Author(s): Shiguo Xu; Ya Sun; Suduan Hu; Tianxiang Wang
Linked Author(s): Ya Sun, Suduan Hu, Shiguo Xu
Keywords: No Keywords
Abstract: The evolution of groundwater system under the dual influence of climate change and human activities is one of the most challenging and cutting-edge fields in current water resources research. This study takes the middle and lower reaches of the Wanghe River in Laizhou, China as an example to analyze the effects of precipitation change and human activities on groundwater level and seawater intrusion, and the response of surface vegetation. Landsat images from 1987 to 2017 were selected to obtain land-use pattern and vegetation classification with reference to surface spectral experiments and local statistical data. The result showed that since 1987, precipitation in the study area has been lower than the historical average, and agricultural, domestic and industrial uses relied largely on groundwater. The over-exploitation of groundwater caused a continuous decline in groundwater levels, which triggered serious seawater intrusion. The invasion range increased with years and reached maximum in 1997. There was a reverse evolution of vegetation in the infested area. The coverage drought- and saline -tolerant plant such as pine trees dramatically increased, while broad -leaved trees represented by poplars decreased sharply. Soil salinity resulted in drop in crop yield, and desertification consumed significant areas of arable land. The offshore aquaculture led to wetland shrinking and reed dying out. In 2001, Wanghe groundwater reservoir was built to conserve groundwater and prevent seawater intrusion. The reservoir raised groundwater level and inhibited seawater intrusion in the reservoir area by adding inf iltration recharge and cutting off downstream groundwater seepage, leading to waste farmland and broad -leaved forests coverage broad-leaved forest restoration in the reservoir area. However, groundwater reservoir level showed a downward tendency after 2010 due to constant groundwater consumption of and poor rains. Since 1998, land -based mariculture downstream the groundwater reservoir consumed a large amount of fresh groundwater and subsea brackish water. The groundwater level declined significantly due to the deprivation of the benefit of groundwater seepage which it received under natural flow regime, reduced rainfall and water consumption. However, pumping brackish water reduced the saltwater head, and unintentionally alleviated seawater intrusion temporarily. Soil salinity continues to deteriorate from lack of rainfall and there was a dramatic pine forest coverage decline.
Year: 2018