Journal of Water and Soil Conservation
Year:2009 | Volume:16 | Issue:2|Papers Count:18

This study was done in order to submit a model for salinity map made with ETM+ satellite data and salinity values in a district in North of Agh Ghala in Golestan province. The Geometric and atmospheric correction of Satellite images were carried out Processings such as; multispectral bands fusion with panchromatic band, tasseled cap transformation, principal component analysis, and ratioing for composite bands creation were done. The regular sampling grid with 2×10 km dimension and different intervals were designed and performed on the study area. Soil samples (169 samples) were taken from 0-5 cm depth with intervals of 50, 100, 250, 1000 m and their electrical conductivity (EC) were measured. The location of the samples was determined by GPS and samples location map was made with GIS software. Spectral values for each sample were extracted by different bands. Correlation between spectral values i.e. (main bands, tasseled cap bands, principal component analysis and composite bands) with electrical conductivity values were investigated for 80% of the samples. By determining correlated bands and selecting desirable bands for contributing in model, primary results showed that correlation between electrical conductivity values with B4 bands, brightness, greenness and fuse B4 were significant in 1% level. After selecting the best model, cross validation was calculated with 20% samples for determinating ME and RMSE parameters. Cross validation results showed the suitable estimation of model with ME and RMSE values was equal to -0.18 and 55.6 dS/m, respectively. Finally, salinity map was prepared using submitted regression model. In this research, results confirmed that salinity changes can be evaluated by digital data of ETM+ and it's composites in district of north Agh Ghala with 2000 ha area.

The vegetation and plant cover decrease the velocity of surface runoff and increase the soil infiltration rate. Consequently plant cover has an important role to reduce destructive floods. The study area with its erodible soil, is faced to natural hazards as well as soil erosion. This paper was prepared according to a research project findings aimed to investigate the relationship between plant cover and surface runoff. The study area is a part of kechik watershed that is distinguished as a set of pair catchment protected for about 5 years. Two catchments including protected and unprotected have been considered as hydrologic units. The basic information including physiography, geology and hydrology were collected. The plant cover was measured through 1*1 random-systematic quadrats. The rainfall and its related discharge were measured. Statistical tests were also performed to determine the difference and relationship between two catchments via Spss and Minitab softwares. The results showed that the differences in plant cover of the catchments were significant at p=0.05 level the average of plant coverages were %96.2, % 52.9 and the runoff amounts were %17.43, %35.38 in protected and unprotected catchments respectively. The regression coefficient between rainfall intensity and runoff were 0.76 and 0.8 for unprotected and protected catchments respectively. The difference between produced runoff of two catchments was significant at %1 level. In general it is believed that the protection at a management plan is one of the most important way of contro surface runoff and related flood that should be considered in watershed management specially in the study area in North-eastern of Golestan province.

Sediment control at lateral intakes is known as a very common problem and the most complicated issue for river engineers. Since a larger portion of the near-bed flow is diverted, the intake will receive a relatively large amount of bed load materials. Thus, appropriate and reliable methods are needed to minimize the amount of diverted sediment materials into the intake of a river. In this research, a laboratory study was carried out to explore a possible solution method using two types of river structures simultaneously including a set of submerged vanes and a single spur dike. Submerged vane by setting a tip vortex and a helical flow in downstream, can reduce the movement of bed sediment flow into a diversion. In this study, the optimum dimensions, number and array of vanes were selected as determined by the regular design method. For guiding flow into the diversion and increasing the vane performance, a single spur dike in opposite side of intake was utilized. The main goal of the experiment was to evaluate the effect of spur dike length, the location of intake, and the angle of attack on reducing the movement of bed sediment into the diversion. Experimental tests included three lengths of spur dike: 15, 20, 25 cm with 0, 40, and 80 cm distance from the intake with angles of 45°, 90° and 135°, respectively. The results showed that the effective performance of the vanes increased and Concequently eliminated the bed sediment ingestion into diversion at qr=0.3 once they used with a single spur dike at opposite side of the intake. An average reduction of 40% in sediment ingestion into diversion was observed a spur dike located at a distance of twice intake width from the centre line as. Furthermore, the results indicated that among the three angles of spur dike investigated, the sediment movement into the intake was minimized by using an angle of 90°.

In order to study the soil clay minerals behavior as affected by land use change and land degradation, a loess hillslope located in Agh-Su watershed, eastern Golestan province was selected. Illite and chlorite are dominant minerals in loess parent material. The major clay minerals in the forest soil and adjacent deforested cultivated area were according to the following orders: illite > smectite> kaolinite > chlorite > vermiculite and illite > chlorite > kaolinite > smectite respectively. Illite, chlorite and kaolinite are mainly of inheritance origin. Deforestation and soil erosion has led to an increase in the amount of these minerals in the cultivated land use due to outcropping of parent material. Origin of smectite is believed to be both inheritance and also transformed in the study area. Illite and chlorite can transform to smectite in the presence of more soil available-moisture mainly due to leaching and release of K+ from their structures. Natural forest cover has provided higher moisture and consequently more smectite in forest land use relative to adjacent cropland. Soil loss, absence of permanent vegetation, weak leaching and lower soil moisture are the main reasons for the rare occurrence of smectite in the deforested area. Vermiculite is mainly observed in weak acidic forest soil where agroclimatological index, P/ET, (ratio of mean annual precipitation to mean annual reference crop evapotranspiration) is more than 0.4. Long-term tillage practices and severe soil surface erosion has distributed subsurface calcareous material through out soil profile and the consequent higher soil pH has led to an increase in vermiculite instability. Increase in illite, chlorite and kaolinite content and decrease in smectite content and also absence of vermiculite in degraded lands which were formerly under the same forest ecosystem and also most probably the same clay mineralogy indicate to the loss of topsoil and landscape instability following deforestation. In general, clay minerals and their variations besides other physicochemical and biological soil parameters can be used as a good indicator for land degradation. 

The purpose of this study was to analyze some physical, morphological and effective factors on landslide occurrence to better recognition of landslide mass behavior in the study area. Based on the mean annual rainfall of 25 years period and elevation above sea level of 12 stations located within and surrounding the study area, the rainfall gradient equation of the area was developed. Based on field surveys, aerial photographs interpretation and filling out questionnaires of landslide, some important morphometric factors including landslide deformation coefficient, landslide longitudinal deformation coefficient, landslide latitudinal deformation coefficient and landslide depth index and some effective factors on landslide occurrence such as distance to fault, manner of relation to drainage network, elevation and mean annual rainfall in 35 land sliding locations were computed. The results of statistical analysis including correlation analysis and linear multiple modeling between effective factors and landslide morphometric characteristics showed that most landslides were long with deep extension and very low longitudinal deformation and latitudinal deformation in comparison to depth. Also, decrease in elevation above sea level and increase in mean annual rainfall, have resulted in deeper and with latitudinal extension landslides, while longitudinal extension of landslides decreased. In the study area considerable amount of sediment was delivered to drainage network. because of the proximity to drainage network and land use change from forest to garden and roads in lower elevations.

This study experimentally measures the 3D flow field around the 90 degree bend as well as the bend with the T-shaped spur dike at 75-degree section. The experiments were carried out in a channel with a mild curvature. The three-dimensional Acoustic Doppler Velocimeter (ADV) was used for measuring the flow field. The three-dimensional time-averaged velocity in the 90-degree bend without spur dike and the bend with spur dike was measured. In addition in the bend with spur dike two cases of rigid bed and the bed with scour hole were compared. The longitudinal and lateral flow pattern was compared. The effects of spur dike on flow pattern were examined. In addition, the vortices and reverse flows in the up and down stream of the spur dike as well as the changes in the secondary flow are addressed in this study. The results showed that reverse flows in downstream and upstream of spur dike with rigid or equilibrium bed were formed. Flows formed in downstream were in the greater distance from outer bank than upstream. Also, the start of reverse flow of spur dike with rigid bed was noticeable within a downstream distance of 8 times spur dike length and in spur dike with equilibrium bed of 3 times spur dike length.

Radial gates are structures for discharge control and regulating the water level. For most efficient use of this instrument and by the recent progress on the automatic flow regulation schemes for the weir and water conveyance, accurate estimating of discharge coefficient of radial gates is very important. There are several experimental relations and charts for estimation of discharge coefficient of radial gates but due to some control conditions the accuracy is not acceptable for practical proposes and are often used for limited conditions. In this study a genetic algorithm program have been used for finding the optimum relation for assessing the discharge coefficient of radial gates in submerged conditions. Also several relations were examined for finding the best one, and then by using statistical assessments between the estimated and experimental data, the best non-linear relation was obtained. The relation was verified by using 50 data sets (experimental and field data) collected by different researchers and statisticd parameters such as mean, standard deviation (estimatul-measured ratio) and standard error were estimated. Theses values were 1.05, 0.204 and 0.1 respectively. The results showed the high accuracy of proposed relation in comparison with the previous studies. 

Drought is one of the most important climatic phenomena which occur in all climate conditions and regions of the earth. When the drought remains for a longtime in a region, it will affect all environmental factors in that region. Drought forecasting, therefore plays an important role in designing and management of natural resources and water resources systems, assessing plant water requirement, etc. In recent decades, (ANNs) have shown great ability in modeling and forecasting nonlinear and non-stationary time series. In this study, two types of artificial neural networks, i.e. Multi Layer Perceptron and Radial Basis Function, and ARIMA time series were applied for drought forecasting. The rainfall data of Now-deh station on Khormaloo River in Golestan province (Iran) were used. Drought conditions were calculated using SPI in short time and long time periods. Among 41 years SPI data, the first 33 years data were selected for training of models and the last 8 years data were used as test data. The results showed that artificial neural networks were able to forecast the SPI and drought conditions with higher accuracy. Meanwhile ARIMA model had also significant results for forecasting.

In this research, the spatial distribution of electrical conductivity and pH of springs, ghanats and the base flow concentration places on the streams of central and south-west and central parts of the Hamedan-Bahar plain were evaluated. Using different geostatistical methods such as Kriging, Minimum Curvature, Inverse Distance, Natural Neighbor, Local Polynomial and Radial Basis Functions, 108 water samples of different sites of the plain’s hydrographical network were sampled during July 2005 and EC and pH values were measured for each sample. The performance criteria for evaluating the used methods were Root Mean Square Error and General Standard Deviation along with the Cross Validation method. The results showed that Local Polynomial and Inverse Distance were the best methods to estimate EC and pH, respectively. Radial Basis Functions were also found as the most unsuitable method for estimating EC and pH.