Hydrological changes and land degradation in the southern and eastern Tarim basin, Xinjiang, China

Abstract

Using the combined methods of digital image processing of remote sensing data, a Geographical Information System (GIS) and analysis of historical books and maps, this paper aims to contribute to a better understanding of the processes and mechanisms of land-use and land-cover changes and hydrological variations during the last 2000 years in a hyper-arid environment. The southern and eastern Taklamakan Desert, one of the driest and ecologically most sensitive regions in China and characterized by a long history of human settlements, was chosen as the study area. A hydrological connection between the Keriya and Niya rivers in former times was recognized for the first time using satellite imagery. After transferring the notes and maps of historical times into a simplified modern map, it shows that the Lop Nuer decreased in size from a large lake in the Han Dynasty (206 BC to AD 220) to a much smaller one in the Qing Dynasty (AD 1644(AD -1911. Areas settled in former times differ morphologically from the dune landscape in satellite imagery because of flat relief along dried river courses. A review of archaeological literature reinforces the fact that in the lower reaches of the Keriya and Niya rivers, in the interior of the Taklamakan Desert, irrigated agriculture was widely practised from ca. 200 BC to ca. AD 500. A possible climatic change toward drier conditions at ca. AD 500 is suggested as the cause of the abandonment of the cities in the desert and for the initial drying of the formerly large Lop Nuer Lake. flat, and would be suitable for agricultural production if there was water. Therefore, the satellite images can help archaeologists select sites of interests. Conversely, the archeological discoveries reconfirm that these areas were used for agriculture in the past. The Sino-French Expedition Team (1997) systematically excavated the ruined settlement Yuansha (Figures 4 and 5A) and found that Yuansha was constructed in the form of an old Chinese city. This archeological team unearthed an urbanized city marked by a 3-4 m high, ca. 1 km long and quasi-round wall. The team also found grains, irrigation channels and bones of household animals. It was concluded that both crop cultivation and animal grazing were significant in the lower reaches of the Keriya River ca. 2000 years ago. The Figure 7. River nets and lakes in southern and eastern Tarim Basin during the Han Dynasty (A) and the Qing Dynasty (B) according to historical books and maps. The geographical names are from former times and can be quite different from present ones.

Socio-hydrologic perspectives of the co-evolution of humans and water in the Tarim River basin, Western China: the Taiji–Tire model

“…One can note that this timeline is coincident with the cooldry tendency of climate shown in Fig. 5 (Wang, 1998;Yang et al, 2006).…”

Hydrological and Climatic Changes in Deserts of China since the Late Pleistocene

“…The human impact on the landscape of the desert margins of northwest China during the last 2000 yr is clearly visible in the remains of ruined cities and abandoned settlements (e.g., Huang, 1958;Huang, 2003;Yang et al, 2006a). Nomadic activity, i.e., Qijia Culture (ca.…”

“…Formation of river terraces and change in the length of the Keriya River, coupled with historical records detailing the distribution of the water bodies (Yang et al, 2006a), suggest that wetlands (rivers and lakes) were much more extensive at ca. 2 ka and during the Little Ice Age in the Taklamakan Desert.…”

Monitoring vegetation dynamics with SPOT-VEGETATION NDVI time-series data in Tarim Basin, Xinjiang, China

“…The Taklimakan Desert is the world's second largest active sand desert. It covers an area of 338,000 km 2 , and as much as 85 percent of it consists of active sand dunes [6,7] . Many researchers believe that the Taklamakan Desert was originally formed in the centre of the Tarim Basin as early as the Tertiary Period and then the desert expanded outwards [8] .…”