Quantifying the Zayandeh Rud River drying effects on land surface temperature and adjacent vegetation cover changes over the past 33 years using satellite images

Monitoring of water changes in human settlements especially in rural areas is essential because of its importance and vital role in sustainability as well as its effect on the natural environment of the village. The current research has investigated the effects of the Zayandeh Rud River drying on the Land Surface Temperature (LST) and vegetation in the years 1990 to 2023 using Landsat-5 and Landsat-8 multispectral and thermal images. For this purpose, two indices of the Normalized Difference Water Index (NDWI) and Normalized Difference Vegetation Index (NDVI), together with LST, and Hot Spot were calculated, and their changes in three levels of the river, One-kilometer buffer from the river and rural settlements were investigated. Based on the results, the years 2000 and 2008 were identified as the years in which the river flow was drier than the other years, and the years 1990, 2013, 2018, 2022, and 2023 were identified as the years with more water flow. The results showed that in dry years, NDWI and NDVI values tended to have small positive values, and in wet years tended to have smaller negative values. Also, dry years had higher LST and occupied a larger area of warm temperature classes. Dry years also had more hot spots than cold spots compared to wet years. The results of the correlation between parameters also showed a negative relationship between LST and NDVI and NDWI in all years and a positive relationship between NDVI and NDWI in drier years. Also, the correlation of the distance from the river was only significant in 1990 and below 100 meters, positive with LST and negative with NDWI. The results of the present study are useful for the planning and proper management of water resources and rivers in Iran