Several indicators have been proposed by researchers for the study of drought, each of which having certain strengths and drawbacks depending on the regional conditions and parameters affecting drought. In recent years, RDI has received greater attention as it accounts for precipitation and evapotranspiration, and is sometimes used as the basis for comparison of drought severity and the assessment of its potential damage at the national level. The present research examines RDI index along with benefits, drawbacks and problems of zoning and generalization of findings at the national level to provinces. For this purpose, the statistics derived from synoptic stations of Yazd province was utilized and after calculating RDI for each station, a comparison was drawn with the results presented in the national RDI map for the same time period. The results of this study provide technical points and considerations for calculating and zoning RDI at the national scale and generalizing findings to provincial levels, with special emphasis on Yazd province. It also offers relevant executive suggestions for improving the precision of drought zonation studies and methods across the country, which have been discussed in details.

Drought is a natural phenomenon with high frequency in arid and semi-arid regions of Iran, especially in the Province of Fars. Monitoring and evaluation of drought is a basic need for agriculture and water resources management to reduce its adverse effects. Reconnaissance drought index (RDI) is one of the agricultural drought indices used to categorize drought intensity. In this study, agricultural drought return period for wheat for the Province of Fars was assessed based on RDI. Twelve synoptic weather stations, with the minimum of 10 years data were selected for this purpose. Evapotranspiration was calculated based on the Penman- Monteith method, and the drought intensityof normalized and standardized RDI for each year was calculated. The results showed that the most severe drought in the Province of Fars occurred in the 2007-2008 hydrological year. After classifying the wheat drought intensity, the results indicated that the normal drought was the most prevalent in all of the selected stations. Also, zoning maps of wheat drought with the return periods of 2, 5, 10, 25 and 50 years were prepared for the Province of Fars. The results showed that the wheat agricultural drought for the Province of Fars is normal in the return periods of 2 and 5 years; however, it was different for the frequency of 10, 25 and 50 years.

Reconnaissance Drought Index (RDI) is based on fitting a Log-normal distribution to the ratio of precipitation to evapotranspiration (ETo) values in selected periods. In this index value of ETo was calculated based on mean temperature by Thorenth-Waite (Th) method. Th method may underestimated ETo values comparing to the actual in arid and semi- arid regions. The log-normal distribution maynot befitted to the ratio of precipitation to ETo values of some regions. In order to investigate the effects of these two limitations on drought situations' changes, meteorological parameters have been used during 50 years period at 8 Synoptic Stations of Iran. In the first step, the values of RDI (Th) for any stations during the mentioned time were calculated. Then, ETo values were calculated from best fitted empirical equation in any situation of lack of parameters. Subsequently RDI (select) index were established. The Kolmogorov–Smirnov (KS) test is used to assess the goodness of fitting most appropriate distribution function to the ratio of precipitation to ETo values. Then, according to equi-probability transformation the values of RDI (Th) were modified to *RDI (Th). The occurrence of different classes of drought according to RDI (select) and/or *RDI (Th) comparing to RDI (Th) showed the elimination of any mentioned limitations may leads to changing the amount of occurrence of any drought classes in RDI (Th). Hence, the RDI (Th) modified to *RDI (select) by estimating ETo values from selected method and applying appropriate distribution function to the ratio of precipitation to ETo values.

Drought is one of the most common natural events that has a great negative impact on agriculture and water resources. Using the indices is necessary in order to monitor, evaluate and statistically analyze drought in each area. Recently, a powerful drought index, the Reconnaissance Drought Index (RDI), is gaining wide acceptance mainly in the arid and semiarid climatic regions. Since RDI is based both on precipitation and potential evapotranspiration (PET), it is interesting to assess the effect of the PET calculation methods on the drought severity characterization obtained by the RDI. This paper compares the results of the RDI for various reference periods using some popular empirical PET methods with minimum data requirements. The selected methods are: Hargreaves-Samani, Thornthwaite, Blaney-Criddle, Jensen-Haise and FAO Penman-Monteith. The FAO Penman-Monteith method is used as reference method. The data used are from meteorological stations in thr Tehran Province representing different climatic conditions. No significant influence on RDI was detected by using the selected PET methods. However, the Blaney-Criddle method performed relatively better. This supports the conclusion that the RDI is a robust drought index not dependent upon the PET calculation methods.

Drought is a severe hydrological event that can cause serious problems in human life. In this context, it can have adverse effects on water supply and quality, public health, agricultural productivity, land degradation, desertification, famine, etc. (Madadgar and Moradkhani, 2014; Li et al., 2020). In a general classification, drought events are classified into four different categories, meteorological, hydrological, agricultural and socio-economic droughts (Wilhite and Glantz, 1985; Khadr, 2016). Some of the well-known and common meteorological drought indices in drought monitoring include Palmer Drought Severity Index (PDSI), Drought Identification Index (RDI), Standardized Precipitation Index (SPI) and Standard Precipitation Evapotranspiration Index. Considering the significant role of evaporation and transpiration in the water balance, it is necessary to consider its effect when studying drought in a particular region. Based on this, RDI, which includes both precipitation and evaporation and transpiration, can be considered as a reliable indicator for drought monitoring (Moeinifar et al., 1400). According to importance of drought as a natural phenomenon in hydrological and meteorological studies, its monitoring and forecasting with a suitable approach can be important. The main role of Drought prediction in risk management, reducing the effects of drought on existing water resources and their optimal use, the possibility of rational decision-making by decision makers to minimize the damages caused by drought, as well as planning and managing resource projects. It has water. (Khadr et al., 2016; Madrigal et al., 2018; Beyaztas and Yaseen, 2019). Among the models worked till date, single Kstar and GPR models are the newest models for drought prediction.

Introduction: Today, development as a process is the most important issue in developing countries, and the goal of sustainable development is to eliminate needs and improve the quality of human life. This research examines the level of development of health and educational indicators in the villages of the coastal area of West Guilan. Research aim: In this research, the investigation of effective health and educational indicators, evaluation and examination of differences to achieve sustainable development in the coastal villages of the west of Guilan province have been considered. Also, examining the strengths and weaknesses of coastal villages in the west of Guilan in terms of having health and educational indicators is also in the focus of attention. Because part of the goals of development is to concentrate and attract the population and prevent migration and turn villages into safe environments for human activity and habitation. Methodology: For this purpose, information related to 4 health indicators and 6 educational indicators for the three census periods of 2006, 2011 and 2019 was obtained from the website of the governorate of Gilan province. Then, using the Rural Development Index (RDI), the Combined Results Index (CRI) and paired t-statistics, we determined the level of development of health and education indicators in 8 parts of the coastal region over time and the significance of the difference in the level of development. It was done in three periods. Studied Areas: The geographical scope of the current study is the villages of the west coastal area of Guilan province. Results: The Variouse indexes, such as: health, education at western villages in Guilan are not suitable level and need to more attention. Conclusion: The significance of the difference of the indices during the three census periods for the two investigated states does not show significant changes that indicate the improvement of the level of development, and between the results of the CRI index of 2010 and 2018, there is a significant difference in Level not observed. The results showed that the development rating in this area is D and C, which indicates the low level of development of the western coastal area of Guilan province in line with health and educational indicators.

Monitoring and analyzing drought conditions are essential for optimal water resource management. Over the past decades, various indices have been developed to quantify drought characteristics. Given the increasing impact of climate change on drought events, selecting an index that performs effectively under changing climatic conditions is crucial. This study investigates drought conditions in the Central Plateau region of Iran from 2000 to 2021 by comparing the performance of three drought indices: The Standardized Precipitation Index (SPI), the Reconnaissance Drought Index (RDI), and the Standardized Precipitation Evapotranspiration Index (SPEI). While SPI relies solely on precipitation data, RDI and SPEI incorporate potential evapotranspiration. The effectiveness of these indices was assessed based on their correlation with soil moisture fluctuations, using the Temperature Vegetation Dryness Index (TVDI) as a remote sensing-based soil moisture indicator.  The study area comprises provinces in Iran’s Central Plateau region. SPI was calculated using precipitation data from 16 selected synoptic stations, while potential evapotranspiration for RDI and SPEI was estimated using the FAO-Penman-Monteith model. Additionally, MODIS-derived NDVI and land surface temperature data were used to compute the TVDI index.  A comparative analysis of the three drought indices, based on their coefficient of determination with TVDI, was conducted for each year of the study period. The results showed that SPI and RDI exhibited lower correlation with soil moisture (average coefficients of determination of 0.51 and 0.54, respectively) compared to SPEI, which demonstrated a stronger correlation (average coefficient of 0.66). Therefore, given its higher agreement with soil moisture data, SPEI is recommended as a more reliable index for drought assessment in arid and semi-arid regions.