The Composite Relationships Among Groundwater, NDVI And Evapotranspiration In The Hailiutu River Catchment, China

The interaction between vegetation growth and groundwater in arid areas is one of the most critical topics in eco-hydrology. In the northwest arid and semi-arid areas of China, research into the ecological effects of vegetation growth, evapotranspiration and groundwater on ecological environmental protection has great significance in science. Based on the groundwater observation data and remote sensing methodology, this paper studied the statistical relationship among vegetation index, evapotranspiration and groundwater level of Hailiutu River Basin in the Ordos Plateau.By the Kriging interpolation technology, the spatial distribution of groundwater level in the study area was studied. Then according to the MODIS and MOD16 remote sensing data and data preprocessing by MRT, the NDVI and ET data were obtained by the batch processing of ARCGIS. This paper analyzed the spatial distribution characteristics of these eco-hydrological factors in Hailiutu River Basin.The statistical analyzing results of annual average NDVI and ETa in growing seasons and in August which were obtained by by Gamma joint distribution function shows that the distribution of NDVI and ETa are skewed, and with tailing phenomena. As well as the overall distribution characteristic can be fitted by Gamma model. By further analysis of NDVI and ETa along with the change of groundwater level, the relationship between NDVI, ETa and groundwater was studied. The results indicate that the NDVI decrease with the increase of groundwater level depth when groundwater level depth is less than 10m; when the groundwater level depth is deeper than 10 m, the value of NDVI fluctuates around a constant value and have no relationship with groundwater level.With 10 m chosen as the boundary groundwater level depth, the NDVI and ETa statistical characteristics in larger groundwater level depth region and shallow depth region were analyzed. The results show that both of them fit Gamma distribution, except that the statistical parameters are different. Then the correlational analysis between NDVI and ETa of different grid points were conducted, the results clarify that there is a linear correlation between NDVI and ETa.The paper’s research methods and results may provide references for understanding the eco-hydrogeological characteristics of Hailiutu River Basin.