Evaluation of quantitative changes in surface water resources, affected by the earthquake of Sarpol-e-Zahab, using satellite data

 Earthquake In addition to the destructive effects of man-made structures, earthquakes also have different effects on surface water resources. Earthquakes always increase or decrease the water flow depending on its intensity, time, direction, and profundity. It may even cause the springtime fountain to flow that has dried up over the years. The use of remote evaluation technology in various earth sciences is very common compared to geocentric methods due to the wide coverage of satellite images, the timeliness of images, and its little cost. Also, one of the important and unique capabilities of digital satellite data is its temporal, spatial, spectral, and radiometric resolution. These important features of satellite imagery allow for important studies such as the evaluation and monitoring of dynamic phenomena such as quantitative changes in water resources in temporal and spatial dimensions. Because in some cases the information obtained from a sensor alone does not meet the desired needs. Although optical multispectral data provide rich spectral information of various effects, it is significantly affected by environmental factors such as smoke, fog, clouds, and the amount of sunlight. Unlike optical sensors, radar data with virtual aperture (SAR) is independent of different weather and radiation conditions, as well as the sensitivity of its signal, scatter to target parameters such as structure (shape, orientation, size), roughness, and moisture content of the features can provide more information about the study area, but on the other hand, radar images cannot clearly identify the details and edges of objects. Therefore, combining different properties of optics images and radar data using image integration techniques can provide a more complete view of the target and provide higher accuracy and reliability for the results obtained from this method. In the present perusal, in order to achieve the above purpose, using satellite data and the image combination method, the data have been standardized in such a way that they can be used together in the form of a dataset for processing.

Using the method of combining satellite images of quantitative changes of surface water resources, affected by the SARPOL-E-ZAHAB earthquake in the course of 7 days, 11/11/2017 to 17/11/2017, using radar data (S_1A-IW-SLC), With 100 m spatial baseline and Landsat 8 (OLI) optical data, and obtained by applying remote evaluation techniques and indicators to detect changes in water resources, including Normalized difference vegetation index (NDVI), Modified normalized difference water index (MNDWI) in ENVI software environment and then analysis in ArcGIS software environment.

Examination of the results of quantitative changes in surface water resources shows that in the time period of 7 days after the earthquake in the study area, the highest amount of small changes (in a decreasing manner) occurred in dams (HAMMAM Strait and GILANGH-GHARB Dam). As the Strait of HAMMAM dam decreased by 0.13 square meters and the Gilan GHARB dam decreased by 0.07 square meters. Also, small changes occurred in the surface (SARPOL-E-ZAHAB SARAB-GARM) (drinking water source of the region), SIRVAN river and canals), and there were a total of 7523421 square meters of changes in the surface water resources of the study area after the earthquake.

The earthquake caused the outflow of groundwater and decreased the volume of dams in the region and fed the surface rivers of the region, including (the Sirvan river) and finally caused water loss and in some places caused the drying of springs and Damage to normal living conditions.