Showing 28 results for خشکسالی
Mrs Zahra Ebadi Nehari, Dr Mahdi Erfanian, Mrs Sima Kazempour Choursi,
Volume 23, Issue 68 (3-2023)
Abstract
Drought is a complex phenomenon caused by the breaking of water balance and it has always an impact on agricultural, ecological and socio-economic spheres. Although the drought indices deriving from remote sensing data have been used to monitor meteorological or agricultural drought, there are no indices that can suitably reflect the comprehensive information of drought from meteorological to agricultural aspects. In this study, the synthesized drought index (SDI) as a synthesized index from the vegetation condition index (VCI), temperature condition index (TCI) and precipitation condition index (PCI) were used for comprehensive drought monitoring in the Urmia Lake Basin (ULB) based on the Principal Component Analysis (PCA). For this purpose, MOD13A3, MOD11A2 and TRMM 3B43 data series were downloaded y for the period of 2001–2012. After initial processing, drought indicators were calculated using LST NDVI and TRMM data, and monthly drought severity maps were prepared. In order to validate SDI index, the Correlation relationship between SDI and SPI indices was obtained in the 3 month period during the growing season. As well as, SDI correlation relationships were investigated with wheat and barley crop yields. The results indicate that drought occurred in 2008 and 2001 in the ULB. The results of validation show that there is a correlation of 80% between the two SDI and SPI indicators. Also, the results of this study showed that the SDI index, as a comprehensive index of drought monitoring, reflects the effects of drought on agriculture.
Fatemeh Yadegarifar, Mohammadreza Poodineh, Morteza Esmaelnejad,
Volume 23, Issue 68 (3-2023)
Abstract
In the meantime it can cause serious and irreparable damage to other social, economic and structural sectors of society. A look at the history of human life on Earth shows that human beings have always been exposed to all kinds of natural hazards. Natural hazards have many types, one of which is drought and water crisis. The recent droughts in Iran and the severity of the damage indicate the continued vulnerability of urban and rural areas. At present, drought management in our country is based on crisis management and thus less attention is paid to drought impacts and preparedness. Therefore, the purpose of this study is to evaluate the resilience of Zahedan city against water crisis and drought. The present study is applied in terms of purpose and in terms of research, descriptive and analytical. The statistical population of the study is all households in Zahedan city based on the census of 1395 168480 households (672589 people). From the household heads, a sample size of 383 people was selected randomly using Cochran formula. Descriptive statistics and inferential statistics were used to analyze the findings. The results of one-sample t-test show that the economic, social and institutional resiliency status in Zahedan city is lower than the average (2.815, 2.873 and 2.886, respectively); The results showed that Zahedan city is not in a good position in terms of resilience to drought and water crisis and this city has many water problems in rural areas and Zahedan city. Rural water shortages and droughts have caused extensive damage to farmers and ranchers. The effects of the water crisis on the economic, social and environmental structure of the villages have been very negative and these negative effects have ultimately led to the migration of villagers to Zahedan
Hadi Zare Khormizie, Hamid Reza Ghafarian Malamiri,
Volume 23, Issue 69 (6-2023)
Abstract
Knowledge of rangeland vegetation characteristics as well as factors affecting it in environmental planning, land management and sustainable development is very important. However, regional and up-to-date maps of pasture vegetation cover are not always available. In this study, in order to plot the vegetation cover percentage of the rangelands and monitor its changes in drought and wet periods, NDVI products of MODIS sensor during the years from 2000 to 2017 with a spatial resolution of 250 m and a 16-day time resolution, and The SPI drought index were used. The study area is the part of the rangelands located in the Southern province of Yazd. In 2013, in order to provide ground truth data, a field work was done to take the sampling rate of vegetation from the rangeland level in the study area. According to the results, the NDVI index has a good ability to map vegetation cover, so the coefficient of determination (R2) between this index and the sample points was 0.71. Based on the results, the average vegetation cover of the studied area was 11.3% during the years 2000 to 2017. The highest and lowest amount of vegetation cover in the study area was in 2000 and 2002, with moderate mild conditions and very severe drought, respectively (14.6% and 9.2% respectively). The most important factors influencing the vegetation cover in the study area are rainfall and drought periods, so that the coefficient of determination (R2) between the SPI drought index and the average vegetation percentage was 0.85. In general, based on the results there is a high potential for assessing and monitoring rangeland vegetation changes using satellite data and remote sensing technique.
Dr Raoof Mostafazadeh, Engr. Roghayeh Asiabi-Hir, Engr. Seyed Saied Nabavi,
Volume 23, Issue 69 (6-2023)
Abstract
Drought is the main causes of significant water imbalance, increase of crop losses or limitation in water consumption, and finally large number of socioeconomic and environmental problems. Precipitation amount is the most important climatic variables that its spatiotemporal variability has a great influence on water resources availability along with the effects of climate change. The Angot index is an indicator to determine the climatic cycles of precipitation as the ratio between the average values of multiannual precipitation over wet and dry periods which highlights the climate significance of monthly precipitation to detect dry or rainy intervals. The aim of this study is to assess and calculation of the Angot inxed in analysis of dry and wet periods of monthly rainfall in rain gauge stations of Ardabil province. The maximum values of Angot index were observed in November and May months. The results proved the suitability of the Angor index in determining wet and dry months and the comparison of the employed index with other common drought indices (e.g. Standardized Precipitation Index) and also different climatic zones of Iran needs further investigations.
Masood Safari Aliakbari, Mohammad Reza Poodineh, Mohammad Azadpour,
Volume 23, Issue 70 (9-2023)
Abstract
The drought occurs in a large number of livelihoods of rural households, especially in villages of border areas facing livelihoods. To deal with these effects, the use of coping strategies in rural areas is essential. Therefore, considering the importance of this issue, the purpose of this study was to investigate the effects of drought on rural communities and identify strategies for coping with its implications in border villages in Zahedan. The present research is in terms of purpose, applied and method of combined (quantitative and qualitative). The data collection tool and questionnaire were observed and interviewed with farmers and villagers. The statistical society is related to rural households in Zahedan (10278 households), which uses a simple quota and random quota sampling 380 Household was selected as the first instance. In order to analyze quantitative data, Johansson's exploratory test was used. Exploratory interviews were used to investigate and analyze qualitative analyzes. The results showed that drought in Zahedan city villages had the greatest effect on reducing water resources, cultivation, employment, income, rural poverty, number of livestock or animal products, rural migration, vegetation loss, erosion and soil salinity and reduced price Had land and land. The results of the use of coping practices among farmers in the region showed that the status of using these actions is not suitable, and more than half of the farmers do not use these methods. However, some farmers have used more relatively simple and low cost methods that do not need to specialize and with the characteristics of border villages. In terms of farmers, such as smuggling fuel and goods, leaving the village and migrate to the city, addressing non-agricultural jobs, flooring or lyrics of Qanat and manual nutrition of livestock as the most important methods for compatibility with drought and decrease The effects are it.
Roghayeh Delaram, Samad Fotohi, Mohsen Hamidianpoor, Morteza Salari,
Volume 24, Issue 72 (3-2024)
Abstract
The subsidence phenomenon is considered one of the most frequent hazards occurring worldwide and imposing irreparable damages every year. This phenomenon affects the ground’s surface and its layers and causes the ground deformation. It can be referred to as a morphological phenomenon that is associated with the gradual sinking of the ground and the vertical movement of materials. Among the various methods used to study the land subsidence pattern, the Differential Interferometric Synthetic Aperture Radar (DInSAR) technique has provided more accurate results. Therefore, this technique was used to investigate the subsidence rate in Mashhad plain from 2003 to 2010 and the Envisat ASAR (C-band) and Sentinel-1 ASAR (C-band) satellite images were employed during the year 2019. The results show that the highest subsidence rate of about 44 cm occurred in Qasem Abad and Kalateh-ye Barfi lands from 2008 to 2010. A subsidence rate of about 37 cm was also observed in the same area from 2007 to 2009. The interpolation results using piezometer well statistics show a decrease in groundwater levels in this area and confirm the accuracy of the results.
Shamsallah Asgari, Tayeb Razi, Mohamadreza Jafari, Ali Akbar Noroozi,
Volume 25, Issue 76 (3-2025)
Abstract
Due to the significance of forests in both the natural and human environment, this study aims to investigate the impact of meteorological drought on oak forest dieback in Ilam province. Specifically, the study seeks to determine the relationship between Zagros Forest drought and droughts in this particular region. The analysis utilizes the Standard Precipitation Index (SPI) to identify the frequency of droughts during different time periods. The results indicate that the years 2007, 2008, 2011, 2015, and 2016 experienced the highest occurrence of droughts. Additionally, remote sensing data from MODIS images were employed to examine the trend in tree greenness (NDVI) from 2000 to 2016. The analysis reveals a significant correlation (R2 = 0.9999) between the greenness trend and the drought index (SPI). Moreover, a land survey of oak drying points and simulation using Landsat satellite images, with a 15×15 pixel output from GIS software, indicate that approximately 17,894 hectares of forests in the region experienced drying and destruction between 2000 and 2016. By combining the oak forest drying layer with the output layers derived from drought zoning, visual indicators were created, and statistical analysis was conducted for three 5-year time series. The results demonstrate a correlation coefficient of 96.6% and an explanation coefficient of R2 = 0.985 for the 2002-2006 time series, a correlation coefficient of 95.4% and an explanation coefficient of R2 = 0.980 for the 2007-2011 time series, and a correlation coefficient of 98.8% and an explanation coefficient of R2 = 0.995 for the 2012-2016 time series. These findings illustrate the influence of drought and its variations in terms of intensity and duration on oak forests in the Zagros region of Ilam. Based on the study results, it is predicted that if the drought persists with the same trend, approximately 1,118.4 hectares of oak forests in Ilam province will dry up and be destroyed annually.
Mr Danesh Nasiri, Dr Reza Borna, Dr Manigheh Zohorian Pordel, Dr. Kamran Jafarpour Ghalehteimouri,
Volume 25, Issue 79 (12-2025)
Abstract
Widespread and frequent droughts in recent decades in Khuzestan province have become one of the most important challenges of this province. The use of remote sensing products in temporal and spatial monitoring of drought can play a key role in managing this risk and reducing and adjusting its destructive effects. The main goal of this research is to provide a remote sensing index for temporal and spatial monitoring of drought in Khuzestan province and its validation using station meteorological drought indices. In this research, by using the products of vegetation (MOD13C2) and land surface temperature (MOD11C3) of MODIS sensor, a drought index based on vegetation called VHI plant health index was produced. SPI Meteorological Drought Index, which was based on station rainfall data during the statistical period of 2000-2012, was used to evaluate and quantify this index. The comparison of VHI drought index with three-month SPI meteorological drought index values showed a significant correlation between 0.68 and 0.75. By identifying 4 years with widespread and relatively severe drought in Khuzestan province (based on both VHI and SPI indices), which included the years 2000, 2005, 2012, 2015, the spatial distribution pattern of meteorological drought and VHI plant drought to In general, it indicated that the northern parts of the province were generally involved in mild to moderate droughts and the southern parts were generally involved in moderate to severe droughts. The spatial correlation matrix based on the number of 2500 pixels with dimensions of 5x5 km, which included VHI and SPI values of selected drought years, indicated the existence of a significant spatial correlation between the two mentioned indicators. In the widespread drought of 2000, at the level of Khuzestan province, two drought indices VHI and SPI, the correlation was equal to 0.47, and in 2005, equal to 0.35, and
