جستجوی مقالات مرتبط با کلیدواژه « هم بستگی » در نشریات گروه « آبخیزداری، بیابان، محیط زیست، مرتع »

This study examines the trend of ET0 changes using the Mann-Kendall nonparametric test and predicts it using time series analysis. To calculate FAO-Penman-Monteith ET0, Tmin and Tmax, RHmin and RHmax, sun-hours and wind-speedy of synoptic station Khorramabad during the 1991-2017 were used. The results showed that the trend of annual change in reference evapotranspiration with the Mann-Kendall statistics 0.2, was not statistically significant. The trend of monthly changes showed that the trend in September and July was decreasing by Mann-Kendall statistics -0.2 and -0.7, and in the rest of the months, it was increasing. In the stagnation time series check, the trend and ACF graph, showed an increasing trend in the series. for staging the series, the method of differentiation was used and the data were stagnant withfirstfirst-ordered differentiation. For modeling with SARIMA model, from period 1991-2015 for the modeling and from period ‎‎2016-2017 model verification was used, and condition of normality, accidentally and independent ‎of residual of the fitted model was examined. The results showed that the SARIMA‎(0,1,1)(1,0,1) for ET0 modeling, has the best accuracy. The RMSE and R2 ‎values for prediction with this model were 0.674 and 0.97 mm/month, which indicates that the ‎model is accurate.‎

Sediment yield estimation for small basins is essential in watershed management planning projects. However، almost all of these basins are ungauged. In this study، in order to determine a range for specific sediment yield and to develop a regression model for estimating annual sediment yield، sedimentation behind small dams within 25 basins in Western Azerbaijan province، were measured. The selected basins with an area ranged 29 to 1200 ha، cover a range of lithology، land uses and climates and all of the sediments had been trapped behind the check dams. The specific sediment yields showed a two digit differences ranged 0. 12 and 12. However، the weighted average of specific sediment yield for all basins was calculated a low value of 1. 3. Study of relationship between annual sediment yield and 18 characteristics of watersheds using correlation matrix showed that the sediment yield is significantly affected by geologic erodibility، basin area and land use factors. From several regression models which were developed، an equation including two independent variables، geologic erodibility and basin area، with a high determination coefficient (R2=0. 899) was chosen.

Homogeneity of soil particles is the potent factor which affects soil spectral signatures and known as the Geometric Standard Deviation of soil particles (σg). This study presents the influence of σg on spectral studying of soil texture using four spectral data sets of LISSIII-P6 and was coincident sampling operations. Subsequent to satellite data preprocessing، some operations were done such as: Normalized Difference Vegetation Index، Principal Component Analysis، Soil Line Euclidean Distance and Unsupervised Classification on acquired data. By stratified randomized sampling method and according to the false color composite and photomorphic units of the main image of the study area، 95 sample points were eventually selected and gathered from 0-5cm of soil surface. Afterwards، geometric standard deviation (σg) and texture fragments were determined for each sample point in the soil lab. Samples were accordingly divided into two parts، on the basis of the computed geometric standard deviation: the first، σg <10 (homogeneous soil) and the second، σg ≥10 (heterogeneous soil). Subsequently via correlation operations for both group، it was expressly displayed which in the first group (σg <10)، clay and sand had about 0. 7-0. 8 correlations with the remotely sensed data، whereas the second group (σg ≥10) had about 0-3-0. 4. Hence، the geometric standard deviation (σg) of the study region can powerfully impress soil spectral reflectance.