Journal of Irrigation Sciences and Engineering
Year:2014 | Volume:37 | Issue:1|Papers Count:12

Scouring around the bridge pier during the flood events threaten the bridge as important hydraulic structure. Thus, designing the economical device in reducing the local scouring needs to be investigated. Cable has been introduced as new and economical countermeasure in local scouring. In the present study, different diameters and thread angles are studied through the experiments. In addition, groove is introduced in reducing the local scouring. The results show that with increasing cable diameter and decreasing thread angles the reduction of scour depth increases. The maximum scour reduction is achieved for pier protected with cable equal to 13% and 17% in front and behind of the pier respectively. While the groove is reduced scouring equal to 17% and 25% in front and behind of the pier respectively. Comparing the efficiency of cable with groove indicated that groove has higher efficiency in reduction of local scouring.

To achieve the goal of high yield, deep understanding of physiological, agronomic and environmental factors is necessary to improve the performance and sustainability of agricultural systems. This may not be practical unless the plant complex systems and the type of response to inputs and environmental conditions are known as important factors. In modern agricultural methods the uses of different models are important for management, optimize productivity, accurate understanding of the system and obtaining a precise formulation of the standard. In order to simulation of soil moisture under different water conditions on wheat (Chamran cultivar) a field experiment was conducted at the Agricultural Research Center- Ahwaz. In this experiment, three irrigation levels include I1 (no water stress), I2 (stop irrigation at the heading stage and I3 (stop irrigation at the milky grain stage) and five levels of nitrogen fertilizer namely N1 (no nitrogen fertilizer), N2=40, N3=80, N4=120 and N5=160 kg/ha were used as treatments. In this research, HYDRUS-1D was used as simulation model. Analysis of results for sensitivity of model showed that soil moisture coefficient of model under saturation condition qs is more than other coefficients and a slight change in coefficient caused a large change in output variation of model. The minimum effect was observed in α, I and qr coefficients. Meanwhile, results indicated that model was estimated moisture content less than reality condition. Also, the amount of moisture on the basis of simulated model was estimated less than the real moisture. The model efficiency that reflects to quality and observed data was estimated between 0.67 and 0.90. This was due to high efficiency of simulated model for soil moisture.

When the dense flow mass intersect to stagnant fluid, dense flow penetrates into statically fluid and plunge depth occurs. In this research, hydraulic parameters of density current and bed slope have been investigated, which these have a considering effect on plunge point. To achieve on purposes of this research a physical model in hydraulic laboratory of Shahid Chamran University was built and various experiments were performed. At all of the experiment, plunge depth was measured in the various discharges of density current, different of density 6, 9, 13 and 16 kg/m3 at three slope 8, 12 and 16 percent. Then using Flow-3D depth of plunge point for these experimental conditions was simulated. Findings show that depth of plunge point derived with Flow-3D is more than measured values as in 12% slope, mathematical model overestimate about 30%. While, for all of the slope bed, simulated results 27 percent is more than corresponding measured values. Statistical evaluation shows that ratio of measured valued to results of Flow-3D is about 0.8.

One of the serious and growing potential in most large urban areas is the shortage of land for waste disposal. An inapproprriate landfill site may have negative enviromental, economic and ecological impacts.Therefore, it should be selected carefully by considering both regulations and constraints on there source.Choosing different factors leads to diversity in data layers and Geographic Information System (GIS) is very suitable due to the ability to manage huge volumes of data with different sources. The main aim of this research is to determine a suitable landfill site with less impact on environment For this purpose, the following data layers and maps have been utilized in this study, maps of slope, use land, soil, the depth of groundwater and the layers related to the distance from centers of waste generation (Ramhormoz), Population centers (village), surface water sources, underground water source (well, Spring), road network. The results of present research represents that the conditions in Analytical Hierarchy process (AHP) method has less certainty and the lack of definite limitations in this method, the sites selected according to Weighted Linear Combination (WLC) and Fuzzy-AHP (FAHP) have more parameters. However in studing the WLC and FAHP methods applied in this study, it was revealed that although WLC is simple, it has deficiencies; this method will locate many areas that may not be suitable, meanwhile FAHP, by ordered weights, offers this chance to the decision marker to include more important subjects which have greater role in site selection. Regarding to this ability, the result of site selection by FAHP has better resolution.

In this paper the results of measurement of three components of flow velocity around the bridge abutment with and without installed submerged vane are presented. Previous studies have shown that installation of submerged vane at the upstream corner of bridge abutment with angle of 40 degrees can decrease the scour depth. Plot of horizontal flow velocity components in different level, for both alternatives, with and without submerged vane, shows that the velocity vector at lower layer closed to the bed are shifted away from the abutment which causes that local bed shear stress are reduced and the scour at the vicinity of abutment reduced.The lower layer of stream lines are compressed at the edge of vane which cause scour at this location. It was proven that using submerged vane does not causes compression of the stream lines more than it usually occur due to abutment contraction. This means that the scour is shifted but the scour depth does not increase. Comparison of water surface profiles for with and without vane shows that the drop or lift of the water surface with vane is not significant and the change is in the safe way. Plot of vertical flow velocity vectors shows that the downward velocity has shifted from the abutment vicinity, in case of without vane, to the lower layers of the edge of submerged vane.

The aim of this study is to compare and calibrate of four different temperature based ETo estimation methods in monthly time scale at Urmia Lake basin. The selected methods were Hargreaves (HG), Thornth waite (TW), Blaney- Criddle (BC) and Linacre (Lin). For this purpose the information of weather parameters in the period 1986-2010 were used. Results of mentioned methods compared with the output of the FAO Penman- Monteith (PM56). Methods calibrated using the two distinct approaches. At first state only one calibration coefficient estimated along every year. At second state calibration coefficientsestimated for each station and every month in a year. Performance of methods evaluated using the R2, RMSE, MBE and MAE statistics. The effectiveness of method’s calibration evaluated using the RaRMSE.Results showed that before calibration larger biases existed for selected methods comparing PM56.Calibration of methods considerably improved their performances. Results indicated that calibration of methods in the case of second state was very effective comparing the first state. The HG method was recognized as a best method either before or after calibration (in the first state) at the Urmia lake watershed. Linacre and Blaney- Criddle methods selected as the best methods following the Linacre method (after calibration at first state). Thornthwaite method had large error and therefore was not suitable method for estimation of E To at the study area. The Linacre method was known as the best method of E To estimation at Urmia Lake basin after calibration (at second state). HG, BC and TW were in the second to fourth rank orders, respectively.

Due to the increasing needs of human societies to groundwater supplies, the resource conservation and pollution prevention is necessary, especially in arid regions. Vulnerability assessment of groundwater can play a vital role in the protection of these resources. The main problem of DRASTIC model as the most widely used models for groundwater vulnerability assessment is the weighting. In this study, the weighting was modified using Analytical Hierarchy Process (AHP). To determine the optimal model, the correlation between the vulnerability index and the groundwater nitrate concentrations were determined using Simple Linear Regression Analysis (SLRA). The results showed that the optimal DRASTIC model has a better correlation rather than normal DRASTIC model. Also, to assess the risk of aquifer pollution, land use parameter added to the parameters and specific vulnerability aquifer map were prepared. The results showed that about 65 and 35 percent of Andimeshk aquifer contamination risk are very low and low, respectively.

Determination of unsaturated soil hydraulic parameters are important for assessment and understanding of many processes. These processes include as: runoff and rainfall infiltration, salt, contaminations and nutrition elements transmission in soil and solution absorption by plant root. Recently, disc permeameter has been recognized as one of most current tool for measurement of unsaturated soil surface hydraulic parameters. In this research, for study of relation between unsaturated soil hydraulic conductivity and sorptivity curve, the field experiments were performed at six iterations to interval of 1 meter each other on three zons (first zone with silty loam texture, second and third zone with loam texture). At all iterations, steady infiltration rates were measuremented on soil surface in consective five suctions, 15, 10, 6, 3 and 0 cm recpectively. Then, sorptivity factors in each suction were estimated by methods of differentiation (unsteady analysis) and steady analysis. The results of this study indicated that, sorptivity curve (s(h)) similar as unsaturated hydraulic conductivity curve (k(h)) is followed an exponential function. Sorptivity factor had inverse relation with suction, so that sorptivity value increased with suction reduction. Also, the results of this study showed that unsteady analysis method estimate sorptivity value at all suctions more than steady analysis method and the differences are significant in suctions of 3 and 0 cm. The study results indicated soil sorptivity factor inverse relationship with α parameter and α parameter inverse relationship with soil structure resistance degree. Also, it is observed that sorptivity factor sensitivity to soil structure is more than hydraulic conductivity.

Forecasting river flow using current models like time series, Physical-theoretical and regression models are very important in water resources management. In this study monthly and daily discharge of Barandouz-Chai River for period of 37 years have been used in order to linear ARMA and Nonlinear 1- Auto Regressive Moving Average (ARMA) Bilinear models. ADF test has been used for stationarity test. Result showed removing nonstasionarity components cause to river series became stationary. For nonlinearity rate of monthly and daily stream flow series BDS test has been employed. As results showed monthly series detect low nonlinearity but daily series has high nonlinearity dependence. For monthly series AR (8) and BL (8, 0, 1, 1) selected as the best models. Regression coefficient and root mean square error of these models are 0.906 and 2.892 (m3/s) for linear model and 0.930 and 2.436 (m3/s) for nonlinear model respectively. For daily stream flow series, AR (25) and BL (25, 0, 1, 1) were best models with regression coefficient and root mean square error equal to 0.873 and 4.116 (m3/s) for linear model and 0.923 and 3.085 (m3/s) for nonlinear model respectively.According to results using bilinear nonlinear model cause to reduction error of daily model up to 33 percent and increased regression coefficient to 5.7 percent. Because of high nonlinearity rate of daily stream flow series the bilinear model accuracy increased.

Minimum environmental flow in rivers provides a certain level of protection for the aquatic environment. In Iran using hydraulic method of wetted perimeter could be a step forward in this field. How to identify the critical point in P-Q curve is still faced with uncertainty in this method. Slope, Curvature and Ideal Point Methods presented by different researchers in this filed. In this article beside description of wetted perimeter method, the environmental flow of Beshar River calculated by using hydraulic parameters. The average of results of Slope, Curvature and Ideal Point Methods is 23%, 8.4% and 20.6% of average annual flow of river, respectively. The results of Slope and Ideal Point Methods are in the acceptable rang of the Tennant method. But the Ideal Point method is superior choice due to the direct use of the chart and more rapidly in calculation.

One method of determining evapotranspiration is zero flux plane (ZFP). This method estimate the evapotranspiration based on water content and soil suction. This method can also estimate the value of evaporation, evapotranspiration and ground water recharge. The data used in this study were obtained from a field experiment at Isfahan University of Technology. The experiment was factorial design [3×8] in the basic design of randomized complete blocks that the first factor was the types of mulch and the second factor was the depth of soil mulch. The field trial was conducted for 44 days. Results obtained from the ZFP model was compared with Ref-ET and OPTIWAT models. The experiment consisted of wood, sand and tire chips mulches with 2.5 and 5 cm thickness in the plots. Three plots were planted with grass and three plots left uncovered. The results showed that the depth of ZFP varied in different mulches. The highest ZFP depth was related to the uncovered plot and the lowest ZFP depth was related to the plot with 5 cm sand thickness. the results indicated that the experiment plot with no mulch had the greatest evapotranspiration (178 mm) and then woody chips mulch with a thickness of 5 cm, tire chips mulch with a thickness of 5 cm, tire chips mulch with a thickness of 2.5 cm, sandy mulch with a thickness of 2.5 cm, the woody chips mulch with a thickness of 2.5 cm and sandy mulch with a thickness of 5 cm, had more evapotranspiration, respectively. the results showed that the amount of evapotranspiration obtained by the ZFP model with the results of the Ref-ET and OPTIWAT model, were different. Ref-ET and OPTIWAT models under-estimated the actual evapotranspiration obtained by ZFP. In Ref-ET model, the equation of modified Blany-Cridle had the closest estimation (159 mm) to the evapotranspiration determined by ZFP model. In OPTIWAT model, the modified Jensen-Haise method had the nearest estimation (161.4 mm) to the ZFP model.

In this study the triangular flip bucket instead of circular shaped- with the same character but with different geometries- was studied. In this regard, the performance hydraulic overflow bucket with a bucket instead of the usual triangular shape, were compared in terms of energy dissipation. In this regard, the hydraulic performance triangular shaped bucket instead of the usual bucket, were compared in terms of energy dissipation. To achieve this goal, a physical model of the ogee spillway was built in the hydraulic physical models laboratory of Shahid Chamran University (SCU) and experiments were performed in 4 discharges that followed by four different Froude number. The for each discharge 3 tail-water depth were used to run experiments. The results showed that in comparison to the Total performance energy dissipation in triangle flip bucket with 45-degree angle insignificantly is better than cup flip bucket. For example, energy dissipation in Froude number 3.13 in the case of the free jet in the triangle and cup flip bucket respectively 66.4 and 54.8 percent. The lowest and most energy dissipation respectively related to triangle flip bucket with 22.5-degree angle and Triangle flip bucket with 45-degree angle with 7 cm approach channel. A comparison with results for the circular shaped bucket geometry indicates a favorable behavior of the novel bucket design.