Dynamic Variation of Groundwater Level in the Middle-Lower Reaches of Shiyanghe River Basin for Nearly 40 Years

Located in the eastern part of the Hexi Corridor, the Shiyang river basin is the most economically developed region in the whole northwest region. However, the water shortage, contradiction and continuous deterioration of environment are also concentratedin this area. According to the time series observation data from 64 observation points during 1977-2015 in the middle and lower reaches of Shiyang River Basin in Hexi Corridor, the seasonal variation, dynamic changes, types and plane distributions over years of the groundwater level in study area have been elaborated. And then, the characteristics of tendency and sustainability of the groundwater level have been analyzed through using Kendall rank correlation coefficient and Hurst exponent.Finally, the reason of the decline of groundwater level has been explained by computed data. The results indicate that both the tendency and sustainability of groundwater level in the plains are different the ones in oasis areas and corresponding peripheral areas, with effectively verified annual and month averages. The groundwater level in oasis areas owes greater decrease amplitude and rate and duration than that in peripheral areas.