mahdieh soltani Gerdfaramarzy; gholamali mozafari; Shahab Shafie
Abstract
Extended Abstract Introduction Droughts are one of the most common climatic changes that occur in many arid and semi-arid regions of the world with high intensities every few years. In many years, the occurrence of droughts is also unknown for a while, therefore, the identification of drought itself, ...
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Extended Abstract Introduction Droughts are one of the most common climatic changes that occur in many arid and semi-arid regions of the world with high intensities every few years. In many years, the occurrence of droughts is also unknown for a while, therefore, the identification of drought itself, is considered as a valuable finding for managing the water resources in areas such as Iran, most of which are formed by arid and semi-arid regions. Precipitation is the most important determinant variable in drought conditions among climatic variables. Rainfall is the most important variable whose variations are directly reflected in soil moisture and surface runoff, variations in underground water reservoirs and others. The purpose of this research is to investigate the best method of drought interpolation in the Yazd-Ardakan plain, to identify areas at risk of this phenomenon and to identify its spatial distribution, and also to investigate the relationship between drought and the salinity of groundwater and the spatial distribution of saline water in the Great Plain of Yazd – Ardakan. Materials & Methods In this research, regarding the lack of long-term statistical period of some stations and considering the distribution of stations in this basin, the annual precipitation data of meteorological stations of Yazd - Ardakan plain during 2 long term period of 7 meteorological stations (1346-1391), and short term precipitation and salinity period of 41 meteorological stations and 47 underground water wells (1375 to 1391) have been used all together. The standardized drought index for the determining drought condition and descriptive statistics methods in SPSS software has been used to describe the state of groundwater salinity using Excel software. The Pearson, Man-Kendhal, and Spearman correlation analyses were also used to determine the relationship between drought and the state of salinity of groundwater. Finally, the Geographic Information System (GIS) was also used to map the zoning of groundwater salinity. Results & Discussion The results of the assessment showed that in the correlation analysis with all 3 Pearson, Man-Kendhal, and Spearman statistics, a negative trend along with inverse correlation is observed between the precipitation (SPI) and salinity based on the Z grade,, in none of which the significant level is observed. The existence of a strong correlation between these two parameters with a one year delay was among the other results of this research. Using GS+ and GIS, the best variogram model was selected and the maps of drought, groundwater salinity and salinity variations were also drawn. Generally, in most stations with negative precipitation trend, a positive trend of underground water salinity is observed, and groundwater quality has also changed more strongly in areas with more drought outbreak and its salinity has also increased. Conclusion The occurrence of droughts, on the one hand, increasing water demand in the area, on the other hand, exacerbate the shortage and need for water. Therefore, the monitoring of future droughts and wet years should be considered very important in terms of management strategies of the region. Passing such crises require the efficient management of water resources under present conditions, especially during drought periods. Usually, during such a period, the region’s water shortage, are provided from the groundwater resources and through increasing the water extraction from wells, to meet basic needs such as drinking. Therefore, in such cases, the quality issue of the extracted water from these wells becomes more important. The available statistics show that the water quality in the Yazd-Ardakan plain (electrical conductivity) is a function of annual precipitation (as the most important feature of droughts in the region), and with the annual precipitation increasing and decreasing, the groundwater quality also undergoes changes. In general, the results of the analysis of the studied parameters indicated that the climate of Yazd-Ardakan plain was associated with a rainfall reduction trend, which is one of the important factors of drought, so that, its consequences have also affected the level and quality of water resources. It has been observed in this research, that droughts have had a considerable effect on the salinity of groundwater in most of the areas. Therefore, it is generally stated that the groundwater quality has changed more strongly in areas with more drought outbreaks and its salinity has increased.
Monir Darestani Farahani; Mahdi Akhondzadeh Hanzaei; Farhang Ahmadi Qivi
Abstract
Abstract
Water salinity is one of the important environmental factors of the sea and plays a significant role in the study and prediction of the oceanic surface currents, location analysis of the fish aggregation, density determination and studying its changes, and also in ecological properties. This ...
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Abstract
Water salinity is one of the important environmental factors of the sea and plays a significant role in the study and prediction of the oceanic surface currents, location analysis of the fish aggregation, density determination and studying its changes, and also in ecological properties. This parameter changes greatly with time and location, and proper recognition of it requires measurements at short time intervals (monthly) of multiple points in the study area.
In traditional ways, the assessment and evaluation of one or several specific factors of water quality is often costly and time-consuming, and cannot be a good indication for the entire area of a vast region. But in recent years, satellite and remote sensing technology have been considered as an appropriate tool for evaluating some water quality parameters because, given the digitality of these data, their wide availability, regular measurements, their repetition in short periods of time, Less cost and time, a wide range of projects can be achieved. The purpose of this study is mapping sea surface salinity of the Persian Gulf in Iran and the Gulf of St. Lawrence in Canada using MODIS satellite imagery. In this regard, a software has been produced in Iran for the first time that can prepare salinity, temperature and density maps of the sea surface in three different models with proper accuracy by entering the MODIS satellite imagery and CTD field data. High capability and flexibility of the Artificial Neural Network in approximation of nonlinear and linear continuous functions in hybrid space, led this study to provide a new method based on using this network in which salinity map is determined by a multilayer perceptron network.
Mohammad Zeinali; Ali Asghar Jaafarzadeh; Farzin Shahbazi; Shahin Oustan; Khalil Valizadeh Kamran
Abstract
Abstract
Soil salinity and salinization of lands as one of the problems facing agriculture, has paramount importance and should be avoided with proper knowledge of its progress. The first step in this way is to identify saline areas and prepare the salinity maps for these soils. With the development ...
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Abstract
Soil salinity and salinization of lands as one of the problems facing agriculture, has paramount importance and should be avoided with proper knowledge of its progress. The first step in this way is to identify saline areas and prepare the salinity maps for these soils. With the development of remote sensing technology and efficient use of satellite imaging, this research aimed to compare the prepared salinity maps with various types of image classification algorithms (Maximum probability, Minimum distance from the mean and Parallelepiped) by Landsat-5 satellite data with TM sensor in a part of the eastern lands of Khoy city. Therefore, 269 soil samples were analyzed with specific geographic coordinates and the results were plotted on TM image. For initial identification, topographic maps and ENVI 4.8 software were used to process satellite images and geometric corrections were made with specific points using GPS. Educational and experimental samples were located on the desired image with an appropriate distribution and salinity classes were determined from 1 to 9. Samples of each class of salinity due to having coordinates were placed accurately and with single pixel size in each image on the corresponding pixel and were stored with ROI format. The results indicate the existence of correlation between bands 1, 4, and 5 of TM image with salinity data, and the highest accuracy of the map among the classification algorithms in the Pixel-based method, is related to the maximum probability. In order to evaluate the accuracy, indices such as error matrix, Producer’s veracity, User’s authenticity, overall accuracy, and kappa Coefficient were extracted. Also, the correspondence of various salinity classes of this map with field observations and measured salinity level indicate the high accuracy of this algorithm in preparing a surface soil salinity map. The aim of the present study is to compare the prepared salinity maps with the results of other researchers by these methods in the area of interest.
