Studies On Multiple-constrained Optimal Pumping Project Of Groundwater In Liu Gu River Section

With the development of economy, the water demand of the industry has increased year by year, the volume of water supply can not meet demand, water supply and demand contradictions have become increasingly prominent. Liu gu river section locates at south-west of Huludao City, under the jurisdiction of Huludao City, with an area of 378.78 km2, the industrial and agricultural water of this area are mostly from alluvial aquifer, development and utilization level of groundwater level has been very high, therefore, whether the pumping layout and project optimal or not has great influence to the economic and social development of Suizhong and Huludao City.The topography of Liu gu river section is higher in the north and lower in the south and terrain is flat open, tilts to the sea slightly, elevation generally is less than 20 m .There is abundant groundwater in the Quaternary layer, which is revealed along the river valley and piedmont. The general characteristics of the aquifer are thin, buried shallow, adequate and easy exploiting. Because bedrock is widely distributed around the study area and groundwater isn't abundant and little significance, Therefore, the alluvial and coastal plain are chosen as the simulation area. The main mining aquifer of study area consists of three parts: the first is the upper Holocene Sediments aquifer, with a thickness of around 20 m; the second is upper pleistocene aquifer, which thickness is 14 to 22 m; the third is middle Pleistocene aquifer, which thickness is 3 to 8 m; these three above aquifers compose unconfined aquifer which is the purpose aquifer of this study. Based on the Liu gu river section's datum including weather, surface runoff, geology, hydrogeology and groundwater exploitation, the thesis analyses the configurable characters of purpose aquifers and the recharge, runoff, discharge and dynamic characters of groundwater. On the foundation, the hydrogeological model has been established, and the study area is generalized as heterogeneous isotropic two-dimensional unsteady flow of phreatic water, then the math equation has been established, which is solved using Visual MODFLOW software. In the following, the established model needs to be identified and validated by the water lever datum The results indicate: the established model fits to the precision demand, and is comparatively right, so it can be used to forecast the coming water level.With the actual situation of the study area, optimal mining project of a variety of constraint conditions (including water level constraints, water volume constraints, the water quality constraints, environmental and ecological constraints, etc.) conduct in-depth analysis, and specified the content an functions of all constraints, On this basis, this papers designs different groundwater mining layout, and simulate groundwater flow and water level changes by the groundwater numerical model at the conditions of different layout of the same exploitation of the total extraction, then determine the west bank of Liu gu river and Da Shibao-Tashan layout as two optimal water exploiting distribution, and by comparing groundwater flow field of two layouts for decades mining, the results show that have to building underground dams to prevent seawater intrusion.On the basis of the determined optimal exploitation layout, the thesis designs different exploiting distribution projects and mining time according to different precipitation guarantee rate. Then Simulated the project of the mining operations under the certain exploitation and meeting all the constraints conditions, analysis the simulation results and determined the groundwater optimization project of Liu gu River section based on the multiple-restrictive conditions. In term of current pumping project, according to water resource requirement of social economy, the groundwater resources is evaluated in the following 10 years. The results show that the study area is in the state of negative balance on the whole, from the view of the total volume of groundwater resources, groundwater recharge guarantee rate was 100.6% in normal years, groundwater resources apart from meeting excretion, there is still residual, and the remaining amount of 243.13×104m3 / a, compensation can be used in the dry storage of -235.08×104m3 / a, groundwater resources to be dynamic equilibrium after regulating in the Feng ku period. From the view of groundwater flow field map: from November to April next year in wet andpeace years, the ground water level larger declined around the DaShibao - Tashan, local areas even landed cone of Groundwater Depression, whose centre the water level was 2.06 m, which is meeting designed constraints, in the wet period, even if to intensify the exploitation of the west bank of Liu gu River, the biggest drawdown is 6.62 m, which accounts for 16% of the aquifer thickness, also meets the water constraints; In the 75 per cent of the guaranteed rate, at the end of the dry season, the water level of cone depression is -1.04 m, account the aquifer thickness of 23%, aquifer partially compensated in the wet period, the water level in the Centre of cone depression is 1.68 m, on the whole, bound to meet water level-constraints requirements.Based on the optimization of mining layout we proposed the three design options, ensures that the normal operation of groundwater source in the circumstance of different constraint conditions and different guarantee rate in the different years, but also meets the region's future water resources planning needs, to provide reference for the study in the future under similar conditions.