Presenter
Prof. Litang Hu, Beijing Normal University
Co-author(s)
Miss. Lin Gan, Beijing Normal University
Prof. Litang Hu, Beijing Normal University
Miss. Shiqi Huang, Beijing Normal University
Mr. Jianchong Sun, Beijing Normal University
Dr. Binghua Li, Beijing Water Science and Technology Institute, Beijing Engineering Technique Research Center for Exploration and Utilization of Non-Conventional Water Resources and Water Use Efficiency
Dr. Xia Wu, Beijing Water Science and Technology Institute, Beijing Engineering Technique Research Center for Exploration and Utilization of Non-Conventional Water Resources and Water Use Efficiency
Dr. Menglin Zhang, Beijing Water Science and Technology Institute, Beijing Engineering Technique Research Center for Exploration and Utilization of Non-Conventional Water Resources and Water Use Efficiency
Sub-theme
4. Supporting Aquatic Ecosystem Health and Functions
Topic
4-7. Groundwater and ecosystem
Body
Accurate groundwater level estimation is of great significance to effective groundwater management all over the world. Numerical simulation is widely used in groundwater level prediction and proper evaluation of management options, however, the uncertainty of hydrological structure and hydrogeology parameters on the accuracy of the model remains a puzzle. Taking the Beijing Plain of Northern China as an example, where ecological water replenishment (EWR) is an important project in recent years, the study constructed a groundwater flow model at daily time scales with refined mesh and consideration of an open channel flow to reproduce the response of groundwater level on precipitation conditions and human activities such as groundwater exploitation reduction and EWR. The study also established a series of stochastic 3D geological models using over one thousand boreholes and applied them to the numerical model. The ensemble average of multiple numerical models considering different hydrogeological structures was used to quantify the uncertainties. During the model calibration, the average groundwater level in Shijingshan, Mentougou and Miyun District varied from 75.0 to 84.5 m, 64.8 to 71.2 m and 35.9 to 41.8 m, respectively, with significant variance of 60 groups of parameter scenarios, suggesting the influence of hydrogeology parameters on the simulation results at the upper part of alluvial fans. While the mean groundwater level in the lower part of alluvial fans, such as Daxing and Tongzhou District, ranged from 11.4 to 14.2 m and 7.8 to 9.2 m, respectively, with the small variance, showing that hydrogeological parameters have little influence on the simulation results. The results also showed that the hydraulic conductivities of gravel played a dominant role in the simulation results, accounting for more than 30%, followed by that of clay layer and silt layer. The prediction of one-year EWR under multiple scenarios and models showed that the increased groundwater level generally varied from 0.20 to 8.47 m, and the groundwater level in the plain area was mainly controlled by rainfall, while the surrounding area of Yongding River was affected by both precipitation and EWR. During the EWR activities, the groundwater level around Yongding River with large runoff got rise significantly in a short time, and the effect was gradually weakened with the increase of the distance from the river and its downstream. The understanding of the influences of hydrogeology structure uncertainty and daily dynamics of groundwater level under multiple scenarios is beneficial to adopting possible preventive and emergency measures.