Hysteresis Effect of Runoff of the Heihe River on Vegetation Cover in the Ejina Oasis in Northwestern China

Abstract

The relationship between vegetation growth and groundwater in arid areas is one of the most actively researching topics in ecohydrology. On account of little precipitation, the oasis is the only form of sustenance for living and economic development, for the local people in the arid areas of Northwest China. During recent years, with the increase of water consumption in the middle stream area of the Heihe river basin, the incoming water has decreased gradually and the area of the Ejina oasis in the downstream area has decreased continuously. It has caused lake drying, land desertification, and eco-environmental degradation. The vegetation growth of the oasis has a close relationship with the water resources. Therefore, research on the quantitative relationship between the runoff and the vegetation growth has significance in improving the eco-environment, and balancing the contradiction of water consumption and reasonable allocation of the water resources in the Heihe river basin. Combined with remote sensing data and runoff of the Heihe river, the quantitative relationship between the vegetation growth of the Ejina oasis and the runoff of the Heihe river has been established from the regional scale in this study. The result indicates that the growth of oasis vegetation depends on the runoff of the Heihe river and the groundwater. The time lag of the impact of the runoff of the river on the vegetation cover of the Ejina oasis is one year, and the groundwater links the vegetation cover and the runoff by this hysteresis effect.