Journal of Water and Soil Conservation
Year:2011 | Volume:18 | Issue:1|Papers Count:14

The aim of the present study, was the micromorphological investigation of development of some loess-derived soils of Golestan province along a climo -topobiosequence, starting from lowlands in north and ending to forest uplands in south. Four soil profiles, situated in aridic, xeric and udic moisture regimes selected for this study were located at 20 to 400m elevation above sea level. Disturbed and undisturbed samples were taken for physicochemical properties and micromorphological studies. The studied soils in north-south direction were classified as Gypsic Aquisalids (pedon 1), Typic Haploxerepts (pedon 2), Typic Calcixerolls (pedon 3) and Typic Hapludalfs (pedon 4). The results showed that soils in xeric and udic moisture regimes, had higher clay. Alfisols with udic moisture regime and forest land use, were weakly acidic, but at the semiarid climate, gypsum and calcite accumulation caused an increase in pH. In Aridisols and subsurface horizons of Mollisols, crystallitic b-fabric was dominant. Whereas Alfisols showed striated-speckled b- fabric. Subangular blocky microstructure is dominant in Alfisols, Aridisols and Inceptisols. The granular and crumb microstructure were also observed in surface horizons of Mollisols. Moreover Mollisols, showed higher porosity. Quantitative microscopic studies were done using Image Tool software and image analysis techniques. From aridic to udic moisture regime more variation in porosity were observed. In soils of xeric moisture regime, various forms of pedofeatures including calcite and Fe-Mn coatings were observed. In soils of udic moisture regime, clay coatings and clay fragments were dominant. Gypsum pedofeatures were dominant in arid soils.

Drought is a creeping natural hazard with large extent of occurrence, causes considerable damages to different economical parts of our country. Because of the vast impact of drought, it is essential to be monitored timely and spatially. Specifically, SPI was used as drought monitoring Index of Sistan and Balouchestan province of Iran, and for zoning proposes three models (Kriging, Spline and IDW) were employed. Results showed that during last 25 years period (1981-2005), occurrence of drought has been more frequent and also lasted longer than the early years. However, the severity of drought has been reduced. It can be seen that the duration and severity of drought is more in the southern and central area than in the northern parts of the province. Cross validation technique with R2, RMSE, MDE and MAE were analyzed to assess the zoning methods. Results of ranking these criteria’s summation showed that the Kriging with Gaussian variogram, with RMSE, MDE, MAE and R2 equal to 0.546, -0.0015, 0.42 and 0.56 (the maximum correlation), respectively, and the IDW with 1 and 2 power were the best methods for drought zoning. Finally, drought’s severity maps were generated, which are useful tools to take management decisions to solve the drought crisis problems.

Considering the relative good potential of ground water in Gharesoo basin, compared to surface water, quantitative and qualitative studies of ground water resources in this area is very important. Followed by the basic studies such as effective pollutant resources, the qualitative studies were done on the selected places. The test points were consisted of deep and semi-deep wells. The distribution of these stations on the basis of uniform distribution has affected the Gharesoo sub-basins and pollutant resources. Thus 57 stations were chosen for sampling. Because of small variation of qualitative parameters of ground water, sampling in both wet (Ordibehesht month) and dry periods (Mehr month) and nessesary qualitative tests of samples were done. The tests consisted of anions, cations, colliforms, EC, TDS, BOD and COD. The results indicated increased rate of pollutants toward the north west or exit point of the Gharesoo basin and this was coordinated with decreasing the depth of ground water and its direction of movement. Furthermore, in more than 90 percent of places, quality of water was suitable for agriculture and drinking. The main reasons for the low quality of water for agriculture and drinking was high EC and TDS parameters in the proximity of Gharesoo exits. On the basis of Gibbs Diagram and ratio of Ca to Mg ions (less than one), dolomite minerals are dominant.

The aim of this study was to investigate the effects of different rates and periods of sewage sludge and sewage sludge enrichment with chemical fertilizer application on some chemical characteristic and enzyme activity of soil in 2008. This experiment was carried out in a randomized complete block design with three replications. Themain factors was fertilizer treatments (T1=no organic and inorganic fertilizer, T2=chemical fertilizer (potassium sulfate, tripill super phosphate and urea 150, 150 and 200 Kg. ha-1 respectively), T3 and T5 20 and 40 Mg. ha-1 respectively, T4 and T6, 20 and 40 Mg. ha-1 with half T2 respectively) and the secondary factor three consecutive times of sewage sludge application (2006, 2006+2007, 2006-2008 years). Soil samples were collected from 0-20 cm depth at end of 60th day of application. Results indicated that with increasing application periods of sewage sludge the amount of soil organic matter enhanced, significantly. An increasing trend was observed in total nitrogen (TN). While mean, with increasing the rates and application periods, the amount of available K and P increased significantly. Activities of urease and alkaline phosphates improved with increasing the organic fertilizers and application periods. Maximum amount of available K, P and total N, activities of urease and alkaline phosphates were observed in 40 sewage sludge ha-1+1.2 chemical fertilizer treatment. Significant correlation was observed among enzyme activity, organic soil matter, TN, K and P. Therefore application of sewage sludge, by increasing the amount of O.C, TN, available P and K, caused to enhance the enzyme activity in soil.

In recent decades, human activities resulted in heavy metals accumulation in soil which is a threat to organisms' health. Nitrification process is one of the important biological indices to assess soil quality. This study investigates the nitrification process with complete randomized design in two calcareous and non-calcareous soils. Different treatments of nitrogen (0 and 100  mg/g), cadmium (0, 10 and 100 mg/g) and zinc (0, 100 and 500 mg/g) with 3 replicates were applied in the laboratory conditions. The results showed that increasing heavy metals concentration, nitrification rate decreased. Inhibition effect of Cd was more than the Zn. In the presence of ammonium at the highest cadmium concentration (100 mg/g) in the calcareous and non-calcareous soils, nitrification rate decreased 78% and 92% respectively. These values in the absence of ammonium were 75% and 90% respectively. Inhibition effect of the heavy metals on nitrification in the calcareous soil was more than the non-calcareous soil. Addition of ammonium to the Cd and Zn treatments led to three fold increase in nitrification rate. However, difference between nitrate values in the two soils, in the presence of ammonium was less than that of its absence. The most decrease in pH was observed in the 100mg Cd/g soil treatment with 1.3 unit. The findings of this research reveal that in the arid and semiarid soils, the CaCO3 can diminish the toxic effects of heavy metals on biological activities.

Dez dam is very important due to water supply, regulating power frequency and flood control. Because of high sedimentation in front of dam structure, there is a risk that fine sediments enter the power intake and endanger the efficiency of turbine runners. In this regards, use of turbidity currents potentials is one of effective solutions. In this study, the results of three stages of field measurements including current velocity and sediment concentrations in various stations was analyzed and sediment volume entering into reservoir, due to turbidity currents was calculated. The results showed that only in one flood event on April 2003 (with flow discharge of 2600 cms), nearly 1.1 Mm3 sediment has been deposited in front of dam structure. Maximum thickness of turbidity current has been evaluated to be 25 m in this flood event. Also, it is revealed that in addition to flood discharge magnitude, the time of flooding is also very important for calculation of sediment volume resulting from turbidity currents.

Traditional modeling techniques such as regression and time series, often fail in the modeling of nonlinear hydrological processes like stream flow forecasts. Therefore, nonlinear techniques such as Artificial Neural Networks (ANNs) could be more efficient tools for forecasting these processes. This study aims to forecast the next 1- to 3-months flow of Karoon basin. For these forecasts, first four input models of ANN have been constructed by Principal Component Analysis (PCA) and Cross Correlation (CC) techniques. Then, using Cross Validation (CV) method and model performance evaluation indices like determination coefficient, mean absolute error and root mean square error, the best input model was identified. Also, to determine the effectiveness of each input variables and principal components, their single and compound role on ANN performance was investigated. Finally, the effect of SOI index at t, t-1 and t-2 times on the best model performance was evaluated. Results showed that thermal variables have the greatest influence on Karoon basin streamflow. Also, SOI index as input variable can improve the performance of model averagely about 5% in MAE and RMSE and 4% in R2 values.

Soil degradation that sometimes occurs as the result of land use change and its vegetation cover is a widespread environmental problem that may lead to the changes in soil structure and porosity. The aim of this study, was the qualitative and quantitative micromorphological evaluation of voids in Mollisols formed on the southern Gorgan River plain. The studied land uses consisted of natural forest, pasture, orchards and cultivated land. A soil profile was dug in each of land uses. Soil samples were collected for physico-chemical analyses in three replications and also undisturbed samples for impregnation with resin by Kubiena box. Following preparation of thin sections and study by polarized microscope, the photographs were prepared and the total porosity, diameter and area of voids were determined by Image Tool 3.0 software. The data were analysed with SAS software and LSD, s test. Results of image analysis indicated that original forest and pasture had the highest percentage of porosity and the cultivated soil had the lowest one. Moreover, because of agricultural machinery in cultivated land and soil compaction, aggregates were mainly broken which reduced the size of voids in terms of feret diameter and area compared with the natural land uses. The dominant size of voids was lower than 2mm in the cultivated land. While the variations of voids in terms of size and area of the voids larger than 500mm2 and also presence of channels and large vughs were higher in forest and pasture than other uses. The presence of such voids can cause better extension and distribution of roots and higher water and nutrient uptake in forest and pasture.

The relationship between soil moisture and soil suction is called soil moisture characteristic curve, and its measurement is time-consuming and expensive. Arya et al., (1999) have derived a model for estimating soil-moisture characteristic curve based on soil particle size distribution curve and bulk density, which contains scaling parameter  a. There are three methods for determining a which contain constant a, linear and logistic methods with available coefficients for some soil textures. In this study, 20 soil samples were selected from Fars province and three equations with exponential, logarithmic and power trend (Alfa-1 to Alfa-3) were derived for estimating a based on soil moisture content, and another equation with linear method (Alfa-4) was obtained. Then by using another 5 soil data sets in Fars and Boushehr provinces, the measured soil-moisture characteristic curves by combination of hanging column and pressure plate, were compared with estimated soil-moisture characteristic curve through eight different methods. These methods were: logistic, linear, Khoshnood Yazdi and Ghahraman (2004), Rezaei et al. (2005), and Alfa-1 to Alfa-4. The results indicated that the Alfa-4 method was appropraite for clay and silty clay loam textures, and the logistic method was appropriate for silty clay, loam and sandy loam textures.

Due to long life and sedimentation, the capacity of Voshmgir reservoir has decreased. Therefore, it is important to think about how to save capital and reduce the shortage volume. The main purpose of this investigation is to estimate the amount of shortage volume of voshmgir reservoir by considering the two-reservoir system in Golestan province. In this research, for simplifying, the node method was used. The optimization of problem was done using linear programming method. By considering the importance of evaporation in reservoirs, the results showed that in optimum operation of Voshmgir and Golestan reservoirs, the evaporation decreased and in present situation and future condition, the Voshmgir reservoir capacity has to be increased by 9 million cubic meters to supply all water demands. The results showed that the linear programming was very useful method in water resources problems.

Artificial neural network is a powerful tool to solve the engineering and technical problems such as water resource problems. In this study, the ability of neural network model for simulating the hydrograph in Jafar Abad River was evaluated. It is notable that the flood hydrograph was estimated 2, 3, 4 and 5 hours earlier using the flood discharges at 2, 3, 4 and 5 previous hours as model inputs respectively. This was carried out using 18 flood hydrographs recorded in upstream gauging station. From this dataset, 12 flood hydrographs were chosen to train the model and 6 flood hydrographs for validation and test the model. The results showed that by increasing the estimation lag time, the accuracy of results decreased and in a given lag time, by increasing the number of input, the accuracy of results increased. The results showed that the amount of efficiency coefficients, which is the representation of performance of flood hydrograph modeling, is 0.92 and 0.93 for two test hydrograph, respectively. The results also showed that the type of transfer function and learning algorithm were the effective factors on model outputs.

At many basins sub of Sefidrood dam the first hydrometric and climatologic data of existed stations were gathered, tested, repaired and finally physiographic parameters were measured. The selected sub-basins were divided into hydrological homogeneity groups by method of hierarchical cluster analysis based on physiographic specifications and annual precipitation. The borders of clusters were then clarified by canonical discrimination function and the annual water yield discharge with different return period was estimated by suitable probabilistic function. The effective factors to model annual discharge recognized were area and average height of sub-basins by method of Principle Component Analysis (CPA). Finally the best and easy equation of estimation of annual discharge was produced only based on area parameter.