In the present study, five parametric and non-parametric methods: linear regression (LR), conventional Mann–Kendall (MK), modified Mann–Kendall (MMK), Spearman's Rho (SR) and Innovative Trend Method (ITM) were used to identify trends in the groundwater levels of 60 piezometers distributed uniformly across Sirjan plain, Iran, from 2005 to 2018. The LR method was found to be affected by the presence of outliers and autocorrelation. The conventional non-parametric tests (MK and SR) were not able to offset the effects of the autocorrelations between the groundwater level data. The ITM method was also found to be a not so comprehensive and precise statistical tool for trend analysis because it does not provide a quantitative index for identifying trend significance. Therefore, the MMK test was found to be the most appropriate trend analysis method among the five trend identification methods used in this study by eliminating the effect of all significant autocorrelation coefficients. The results of the MMK test showed that the groundwater levels in Sirjan plain had witnessed significant decreasing trends during the study period. In only 24 months (out of a total 10,080 studied months), no significant decreasing trends in groundwater levels were observed.

在本研究中，使用了五种参数和非参数方法：线性回归（LR），常规的Mann–Kendall（MK），改进的Mann–Kendall（MMK），Spearman的Rho（SR）和创新趋势方法（ITM）确定2005年至2018年期间在伊朗Sirjan平原均匀分布的60个压力计的地下水位趋势。发现LR方法受到异常值和自相关的影响。常规的非参数测试（MK和SR）无法抵消地下水位数据之间自相关的影响。还发现，ITM方法不是一种用于趋势分析的全面而精确的统计工具，因为它没有提供用于识别趋势重要性的定量指标。因此，通过消除所有显着的自相关系数的影响，发现MMK测试是本研究中使用的五种趋势识别方法中最合适的趋势分析方法。MMK测试的结果表明，在研究期间，Sirjan平原的地下水位呈明显下降趋势。仅在24个月内（总共研究了10,080个月），没有观察到地下水位明显下降的趋势。