01.03.2023 Ι A group of researchers from the German Research Centre for Geosciences found out that the main reason for the increasing water scarcity in Iran is the unsustainable use of water in agriculture.

High spatial and temporal resolution results

Researchers from the GFZ German Research Centre for Geosciences, together with colleagues from the University of Stuttgart and the Karlsruhe Institute of Technology KIT, have traced the development over the last twenty years for Iran as a whole. The study was recently published in the journal Scientific Reports.

In their work, the researchers led by first author Robert Behling of the GFZ’s Remote Sensing and Geoinformatics Section quantified the spatial and temporal dynamics of meteorological water availability, land cover, and plant growth, as well as their interactions. Special attention was paid to the development of agricultural vegetation.

The use of MODIS satellite data and other remote-sensing land cover parameters allowed obtaining results in high spatial and temporal resolution for whole of Iran. The data series from the satellite missions are of particular importance, as these missions record total water storage (surface water and groundwater) globally from space.

Agriculture expands and becomes more intensive

In recent decades, the area of land used for agriculture in Iran expanded by about 27,000 square kilometers (nine percent) and cultivation intensified on 48,000 square kilometers. By comparison, Iran’s total agricultural land covers about 300,000 square kilometers.

“At the same time, we observe a significant decrease in total water storage, which is not represented by a decrease in meteorological water input,” says co-author Sigrid Roessner of GFZ.

For the researchers, this clearly speaks for an unsustainable use of groundwater, which is mainly consumed for agricultural irrigation.

Analysis of the data showed that, as a result of water scarcity, around 10,000 square kilometers of agricultural areas experienced a loss or a reduction in vegetation growth, especially in irrigated agricultural areas under dry and extremely dry conditions. Sigrid Roessner says, “this also highlights the high vulnerability of irrigated lands to degradation and overuse in drylands.”

Natural vegetation affected by water scarcity

In Iran’s natural biomes, the results show declining trends in vegetation growth and a reduction in land cover from sparse vegetation to barren land over 40,000 square kilometers, especially in the western plains and the foothills of the Zagros Mountains. Higher regions, on the other hand, show widespread greening trends. Overall, the areas with natural vegetation show a much stronger correlation between vegetation growth and hydrometeorological water availability.

The team concludes, “overall, our results provide detailed insights into vegetation development across Iran, as well as anthropogenic and natural causes and consequences over a period of nearly 20 years. Our results allow further analysis both at the state level and at any other freely selectable spatial reference unit, and are thus usable at all administrative levels. Hence, they can support the development of sustainable management plans for the country. Our methodology, built exclusively on globally available datasets, is also applicable to all other semi-arid regions worldwide, which often face similar conditions.”