Effect of the membership function type on the fuzzy risk of allowable groundwater drawdown calculation results
2021
Liu, Peigui | Zhang, Su | Shang, Manting
Because of the complexity of groundwater systems and human activities, fuzzy and random uncertainties are two kinds of uncertain factors that exist widely in groundwater systems. The fuzziness of the variables is usually described by membership functions. When the variables obey different membership functions, the fuzzy risk of adverse events may be different. To explore the influence of the membership function type on the reliability of the estimation results of allowable groundwater drawdown, taking groundwater exploitation in desert oasis areas that have great dependence on groundwater as an example, a fuzzy stochastic coupling model of the allowable groundwater drawdown is established. Using the theory of the cut level λ, fuzzy variables are transformed into random variables to obtain the fuzzy risk. The results show that unlike the random risk, the fuzzy random risk is an interval. The membership functions with a normal distribution and quasi-normal distribution have little effect on the fuzzy risk in the case study. 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, with a fuzzy random risk of 57.68% at λ = 0.5. The results of this paper can also provide references for groundwater exploitation risk assessment.
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