Sensitivity analysis of the effect of climatic and non-climatic factors on groundwater level fluctuations (Case study: Najafabad plain)

This study was conducted to investigate the main factors affecting groundwater level fluctuations in the Najafabad plain. For this analysis, the 10-year period from 2004 to 2014 was considered and changes in temperature, precipitation, in river discharge between the beginning and end of the study area, groundwater withdrawal and in water flow in irrigation and drainage networks, were analyzed. In order to establish the relationship between each of the mentioned components with the changes in groundwater level in the study area, two general classifications were considered to determine the groundwater unit hydrograph. In the first classification, a groundwater unit hydrograph was prepared for all observation wells in the study area. In the second category, this hydrograph was prepared for observation wells around the river. Then, using multivariate regression analysis in SAS software, the best relationship between these components with changes in groundwater level was determined. Results showed that if the changes of groundwater unit hydrograph level are considered in the first group, changes in groundwater withdrawal with a share of 36.19%, had the maximum impact on changes in groundwater level. After that, the changes in the river flow with a share of 28.60%, had the greatest share in groundwater fluctuations. On the other hand, when the groundwater unit hydrograph is considered for the second group, changes in flow in the river with a share of 34.64% will have the maximum effect on changes in groundwater level and the share of groundwater withdrawal will reach to 28.53.