The Safety Evaluation Of The Phreatic Water Quality

With the accelerated process of industrialization and rapid increase in human activities,the groundwater quality of its own security is seriously threatened. This article rely on theMinistry of Education, the State Foreign Experts Bureau of the disciplinary innovation talentfrom overseas plan ("111")━Arid and semi-arid regions hydrological and water safetydisciplines innovative talent from overseas base project (No.: B08039), carried out the studyof the safety evaluation of the phreatic water quality.The protection targets of the "The safety evaluation of the phreatic water quality" isphreatic water. The purpose of the evaluation phreatic water quality is threatened, or in a stateof insecurity. Phreatic water safety reasons, including internal and external causes. Amongthem, the "external causes" means outside influence, is the external forces that affect phreaticwater safety, which is the external environment is applied to the phreatic water, when thiseffect was negative, diving safety is a threat, or the invasion force."Internal causes" meansthe "defense capabilities" of phreatic water system to the outside influence or called"anti-pollution capacity", is the unconfined aquifer itself to resist against the defensecapabilities of its own inherent properties."Internal causes" and the negative impact of"external causes" constitute two interacting opposites, the negative impact of external causesis stronger than internal causes, and unsafe phreatic water conversely, if the internal causesstrong negative impact of external causes, the phreatic water safety.The content of this master’s degree thesis is "The safety evaluation of the phreatic waterquality", belongs to the decomposition of the project of"111"project━"Typical cities in thearid and semi-arid areas groundwater safety evaluation"."Groundwater safety evaluation" isthe decomposition of the contents of the research projects, both with phreatic water safetyevaluation, but also includes the safety evaluation of pressurized water, and contains both asafety assessment of the quality, but also contains a number of security evaluation. Thecontent of this master’s degree thesis, include only the safety evaluation of the phreatic waterquality.Around "The safety evaluation of the phreatic water quality", this article carried out thecorresponding theoretical research and case study achieved the following results:1. The article define what is the safety evaluation of the phreatic water quality firstlyThe safety evaluation of the phreatic water quality is defined like this:with the phreaticwater as protected target subject, the external environment has an effect on phreatic water,what we study is to determine which level the phreatic water quality belongs to under the contradiction between pollution threat outside and defense inside. It studies and evaluates thesafety level of the phreatic water itself and not the safety problem of the user.The article emphasizes the safety evaluation of the phreatic water quality is differentfrom the quality evaluation of the phreatic water. The quality evaluation of the phreatic waterdoesn’t evaluate the safety level in which the phreatic water itself is threatened but evaluatesif the user is threatened by water quality and if the water quality is available to the user. Itevaluates water according to water quality standards which is the requirements of the waterusers. The purpose is very clear, It only pays attention to the safety of the water user, the maingoal of protect is water user. Water is applied in the role of the active party, water user is thepassive role, and the safety of water user is depended on the quality of the phreatic waterwhich can be obtained by analyzing water sample. We can judge if using the water is safewith the water analysis data.2. Create the safety evaluation index system of the phreatic water quality DRAUGHTSTo evaluate the safety level of the phreatic water quality, the article creates the safetyevaluation index system of the phreatic water quality DRAUGHTS and discuss thedifferences between DRAUGHTS and DRASTIC which means the phreatic watervulnerability evaluation index system. The DRASTIC system researches and evaluatesdefense capabilities against violations of water, it can be called the ability to fight pollution,and it is the inherent attributes and can not be threatened by outside pollution. TheDRAUGHTS system not only involves the evaluation of ability to fight pollution of thephreatic water but also the evaluation of effect intensity on which the phreatic water quality issustained from the outside3. We make the application study with Xi’an plain area as the exampleWith Xi’an plain area as the example, the article evaluates the safety evaluation of thephreatic water quality with the DRAUGHTS system and draws the sectorized picture of thesafety level of the phreatic water quality in Xi’an plain area, we get several rules from thepicture: the quality and quantity of pollution sources is the dominant factors which is todetermine the safety level of the phreatic water quality. The hydrogeology condition of theunconfined aquifer is also a very important factor. The unconfined aquifer has a very weakability to resist the invasion of external pollution, because it does not have upper confiningbed. By this rule, the minimum lower level of the phreatic water quality safety is distributedin such area where the unconfined aquifer can be polluted by class V surface water,but thehighest and higher level of the phreatic water quality safety is distributed in such area wherethe unconfined aquifer can not be supplied by class V and class Ⅳ surface water. With the supply of the safety evaluation of the phreatic water quality in Xi’an plainarea, we can prove the DRAUGHTS system is available and can be used widely.