The Research Of Delineating Water Source Protection Areas For Groundwater In Panshi City

Panshi locates in the hilly areas of south central Jilin Province, and the urban water supply currently relies on the groundwater. In recent years, because of the sustaining economic development, the increasing exploitation of groundwater, increasing pollution sources and ignoring the protection of the water sources, the groundwater quality makes a downward trend. Especially, without water purification factories, the water is directly supplied in Panshi City, so protecting water resources from pollution is particularly important to us. At the same time, since groundwater pollution characteristics (not easy to find, and difficult to resume), the water quality should mostly be protected, and the main method is to establish a groundwater source protection areas. Therefore, it is of great significance to the groundwater sustainable use of Panshi that we establish the groundwater protection areas.There are two methods of the delineation of Groundwater source protection areas. One is experience method and the other is numerical method. It is the key to select the time criterion of the protection area when using these two methods in the delineation of water source protection areas for the groundwater. In recent years, with the evolution of pathogenic bacteria, a unitized time standard was not given. According to the purposes, principles of the delineation of groundwater protection areas, with the state of domestic and international research and quoting "Technical Guideline for Delineating Source Water Protection Areas", the paper shows us the time criterion of delineation of Groundwater source protection areas: the time criterion of the primary protection area is 100 days, the time criterion of the secondary protection areas is 1,000 days, the time criterion of and the terriary protection areas is 25 years. Through the deeply study of the geography, geology and hydrology geological conditions of the areas, the paper finds the conditions of groundwater cycle characteristics, dynamic characteristics and types, then the paper continue to study the actuality of the utilization of groundwater and the exist problems.We conducted on the sources of pollution investigation and pollution analysis to this research areas. According to the analysis results of the samples for groundwater quality, we selected environmental indicators to reflect the water environmental conditions,and establish the regional water quality indices, and lead in R-type main factor analysis, then we consider the factor score of "the main factors" as the foundation, adopt the Ward Method to analyze.Then select the sorted critical value to establish the spatial variation model of water environmental quality, to describe the spatial classification of the water environmental pollution feature (surface water and groundwater). The low-polluted areas of surface water and groundwater has a widely distribution, The high-polluted areas only appear in urban areas and Dangshi River, thereinto the groundwater environmental elements are divided into five spatial variation categories in groundwater pollution spatial variability analysis and the surface water environmental elements are divided into three spatial variation categories. In order to get the parameters that it will be used when forecasting the groundwater quality , the dispersion test is carried out: a artificial rock sample with the same soil density and porosity with natural state is prepared ,then we carry out the one dimension and two dimension indoor dispersion test. The diffusion coefficient is achieved with dispersion equation analytic result, and according to these two results it is achieved that the vertically integrated hydrodynamic dispersion coefficient is 0.7417 m2?d-1.According to the parameters of the test the paper forecasts the water quality of the groundwater source: the groundwater solute transport rule is considered as a solute transport that pollutant is continuously infused in semi-infinite aquifer, and the river water to groundwater quality influence is forecasted according to the analytic solution of one-dimensional flow field. And it is shown that when delineating the primary protection areas the river pollution is unnecessary to be considered, and the river border must be considered when delineating the secondary protection areas. Vertical migration of the contaminant is described with the one-dimensional convective migration-dispersion-reaction equation in homogeneous isotropic porous medium. And the possibility of the contaminant leaking from the earth surface into the groundwater through the vadose zone is forecasted with its simplified model of the migration ability index. And it is shown that the contaminant will not pollute the groundwater because the contaminant is completely degradated at 0.5m depth of the vadose zone and the depth of the vadose zone in Panshi city exceeds 6m.The groundwater protection areas are delineated with Experience method: According to the forecasting result of the water quality, the radius of protection areas are obtained with empirical formula.The groundwater protection areas are delineated with Numerical method: First, the hydrologic geological conceptual model and the groundwater flow field forecasting model of two-dimensional unsteady flow are established. Then, with the MODPATH in the software of Visual MODFLOW, the inverse trace of the tracing particle in time criterion of the protection areas is fixed with the inverse particle-tracing scheme. Thereout the flow contours is achieved through linking up the start point of the inverse trace. Finally the borders of the protection areas of all level are determined.From the results achieved by both methods above, it can be seen that the result achieved by Experience method is quietly bigger than the result achieved by Numerical method. The Experience method is more macroscopic and subjective, and usually obtains a coarse scope. And the Numerical method gains the precise scope. But, for the water sources of complex hydrogeolgical condition, he Numerical method is easy to form generalized error, and when it is used for delineating water source protection areas in this article, Numerical method had not considered the problem of radius increase that it is caused by increasing the groundwater mining quantity, only calculated according to the present state of groundwater mining quantity.It can be seen that there will inevitably be some error when choosing only one method. This paper synthesizes two approaches to re-delineate the protection areas of the water source, leads the longest flow line values of every well in time criterion of the protection areas which is calculatd by Numerical method into the selected empirical equation, then according to hydrogeology conditions and the social environment conditions of the research areas, delineates the border of water source protection areas. The results not only overcome the problem that it is caused by ignoring the change of the groundwater mining quantity when using Numerical method to delineate the water source protection areas, but also overcome the drawback that it is caused by the given value of flow rate which is more macroscopic when using Experience method to delineate the water source protection areas.Meanwhile, to protect water sources, not only the delineation of protection areas, but also the management of the protection areas should be carried out. The management of protected areas should not only comply with the technical management measures, but also implement administrative management measures.It is concluded that it is inevitable trend that delineating the water source protection areas should combine the Experience methods and Numerical methods.