Mehdi Ahmadian; Moloud Sadat chavoshian; Mohammad Darvish
Volume 22, Issue 1 , June 2015, , Pages 109-120
Abstract
In recent years, the depletion of groundwater resources has been increased by the population explosionand the development of agriculture and industry. In this study, the geo-statistical methods were used to study the spatial and temporal variations in groundwater level in Kaboudrahang-Famenin plain. ...
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In recent years, the depletion of groundwater resources has been increased by the population explosionand the development of agriculture and industry. In this study, the geo-statistical methods were used to study the spatial and temporal variations in groundwater level in Kaboudrahang-Famenin plain. For this purpose, available data of region including information about piezometers and monitoring wells were collected and then, database was composed. Next, the control of data accuracy was carried out. For comparison of geo-statistical methods, the variograms were plotted respectively and the different interpolation methods such as kriging (simple model), cokriging and Inverse Distance Weight with powers 1 to 5 (IDW) and radial basis functions (Thin Plate Radial Function, Inverse Multi Quadratic and Multi Quadratic) for groundwater zoning were used. The best interpolation method was selected by using two criteria, Root Mean Square (RMSE) and General Standard Deviation (GSD), and finally the zoning map of groundwater level was drawn in Arc-GIS software. The results of spatial statistical analysis indicated that the best variogram models for groundwater level data in the first period (1989), in the middle period (1993&1999) and the last period (2006) were spherical, circular and pentaspherical models, respectively.Evaluation of various interpolation methods with using "cross validation criteria" showed that in the investigation period, cokriging had the lowest estimation error compared with other interpolation methods. Thus, Cokriging was the most suitable interpolation method. The results of interpolated digital maps during the study period showed that the maximum fall of water table in 17 years was recorded to be 55 meters for central east region of plain. This shows the dramatic reduction in groundwater reserves of the region, which would not lead to industrial and agricultural sustainable development.
Marzieh Ghomishoun; Arash Malekian; Khosro Hosseini; Saeed Gharachelo; Mohammad Reza Khamoushi
Volume 19, Issue 3 , December 2012, , Pages 535-545
Abstract
Nowadays, water resources scarcity has become one of the most important issues in arid and semi arid regions including Iran which makes it necessary to optimize the utilization of these limited resources. This research surveyed the variations of EC, TDS, Cl-, SO4--, Na+ for an eleven-year period base ...
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Nowadays, water resources scarcity has become one of the most important issues in arid and semi arid regions including Iran which makes it necessary to optimize the utilization of these limited resources. This research surveyed the variations of EC, TDS, Cl-, SO4--, Na+ for an eleven-year period base on the data collected from selected wells of Semnan Plain. In order to select the appropriate model to fit to experimental variogram, Residual Mean Square Error was used. Several geostatistical approaches such as simple kriging, ordinary kriging, simple cokriging, and ordinary cokriging as well as other deterministic interpolation methods including Inverse Distance Weighing (IDW) with different powers were considered. Then, validation approach and Mean Absolute Error (MAE) criteria were considered to determine the most appropriate interpolation technique. Meanwhile cokriging method was selected as the fit method for qualitative parameters which illustrated the variations of groundwater quality in almost 67% of the cases. Comparison of quality parameters of spatial zoning maps showed that the rate of these parameters was developing in the core shape to the selected wells 15 and 13 and also, it had an increasing trend in plain boundaries for an eleven-year period. But there were no significant changes in the centers of plains. According to the results, lithology, unsustainable harvesting of wells, increased evaporation and thus reduced level of ground water and inappropriate methods of irrigation and agriculture were identified as the most effective factors.
Reza Bagheri; Sedegheh Mohammadi
Volume 19, Issue 2 , September 2012, , Pages 283-296
Abstract
This study was performed in order to determine spatial variations of drought in Kerman province by Standard Precipitation Index (SPI) and comparing interpolation methods of Kriging and inverse distance weight with powers of 1 to 5, over a thirty-year period (1970-71 to 2000-2001). According to the results ...
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This study was performed in order to determine spatial variations of drought in Kerman province by Standard Precipitation Index (SPI) and comparing interpolation methods of Kriging and inverse distance weight with powers of 1 to 5, over a thirty-year period (1970-71 to 2000-2001). According to the results during the study period (10-year intervals), maximum and minimum average amounts of SPI were respectively recorded for 1990-91 and 2000-2001. In all studied years, exponential model was determined to be the best variogram fitted to the spatial structure of data and the effective range of each station was a distance of almost 18.03 kilometers for all years except 1990-91 with an effective range of 5, 02 km. Cross validation techniques introduced Kriging as the best interpolation method for all years except 1990-91 in which IDW to the power of 5 was the best interpolation method. Spatial zoning map of SPI showed that moderate drought was recorded for southern parts of Kerman province such as Anbarabad and Jiroft in 1970-71 while in other parts of the province slight drought was observed except Rafsanjan. In 1980-81, slight drought was observed for most parts of the province while in Bam, Bardsir and east of Jiroft slight moisture was observed. In 1990-91, there was a slight drought was recorded for Kerman, Baft, Kahnooj and east of Jiroft. In 2000-2001, all parts of the province were at risk of drought as in the southern half of the province (Baft, Anbarabad and Kahnoj) moderate drought and in the northern half of the province(Kerman, Rafsanjan and Bardsir) slight drought were observed. Error maps showed considerable accuracy of interpolation, especially near the stations.
Sadigheh Mohammadi; Ali Salajegheh; Mohammad Mahdavi; Reza Bagheri
Volume 19, Issue 1 , June 2012, , Pages 60-71
Abstract
Due to the variation of ground water properties in temporal and spatial scale, these properties can not be assumed constant over time and space. This research was conducted to assess spatial and temporal variations of ground water table in Kerman plain during a 10-year period (1375-1385) by using the ...
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Due to the variation of ground water properties in temporal and spatial scale, these properties can not be assumed constant over time and space. This research was conducted to assess spatial and temporal variations of ground water table in Kerman plain during a 10-year period (1375-1385) by using the best geostatistical estimator. Firstly, available statistical resources related to the ground water table of this plain (including 67 wells) were collected. After controlling for quality, accuracy and normality of the data, different interpolation techniques were used including kriging (with and without logarithm), cokriging, inverse distance (with exponents of 1 to 5). The best technique was selected based upon MAE and MBE criteria and provided spatial zonation maps in the beginning and end of the period. Spatial zonning maps were prepared at the beginning and end of the study and ultimately, iso-falling map was provided in Arc GIS 9.1 package. Our findings showed that Gaussian variogram model was the best for spatial structure of these data and inverse distance method with exponents of 5 and 4 were the best interpolation methods in the beginning and end of the period, respectively. Zonation maps showed a falling trend of the ground water level in majority of the plain. Maximum falling data (32 meters), was recorded respectively for the northern outlet of the plain with an effective range of 17 and 62 pizometers and western outlet with an effective range of 8 pizometers. Also, the results showed an upward trend of water, as 7 meters, in effective range of some wells with 50 and 52 pizometers in Kerman city due to being located in sewage and waste water zone of the city.