Showing 7 results for Spatial Distribution
B. Ghahreman,
Volume 7, Issue 2 (7-2003)
Abstract
An intense storm occurred on June 6, 1992 in Mashhad city and its suburb, which caused a flood in the residential areas of Najafi, Chahar-cheshmeh and Nodareh. As a consequence of the abnormally huge flood, 25 people lost their lives and many structures were destroyed. Three recording rain gages located in Mashhad city (airport, College of Agriculture, and Water Authority) and one in the suburbs (Toroq dam) recorded the temporal distribution of the storm. Twenty five other nearby rain gages in the region also recorded the event. The rainfall hyetographs and rainfall amounts were analyzed.
The results of this survey showed that: a) maximum rainfall intensity over a 15-minute duration in the College of Agriculture station, one of the centers of the storm, was 112 mm/hr, b) temporal distribution of rainfall for all recording stations were nearly the same, c) these patterns were in close agreement with all historic storms, and d) a return period of 380 years was implied via comparing the maximum rainfall intensity with relevant IDF curves. As a consequence, although an intense storm had happened, it was simply an outlier.
E. Sahebjalal, F. Dehghany, M. S. Tabatabaeezade,
Volume 17, Issue 65 (12-2013)
Abstract
Groundwater is the most important source of water supply for agricultural purposes in arid and semi-arid areas. In many areas, excessive use of high quality water resources leads to reducing the available water resources and turning to the use of low quality water resources. Thus, knowing the temporal and spatial variation of groundwater quality is a necessary factor for implementation of sound water resource management and establishment of the suitability between water quality and its usage. In order to investigate water quality changes, this study was divided into two phases. In the first phase, for evaluation of the quality of groundwater for irrigation 76 wells were sampled in Bahadoran plain, in the year 2006. The SAR, EC, ions B3+ and Cl- were analyzed as the evaluation indexes. Then, using geostatistical methods the maps of each parameter were prepared. Finally, considering FAO criteria, these maps were overlaid and separate water quality maps were derived. The EC map indicated that in 48 and 52 percent of the groundwater lies in severe and slight to moderate restriction class for irrigation purposes. Moreover, the thematic map of infiltration restrictions indicates that the groundwater has no restriction in 66 percent of the area while 11% of groundwater causes low to moderate and 23 percent causes severe limitation. In the next phase, to examine changes in groundwater salinity during a 5-year period, 38 wells were sampled and the groundwater salinity map for the year 2011 was prepared. Finally, using subtraction of the salinity maps of given years, the salinity changes map was derived. The results of thematic map showed that groundwater salinity increased in 26.47 percent of the study area. In contrast, there was a decrease of about 31.14 percent in groundwater salinity over the 5-year period while 42.39 percent of the region’s groundwater remained unchanged. Since the study area is under cultivation of pistachios and salt threshold of this tree is 8 ds/m so the area of about 8 percent of the area was added to the previous limited areas. Therefore, irrigation management and planting development plan in Eastern and Southeastern areas should be revised.
F. Jafari, H. Khademi,
Volume 18, Issue 70 (3-2015)
Abstract
Dust deposition occurs extensively in arid and semiarid regions of the world. Since dust particles are fine-sized, they have a high adsorption capacity and also high contamination potential. The objective of this study was to evaluate the temporal and spatial distribution of the rate of atmospheric dust deposition in different locations in Kerman urban area. Dust samples were collected monthly using glass traps installed on the roof of 35 one-story buildings in Kerman for 7 months from April 20 to Nov. 20, 2012 (a total of 245 samples). After each monthly sampling, traps were washed and dust samples transferred to the laboratory and weighed. The mean dust deposition rate of 7 months was mapped using the inverse distance weighting (IDW) approach. The wind rose of Kerman was drawn by WRPLOT 7.0.0. The results showed that the average rate of dust deposition decreased during the 7 months studied from 17.4 to 5 g/m2. month, which could be attributed to the decrease in wind velocity. The spatial distribution of the samples also showed that the dust deposition rate varied from 4.84 in the southern parts to 14.84 g/m2.month, mostly in the northern locations of the city. The wind rose based on the average wind speed of the 7 months of sampling indicated the prevailing wind blows from north, northeast and northwest and the dust spatial distribution well follows the wind direction. In general, the rate of dust deposition in Kerman city is high and therefore, the source of dust has to be well detected and proper management practices are necessary.
S. Norouzi, H. Khademi,
Volume 19, Issue 72 (8-2015)
Abstract
Spatial and temporal distribution of dust deposition rate (DDR) in Isfahan city and the influencing climatic parameters were studied. Dust samples were collected using glass trays placed on the roof of one-story buildings from 20 sites in Isfahan city for 12 months. Climatic data were obtained from Meteorological Organization and analyzed. The highest and the lowest amount of DDR in agreement with the direction of prevailing wind were observed for dry months with eastern and northeastern wind directions and wet periods with western and southwestern wind directions, respectively. This can indicate dust emission from the desert located in eastern part of Isfahan city. Statistically significant inverse correlation between DDR and precipitation and relative humidity, and significant and positive correlation of DDR with Min and Max temperatures in all the studied months and also with Max and average wind speed for dry sampling months may well justify the temporal distribution of DDR in the city. In dry months, finer particles from eastern desert can be transported a longer distance and deposited in the western part of the city, far from the source area. In wet seasons, however, soil aggregates become coarser as a result of particle adhesion. This, in turn, results in the deposition of dust near the source area as the transporting power of dust reduces.
A. Khosravi-Dehkordi, M. Afyuni, A. Soffianian,
Volume 20, Issue 77 (11-2016)
Abstract
Pollutants are considered the disturbing factors of environment, and among them the heavy metals are more important considering their non-degradability and physiological effects on organisms in low concentrations. The goal of this research was to investigate the effect of industrial landuse on Cd and Pb concentrations in surface soils of the southwest Isfahan. According to satellite images and topographic maps (1:50000) of the study area, soil samples (depth: 0–20 cm) were collected using random sampling. A total of 38 surface soil samples were obtained from industrial areas (lowest distance = 1480 m) in the area of 73481 ha. Total concentrations of Cd and Pb in the digested solution were measured by Atomic Absorption Spectrophotometry (AAS). Using Arc GIS, the spatial distribution patterns and Cd and Pb variography of samples were analysed and finally the best models of spatial distribution of heavy metals were achieved. The primary results showed that the mean concentrations of Cd, and Pb of surface soil samples in industrial areas were 1.8 to 31.5 mg Kg-1 higher than the world’s mean values, respectively. Although the mean concentrations of Cd and Pb were respectively 8 to 700 mg Kg-1 lower than the standard of Iranian Department of Environment for industrial landuse.
E. Moradi, D. Namdar Khojasteh,
Volume 24, Issue 4 (2-2021)
Abstract
Wind erosion is one of the environmental problems worldwide, particularly in arid and semi-arid areas of Iran. Different methods and models have been proposed to measure and monitor wind erosion in the recent years. One of the accurate models for measuring f wind erosion is the USEPA model. The purpose of this study was to evaluate the quantification of wind erosion with the USEPA model and the comparison of different interpolation methods for drowsing high-precision soil erosion mapping. For this purpose, 50 samples from 0-30 depth were taken from the study area. Based on the analysis of the physical properties of the soil, including the distribution of the primary and secondary particle sizes, climatic parameters such as evaporation and transpiration, rainfall, wind speed and also, the vegetation and topography characteristics of the area, the erosion rates of Q, Q30 and Q50 were measured. Interpolation methods including general kriging, IDW, LPI and RBF were compared. The results showed that the highest erosion emission rate of Q50 was 39 ton ha-1. The highest and lowest erosion rates for the Q30 index were 0.060 and 2.694 ton ha-1, respectively; for the Q index, the highest and lowest erosion rates were 0.009 and 0.055 ton ha-1, respectively. The results also showed that the IDW method for the Q50 index with the minimum error rate (RMSE) values of 3.94 and the mean absolute error (MAE) with the valueof 1.89 had the best performance among the studied models. The LPI model Q had the best performance with the lowest error (0.0086) and absolute absolute error (0.0021).
Z. Savari, S. Hojati, R. Taghizadeh Mehrjerdi,
Volume 25, Issue 3 (12-2021)
Abstract
Soil salinity and its development are the main problems that should be prevented by correct management methods. Recognition of saline districts and the preparation of salinity maps are the first steps in this way. Nowadays, the application of auxiliary data in digital soil mapping is increasing due to the current associated problems in the preparation of traditional maps. The objectives of this study were to map soil salinity by the Regression Kriging (RK) method, to identify areas with high salinity, and to investigate the relationship between soil salinity and soil-forming factors in Khuzestan Province. For this purpose, 291 surface soil samples (0-10 cm) were randomly collected in April 2014. Auxiliary variables or soil-forming factors were included in the land parameters such as slope, watershed and wetness index, OLI and TIRS images of Landsat 8, and the category maps (soil, land use, and geological maps). Also, kriging approaches were used to compare the precision of different mapping methods. The results indicated that the Regression Kriging method has a higher precision compared with other methods so that the coefficient of determination, Mean Absolute Error (MAE), and Root Mean Square Error (RMSE) were estimated as 0.84, 0.41, and 6.21, respectively. The Decision Tree Regression method could also create a good relationship between soil salinity and auxiliary variables. The results showed that some auxiliary variables were more effective on the prediction of soil salinity including 2, 4, 5, and 7 bands of Landsat 8, Brightness Index, Wetness Index, Multiresolution index of Valley Bottom Flatness (MrVBF), Channel Network Base Level (CNBL), NDVI, SAVI and soil map. A Digital map of soil salinity was prepared by the obtained rules, and then it was assimilated with the map of error of variance to prepare the final soil salinity map. Accordingly, soil salinity was found to have an increasing trend from north to south in Khuzestan Province which indicates a salinity problem in the south of the Province. The main reasons for the high salinity in the south and southwestern parts of the area could be attributed to the high water table levels, differences in topography, capillary movement of salt to the soil surface, the difference in the type of land uses, and also groundwater quality and irrigation water which is altered by the frequent application of wastewaters and animal manures.
