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Abstract. The Tarim River basin, located in Xinjiang, NW China, is the largest endorheic river basin in China and one of the largest in all of Central Asia. Due to the extremely arid climate, with an annual precipitation of less than 100 mm, the water supply along the Aksu and Tarim rivers solely depends on river water. This is linked to anthropogenic activities (e.g., agriculture) and natural and semi-natural ecosystems as both compete for water. The ongoing increase in water consumption by agriculture and other human activities in this region has been enhancing the competition for water between human needs and nature. Against this background, 11 German and 6 Chinese universities and research institutes have formed the consortium SuMaRiO (Sustainable Management of River Oases along the Tarim River; http://www.sumario.de), which aims to create a holistic picture of the availability of water resources in the Tarim River basin and the impacts on anthropogenic activities and natural ecosystems caused by the water distribution within the Tarim River basin. On the basis of the results from field studies and modeling approaches as well as from suggestions by the relevant regional stakeholders, a decision support tool (DST) will be implemented that will then assist stakeholders in balancing the competition for water, Published by Copernicus Publications on behalf of the European Geosciences Union. 84 C. Rumbaur et al.: Sustainable management of river oases along the Tarim River acknowledging the major external effects of water allocation to agriculture and to natural ecosystems. This consortium was formed in 2011 and is funded by the German Federal Ministry of Education and Research. As the data collection phase was finished this year, the paper presented here brings together the results from the fields from the disciplines of climate modeling, cryology, hydrology, agricultural sciences, ecology, geoinformatics, and social sciences in order to present a comprehensive picture of the effects of different water availability schemes on anthropogenic activities and natural ecosystems along the Tarim River. The second objective is to present the project structure of the whole consortium, the current status of work (i.e., major new results and findings), explain the foundation of the decision support tool as a key product of this project, and conclude with application recommendations for the region. The discharge of the Aksu River, which is the major tributary of the Tarim, has been increasing over the past 6 decades. From 1989 to 2011, agricultural area more than doubled: cotton became the major crop and there was a shift from small-scale to large-scale intensive farming. The ongoing increase in irrigated agricultural land leads to the increased threat of salinization and soil degradation caused by increased evapotranspiration. Aside from agricultural land, the major natural and semi-natural ecosystems are riparian (Tugai) forests, shrub vegetation, reed beds, and other grassland, as well as urban and peri-urban vegetation. ...

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Over one hundred artifacts, including shards, chopped wood, bronze and iron ware debris as well as footprints, have been discovered during archaeological investigations at and around the central Taklamakan Desert Yuansha Site (38°52′N, 81°35′E). Dating ( 14 C and OSL) and landform study show that the present-day dry Keriya River once sustained an oasis human settlement in 2.6 ka BP, historically falling into the Spring and Autumn Period (716-475 BCE) of Chinese history. The chronology and archaeological interpretations also show that some 400 years later, the local Keriya River channel had shifted 40 km southeast to sustain a Western Han (206 BCE-25 CE) Wumi settlement at the Karadun site. In the meantime, river-channel migration had allowed reoccupation of a site west of Yuansha City around 1.9 ka BP (abandoned again by 1.6 ka BP). The remains' chronology shows that this site was affiliated to Wumi culture and Eastern Han (24-220 CE) dynasty rule. Palaeoclimatic records indicate that the migrations of the river and oasis settlers between 2.7 and 1.6 ka BP were coeval with Central Asian climate changes. Yuansha City was built just after the end of 2.8 ka BP glacier advances in western China, suggesting that release of more water during the subsequent glacier recession may have facilitated oasis development such that Iron Age European peoples could settle in the Tarim Basin. As shown from analysis of archeological remains, not only at Yuansha but also in other ancient cities in the Tarim such as Loulan and Jingjue (Niya), conditions around 1.6 ka BP were dry enough to cause oasis decline. Thus, the results reported here enhance our knowledge about environmental changes and their effects on human activities and cultural evolution in western China and will stimulate further interdisciplinary studies of landscape and oasis history in the Tarim Basin. Taklamakan, Keriya, river, Yuansha, settlement migrate, 2.8 ka BP, 14 C, OSL Citation: Zhang F, Wang T, Yimit H, et al. Hydrological changes and settlement migrations in the Keriya River delta in central Tarim Basin ca. 2.7-1.6 ka BP:

Satellite data and the published coefficients about the world's and China's ecosystem were used to analyze the effects of land-use changes on the ecosystem service in the Yanqi Basin. Both economic developments and arid, fragile ecosystems have strongly affected the land use. A sensitivity analysis determined the effect of manipulating the coefficients on the estimated values. Results indicated that (1) the total value of ecosystem services in the Yanqi Basin were 9,374.66, 10,450.52, 9,964.20, and 9,8707.77 million Yuan in 1990, 2000, 2005, and 2011, respectively. The net increase in ecosystem service values were about 496.11 million Yuan within 1990-2011; (2) The aggregated ecosystem service values of water body, wetlands, grasslands, and croplands were about 99.25 % of the total value; (3) Waste treatment and soil formation were the top two ecological functions with high service values and contributing about 61.70 % of the total service values; and (4) Ecosystem service values estimated in this study were inelastic with respect to the value coefficients; therefore, the estimation was robust in spite of uncertainties on the value coefficients. A reasonable land-use plan should be based on rigorous environmental impact analyses for maintaining stability and sustainable development of the Yanqi Basin.

In order to evaluate the soil salinization risk of the oases in arid land of northwest China, we chose a typical oasis-the Yanqi basin as the research area. Then, we collected soil samples from the area and made comprehensive assessment for soil salinization risk in this area. The result showed that: (1) In all soil samples, high variation was found for the amount of Ca2+ and K+, while the other soil salt properties had moderate levels of variation. (2) The land use types and the soil parent material had a significant influence on the amount of salt ions within the soil. (3) Principle component (PC) analysis determined that all the salt ion values, potential of hydrogen (pHs) and ECs fell into four PCs. Among them, PC1 (C1-, Na+, SO4 2-, EC, and pH) and PC2 (Ca2+, K+, Mg2+and total amount of salts) are considered to be mainly influenced by artificial sources, while PC3 and PC4 (CO3 - and HCO3 2-) are mainly influenced by natural sources. (4) From a geo-statistical point of view, it was ascertained that the pH and soil salt ions, such as Ca2+, Mg2+ and HCO3 -, had a strong spatial dependency. Meanwhile, Na+ and Cl- had only a weak spatial dependency in the soil. (5) Soil salinization indicators suggested that the entire area had a low risk of soil salinization, where the risk was mainly due to anthropogenic activities and climate variation. This study can be considered an early warning of soil salinization and alkalization in the Yanqi basin. It can also provide a reference for environmental protection policies and rational utilization of land resources in the arid region of Xinjiang, northwest China, as well as for other oases of arid regions in the world.

Groundwater levels and salinity are significant contributors to soil salinisation in irrigated areas. In this study, spatial and temporal variations of groundwater levels and salinity in the Ili River Irrigation Area in the western arid zone of China were analysed using a geostatistical approach. Results showed that: (1) groundwater salinity varied widely, with a maximum of 30.70 g/L and minimum of 0.20 g/L, while maximum groundwater level was 31.10 m and minimum was 0.54 m. The abundance of major ions in groundwater was in the order:Groundwater salinity had a good positive correlation with EC, Cl − , Na + , HCO 3 − and Mg 2+ (correlation coefficient >0.90); (2) a Gaussian model was the most suitable semivariogram model to describe groundwater levels for four measurement periods, while a Spherical model was most suitable semivariogram model to describe groundwater salinity in March, September and November, and an Exponential model was most suitable variogram model for June. RA relatively strong spatial and temporal structure existed for groundwater levels and salinity due to very low nugget effects. The nugget-to-sill ratio indicated that groundwater levels and salinity in the study area have relatively strong spatial dependence. The groundwater levels and salinity showed an east-west, north-south U-shaped distribution in each measurement period; (3) maps of kriged groundwater levels and salinity showed that deeper groundwater was found in southern parts, with more shallow groundwater in northern parts of the study area. Higher groundwater salinity was found in central parts, with lower salinity in marginal parts of the study area. It is clear that substantial soil salinisation has taken place in central parts of the study area, and more attention should be paid to these areas to prevent future problems.

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