Abolghasem Dadrasi Sabzevar; Alimohammad Akhondali; Fereydon Radmanesh; Aliakbar Norouzi
Volume 24, Issue 2 , July 2017, , Pages 370-382
Abstract
The purpose of this paper was to make the preparation of soil surface moisture map applied in arid and semi-arid regions using satellite imagery of OLI and TIRS along with the calculated values for spectral reflectance, principal component analysis and Tasseled Cap transformation.Twenty-four predictor ...
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The purpose of this paper was to make the preparation of soil surface moisture map applied in arid and semi-arid regions using satellite imagery of OLI and TIRS along with the calculated values for spectral reflectance, principal component analysis and Tasseled Cap transformation.Twenty-four predictor variables were used and the most correlated ones were identified at three moisture levels of 4 to 5 percent, more than 5 percent and less than 4 percent by exploratory regression and bivariate correlation method through calculating the inflation factor of variance, Pearson coefficient and coefficient of explanation. The Moran'sI index was used for geo-spatial autocorrelation. Forty-seven soil samples were collected randomly by creating 1800-meter networks in a systematic algorithm and the soil moisture was calculated by W-thermal method. The estimation functions of soil surface moisture were derived in the form of partial least square regression (PLSR), enter regression and stepwise regression. All models had acceptable calibration. Our results clearly showed that the Landsat 8 data could be useful in estimating soil surface moisture and the accuracy of the functions extracted with stepwise regression method was more than that of other methods (RMSE=0.585 to 1.425 %). The models introduced for a moisture level of ≤5%, tend to over estimate (MBE= 0.788) and for other moisture levels tend to underestimate.
Abolghasem Dadrasi Sabzevar; Mohammad Khosroshahi
Volume 17, Issue 1 , September 2010, , Pages 127-148
Abstract
Low quality flood irrigation are used on desert area of KaleShoor river of Sabzevar since 1992. The main objective of this research was to asses changes in soil salinity affected by low quality flood irrigation. To meet this, 51 soil samples were taken and tested in the laboratory for salinity and indicators ...
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Low quality flood irrigation are used on desert area of KaleShoor river of Sabzevar since 1992. The main objective of this research was to asses changes in soil salinity affected by low quality flood irrigation. To meet this, 51 soil samples were taken and tested in the laboratory for salinity and indicators require. soil samples taken from depth of 0-30cm, 30-60cm and 60-90cm at the beginning, middle and end of the cultivated rows of the land. Three soil samples were also prepared from the control area. The results showed that EC and PH values reduced in all samples, compared with control points. In addition, organic materials and sand particles which carried by flood water, improved the soil structure and texture of the study area. This study also showed that flood irrigation has been able to reduce gypsum from range of root zone and transported to lower layers.
Abol ghasem Dadrasi; Mohammad khosroshahi
Volume 15, Issue 2 , January 2008, , Pages 227-241
Abstract
One of the major consequences of desertification is development of destructive floods in spite of ground water level falling in the lower parts of basins, which will lead to water quality/ quantity decline, landslide and blending of saline and fresh water tables. Each of these symptoms individually or ...
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One of the major consequences of desertification is development of destructive floods in spite of ground water level falling in the lower parts of basins, which will lead to water quality/ quantity decline, landslide and blending of saline and fresh water tables. Each of these symptoms individually or in combination with the others clearly notifies the development of desertification. Identification of suitable areas for flood control will assist the natural aquifer recharge in the basin’s upstream and will reduce the development saline and gypsiferrous waters in the ground water of basin’s downstream and surrounding area, which in turn will cause secondary salinization in the lower parts of basins. Off course computer models are the most suitable methods for determination of the best sites in this regard, and because of variety of available models in the first step we should determine the best model. In this research compiling of effective factors using establishment of information layers and then regionalization in conceptual models which were applicable in GIS media like as Boolean logic model, overlap index model and Fuzzy logic model was used. The main research technique is analytical comparison of results using these models. These models were done in GIS media by scoring to the variables affecting flooding and aquifer recharge based on their effectiveness. We compared models due to natural conditions of the region to determine the best model for quantitative analysis of flooding in 6 towns of Khorasan-e-Razavi province, with emphasis on determination of flood control capability of these regions to combat desertification. Results showed that Fuzzy model with summation operator gives the best adaptivity compared to the other models to determine the floodable and capable for flood control areas.