Investigating the role of climatic factors and human activities on water level changes in Maharloo Lake - Iran

Over the last few decades, the water level appears to have declined for most of the Lakes as a consequence of global warming. Besides, in addition to climatic factors, human activities have had a profound impact on lowering the lake's water level and ecosystem changes. In this research, Landsat satellite images from 1987-2021 for mapping the water level changes in Maharloo Lake and simple image difference technique and principal component analysis (PCA) and fuzzy logic have been used to map the intensity of changes. Then, the trend of climatic factors (rainfall and evapotranspiration) and water balance (flow and underground water withdrawal) in the Maharloo Lake region was analyzed during the last five decades, using Man Kendall and Petit Tests. The results of changes in the water level of Maharloo Lake show that during the years 1987 to 2021, the water level of the lake has decreased by 78%. With the decrease of the lake water level, the amount of uncovered and saline soils has increased to 46% and 85%, respectively. The results of the intensity of the changes show that 82% of the changes were between 100-50%. Therefore, the highest intensity of change with a 22% reduction in its area is related to the water area of Maharloo Lake. According to the results of the two tests, rainfall in recent years has not changed significantly at the level of 1% probability, but potential evapotranspiration has been the most important climatic factor in reducing the lake water level. Human activities in the Maharloo basin have been significant through an uncontrolled increase in groundwater utilization and a decrease in the inflow of Shiraz Dry River to Maharloo Lake.