Evolution law of the phreatic aquifer water table in the water intake area of South-to-North Water Diversion Central Line in Henan Province

The water supply of the South-to-North Water Diversion has presented a significant impact on the phreatic aquifer water table and the water consumption structure in the intake area of Henan Province. This paper firstly reviews the previous changes of groundwater level burial depth in the plain area of Henan Province, and by collecting and counting the monitoring results of shallow groundwater level in the receiving area of Henan Province from 2008 to 2018, we quantified and partitioned the changes of shallow groundwater level in the receiving area of Henan Province before and after the water supply of the South-to-North Water Transfer Central Line based on ArcGIS software. Then we analyzed the changes of water use structure in the receiving area of Henan Province before and after water supply by combining the information of rainfall, underground water resources and water supply. The results show that from the 1960s to 2008, the average buried depth of shallow groundwater in plain area of Henan Province has gradually increased; the groundwater resources increased linearly with the increase of precipitation. The average groundwater output from 2015-2018 is reduced by 9.55% compared with that of 2008-2014 due to South-to-North Water Diversion Project on Henan section. The phreatic aquifer water table presents recovery, with the area of phreatic line depth of > 8-12m changing into > 4-8 m and ≤4 m. The area of phreatic line depth of > 2-20 m remains at stable, and the area of phreatic line depth larger than 20 m reduces gradually. The phreatic aquifer water tables in the monitoring points area showed a downward trend before the water supply, which presented a gradually recovery after the water supply in more than 2/3 of the counties. The proportion of water used for agriculture, forestry and fishery and industrial use decreased after the water supply, while the proportion of water used for urban and rural living and environmental integration increased significantly. The research results indicate that the South-to-North Water Diversion Project has a positive and effective impact on the restoration of shallow groundwater level in the receiving area of Henan Province and the alleviation of water supply contradiction problems.