This paper studies, through the principles of fuzzy set theory, groundwater response to meteorological drought in the case of an aquifer system located in the plains at the southeast of Xanthi, NE Greece. Meteorological drought is expressed through standardized Reconnaissance Drought Index (RDI^St) and Standardized Precipitation Index (SPI), which are calculated for various reference periods. These drought indices are considered as independent variables in multiple fuzzy linear regression based on Tanaka's model, while the observed water table regarding two areas is used as a dependent variable. The fuzzy linear regression of Tanaka is characterized by the inclusion constraints where all the observed data must be included in the produced fuzzy band. Hence, each fuzzy output can get an interval of values where a membership degree corresponds to each of them. A modification of the Tanaka model by adding constraints is proposed in order to avoid irrational behavior. The results show that there was a significant influence of the meteorological drought of the previous hydrological year, while geology plays an important role. Furthermore, the use of RDI^St improves the results of fuzzy linear regressions in all cases. Two suitability measures and a measure of comparison between fuzzy numbers are used.

本文通过模糊集理论的原理，以位于希腊东北部克桑西东南部平原的含水层系统为例，研究了地下水对气象干旱的响应。气象干旱通过标准化的侦察干旱指数 (RDI ^St) 和标准化降水指数 (SPI)，它们是针对不同参考时期计算得出的。在基于田中模型的多元模糊线性回归中，这些干旱指数被视为自变量，而两个区域的观测地下水位被用作因变量。Tanaka 的模糊线性回归的特点是包含约束，其中所有观察到的数据必须包含在产生的模糊带中。因此，每个模糊输出都可以得到一个值的区间，其中一个隶属度对应于它们中的每一个。为了避免非理性行为，建议通过添加约束来修改 Tanaka 模型。结果表明，上一水文年气象干旱的影响显着，地质因素起重要作用。此外，^St在所有情况下都改进了模糊线性回归的结果。使用了两个适用性度量和模糊数之间的比较度量。