Showing 72 results for Drought
M. Motavallizadeh Naeini, R. Modarres,
Volume 25, Issue 4 (3-2022)
Abstract
Dust storms in arid and semi-arid regions have harmful impacts on the environment, the economy, and the health of local and global communities. In this study, the frequency of annual dust events in twenty-five stations and five climatic variables including rainfall, maximum annual wind speed, average annual wind speed, maximum annual temperature, and average annual temperature in arid regions of Iran up to 2014 were used to show the effects of climatic change on dust storms. Annual correlation coefficient time series between climatic variables and dust storms were first calculated based on monthly observations. Then, the trend in climatic variables, dust storm frequency, and their correlation were assessed using the Mann-Kendal method. Results indicated that the correlation coefficients had fluctuations in time and are both significant and insignificant in different years that reach from 0.6 to 0.9 for wind speed and temperature and -0.2 to -0.6 for precipitation. This trend in correlation has the same direction with climatic variables and shows co-movement between climatic change and dust storm fluctuations in central Iran. Results also showed that wind speed and temperature have a high impact on dust storm fluctuations and rainfall reduction has an increasing effect on dust storms.
S. Parvizi, S. Eslamian, M. Gheysari, A.r. Gohari, S. Soltani Kopai, P. Mohit Esfahani,
Volume 26, Issue 3 (12-2022)
Abstract
Investigation of homogeneity regions using univariate characteristics is an important step in the regional frequency analysis method. However, some hydrological phenomena have multivariate characteristics that cannot be studied by univariate methods. Droughts are one of these phenomena their definition as univariate will not be effective for risk assessment, decision-making, and management. Therefore, in this study, the regional frequency analysis of drought was studied in multivariate methods using SEI (Standardized Evapotranspiration Index), SSI (Standardized Soil Moisture Index), and SRI (Standardized Runoff Index) indices in the Karkheh River basin from 1996 to 2019. The indices calculated probabilistic distribution between the variables of evapotranspiration, runoff, and soil moisture using multivariate L-moments method and Copula functions and considered meteorological, agricultural, and hydrological droughts simultaneously. The results of multivariate regional frequency analysis considering the Copula Gumbel as the regional Copula showed that the basin is homogeneous in terms of severity of SEI-SSI combined drought indices and is heterogeneous in terms of severity of SEI-SSI combined drought indices. However, after clustering the basin into four homogeneous areas in terms of characteristics of SPI (Standardized Precipitation Index), the basin is homogeneous in all areas in terms of univariate SEI, SSI, and SRI indices and is heterogeneous in the third and fourth clusters of SRI and SSI drought indices. Pearson Type (III), Pareto, normal, and general logistics distribution functions were found suitable to investigate the characteristics of SEI, SSI, and SRI drought indices in this case. Finally, large estimates of the types of combined droughts and their probability of occurrence showed that the northern and southern parts of the Karkheh River basin will experience short and consecutive droughts in the next years. Droughts in areas without meteorological data can be predicted in terms of joint probability using the multivariate regional frequency analysis method proposed in this study.
H. Babajafari, Sh. Paimozd, M. Moghaddasi, M. Hosseini Vardanjani,
Volume 26, Issue 3 (12-2022)
Abstract
Drought is one of the most complex natural disasters due to its slow onset and long-term impact. Today, the use of remote sensing techniques and satellite imagery has been considered a useful tool for monitoring agricultural drought. The objective of the present study was to evaluate spatial and temporal monitoring of agricultural drought in the lake Urmia catchment area with the ETDI drought index which is calculated from Nova satellite images based on actual evapotranspiration from the SEBS algorithm and compared with the ground index SPI. For this purpose, 248 AVHRR sensor images and NOAA satellites during the statistical period of 1998-2000 and 17 meteorological stations with a statistical period of 30 years were used to calculate the indicators. To determine agricultural lands, six thousand points were marked for different uses and their actual evapotranspiration was calculated using the SEBS algorithm. The results showed that with the onset of the drought period in 1998, the ETDI index indicated 9.4% in weak drought conditions in May and 90.6% in normal conditions. Over time, in June of 1998, the situation was different with 95% in a weak drought situation and 5% in a normal situation for the city of Tabriz. In July, the entire catchment area experiences a slight drought. Then, in August, 84% of the basin is in normal condition and 16% in Tabriz and Urmia are declared weak drought. It was also founded that the ETDI drought index due to the combination of visible and infrared bands and its combination with terrestrial data has a physical meaning and has high certainty and predicts drought faster and more accurately.
H. Nazaripour, M. Hamidianpour, M. Khosravi, M. Vazirimehr,
Volume 26, Issue 4 (3-2023)
Abstract
In this study, the decade variability of frequency and severity of drought in Iran has been investigated. The one-month scale data from the standardized precipitation-evapotranspiration index (SPEI 01) in the period 1956 - 2015 have been used. Based on the common numerical thresholds, the characteristics of the frequency and severity of drought for each pixel have been calculated and they are the basis for the analysis of the drought situation. Then, the frequency of drought severity classes was calculated and its trend was investigated using the non-parametric Mann-Kendall test. The findings indicated the spatio-temporal variability of drought frequency and intensity patterns in Iran. The frequency of mild droughts has decreased from south to north and from east to west; while the frequency of more severe droughts has increased from north to south and from west to east. The frequency of mild droughts in the southeast, northwest, and northeast has increased by 5 to 40 percent. While the frequency of more severe droughts in most parts of Iran has increased between 10 and 20 percent. Variability in the frequency of more severe droughts is more pronounced in the Central Plateau catchment area as well as in the Persian Gulf-Oman Sea. The trend of drought intensity is decreasing (drought intensification) at the same time as the prevailing rainfall regime in Iran. A significant increase in drought intensity (wet season intensification) is observed only in southeastern Iran at the same time as the monsoon regime. However, extra-arid and arid regions of southeastern Iran are affected by the frequency and severity of drought and have a high degree of vulnerability.
M. Khoshoei, H.r. Safavi, Abbas Kazemi,
Volume 27, Issue 1 (5-2023)
Abstract
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.
M. Ahmadi, H. Ramezani Etedali, A. Kaviai, A.r. Tavakkoli,
Volume 27, Issue 1 (5-2023)
Abstract
Studying the effects of drought in mountainous areas is facing problems due to the inappropriate distribution of stations, the lack of long-term data, and areas lacking statistics. Therefore, the main objective of this research was to investigate the drought indices of Kurdistan province using TRMM satellite data and ECMWF dataset, as well as to evaluate their accuracy against the data of land stations in Kurdistan province. First, ECMWF precipitation data for the 2000-2020 period and TRMM precipitation data for the 2000-2019 period were obtained and evaluated using RMSE, MBE, and correlation coefficient statistics. Spearman's correlation coefficient showed a significant relationship between the TRMM satellite precipitation data and the ECMWF dataset with ground stations at the 5% level, and the value of this coefficient was between 0.95-0.85. According to the results, it can be acknowledged that the TRMM satellite rainfall and ECMWF dataset in the monthly time scale had proper accuracy at the Kurdistan province level. Therefore, these two sources were used to examine the drought indices. SPI, SPEI, and ZSI drought indices were calculated in different monthly periods (1-48), PNI in different monthly, seasonal, and annual periods in Kurdistan province (Saqqez, Qorveh, Bijar, Sanandaj stations). Spearman's correlation coefficient indicated a significant relationship at the 5% level between the SPI, ZSI, PNI, and SPEI index of the ECMWF dataset with ground stations. The results of the SPI index showed that the lowest RMSE value for the TRMM satellite at the Saqqez station and the three months was equal to 0.45, and for the ECMWF dataset at the Sanandaj station and the 24 months was equal to 0.35.
F. Meskini-Vishkaee, A. Tafteh, M. Goosheh,
Volume 27, Issue 1 (5-2023)
Abstract
Salinity and water scarcity are limiting factors for sustainable agricultural production. The cultivation of resistant plants to environmental stresses is one of the important management factors for sustainable production. The objective of this study was to determine the water requirement and plant response coefficients to water deficit stress (Ky) in different growth stages under the Khuzestan province climate. This study was performed on the quinoa cultivar Titicaca in Ahvaz City in 2019 in a randomized complete block design with 13 treatments and three replications. Treatments include full irrigation and application of three levels of water deficit stress (30, 50, and 70% of allowable soil moisture depletion) at four different stages of plant growth. The duration of the initial, developmental, middle, and late growth stages of quinoa was 24, 28, 32, and 18 days, respectively (total growth period=102 days). The highest quinoa yield was obtained in full irrigation treatment (3700 kg ha-1) with a water requirement of 312 mm. Plant response coefficient to water deficit stress in the initial, developmental, middle, and late stages were 0.8, 0.65, 0.74, and 0.47, respectively. Although quinoa is a drought-resistance plant, it should be noted that the water stress in the two initial and middle stages (quinoa sensitive growth stages to water stress) reduces the quinoa yield significantly that should be considered in the planning of deficit irrigation.
H. Jafarinia, A. Shabani, S. Safirzadeh, M.j Amiri,
Volume 27, Issue 2 (9-2023)
Abstract
Due to the climatic conditions of Iran, increasing water scarcity, and the effect of drought stress on the efficiency of irrigation water consumption and chemical fertilizers application, an experiment was conducted to investigate the effect of irrigation intervals (6, 9, and 12-day intervals), different levels of nitrogen fertilizer (200, 300, and 400 kg urea per hectare) and cultivation methods (on-ridge or heeling up and in-furrow) on yield and productivity of sugarcane as a factorial design based on randomized complete block design in 3 replications at Hakim Farabi Agro-Industry Company in Khuzestan province. The results showed that the maximum (106.73 tons/ha) and minimum (59.10 tons/ha) sugarcane yields were observed in 9-day and 12-day irrigation intervals, respectively. Also, the highest sugarcane yield (99.89 tons per hectare) was obtained in the treatment of 400 kg urea per hectare and the in-furrow planting method resulted in a higher yield compared to the on-ridge planting method. The highest water productivity in sugarcane stem yield and sugar production with 3.55 and 0.34 kg per cubic meter of applied water, respectively, was obtained in a 9-day irrigation interval. A significant increase in water use efficiency in sugarcane stem yield was observed in 400 kg urea/ha compared to the other two fertilizer levels. However, there was no significant difference in water productivity of sugar yield between different fertilizer treatments. The results showed that 6 and 9-day irrigation intervals in most of the studied traits were not significantly different. Therefore, using a 9-day irrigation interval is suggested in the studied area when the sugarcane cultivation area is high and the amount of available water is limited. In-furrow planting method can also be effective in reducing water consumption. Therefore, deficit irrigation and proper nitrogen fertilizer consumption can be very effective in sugarcane cultivation.
E. Taheri, F. Mousavi, H. Karami,
Volume 27, Issue 2 (9-2023)
Abstract
One of the basic steps in water resources management and planning according to population increase and lack of water resources in Iran is to optimize the use of dam reservoirs. In this research, the effect of meteorological droughts on the optimization of the Aydoghmoush dam reservoir in the northwest of Iran was evaluated by applying metaheuristic algorithms under the impact of future climate change. Three models and two scenarios of SSP2-4.5 and SSP2-8.5 of the sixth IPCC report, and the LARS-WG downscaling model were used for Aydoghmoush dam weather station for the base period (1978-2014) and future periods of 2022-2040 and 2070-2100. The inflow and outflow of the dam, as well as the optimal utilization of the dam reservoir, were evaluated using standalone, and hybrid mode of genetic, slime mold, and ant colony algorithms. Results of the best release scenario (SSP2-8.5) showed that the annual rainfall in the future periods will decrease by 8.9 mm, and 14.5 mm, respectively, compared to the base period. The objective function of optimizing the use of the dam reservoir was defined as minimizing the sum of squared relative deficiencies in each month and maximizing the reliability in the statistical period of 2011-2021. The results showed that in terms of time reliability, vulnerability, and stability, the hybrid slime mold-genetic algorithm was better than other algorithms with values of 0.73, 0.32, and 28.78. Prediction of the dam's inflow and outflow using the hybrid slime mold-genetic algorithm indicated high accuracy compared to other models by 13% and 19% errors, respectively.
S. Afshari, H. Yazdian, A. Rezaei,
Volume 27, Issue 3 (12-2023)
Abstract
Awareness of the types of vegetation changes and human activities in different parts has particular importance as basic information for different planning. It is very difficult and expensive to collect information about the continuous changes in vegetation cover by conventional methods. Therefore, the use of new technologies such as remote sensing is very beneficial. The objective of the present research was to introduce the appropriate vegetation index and determine the vegetation cover of the Abshar network. NDVI, EVI, SAVI, and MSAVI vegetation indices were calculated from 2000 to 2021 every year and monthly in the Google Earth Engine system using Landsat 7 satellite images of the ETM+ sensor. Also, the SPI drought index was calculated using the precipitation statistics of Kohrang station in Excel software. The results of the comparison of four indices showed the superiority and higher performance of NDVI compared to the other three indices for detecting vegetation changes. Then, vegetation changes were calculated. The results showed that the trend of agricultural development in the Abshar network is downward and has a direct relationship with precipitation and the SPI drought index. Also, the results indicated that the SPI drought index was equal to -1.73in 2008, which showed a severe drought in the region. Comparing these results with the vegetation area showed that the vegetation area was 35721 hectares in this year and the year after the drought (2009), the vegetation area was 22950 hectares. Therefore, there was a decrease in precipitation and a sharp decrease in the SPI index in 2008, which led to a sharp decrease of 35% in the vegetation area in 2009.
S. Gholizadeh Tehrani, S. Soltani Koupai, R. Modarres, V. Chitsaz,
Volume 27, Issue 3 (12-2023)
Abstract
Drought is one of the most destructive and important climate phenomena, whose effect is usually more important on a regional scale. The importance of this phenomenon is more evident in the Karkheh basin due to its size and important role in providing the country's water resources. We aim to monitor hydrologic drought using the accurate calculation of standardizes streamflow index (SSI) in one month time scale based on fitting frequency distribution to monthly data and goodness of fit test for each station in Karkheh basin for 30 years (1986-2016). The findings of this research showed that the generalized Pareto distribution was selected as the most appropriate distribution in most months, unlike the previous research that fitted and used only the Gama distribution on the data. The time series of the standard flow index indicated the occurrence of super-drought in 2008 to 2015 years. Also, the significant impact of the construction of hydraulic structures upstream of the basin on the average flow rate was observed in some stations. The results of direct and annual monitoring of the drought situation showed that the Karkheh basin has experienced hydrological drought in recent years, and the drought trend is increasing.
M. Salari, V. Rahdari, S. Maleki, R. Karami,
Volume 27, Issue 4 (12-2023)
Abstract
the countries of Iran and Afghanistan. A long period of drought has happened in this area by human interventions after 1999. The objective of current study is to predict the Hamoun wetland situation in scenarios with and without human intervention using the Markov model-automated cellular for 2019 and the next forty years. Land cover maps of the study area using satellite images for 1987 as a normal year, 1991 as a wet year, and 2019 as a year with human effects were prepared. Then, prediction model for 2019 were prepared using 1987 and 1991 cover layers in four scenarios, prediction models were prepared for the next forty years in normal, drought, and wet conditions. If the natural process of watering of Hamoun wetland continues, lower than 362735 hectares of wetland should become watering in 2019, while, according this year land cover map, less than 50000 hectares of wetland have water. Also, by continuation of the current trend and the effect of human activities in the 40-year models, 11230 hectares of the area will be watering, and if the natural process of the wetland continued using the model of 2019 this amount was equal to 373311 hectares. The results of the research show the completely different situation of the Hamoun wetland in the case of no human intervention in the watering of this wetland in 2019 and the model of the next forty years.
