Investigation and trend identification of groundwater level variations using discrete wavelet transform and non-parametric tests (case study: Azarshahr plain)

Groundwater resources due to lately affected by climate changes and precipitation fluctuations are valuable. Given that the interaction between climate and groundwater components are more complicated than interaction between climate and surface waters components, therefore investigation of changes in groundwater has an important role in planning and sustainable water resources management In this research, trend of groundwater, precipitation and stream flow time series in monthly, seasonal and annual time scales and dominant periods of trend in original time series for stations located in Azarshahr plain, East Azerbaijan Province and part of the watershed of Urmia Lake were found by using the hybrid Mann-Kendall method with wavelet transform during 45 years. Results showed that, all the stations have a downward trend for all the time scale studied. Accurately, in the results, 16 months, 6 months and 8 years periods were detected as dominant periods for groundwater time series in monthly, seasonally and annual scales, respectively. According to sequential Mann-Kendall results, it can be obtained that a decreasing trend starts from 1378 in the stations. In addition, Sen’s method was used to confirm the proposed MK test and its accuracy was confirmed.