含水层参数不确定性与地下水开采量可靠性评价

UNCERTAINTY OF AQUIFER PROPERTY AND ASSESSMENT OF GROUNDWATER YIELD RELIABILITY

应用区域化变异函数理论和条件模拟,对内蒙古霍林河市主要含水层的渗透系数的分布特征进行了分析;用有限单元法和条件模拟方法计算了研究区地下水的可开采量和水位,并对地下水开采量的可靠性进行评价.研究表明。

The uncertainty of hydraulic conductivity with some degree of continuity in space affects groundwater flow modeling.In order to study the uncertainty and assess the reliability of groundwater yield,the geostatistical approach and finite element method are used. A case study on Huolinhe area located in east Inner Mongolia, is presented in the paper. Geostatistics is a branch of applied statistics that deals with phenomena spread in space with some degree of continuity. It is foremost data analysis and spatial uncertainty. The basic concept of geostatistics such as regionalized variable, variogram,kriging estimate and conditional simulation are introduced into the paper briefly. Huolinhe area is a basin formed from faulting and sinking between mountains. The upper aquifer is Q 4 porous sand and the lower aquifer is Jurassic(J) porous-fractured rock; two types of aquifer are continuous and unconfined. A lot of hydraulic conductivity data regarded as regionalized variable has been obtained by aquifer test. The variograms fitted with spherical model are calculated in parallel and perpendicular groundwater flow directions; the correlation length in parallel groundwater flow is twice longer than in another direction. These explain that there is a statistical anisotropy of hydraulic conductivity in Huolinhe area aquifer and that the correlation of hydraulic conductivity in parallel groundwater flow is better than in another direction. The Kriging estimate of hydraulic conductivity is compared with conditional simulation conductivity. On the basis of spatial distribution of hydraulic conductivity, the well location is determined. The Kriging estimate value and 300 conditional realizations of hydraulic conductivity are inputted into groundwater flow model solved by finite element method to obtain groundwater yield. Finally, the reliability of groundwater yield is assessed in Huloinhe area by statistically analysing a larger number of groundwater yields. The result of studying shows that a Kriging Estimate can describe the variability and spatial distribution of hydraulic conductivity .The conditional simulation of hydraulic conductivity indicates that conditional simulation of hydraulic conductivity can not only describe preferably characteristics of the spatial distribution of hydraulic conductivity but also provide alternative inputs into numerical model of groundwater flow. The statistical analysis of groundwater yield obtained from solving groundwater flow model according to conitional simulation realization of hydraulic conductivity can assess thee reliability of groundwater yield.These offer a new idea and method for the assessment of groundwater yield ,The case study demonstrates that the mean of the groundwater yield is 89?600m 3/d ; groundwater yield is 63?800～115?400m 3/d when guarantee degree is 68% in Hhuolinhe area.