نشریه دانش آب و خاک
سال سی‌ام شماره 2 (تابستان 1399)

Bacteria with high phosphate solubility and resistance to high temperature are suitable candidates for use in granular phosphatic microbial fertilizers (PMF). The prepared product in processing of these fertilizers (PMF) is exposed to high temperatures (50-55 ° C) under very low moisture conditions. Accordingly, in this research, the efficiency of phosphate dissolution and temperature tolerance of 150 bacterial isolates were evaluated. These bacteria were prepared in the soil biology laboratory of University of Tabriz. The phosphate solubility of these bacteria was evaluated by semi-quantitative and quantitative methods in solid and liquid Sperber medium in the presence of low-soluble tricalcium phosphate (TCP) source at the temperatures of 28 °C and 55 °C. The results showed that there was a significant difference between bacteria in terms of dissolution of phosphate. At a typical temperature among 150 bacteria, 25 bacteria (17%) had no phosphorus dissolution capacity, and the HD/CD ratio for these 25 bacteria was 1.2 to 2.8. In the quantitative method, the solubility potential of 25 isolates was 175.88- 292.98 mg P/l. Among the 25 isolates, only 7 bacteria were able to survive at 55 ° C for 16 hours, witch between them the C1-4O, C19-4O and C8-12M bacteria had the highest halo diameters with values of 2.5, 2.4 and 2.2 for the HD/CD ratio, respectively. The amounts of phosphorus release by these bacteria in the liquid medium were 244.08, 256.44 and 216.14 mg/l, respectively. The molecular identification of these bacteria showed that they were belonged to the genus Enterobacter and Stenotrophomonas.

In the present study, the flow pressure fluctuations have been measured on the bed of the USBR Type II stilling basin downstream of an Ogee spillway using pressure transducers. The experiments were carried out in a laboratory flume under different flow conditions. In addition, the pressure field in submerged hydraulic jumps was investigated to help better understanding the energy dissipation process and optimum designing the stilling basins. Using the dimensionless parameters, the submergence effect on the longitudinal distribution of the mean pressure and the pressure fluctuations intensity were evaluated. Pressure data acquisition was conducted for different incident Froude numbers (Fr1), ranged from 6.4 to 8.3, and submergence factors (S) in the range of 1 to 1.4. Based on the dimensional analysis, the values of the intensity coefficient of pressure fluctuations (CʹP) were a function of parameters of Fr1, S and the relative distance from the beginning of the basin (X/Y1). The results showed that the maximum values of CʹP coefficient for the Type II stilling basin decreased around 30% compared to the smooth basins. The mean values of CʹP in submerged jumps decreased around 25% compared to the free jumps at the downstream zone of the stilling basin (X/Y1>10).

Prediction of water table oscillation, especially in arid and semiarid areas is essential for better planning. In this study, monthly data of water table elevation, during the period of 1380 to 1390 for Ajabshir plain with an area of 130 km2 were used by application of two methods to estimate and predict the water table elevation. The date of 1380 to 1390 were used for estimating and the water table elevations were predicted for the three years of 1391 to 1393. The first method is solving partial differential equation for consecutive time steps and the second one is time series model. The GMS software was used for numerical solution of the differential equation by finite difference method. The correlation coefficient value of 0.9 and RMSE value of 0.41 between the estimated and observed amonts of groundwater levels were obtained using this method. The best fitted model for the water table elevation data using time series was ARMA (3, 2), correlation coefficient and RMSE values of this method were 0.85 and 0.49 respectively. According to the evaluation criteria, the partial differential equation method was more accurate than the time series method.

Application of agricultural residue biochars as an adsorbent is one of the most cost-effective and widely used methods to remove contaminants such as phosphate from water resources. In fact, the bagasse is the waste residues of sugar cane which is abundant in southern parts of Iran. The aim of this study was to investigate the kinetics of phosphate adsorption by bagasse biochar and determine the best kinetic model to interpret this phenomenon. After determining optimal pH, the effects of initial phosphate concentration and contact time on phosphate adsorption by sugarcane bagasse biochar were investigated and 7 kinetic models were used to study the patterns of P adsorption. Maximum adsorption obtained at the time of two hours. Kinetic models of the exponential function, parabolic diffusion, Elovich and first order reaction were compatible with the results but the exponential function model was the best. The half-life of phosphate adsorption in different concentrations varied from 30 minutes to 100 minutes and decreased with increasing initial P concentration. P adsorption rate constants increased as initial concentration of phosphate increased. High values of P adsorption parameters demonstrated that the sugar cane bagasse biochar could be used as an appropriate adsorbent for phosphate removal from aqueous solutions.

Study of factors that affecting soil erosion and its temporal variation is prerequisitethe for management of soil and water resources. The purpose of This study was to determine susceptibility of soils to erosion and its temporal variations in three soil textures (clay loam, loam and sandy loam) on different slopes (5, 10, 15, 25, and 30 degree) under simulated rainfalls (40, 60 and 80 mm h-1). The experiment done by flume (160 cm × 65 cm) and in a completely randomized design with two replications. Soil losses measured at various times (0/5, 1, 1/5, 2, 3, 4, 5 10, 15, 20, 30, 40,50 and 60 minutes) to achieve steady-state flow of surface runoff. There was a Significant difference between  the soils in  terms of soil loss (p< 0.01). Clay loam was the most susceptible on to soil erosion. In this soil, Most of erodible soil particles eroded by surface runoff at the beginning of rainfall and soil loss decrese with continuing of rain. Soil loss in soils was strongly influenced by slope gradient and rainfall intensity (p< 0. 01). by increasing slope gradient,due to lower rain water retention on the surface, runoff was occurred quickly, and then soil loss increased. in soil loss of sandy loam,Slope steepness and rainfall intensity showed dominant roles in soil losses. The results revealed that in erodible soils, sensitivity to erosion by changing the slope and rain intensity is lower, and these two factors (slope steepness and rainfall intensity) has greatest impact on soil loss in highly resistant soils to erosion .

Management of irrigation networks can play a very important role in the hardware and software performance of these networks. In this research, by conducting field studies on suspended sediment transport and conveyance efficiency, the effect of operating conditions on sedimentation and water losses at Khouzestan province irrigation networks was analyzed. The inflow-outflow method and sediment flux continuity equation were used to determine the canal losses and sedimentation of suspended load in the studied reaches, respectively. The investigation was done on 4, 21 and 16 reaches of the main, secondary and tertiary channels, respectively. The ratio of free board of flow in canal as operation index was computed. The effects of this index on sedimentation rate and water losses relative to input discharge were studied in each kilometer of the canal. Results showed that 10% decreasing in the operational discharge relative to the designed discharge caused 0.23 and 0.26 kg s-1 km-1 increasing in sedimentation rates of the main and secondary channels, respectively. As the distance from the upstream of the main channel increased, the channel efficiency decreased. So that the increasing rate of the water losses in main channel of Karkheh irrigation network was 0.12 percent of the entrance discharge in each kilometer distance from the beginning of the channel. The increasing rate of water losses for the western and eastern channel of Dez irrigation network were 0.16% and 0.09%, respectively.

Spur dikes are one of the structures used for protection of river banks from erosion and rivers organization. They are usually rectangular and perpendicular to the flow. Unfortunately, the scour development in the tip of those can lead damage to the structure. Furthermore, sedimentation between the spur dikes as well as increasing the flow velocity in the middle of the channel due to the large obstruction, are among the factors that create problems for aquatic life of the river. These problems are minimal in the triangular vanes. The main purpose of this paper is to evaluate the performance of the triangular vanes on bed topography changes in the different flow conditions. For this reason, some tests were carried out at a straight flume for different flow conditions (five Froude numbers of 0.18, 0.20, 0.22, 0.24 and 0.26) by installing series of triangular vanes with space of 4Le (Le is the effective length of structure) at the angle of 30 degrees to the upstream bank. At the end of each test the bed topography was measured by laser distance measurer. The results showed that, the geometric dimension of the scour hole for the rectangular spur dikes was larger than that for the triangular vanes. On average, the length and depth of scour hole for the rectangular spur dikes were 1.3 and 1.5 times higher in comparison to those for triangular vanes, respectively. In addition, the position of the maximum scour depth for the triangular vanes was about 40% farther from the bank than that case of rectangular spur dikes that was an advantage for the triangular vanes.