Application Assessment of GRACE and CHIRPS data in the Google Earth Engine to investigate their relation with groundwater resource changes (Northwestern region of Iran)

چکیده مقاله

In recent years, drought has become a global issue, especially in dry and semi-dry areas. It is without a doubt that the identification and monitoring of the drought phenomenon can result in a decrease in the damages humanity would face. In addition, rain is one of the factors which directly affects the water levels of underground water reservoirs. This research applied a linear gradient regression developed on the basis of the GRACE, the CHIRPS, and the monitoring wells data to monitor groundwater resource changes. These data have been analyzed in the Google Earth Engine platform. In order to conduct temporal and spatial analyses, the water level of the aquifer was zoned. Also, the amount of water storage and the amount of rain from the year 2003 to 2017 in the West Azerbaijan province were investigated using the GRACE satellite and the CHIRPS data, respectively. The results obtained from the GRACE satellite data show that the decreasing trend of the average water level in Iranian reservoirs had started in 2008 and reached its peak in 2016 with an average decrease of 16 cm in that year. In addition, the average decline of reservoir water levels in the studied time period was 5 cm. A chart developed using the CHIRPS annual rainfall data indicates that the most amount of decline in rainfall occurred in 2008, and this continuous declining trend has remained steady. The regression of GRACE and CHIRPS results by Monitoring wells data caused in 86 and 97 percent correlation, respectively. Furthermore, the results obtained from the zoning of the aquifer showed that in the 2006-2016 time interval, due to the decrease in rainfall and the excessive withdrawal of the water in reservoirs, the water table levels decreased.