Why water bodies of Iran have been dried up?

The status of natural water bodies in terms of water quality and quantity can be considered a criterion for the environmental status of their upstream catchment. The presence of natural water bodies with good condition can be a sign proper of water resource management activities in the upstream catchment for sustainable development. Iran has been undergoing a rapid development process in recent decades. Nowadays, in most water bodies in Iran, the water level has been decreased and even disappeared in some cases. Lake Urmia is a well-known example of drying lakes in Iran. This study aims at identifying the main effective drivers in drying up of the main lakes in Iran.

Iran is a country with an approximate area of 1,648,000 km2 that has an arid and semi-arid climate with an average precipitation of 311 mm/year. The most important water bodies in Iran are Lake Urmia and Maharloo, Hoor-al-Azim and Gavkhuni Wetlands, and Gorgan Bay. This study focuses on the mentioned waterbodies and upstream catchment information.

At first, climate conditions and changes such as drought and changes in their properties are studied to find the answer to this question. Then, non-climatic factors and their changes such as urban/rural population changes, industrial growth, agricultural changes such as land area, crop yield, and the type of irrigation were studied. To achieve this purpose, the time series of the surface level of these five waterbodies was measured using satellite images. Then the time of significant changes in the time series of the surface level of each waterbody was determined using the Pettit test. As a result, the time interval for each waterbody was divided into a two-time span, before and after the change point. This created a time interval for climatic and non-climatic comparisons to identify effective factors.

The climatic data from the synoptic stations located in and around each waterbody catchment have been used to study the climatic conditions, and the sum of precipitation and mean temperature have been evaluated as the main climate parameters along with the SPIE drought index and characteristic changes. In order to evaluate effective non-climatic factors, changes in urban/rural population factors, agricultural land level, the number of agricultural products, and industrial units were used based on official statistics.

The results of this study indicate that the year of significant changes in the time series of lakes was between 1996 and 2001. Crop yield change growth was the main factor in the upstream catchment of all lakes as a result of changes in the irrigation patterns.