| Changli County is located in the northern part of Hebei Province on the Bohai rim region. It's a agriculture county of Qinhuangdao City, Hebei Province base with shallow groundwater as the main supply. In recent years, the groundwater level continuously dropped caused by excessive explotation of shallow groundwater and the groundwater quality worsened gradually caused by industrial and agriculturai pollution, and with economic development and population growth, Changli County's water demand is increasing year by year, making the contradiction between water supply and need becomes extremely serious. Groundwater has become an important limiting factor of county's economic and social development. Therefore, assessment of the quality and quantity of groundwater and protection method research in Changli County has great practical significance to guide the groundwater exploitation and protection.Based on the meteorological, hydrological, geological and hydrogeological data collected in study area, make clear of the distribution of groundwater aquifer, hydraulic, dynamic and cycling characteristics. The grounawater flow numerical simulation model is founded via Visual MODFLOW software, and combined water consumption forecast to analyze the supply and demand balance of water resources. Based on analyzing groundwater samples results, grounawater quality has been evaluated by single-norm evaluation method and fuzzy comprehensive evaluation method. And using a modified DRASTIC model for the study area to evaluate the vulnerability of aquifer Futhermore, based on the result of groundwater resources assessment and vulnerability assessment, groundwater pollution prevention zones are divided, and the corresponding protection scheme is proposed. The mainly conclusions are derived:(1) On the basis of numeric groundwater-flow modeling in the study area, the groundwater balance is analyzed. The exploitable quantity of groundwater is 16064.53×104m3·a-1 under the 95% guarantee rate condition, and the county water supply will be short of 11497.37×104m3·a-1 and 15899.57×104m3·a-1 respectly in 2015 and 2020 by water demand forecasting. Therefore, with the development of social economy, the groundwater exploitable quantity can't meet the total water requirement; new surface water should be built to increase water supply capacity.(2) The quality of shallow groundwater is generally poor, the qualities of points located in coastal towns are good, and the points located in urban area and farmland area are poor.(3) The vulnerability assessment results from the modified model show that the groundwater system of Changli County is high vulnerability as a whole, 40.9% of the area is extremely high vulnerability and 32.4% is high vulnerability. The high risk areas are distributed in the urban area and farmland area in the moddle part of Changli plain, where should be taken as key protection.(4) Five groundwater pollution prevention zones are divided in Changli County. The first is groundwater source protection zone. And the polygon region of the first-grade protection zone of groundwater source is 1.9 km2 that extends outward 360 m with the boundary of circumscribing polygon for peripheral well, the polygon region of second protection zone of groundwater source is 19.5 km2 that extends outward 2070 m with the boundary of circumscribing polygon for peripheral well. The second is governance and restoration zone mainly distributed in the county town and agricultural land. The third is key protection zone mainly distributed in agricultural land around the governance and restoration zone. The forth is general protection zone mainly located in the coastal area. The last is nature preservation zone located in the northern mountain. Finally, remedial measures are proposed for pollutant source in groundwater pollution protection zones. |
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