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 ...
Read More
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.
Aziz Arsham; Ali mohammad Akhund ali; Abdolkarim Behnia
Volume 16, Issue 4 , January 2010, , Pages 445-455
Abstract
Antecedent soil moisture is one of runoff and sedimentation crucial factors affected by parameters such as soil properties, topographic-, climatic-, and coverage circumstances etc. The work aimed at determining effects of soil properties and rainfall on runoff and sediment load at various antecedent ...
Read More
Antecedent soil moisture is one of runoff and sedimentation crucial factors affected by parameters such as soil properties, topographic-, climatic-, and coverage circumstances etc. The work aimed at determining effects of soil properties and rainfall on runoff and sediment load at various antecedent moisture levels. Heavy, medium and light textured field soils were selected, exposed to a constantly intensified 80mm/hr rainfall under air-dried, air-dried to field capacity point, field capacity point and nearly saturated conditions, and two slopes of 5 and 15%. Recording runoff and sedimentation values every 2-5 min; populated values were calculated within 10, 20 and 30 min. intervals. All experiments were carried out with simulated rainfall technique in a 1×1×0.1m flume. Treatments showed most significant differences within first 10min. decreased with increasing rainfall duration. Maximum runoff coefficients increased as 2-5 folds as minimum ones with all durations. When moisture increased to field capacity point, light, medium and heavy textured soils had the lowest to the highest values of runoff coefficient, respectively. Under nearly saturated condition, increasing runoff trend decelerated with heavy textured soils and decreased to a lesser extent as compared to medium textured samples. Also, sedimentation process was consistent with runoff fluctuations. Medium textured soils showed a significant level of sedimentation under nearly saturated conditions. Runoff coefficients were unnoticeably different with 5 and 15% slopes; however, a more significant sedimentation increase occurred with 15% slope.