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To identify genotypes tolerant to drought stress in rice germplasm, a factorial pot experiment was carried out in the form of a completely randomized design with three replications and 70 rice genotypes originating from Central and West Asian countries in non-stress and drought-stress conditions at the Rice Research Institute of Iran, Rasht, north of Iran, in 2019. Based on the results of this year (i.e. 2019), 19 genotypes selected and cultivated in the form of randomized complete block design with three replications in two environments (normal and drought stress) in 2020. Based on tolerance and sensitivity indices and the results of cluster analysis, rice genotypes were divided into two groups, and based on the comparison of means and deviations from the total mean, genotypes of the second group (Shirodi and Neda (Iran), Sela-Zodras and Shisham-Bagh-2014 (Afghanistan) and Dijla (Iraq) recognized as stresstolerant genotypes. Also, six genotypes (Nada and Shiroudi (Iran), D3 (Iraq), Sela-Zodras, Jalal-Abad Indica-2014, and Shisham Bagh-2014 (Afghanistan)) were identified by biplot analysis and the ranking method of seven genotypes (Shirodi, Neda and Gilaneh (Iran) Sela-Zodras, Jalal Abad Indica-2014 and Shisham Bagh-2014 (Afghanistan) and D3 (Iraq) were recognized as drought stress tolerant genotypes. Altogether, based on the methods of cluster analysis, biplot, and ranking, the genotypes of Shiroudi and Neda (Iran), Sela-Zodras, and Shisham Bagh-2014 (Afghanistan) were recognized as drought tolerant genotypes. The mentioned selected genotypes can be used in advancing breeding programs for developing new rice genotypes with higher tolerance to drought stress. [ABSTRACT FROM AUTHOR]

Drought is a continuous period of lack of rainfall that leads to damage to a variety of water consumers, especially in the agricultural sector and reduces their yield. Drought is considered one of the unpredictable disasters. Drought is different from other natural disasters such as floods, earthquakes, storms, etc. Based on the type of meteorological, hydrological, or agricultural droughts, various indices are designed to assess droughts such as SPI, PDSI, and SWSI. The objective of this study is to evaluate an integrated index that includes the main causes of drought. The integrated index includes various drought factors such as meteorological, hydrological, agricultural, socio-economic, and environmental. Isfahan province has been selected as a case study due to successive droughts in recent decades. A combination of static and dynamic layers has been used for designing the integrated index. Static layers include land use, slope, and soil type of the basin. Dynamic layers include precipitation, average temperature, available surface water, available groundwater, groundwater quality, and cultivated area. The results showed that the highest water stress occurred in the 1386 and 1391 years in the province and the lowest water stress and wet season in different parts of the province in 1387 and 1390 years. [ABSTRACT FROM AUTHOR]

At present, the occurrence of dust storms is one of the most important environmental problems in Khuzestan Province, and the south and southeast regions of Ahwaz have been recognized as one of the interior dust sources and are the priority of corrective operations. Given that land use change is one of the desertification factors in the mentioned region, therefore, modeling its changes is necessary and provides useful information for planners to control and revive the degraded lands. The objective of this study was to evaluate the efficiency of the CA-Markov model in predicting land use changes in the dust source of south and southeast of Ahwaz based on two long-term and short-term approaches. In the long-term approach, land use maps of 1986 and 2002 years and in the short-term approach, land use maps of 2002 and 2007 years have been used to predict land use for the year 2016 and then the simulation results were validated. The results showed that the values of allocation error, quantity error, and kappa coefficient for the long-term approach were 42.55%, 13.95%, and 0.08 respectively, and for the short-term approach were 12.56%, 10.42%, and 0.22 respectively, which indicates the weak ability of the CA-Markov model to evaluate the desertification trend in the dust Source of south and southeast Ahwaz. Use of uniform transition rule throughout the simulation period without considering the factors and processes affecting land use change, the non-same trend of land use change during study periods, changes due to human activities, drought, and long forecast period can be the reasons for the poor performance of the CA-Markov model to predict the desertification trend the dust Source of south and southeast Ahwaz. [ABSTRACT FROM AUTHOR]

In drought risk management, the regional analysis of drought is significant. In this paper, this important issue is investigated by presenting the new hydrological regional drought index (RDI). For this purpose, the Ajichai basin was selected as the study area. First, the time series of the streamflow drought index (SDI) was calculated for each of the hydrometric stations in the basin f regional analysis of hydrological drought. Then, to determine the homogeneous regions in terms of hydrological drought, the k-means method was used for clustering analysis. Based on the clustering results, 6 Homogeneous regions were identified in the basin. For each of these regions, the time series of the RDI index was calculated from 1365 to 1393. The results showed that during the study period in each of the regions 1, 2, 3, 4, 5, and 6, mild Wet and mild drought has occurred at 82.1, 80.1, 78.9, 83.3, and 84.3 percent of regions, respectively. Also, the total percentage of drought events (moderate and high) is higher than the total percentage of wet events (moderate and high) in all regions. So, during the study period, the total percentage of drought events (moderate and high) is more than twice the total percentage of wet events (moderate and high) in regions 2 and 3. [ABSTRACT FROM AUTHOR]

In order to evaluate dry matter remobilization to seeds in the winter type rapeseed cultivars grown under drought stress conditions, an experiment was carried out using a randomized complete block design arranged in a split plot with three replicates in Shahre-Qods, Iran, in the 2011-2012 growing season. Irrigation treatments including control (irrigation after 80 mm evaporation from evaporation pan class A) and drought stress (irrigation withholding starting from stem elongation, flowering and silique formation stages) were allocated to the main plots and three winter type rapeseed cultivars (GKH2005, Opera and SLM046) were considered as the subplots. The results showed that drought stress increased dry matter remobilization and remobilization efficiency. By contrast, agronomic traits such as the number of siliques on the main stem and secondary branches, number of seeds per silique, 1000 seed weight, oil yield, harvest index and productivity effort (silique dry weight/biomass ratio) were decreased. The GKH2005 cultivar showed the maximum seed yield, which was 1058, 1409 and 2099 kg ha-1, when irrigation withholding started from stem elongation, flowering stage, and silique formation stages, respectively; this was due to the higher amount of remobilization and the efficiency of remobilization and maximum number of silique in the secondary branches. In general, the results suggest that higher remobilization and remobilization efficiency are among the most important drought stress tolerance mechanisms in the oilseed rape. [ABSTRACT FROM AUTHOR]

The first and most important issue in forest drought management is knowledge of the location and severity of forest decline. In this regard, we used geostatistics and artificial neural network methods to map the dieback intensity of oak forests in the Ilam province, Iran. We used a systematic random sampling with a 250 × 200 m grid to establish 100 plots, each covering 1200 m2. The percentage of the declined trees in each plot was measured and recorded. Also, a composite soil sample was extracted from the center and the four corners of each plot in order to determine their physical and chemical properties. After examining the normality of the data, the dieback intensity map was made using interpolation methods and the artificial neural network. The results showed that the best method for dieback intensity estimation was the artificial neural network with an accuracy of 85%, by using the multilayer perceptron algorithm. Oak decline was found to be mainly related to the slope, soil moisture, soil organic content and soil bulk density. [ABSTRACT FROM AUTHOR]

Droughts are natural events and could lead to declining surface water quality of regional basin. Understanding the complex impacts of drought may help authorities to monitor changes in different regional basin and to make appropriate decision on development of a river basin management plan. In this study 20 years annual precipitation time series from 1994-2013 from 7 synoptic weather stations located in the Halil-Rood basin were analysed using both Standard Precipitation Index (SPI) and Reconnaissance Drought Index (RDI) and then dry (-1.35 to -1.75) and wet years (1/7 to 2.45) were determined by model simulation studies. Several climate based drought indices and remotely sensed based drought indices were used for monitoring and evaluating of drought. The impact of drought on the water quality parameters in the study area was evaluated. Results showed that there was significant relationship between most of the examined water quality parameters (Ca2+, Mg2+, HCO3-, SO42+, Na+, total dissolved solids TDS, SAR) and drought, however there was no significant relationship between water pH and drought. The study indicated that focus on the drought indices might be helpful as a tool in improving surface water resources management under drought condition and may promote sustainable water resources utilization and management in the study area. Also, dividing the Halil-Rood basin into several homogeneous regions is recommended for future studies to prepare a better ground for studying the effect of drought on the quality of water at a regional scale. [ABSTRACT FROM AUTHOR]