Landscape change under the surface water allocation in Ejina oasis, northwestern China

Exploring the relationships, which are strictly influenced by water resource conditions, between oasis landscape pattern and hydro-ecological process in arid area, becomes the hot topic and difficult challenge in arid landscape ecology and one of the most important issues in arid areas ecological protection and reconstruction. The Heihe river basin, as the (2)nd longest inland river basin, is located in the northwest arid regions of China. During the past few decades before 2001, increasing local population and social-economic development in the upper reaches of Heihe river basin have consumed surface water resource enormously. Consequently, a lot of serious ecological and environmental problems were occurred in the Ejina natural oasis, which is in lower reaches of Heihe river basin. Especially, the Ejina natural oasis was in face of disappearing in the world with no surface water provided from the upper reaches for continuous several years around 2001. From the beginning of 2001, appropriate amount of surface water has been allotted to Ejina oasis from the upper reaches by the Chinese government every year to prevent the rigorously ecological crisis continuing and retrieve the environment restoring. Based on field investigation, remote sensing, and GIS technologies, Ejina natural oasis landscape spatial pattern and its dynamic change in different temporal and spatial scale before and after surface water allotted (1987 similar to 2001 similar to 2009) were analyzed in this paper. Three Landsat TM/ETM+ images in 1987, 2001 and 2009 were collected to analysis the characteristics of oasis landscape spatial pattern dynamics over the past few decades. The main results show that: before and after water resource allocated, the area of oasis classes decreased during 1987-2001 and increased during 2001-2009, but simultaneously the desert classes changed to an inverse direction; the landscape diversity and ecological stability for Ejina oasis after water allocated was much higher than before water allocated.