This study aims at identifying suitable sites for underground or subsurface dams using a spatial multicriteria evaluation (SMCE) for water supplies in an arid watershed in southwestern Iran. Specific constraints and three groups of criteria were used in developing a spatial decision model. Constraints included slope, fault, land use, and geology. Site characteristics were classified based on slope, geomorphology, infiltration, precipitation, geology, and distances from roads, from rock materials sites, from faults and springs, from rivers and streams, and from various land uses. A criteria tree was designed and standardized using Boolean logic and fuzzy membership on factors. Factors were weighed by both ranking and direct methods. Finally, the composite index map (CIM) was used to identify three best sites. With valley shape consideration, Site2 was the most suitable for construction of a subsurface dam. Interpretation of valley profile, optimum decisions on subsurface dams, and multicriteria for site selection can be used in water resource planning.

Air pollution has very damaging effects on human health. In recent years the Coronavirus disease (COVID-19) pandemic has created a worldwide economic disaster. Although the consequences of the COVID-19 lockdowns have had severe effects on economic and social conditions, these lockdowns also have also left beneficial effects on improving air quality and the environment. This research investigated the impact of the COVID-19 lockdown on NO2 and O3 pollutants changes in the industrial and polluted cities of Arak and Tehran in Iran. Based on this, the changes in NO2 and O3 levels during the 2020 lockdown and the same period in 2019 were investigated in these two cities. For this purpose, the Sentinel-5P data of these two pollutants were used during the lockdown period from November 19 to December 05, 2020, and at the same time before the pandemic from November 19 to December 05, 2019. For better results, the effect of climatic factors such as rain and wind in reducing pollution was removed. The obtained results indicate a decrease in NO2 and O3 levels by 3.5% and 6.8% respectively in Tehran and 20.97% and 5.67% in Arak during the lockdown of 2020 compared to the same time in 2019. This decrease can be caused by the reduction in transportation and socio-economic and industrial activities following the lockdown measures. This issue can be a solid point to take a step toward controlling and reducing pollution in non-epidemic conditions by implementing similar standards and policies in the future.