Characteristics of land cover change in the Kyoen Delta of the Ejina River basin in Inner Mongolia, China

The environment is deteriorating on a long-term basis in the Ejina River Basin in Inner Mongolia, China as a result of a water shortage. The shortage was caused by increased water use by industries and agriculture after 1992 along the upper part of the Ejina River. In 2002, the Chinese National Water Resource Agency instituted a water sharing plan which resulted in more water being released downstream to a region including the Kyoen Delta. The repartition will have an effect on vegetation increase in the Kyoen Delta area. The goal of the present study was to determine the land cover and vegetation changes between 1977 and 2010 to understand the cause of the land cover and vegetation change. To do this, we visually interpreted four Landsat images by making field surveys in the Kyoen Delta. One image (a Thematic Mapper image (TM2010) acquired on June 11, 2010) was interpreted visually with high resolution images of Google Earth. Three other temporal Landsat images, which were a Multispectral Spectral Scanner, a Thematic Mapper, and an Enhanced Thematic Mapper Plus images obtained on June 11, 1977, June 23, 1991 and June 14, 2000, respectively, were interpreted based on the TM2010 interpretation, and then land cover changes were analyzed over the Kyoen Delta. We found the following changes between 1977 and 2010: Open forest increased remarkably by 64% and Koryu tamarisk forest increased by 32%, resulting in an increase of green land. The areas of sandy soil, desert and bare land decreased by 21.4%, 16.9% and 28.9%, respectively, and changed to Open forest, Koryu tamarisk forest and Other forest. Logging records from the 1940's to the 1970's showed that trees had been cut largely for building material for the military and fuel for residents until the late 1970s, after which fuelwood was largely replaced with coal. After logging stopped, the land changed to Open forest, Koryu tamarisk forest and Other forest. On the other hand, the water table level has been dropping since 1990 and the vegetation area decreased between 1977 and 2010 in the lower Kyoen Delta. Falling water table level appears to be the cause of the decrease of vegetation.