ABSTRACT
North China suffers serious water shortage due to bilateral influence of semi-arid climate and dramatically increasing water demand along with economic growth. Groundwater overexploitation with deeper wells is a typically adopted measure to relieve the water issue in this area, while such activities cause various eco-environmental problems. To utterly solve the chronic and deteriorating crisis, the South-to-North Water Transfer Project (SNWTP) was put forward as a strategic approach. The planning of this project has been studied since five decades ago; the Middle Route and East Route are initiated at 2002. It is a significant issue that what will happen after uncertain change of water use and the impact of large scale inter-basin diversion to this area. However, the trend of groundwater table change in future is influenced by multiple factors, mainly the natural precipitation, water pumping and artificial recharge. These main factors cannot be only forecast by groundwater model. Therefore, analysis of uncertainty on the water demand, water allocation under dramatically changing economic growth, strategic design and regulations are the key point for forecast for the North China region.
To probe the possible approach to solve this problem, a methodology of model coupling to combine water allocation model and numerical groundwater model is put forward based on summary of current achievements of studies related to of surface-groundwater combination model. The coupling model is applied in North China Plain to forecast the evolution of groundwater under different scenarios of water utilization and other changing boundary conditions. Method of data processing from output of water allocation model to groundwater model is analyzed and designed based on data distribution on both spatial and time scale to solve the critical point of down scaling for model coupling. To simulate the continuously changing process of balance of groundwater situation, interpolation is applied to transfer the results of water allocation on level year to time series for groundwater model. The simulation of groundwater evolution is initiated from the current status with the interpolated time series represented future water pumping and recharge. Firstly, the water cycle in Haihe River Basin (mainly including North China Plain area) and water use is simulated by water allocation model with different water allocation scheme. Secondly, the groundwater pumping from water allocation model is taken as input of groundwater simulation model to calculate the groundwater table. The results of simulation in the plain areas of Haihe River Basin shows the deficit of groundwater will approach to 5 billion m3 without South-to-North Water Transfer Project (SNWTP) compared with only 1.4 billion m3 deficit if the Phase I of SNWTP is commenced in 2015. Meanwhile, the decline of groundwater table will be averagely 5-25 m less if the SNWTP take effect although the water table continues declining. The trend of deteriorating groundwater environment will be totally relieved with the SNWTP, but more strategies and strict measures are still necessary to reach water balance of groundwater and healthy evolution. Application in Haihe River Basin verifies the feasibility of the coupling method.
