The impact of land cover and land use changes on the hydrological cycle of the Tarim Basin, NW China

Author / Creator

Yang, Yang, 1983 November 22- author

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Online

Physical

Summary

The Tarim Basin, located in NW China, is the largest inland basin in the world. Since the 1970s, the basin became modernized agriculturally through unprecedented reclamation, which were initiated a...

The Tarim Basin, located in NW China, is the largest inland basin in the world. Since the 1970s, the basin became modernized agriculturally through unprecedented reclamation, which were initiated and controlled by the central Chinese government to promote cotton production. In 2013, 40% of China's cotton production was harvested from agricultural lands in the Tarim Basin, representing 15% of world production. However, these large scale land use transformations lead to overuse of water resources in the upper and middle reaches for irrigation, with severe unintended ecological consequences in the lower reaches. The lower reaches of the Tarim River dried up gradually during the 1970s. In 2000, a water release project was launched to meet the ecological water demands of the river's lower reaches. So far there have been 15 water releases with 1.7 billion USD invested. This work aims to improve our understanding of the impacts on the hydrologic cycle from land-use/land-cover change activities in the Tarim Basin by working across different disciplines and integrating them to portray all the key processes involved. This multidisciplinary approach includes analysis of remotely sensed data, application of a dynamic crop modeling framework, and simulation analyses with a transient, 2D, variably-saturated groundwater model. My primary findings show that in 2006, over 25000 km2 were identified as irrigated field. This is a 41% increase from 1970s, when the total irrigated area was only 18250 km2. The rapid expansions in irrigate fields, together with climate change, have affected the partitioning of water between the land surface and the lower atmosphere through changing evapotranspiration patterns. Approximately 7 km3 of water entered the atmosphere through crop evapotranspiration in 1971, but by 2006 this value had increased to nearly 11 km3. But changes in climatic conditions accounted for only 20% of the total increase in ET. In terms of ecological restoration, the study shows that although the current water release protocols can maintain the present habitat for Populus euphratica, they are not sufficient to expand or restore this valued riparian vegetation to its former state. By addressing the hydrological and ecological implications of agricultural expansion, the overarching goal of this research is to identify sustainable strategies to reverse these negative environmental effects in the Tarim Basin.

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