Nowadays, dried lakes have turned into important dust sources with serious environmental, climatic and socio-economic impacts. In this study, climatic, terrestrial and anthropogenic effects that caused desiccation of the Urmia Lake, NW Iran are investigated. The main objective is to assess the influence of climatic and regional factors against anthropogenic and local ones in the dryness of the lake during the last two decades. Annual temperature, precipitation and wind speed data measured at nearby meteorological stations, along with water discharge of eight main rivers flowing into the lake are analyzed. The results reveal that the main cause for turning Urmia into a dried lake bed was human interference, since climatic factors contributed positively but to a lesser degree, while terrestrial factors may also play a crucial role. Among anthropogenic interferences, the construction of a causeway had a weak effect in the lake's dryness, while construction of many river dams highly contributed to this disaster. Furthermore, four machine learning models showed that groundwater decline is also an important factor for lake's desiccation. Analysis of dusty days at stations in the Urmia Basin showed similar inter-annual and seasonal dust variability over the whole western Iran. This indicates that dust over the Urmia Basin is mainly affected by the regional dust activity, while the dried lake beds contribute to a lesser degree to the enhanced dust loading. The dominant wind flow is mostly southwesterly, carrying Urmia saline dust toward NE directions, affecting Tabriz city. Three main synoptic clusters, with dipole features consisted of high-pressure systems over Europe, Central Mediterranean and North Africa and low pressure over SW Asia, facilitated strong westerly winds from arid, desert areas of the Middle East toward the Urmia Basin during 118 dust storms in the region.
