Climate Study of Changes of Major Water Resources in Qom Province Using Satellite Data and Remote Sensing Technologies

Numerous studies have been carried out on climate change and weather change. Some of these studies include the study of surface water resources. Because these water resources are, on the one hand, highly affected by climate change, they also affect the Peripheral environment and the Environment. Most of the studies in this field are based on the data of meteorological stations, hydrometer stations and different satellite images. Landsat satellite imagery is well suited for studying for decades, due to its relatively old age. The purpose of the present study is to study the changes of Namak (salt) Lake and Hoz-e Soltan Salt Lake using quantitative and qualitative meteorological data of ground stations and Landsat satellite images.

First, using the available climatic parameters, the period and time steps of the study were determined. These parameters included mean temperature, maximum and minimum temperature, rainfall, relative humidity, evaporation and so on which were measured at three stations of Qom province including Qom, Salafchegan and Kahak stations. This was done by routing and examining climate change and climatic mutations in each of these parameters. In such a way, by using graphical representation and appropriate statistical test, unusual changes were extracted and that special year were excluded. Next, images of Landsat satellites were taken at selected times in the previous step. These images were pre-processed, processed and post-processed. Classification indices of four classes of water, salt land, common soil land and vegetation were applied and localized in Qom province.

Based on the study of changes in climate parameters, inappropriate years eliminated and study times from 1989 to 2019 with 5-year time steps were selected. Images of these times were classified for the Namak Lake, Hoz-e Soltan Salt Lake and their surrounding environment using the Support Vector Machine (SVM) method in ENVI software. This classification was applied to the images every seven steps and yielded the area of each class of water, salty soil, common soil, and vegetation. The results of classification were controlled by the visual method and a number of ground samples. Next, the class changes were modeled and calculated. The rate of change of each class and its conversion into other three classes were calculated between the time steps and its results were presented as a change matrix. The change matrix was expressed as a percentage of change and as a change in metric units (square meters). On this basis, it was possible to survey the major changes of each class and study it.

In general, the trend of climatic parameters and the water zones of Qom province changes have been similar. During the study period for the Hoz-e Soltan wetland basin, the mid-study period of about 2004 with a surface area of 61667 hectares can be considered the driest year in the period of study. In the case of the Namak Lake, the years 2004 to 2014 are also the driest years. 2009 is the driest year in the study area, with an area of about 281 hectares. Investigating these changes by identifying the basin of both water resources and their differences will provide valuable information to researchers.