Optimal Allocation Of Water Resources System In The Bayan Ebo Mining Area Based On Ecological Water Demand Prediction

Bayan Obo mining area is a typical rare earth mining area in the north,and the ecological environment problems caused by mining are more prominent,while drought and water shortage seriously restrict the ecological restoration process of the mining area.Therefore,it is vital to study the ecological water demand and water allocation in mining areas in the context of the imbalance between water supply and demand.In this thesis,firstly,we conducted a full survey on the natural profile and socio-economic situation of the mining area,collected the background information on vegetation,land use and water resources,and analysed the current situation of water resources.Then,we considered the problem of classifying the ecological water demand types of the mine area in the absence of background information,and classified the ecological water demand of the mining area into two types:natural and artificial ecological water demand with the actual situation.Next,we calculated and forecast the ecological water demand for each type of water in the mining area for the current and planned years,and conducted a water supply and demand balance analysis in the planned year.Finally,on the basis of this,a water resources system optimisation model based on ecological water demand guarantee was established and multiple sets of water resources optimisation schemes were obtained.And by establishing the Analytic Hierarchical Process model to comprehensively evaluate each option,the optimal water allocation option for the Bayan Ebo mining area was selected,which will be dedicated to the development and utilisation of water resources,ecological protection and sustainable development in the region.The following conclusions were mainly obtained:(1)Water resources were extremely scarce in the Bayan Ebo mining area,and there was no obvious flowing water system in the mine area,and groundwater was recharged by precipitation.The average annual precipitation in the mine area from 1990 to 2020 was about250 mm,which was only 1/10 of the evaporation.The source of water in the mine area was external water transfer,including the water transfer from the"Diversion of Yellow River into the Bayan Obo mining area"project and the underground water supply of Damao Banner,which was used for the domestic and industrial water use.There was no record of water consumption for the ecological environment.(2)The total ecological water consumption in the basic year(2019)of Bayan Obo mining area was calculated to be 1.58×10~8 m~3,with natural ecological water consumption of 1.54×10~8 m~3 and artificial ecological water consumption of 3.84×10~6 m~3.The qualitative,quantitative and quantified methods were used to predict the ecological water demand in the planning years(2025,2030 and 2035)of the mine area.The total ecological water demand in the planning years of the mine area was 1.49×10~8 m~3,1.42×10~8 m~3 and1.36×10~8 m~3 respectively,showing a decrease compared to the base year,with a decrease of5.66%,10.04%and 13.99%respectively.The changes in the area of natural grassland and artificial green space were the main causes of the changes in ecological water demand.(3)Based on the prediction of social and economic water demand in the Bayan Ebo mining area,a water resources supply and demand balance analysis was carried out.And according to the actual water supply and demand in the mine area,the ecological water demand allocated was defined as artificial ecological water demand.Then we established a water resource optimisation model based on ecological water demand guarantee,with the objectives of social,economic,environmental and comprehensive benefits respectively.The results of five water resources optimisation allocation options were obtained for each of the mine area in the planning year.Finally,the option 3 was determined to be the optimal option by comprehensive evaluation through the Analytic Hierarchical Process model.In Option 3,the domestic water demand was supplied by groundwater,which could meet the domestic water demand;the production water demand and ecological water demand were both supplied by groundwater,engineering water and water triangulation,which could meet the ecological water demand of the city,but the water shortage rate of production water demand was 48.3%,which needed to be reduced by taking corresponding measures.