Iran Drought Monitoring in April 2021 - Research Square

Iran Drought Monitoring in April 2021
 Omid Memarian Sorkhabi

 (omidmemaryan@gmail.com)

 Department of Geomatics Engineering, Faculty of Civil Engineering and Transportation, University of Isfahan,
 Isfahan, Iran.

Abstract
About a third of the world's continents and large parts of Iran are facing drought,
which is hampering water supply and water supply management. The problem of
drought is a natural phenomenon that causes water shortages in many countries every
year. Currently, about 80 countries are located in arid and semi-arid regions of the
world and Iran is one of these countries with an average rainfall of about 250 mm.
In this study, a new drought index called OMI based on GRACE-FO total water
storage (TWS) observations is developed in April 2021. The northern and
northwestern regions of Iran have lost about 0.32 meters of TWS. Central and eastern
Iran have lost about 0.18 meters of TWS. The southwestern regions of Iran are in a
better situation this month than other regions. The eastern and southeastern regions
are very mid drought, the northern, northeastern, and northwestern regions are very
severe drought. The southeastern areas are moderately drought.
Keywords: Drought Monitoring, GRACE-FO, Iran, TWS

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Introduction
The GRACE and GRACE-FO satellites have become very important in drought
studies by estimating TWS. Due to the complexity of hydrological phenomena,
satellite monitoring of water movement plays a key role. Various studies show the
success of TWS in drought monitoring [1-3].
In this research, GRACE-FO satellite data in April 2021 has been used to examine
the drought situation in Iran by province.
Methodology
The following index has been developed for Iran's drought called OM Index.

 TWSi − min(TWSm)
 OMI =
 m (TWSm) − min(TWSm)
 )1(
Where TWSi is the TWS in different areas, TWSm average monthly TWS. OMI
values are between 0 and 1, and the closer it is to zero, the drier the region than
normal, and the closer it is to one, the wetter the region than normal. Of course, the
positive and negative of TWS change the interpretation of OMI .
Results
In this research, the GRACE satellite has been used to estimate TWS based on the
proposed in-depth learning and wavelet process [4-16]. Figure 1 shows the TWS
changes in April 2021 by the GRACE-FO satellite. The northern and northwestern
regions of Iran have lost about 0.32 meters of TWS. The central and eastern areas
have lost about 0.18 meters of TWS. The southwestern regions of Iran are in a better
situation this month than other regions.

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Figure 1 TWS changes in April 2021 by GRACE-FO satellite
Figure 2 shows the OMI drought index for April 2021. The eastern and southeastern
regions are very mid drought, the northern, northeastern, and north-western regions
are very north drought. The southeastern areas are moderately drought.

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Figure 2 OMI for April 2021
Conclusion
Drought is one of the most important and destructive climatic phenomena, the
impact of which is usually more important on a regional scale. The average rainfall
of Iran in the water year 2019-2020 with a record of 342 mm caused this year to
break the record of the rainiest year in the last 50 years. However, in the following
year, 2020-2021, the amount of precipitation was 317 mm and a lower average was
recorded. The new OMI is suitable for drought studies. The eastern and southeastern
regions are very mid drought, the northern, northeastern, and northwestern regions
are very severe drought. The southeastern areas are moderately drought.
Competing interests:
The authors declare no competing interests.
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