Effect of Drought on Groundwater Level in the Past Two Decades (Case study: Ardebil Plain)

Study of changes in groundwater resources in any region is important from the view point of planning and sustainable water management. Scientific management of water resources needs to know the relationship of drought and groundwater level. In the present study trend analysis was conducted on groundwater level of 32 piezometeric stations located in Ardebil plain for the observation period of 1367-1387 using Mann-Kendall non-parametric test. Trend line slope was estimated by Sen’ s estimator for each time series. Homogeneity of trends was tested using the Van Belle and Hughes method. Results showed that trends of groundwater level for all stations (except Niare-Madrase, Yengjeh-Molla-Mohammd Reza, Agche-kandi and Darvazeh Astara) were negative. Significant negative trends were detected for more than 72 percent of the stations. Results of trend line slopes revealed that in average the groundwater level of Ardebil plain declined about 18 cm/year. The strongest decline belonged to Khalife-loo-sheikh station, which had negative trend of 1.93 m/year. Results of homogeneity test of trends showed that trends were homogeneous for different months and heterogeneous for various stations.