of years by the uplift, crustal shortening, and northward advance of the Tibetan Plateau, a landform of which the Hexi Corridor forms the northeastern margin. The region is seismically active, having experienced five earthquakes of magnitude 7 or greater since 180 AD, and is dominated by northwest-trending reverse faults. It is internally divided by three uplifts into four depressions filled with thick fluvial and lacustrine sediment deposited during the Quaternary era.
The area of the present-day Hexi Corridor was successively part of various foreland and strike-slip basins throughout the Paleozoic and early to mid-Mesozoic. During the Cretaceous, the region encompassing the Hexi Corridor and Qilian Mountains was lifted above its surroundings and tectonic activity waned, causing the region to be dominated by erosional activity until the early Oligocene.
During the Oligocene, crustal shortening as a result of the India–Eurasia collision and the growth of the Tibetan Plateau caused the down-faulting and subsidence of the Hexi Corridor. As a result, the region likely became the northern margin of a wide basin extending northward from the Kunlun Mountains, interrupted by a low rise roughly to the south of the Hexi Corridor in the present-day southern Qilian Mountains. Sedimentation in the Hexi Corridor during this time was dominated by fine and highly eroded material derived from this low rise and transported by long meandering streams, with deposition likely occurring in shallow terminal lakes within the basin.
During the Miocene (around 13 million years ago), the northeastward propagation of the Altyn Tagh Fault reached its maximum extent at the Hexi Corridor; subsequent crustal shortening around this new terminus led to the formation of the Qilian Mountains, separating the Qaidam Basin to the south from the Hexi Corridor. During the Pliocene and Pleistocene, crustal shortening spread into the Hexi Corridor itself and formed multiple uplifts. Since the mid-Miocene, deposition in the Hexi Corridor has been dominated by coarse weakly-eroded material owing to the close proximity of the Qilian Mountains and short sediment transport distances.
Sedimentation rates in the Hexi Corridor increased significantly during the early Pleistocene. 1.7 million years ago, the terminal lakes in the Hexi Corridor began to contract as the deltas of rivers prograded into the basin. By 1.1 million years ago, the lakes and former river deltas had disappeared with the formation rivers such as the Heihe and Shiyang, which cut through the former systems by running parallel down the length of the corridor rather than perpendicularly across it. Continued tectonic activity steepened the Qilian Mountains and caused the alluvial fans of many rivers to shift toward the basin's center, converting them into tributaries of the new longitudinal channels.
Climate
The dominant climate types in the Hexi Corridor are temperate semi-arid (Köppen: BSk) and temperate arid (Köppen: BWk). The region experiences an average annual temperature of and an average annual precipitation of less than which generally decreases from southwest to northeast. The climate in the Hexi Corridor is heavily influenced by its location at the intersection of a humid zone in the east dominated by the East Asian monsoon and an arid zone in the west dominated by the westerlies, and has varied over thousands to millions of years as a result of Milankovitch cycles.
Climate fluctuations in the Hexi Corridor have historically played a dominant role in shaping human settlement and interaction in the region. Between the Last Glacial Maximum and the late Holocene, the northern boundary of the East Asian Monsoon migrated at least northwest of its current location near Zhangye. Further intensification during the middle Holocene led to high lake levels and abundant vegetation, and it was during this time when human settlement first expanded into the Hexi Corridor. From 4000–2000 BP, the East Asian monsoon retreated and the climate became cold and arid, leading to a period of cultural and agricultural decline in the region. Since 2000 BP, the influence of climate variability in the Hexi Corridor has increased; for instance, the abundance of early Han dynasty sites may be attributed to relatively warm and humid conditions at the time, while the Little Ice Age during the Ming to Qing dynasties likely contributed to the decline of the region's sites and the Silk Road. Ecology Habitats The Hexi Corridor spans three ecoregions, with most of its area lying within the Alashan Plateau semi-desert, while its southern portion extends into the Qilian Mountains subalpine meadows and the Qilian Mountains conifer forests. The region contains 11 provincial-level and 10 national-level nature reserves which collectively occupy 28% of the corridor's land area, including three Ramsar-listed wetlands.
The distribution of habitats across the Hexi Corridor broadly follows a north–south gradient determined by precipitation patterns and the position of the Qilian Mountains, the primary source of water in the corridor. Desert covers around 70% of the region's land area, mostly in the lower-lying regions of the north and west, where it is characterised by saline soil, sparse vegetation dominated by halophytic and xerophilous shrubs, and low biodiversity. More vegetated ecosystems, such as semideserts and steppes, occur along rivers and oases in the lower corridor; while in the south, they appear as the terrain rises past above sea level on hills and mountain slopes. Forests cover just 3.32% of the corridor's total land area and occur above in the Qilian Mountains.
Flora
There are 326 recorded species of seed plants in the Hexi Corridor. Most of the Hexi Corridor is covered by Reaumuria soongorica desert rangelands, within which semishrubs like Nitraria tangutorum, Zygophyllum xanthoxylon, and Artemisia ordosica occur; these plants contribute to sand fixation and are thus often found near or upon sand dunes. Dwarf trees such as tamarisk and saxual are also often found in these rangelands, as well as near water accumulation areas such as floodplains and groundwater sources.
Grasses, in particular bunchgrasses, are found in ecosystems with greater water availability in the Hexi Corridor, such as steppes. Species such as Achnatherum splendens occur in the meadows surrounding the major river basins at the foothills of the Qilian Mountains. Further up the mountains, steppes dominated by Stipa gobica and Stipa breviflora occur at , and above sea level, respectively; the latter also appears irregularly in the southeast of the lower corridor. Cleistogenes songorica occurs alongside all of the above, often in association with the shrub Caragana tibetica.
Alpine steppes and other montane ecosystems appear in the Hexi Corridor at elevations past around , with vegetation patterns closely resembling those of the rest of the Tibetan Plateau. Stipa purpurea is dominant in this region, occurring alongside shrubs such as shrubby cinquefoil and various rhododendron species (e.g Rhododendron oreodoxa, Rhododendron capitatum) to form open meadows in the mountain's gullies and slopes. Other shrubs that occur in these meadows, such as Caragana jubata and alpine willow (Salix oreophila), also form mosaics with patches of Qinghai spruce and Qilian juniper forest.
History Prehistory The Hexi Corridor has been the site of cultural exchanges across Eurasia since prehistory. It was first settled around 4800BP in Neolithic times by millet farmers from the Yangshao Culture in the western Loess Plateau, who enabled the spread of millet to Central Asia and the rest of Eurasia and Africa. These farmers also used pottery production techniques from Northern China. Several cultures developed in the Hexi corridor during this time, such as the Majiayao, Banshan, and Machang.