| Huanan County belongs to Jiamusi City, Heilongjiang Province, an important grainproduction base with groundwater as the main supply. In recent years, the water level droppedsignificantly caused by excessive exploitation of groundwater and the water quality deteriorationcaused by industrial and agricultural pollution, making the contradiction between water supplyand need becomes extremely serious. Since groundwater has become an main constraint to thecounty’s economic and social development, emergency assessment of the quality and quantity ofgroundwater in Huanan County are urgently needed to provide a scientific basis for groundwaterexploitation and protection.GMS software is used to create three-dimensional model of the geological structure and todisplay the strata information Water level dynamics are analyzed by long-term monitoring ofgroundwater level data and water chemistry type is analyzed by Aquachem software. Themathematical statistics and factor analysis methods are used to analyse the mechanisms ofhydrochemistry formation. Furthermore, groundwater quality was evaluated by the Nemerowindex method and fuzzy comprehensive evaluation method. The hydrogeologic conceptualmodel and mathematical models are established according to the geological and hydrogeologicalconditions and the Visual Modflow software is used to simulate the groundwater flow. PearsonType III frequency curve is used to calculate the precipitation of typical years. The exploitablequantity of groundwater is calculated by the exploiting coefficient method and the exploitationpotential is also evaluated. The groundwater level in the next decade is predicated and analysedby numerical model. The main results are as follows:(1) Formations of the aquifers in both unconfined and confined conditions were indicatedby the three-dimensional geological structure model, which shows that the unconfined aquifercontains the Quaternary Holocene, Upper Pleistocene and Middle Pleistocene aquifer and theconfined aquifer contains Upper Tertiary and Upper Cretaceous aquifers. According to thegroundwater level dynamic data, the unconfined aquifer mainly recharged by the infiltration ofprecipitation and lateral runoff and discharged by artificial exploitation, evaporation and lateralrunoff, the confined aquifer mainly recharged by lateral runoff and discharged by artificialexploitation and lateral runoff.(2) The chemical type of confined aquifer is relatively simple (HCO3-Ca·Na、HCO3-Ca andHCO3-Ca·Mg) compared with unconfined aquifer. hydrochemistry formation are mainly resulted from the lixiviation and the impact of human activities, more specifically, the lixiviation is thedominant factor. Three nitrogen, volatile phenol, iron and manganese ions exceedes the drinkingwater sanitary standard due to the continued contamination of agricultural fertilizers, industrialwastewater, domestic sewage and strata sources. The phreatic water and artesian water are bothsuitable for boiler water and irrigation water. Quality types of phreatic water is classⅠin firstgrade terrace, and class III in floodplain, and class Ⅴ in pediment tableland. The water qualitytype of artesian water is classⅠ and class Ⅱ.（3）After the identification and validation of model, it is clear that the water table fittingresults are quite satisfied with81.71％and64.12％of0.5m fitting errors points respectively,which shows that the current model is suitable for water table predication. Besides, thesensitivity analysis results demonstrated that water table is influenced mostly by the permeabilitycoefficient.4）Exploitation potential were calculated by water balance under high, mean and lowprecipitation amount, which were17571.12m~3/d,16184.76m~3/d,15120.31m~3/d,16293.82m~3/d,respectively. According to the results we could draw the conclusion that: under currentexploitation conditions, shallow aquifer was over-exploited and this situation in confined aquifereven worse. More specifically, both shallow and confined aquifers were not meeting the waterdemand.(5) Dramatic decline of groundwater table expansion of depression cone will be acceleratedby over-exploitation will continue according to the model precipitation. Adjustments ofexploitation strategy can be an effective approach to control the decreasing water in the centralof depression cone due to the centralizing exploitation in shallow aquifer. Furthermore,replacement of outside water resource and efficient utilizing of surface water should be adoptedto sustain water requirement.(6) For the purpose of groundwater management and conservation, there are severalreasonable solutions should be take into account: optimizing exploitation strategy, developingsurface water diversion project, contamination source controlling and online monitoring ofgroundwater table floatation and water chemical composition. |
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