Study On The Penetration Mechanism And The Influence On Groundwater By Pollution Of Weihe River Using The Field Test And Numerical Model

Weihe river is the mother river and the basin is the economic center of Shaanxi province. Along the river, there are five big cities such as Xi'an, Xianyang, Tongchuan, Weinan and Yangling sample region of advanced agriculture, Yanliang plane city and other many small cities in Guanzhong region. This region, with centralized industry, developed agriculture .abundant travel resources and solid strength of education, science and technology, is the core for the development of society and economy in Shaanxi province. And it elaborates the unsubstantiated effect for economic development of the province. Beside the river there are more than thirty water sources which supported the water demand for producing and living along the Longhai railway effectively. In recent decades, the serious polluted river affected the water quality of both the lower reaches of the Yellow river and the water sources, and influnced living of people. However, the real quantity of water resources about water sources beside the river is smaller than that of previous evaluation after exploitation because the penetration mechanism of water sources beside the river couldn't be understood clearly and the evaluation models aren't the best.Under the support of "973"term-"the Study on Groundwater Renewability Law in the Yellow River Watershed(G 1999043606)", taking the penetration mechanism of the river and the influence on groundwater with the polluted river as a goal, the thesis designed and developed the field test on its penetration mechanism and the influence on groundwater with the polluted river in the typical section of the basin. By the field test, this paper reveals infiltration and transformation law of stream under certain pressure and stream being disconnected to groundwater, and attains the characteristic soil moisture parameters of different lithological medium. The numerical model of moisture flow after stream disconnected groundwater had been established .Also this paper simulated the condition after stream is disconnected to groundwater using the GMS software and parameters, discussed the penetration mechanism of steam in unsaturated soil as well, and analyzed its influencing factors. In addition this thesis had carried out the field test to study influencing on groundwater with the polluted river taking Cr6+,NH4+,HCO3 as pollutants. These studies had showed that stream infiltration and transformation in unsaturated soil is related to depth of incision of a river, the medium and structure of unsaturated soil, thickness of weakpermeable strata and their assorted relation under stream being disconnected to groundwater, and that ignoring these factors such as vadose zones, media and structure of unsaturated zones must be emphasized during researches about groundwater resource evaluation of water sources and influence of polluted stream on groundwater.The field test has proved that Cr6+and "Three Nitrogen" have strong ability of transportation and transformation with carriers and threaten the groundwater quality seriously. However, weak permeable strata in unsaturated zone play an important role of taking precautions against pollution although it hampers stream recharge, pollutants can still contaminate the groundwater by penetrating the weak permeable strata . These researches also prove that the mechanism about stream recharge should be emphasized during water resource evaluation of water sources beside rivers, otherwise the evaluation would be deviation.