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Hefei University of Technology (合肥工业大学) 2021

Research on Uncertainty Analysis of Groundwater Ecological Water Level Threshold in Desert Margin

张苏

Titre : Research on Uncertainty Analysis of Groundwater Ecological Water Level Threshold in Desert Margin

Auteur : 张苏

Grade : Master 2021

Université : Hefei University of Technology (合肥工业大学)

Résumé partiel
The groundwater level is important to maintaining regional ecological environment in desert oasis region,and because of its special geographical location and complicated hydrogeological conditions,it is difficult to survey the groundwater system of the oasis region,so there are many uncertainties in the determination and simulation of the groundwater ecological level.In this paper,taking a study area in Pishan as an example,through establishing groundwater numerical simulation model,determine the ecological groundwater level threshold value in the study area,analyze the uncertainty factors during determining the ecological water level threshold value,constructs the ecological water level fuzzy random risk model,and aiming at the uncertainty of groundwater system model structure,the probabilities of different models reflecting actual conditions are estimated.Firstly,the relationship between ecological groundwater level and crop vegetation growth,soil salinization,evaporation limit depth and groundwater salinity was analyzed.Combined with the numerical model,the threshold of ecological groundwater level in the study area was determined to be 3~11.3m.At the same time,based on the modeling process and actual hydrogeological conditions,the uncertain factors affecting the of groundwater ecological water level threshold were divided into random,fuzzy,gray and unascertained uncertain factors.Secondly,considering the widely existing randomness and fuzziness of groundwater system in the study area,the λ cut set method is used to calculate the fuzzy random risk when the parameters obey different membership functions.The results show that the risk rate calculated by the cut set method is a series of interval values.When the membership function of the fuzzy random variable has a normal or quasi-normal distribution,the difference in the fuzzy risk is smallest.When λ<0.67,the fuzzy risk interval of the triangle membership function is the largest,and its risk interval maximum value of 98.36% can be obtained at λ=0.1 ;however,when λ>0.8,it has the smallest risk interval of all the membership functions.If the skewness of the design parameters is taken into consideration,the lognormal membership function is a better choice.

Mots clés : Desert marginal area ;Ecological water level threshold ;Fuzzy-stochastic model ;Membership function ;Model structure uncertainty ;

Présentation (CNKI)

Page publiée le 8 mars 2022