RS-Based Evaluation of Water Re-Allocation and Eco-Environment Evolution in an Arid Natural Oasis

The Ejina natural oasis, located on the downstream delta area of the inland Heihe river basin, is surrounded by gobi and desert and featured by poplar forest. It has been under serious threat of water shortage and eco-environmental deterioration starting from the late 1950's, especially from 1980's, due to over agricultural water diversion at the middle reach. Water into the oasis became less and less since then. A whole basin trans-provincial water allocation program, as the first step, has been implemented since 2000 to hold back the rapid withering trend of the oasis as quick as possible. A three year emergent water saving and environment protection project, as the second step, was also carried out during 2001 to 2003. This has directly resulted in a step by step increase of water volume into the oasis during the last five years. In this paper, two questions regarding the evolution of the oasis eco-environment during the past two decades will be answered using multi-temporal satellite images. The first question is how fast the oasis had withered from the middle 1980's. The second question is to what extent the oasis has recovered from 2000 to present. Based on the results from remote sensing analysis, the relation between water reallocation and eco-environment evolution will be assessed.