Technique And Application On Security Evaluation Of Groundwater Drinking Source In Towns

With the development of social economy and a surge in population, waterpollution has gradually transfered from the surface water into the groundwater.Previously, groundwater was used to be the best water resource in most of NorthChina or arid and semi-arid regions to stabilize the amount of water owning the highquality and ample quantity. But in recent years, with the speeding up ofindustrialization, the frequent agricultural activity and the lag of pollution controlproject, today’s groundwater pollutants have been diversified and complicated, and thegroundwatger resources have reduced seriously. Therefore, how to ensuregroundwater resource safety has become to the crux that maintain today’s social andeconomic development and ensure people’s health.The paper, using modern scientific idea and advanced technology,carred out anin-depth research on evaluation indices system for groundwater drinking sourcesecurity, and it has achieved ideal results as follows;1. Through the collection and analysis of groundwater drinking source securitysituation, refer to the relevant references home and abroad, combined with the currentdefinition of groundwater drinking source security, a more comprehensive andcomplete connotation of the groundwater source security was summarized: Underpressure from both nature and society, groundwater source must own adequate wateryield on the basis of sustainable supply capacity, safe water quality, stronggroundwater vulnerability, well capability of anti-risk and emergency and meet therequirements of the surrounding ecological environment. Meanwhile, before and afterthe operation, it will not cause environmental geological problems and maximize meetthe needs of safe drinking for society.2. For the first time, an improved DPSIR framework was established for thegroundwater drinking source security evaluation indices system at the town level.Then through the individual and whole test, the43indicators of evaluation systemwas established, which contains Driving fouces-Pressure-State-Impact-Response-Risk6criterion layers,13elements layers, including water quantity, water quality, vulnerability, ecological environment, social economy and management，environmental geology, and many other aspects.3. The definition of the index, the corresponding evaluation standard and calculationmethod was carried out generally and completely. And groundwater drinking sourcesecurity level was divided into five states: ideal safety and safety, the critical state,unsafe state, highly unsafety.4. Innovatively, by both the fuzzy analytic hierarchy process (FAHP) and the theory ofgroup decision-making, the weight set was comprehensive computed.5. The construction scheme of the groudwater drinking source at Bayan town wasresearched. At the same time, this water source, as an example, was evaluated throughthe security evaluation index system, which could verify the applicability of the indexsystem.(1) To evaluate groundwater environmental quality in the study area, mainly includesgroundwater quality evaluation and water quality health evaluation, of which thegroundwater quality evaluation was realized by the Nemerow method, analytichierarchy process and improved grey correlation method. Meanwhile, the immuneevolutionary algorithm universal formula was also used for verification result. Theresults indicated that the results of three methods were Ⅳ class. Health assessmentresult was1.536×10-7, which was in a state of perfect security in the region.(2) Through data collection, field investigation and test means, with the numericalmethod and analytical method, the hydrogeological parameters of the aquifer wereobtained in the study area, and the distribution and structure of the aquifer were foundout: the distribution of aquifer floor in the northeast and the south watershed of thestudy area buried The aquifer sloped from the east to the west slightly. The deepestaquifer floor is located in the washland of ShaoLing river, and there appeared doubleaquifer structure, in which two groups of clay in Q2and Q4have been deposited, sandgravel layer respectively. They can be seen as the pore phreatic water and poreconfined aquifer closely linked with Shaoling river.Through analysis about thecontour maps of the roof, the floor and the groundwater level, it can be founded thatthere was a groundwater watershed in the south of the study area for the first time.(3)The groundwater resources and the allowable exploitation in the study area werecalculated.The results were as following: the groundwater average recharge from1960to2012is2630.82×104m3/a, the groundwater resourcewas2492.95×104m3/a.The mean allowable groundwater exploitation was5.30×104m3/d in the study area. (4) By the numerical method, the groundwater flow field in the studied area wassimulate and forecasted. The forecast period was from2013to2023, which meanttotal10years after the completion of the third waterworks construction. In this paper,there were four schemes to forecast. And the results show that when the study areasuffered continuous10dry years (75%), the groundwater drawdowns in the secondand third water plants would reach6.40m and10.20m, but less than50%of theaquifer thickness. In the other parts of the study, the groundwater drawdown appeareda downward trend, but not obvious.(5)Through the evaluation about groundwater quantity and quality in the study areaand simulation predictions on the groundwater field, it was known the newly-bulitthird water plant shceme was feasible, and it can satisfy the water demand of3×104m3/d under the condition that it did not threat the local groundwater resources andenvironment.(6) The safety assessment results in the study area could be divided into two periods,which can be summarized as the security status before and after the change of waterextraction project: the groundwater security evaluation results were2.591and2.264,respectively, which were in the critical state and in the security status. Under thestatus system, the groundwater quantity security status were3.365and3.170,respectively, in the critical state, and the groundwater quality security status was2.620,in the critical safety state. From the status quo to the forecast year, the biggest changewas the response system,also named pollution control engineering index. Its value hasfallen by1.158, improved from the critical state to the safety status; The smallestchange was the pressure system,only dropped by0.125, which was still in thesafetystatus. From the evaluation process and results in this paper, the established evaluationindex system has a high practicability. On the basis of reflecting the generalcharacteristics of the drinking water source security, each index, each system andstatus can be grasped.And the evaluation conclusion also has a certain reference andguidance significance for the operation and management of water source in Bayan.To sum up, this paper mainly completed the following innovations: A morecomplete and comprehensive connotation of groundwater resource was put forward;The groundwater drinking source security evaluation indices system at the town levelwas established firstly, which supplemented by the corresponding evaluationstandards and calculation methods; Innovatively, by both the fuzzy analytic hierarchyprocess (FAHP) and the theory of group decision-making, the weight set was comprehensive computed. Using the theory of wavelet, combined with SOM-RBFneural network, the precipitation in the study area was forecasted.