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.
Mehdi Ahmadian; Mohammad Darvish; Mohammadreza Sadeghi Manesh
Volume 21, Issue 4 , March 2015, , Pages 604-619
Abstract
A temporary model to assess desertification and providing the map of land susceptibility to the reducing processes of land efficiency was proffered by FAO and UNEP. The results of regional implementation of the FAO and UNEP method in Gharachay watershed are presented in this article. In this method, ...
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A temporary model to assess desertification and providing the map of land susceptibility to the reducing processes of land efficiency was proffered by FAO and UNEP. The results of regional implementation of the FAO and UNEP method in Gharachay watershed are presented in this article. In this method, five major processes of land degradation were evaluated with two aspects including "current status" and "inherent risk". For any of these aspects, the maps of low, moderate, severe, and very severe desertification were separated and the area of each class was calculated. Then, the maps of main processes affecting desertification were integrated together and two maps including "current status and inherent risk" were provided. Afterward, the maps of livestock pressure and human population were prepared. In order to obtain the total risk of desertification, the four mentioned maps were integrated and finally the risk of desertification classes were calculated. In view of the current desertification status in the studied region, the following results were obtained: The highest vegetation decline (76%) was observed in the east, south, and center of the region. The highest percentage of water and wind erosion (45.2%, 57.9%) was obtained in the south and east respectively; the highest soil salinization (34.7%) was observed in the east. In addition, the highest loss of groundwater resources was observed in the center and east of the region. The highest livestock pressure (58.3%) was recorded in the center of region; however, population pressure had little impact on environmental degradation. The area of each category, including low, moderate, severe, and very severe, was calculated to be 39.4, 27.9, 25.1, and 7.3 percent, respectively. Overall, according to the obtained results, the natural and human factors, particularly livestock pressure, were effective to create these conditions.