Estimation of Proper Nonparametric SPI using Water Table Fluctuations in Talesh Region

Time-lag responses of groundwater to precipitation is very important for optimal management and programming of water resources in any catchment. This study explores the time-lag responses of groundwater to precipitation and drought in Talesh Region using correlation coefficient between groundwater fluctuations at 19 piezometers and different time scales of standard precipitation index (SPI) in 6 rainfall stations. Some MATLAB codes are written for calculating correlation coefficients values. The results indicate that the time-lag response is various across Talesh Region depends on groundwater depth. The piezometers with shallow water table show the better correlation coefficient with 1 to 2 month SPIs. By increasing depth of groundwater (specially near the Rainfall station of Kharjgil). The average lag-time of responses of Talesh Region groundwater to precipitation is 2.5 months.