Trend Analysis of Qualitative Changes on Groundwater Resources Using Non-parametric Tests: A Case Study of Dehgolan & Qorveh Plains, Kurdistan Province, Iran

Trend analysis of water resources quality changes has a substantial effect on sustainable water resources planning and management in each region. In this study، Mann-Kendal and Spearman tests were used for analyzing the trend of both temporal and spatial distribution for subsurface water resources quality changes during 1992 to 2011 in Dehgolan & Qorveh plains، Kurdistan province، Iran. In this regard، hydrogeochemical parameters such as pH، TH، EC، Na+، SO4-2، Na، Mg+2، TDS، SAR، Ca+2 and HCO-3 were analyzed in September (waterful) and June (low water). For time series، trend line was extracted using Sen’s estimator and the inverse distance weighting method was used to see trends. Results showed that maximum trend gradient was achieved for a confidence 95 %، in Sandoghabad station (Dehgolan plain) and Mobarak-abad station (Qorveh plain) for EC. Also، EC had increased in southern and north eastern parts of Dehgolan & Qorveh plains. Furthermore، Mann-Kendal and Spearman tests، showed good capability in determination of the trend at verified confidence level.