Journal of Irrigation and Water Engineering
Year:2017 | Volume:6 | Issue:26|Papers Count:12

Transient flow is generated by an instantaneous reduction in flow rate due to rapid valve closure or pump failure in a water network. Transient flow creates high and low pressure waves that it may be to damage pipelines. Comparison of experimental and numerical results in previous studies revealed that quasi-steady models with assumption of uniform and 1D velocity profile could not correctly predict the damping process of the pressure waves. So, the aims of this study are investigation of velocity profile at the downstream end section of pipeline to give a correct understanding of transient flow dynamics. Also, this paper evaluates the ability of the instantaneous acceleration–based (IAB) unsteady friction models to estimate pressure history in transient flow using the method of characteristics. To achieve this goal, a pipeline, made of PVC, with a nominal diameter of 63 mm in the two different lengths of 40 m and 80 m was used. In addition, a ball valve at the downstream end was installed to create transient flow. The data of velocity distribution and dynamic pressure oscillation during these transient events were collected by Ultrasonic Doppler Velocimetry and Pressure transducers. Results of experiments indicate existence of inflection points in the base flow velocity profile and the large velocity gradient near the pipe wall. Furthermore, the results show that two-coefficient models produce a better match with the experimental measurements. The terms ¶V / ¶t and ¶V / ¶x in unsteady friction models affect the phase shift and the damping of transient pressure waves, respectively. Moreover, the coefficients of acceleration terms vary from 0.0037 to 0.006 for kt and from 0.0325 to 0.052 for kx-.

Application of optimum operational approaches would be effective due to existing poor operational performance of irrigation canals and its direct effect on decreasing agricultural water productivity. In this study, automation system is introduces to improve operational performance of Roodasht main irrigation canal suffering from drastic in fluctuations of water inflow. To this end, a centralized Model Predictive Controller (MPC) is designed to be applied for operation of mathematical model of the test case. Both of the mathematical models, including the existing operation of the canal and the MPC system, are tested by inflow fluctuation scenario. The results of the simulation are evaluated by the operational performance evolution indices. The results indicate that operational level is improved by applying automatic control system since the performance evaluation systems of IAE and MAE are respectively improved from 21.49% and 12.63% to 5.32 and 3.21%. Also, the results approves that automatic systems could be introduced as safe and reliable options for rehabilitation and modernization projects.

Soil hydraulic parameters (soil water retention curve) is a fundamental soil property employed to quantify plant available water and for modeling water and solute movement in soils that the determination of this property via direct methods is expensive and time consuming. For solve this problem Indirect methods have been proposed that fractal analysis is one of the methods.Pore- Solid Fractal model was used for modeling soil structure and soil water retention function by many researchers. PSF model is a public expression for maintenance function soil water that is provided by other researchers in special form. The aim of this study was to assess PSF public function based on fractal dimension of soil water suction data and comparison with Brooks-Corey and Tyler-Wheat craft models. In this study, with using laboratory data from unpublished sources, obtained soil water retention curve for soils under investigation by the PSF, special cases (Brooks-Corey and Tyler-Wheat craft).To verify the results, a comparison between the predicted and measurement soil water content for many soil of UNSODA database. The results showed that for the soils investigated Tyler–Wheat craft function were better match in compared with the PSF and the Brooks-Corey function. To calculate the intake air (h min) and soil saturation (q s), using any of the equations PSF, and Tyler and Wheat craft, and Brooks-Corey not significantly different from each other. But for calculating the fractal dimension (D) using Eq Tyler-Wheat craft was recommended. Empirical simple models was developed with ready available data by relationship between the geometric mean (dg) and geometric standard deviation (sg) with min h min, q s q and D. Then, soil water retention curve was calculated For many soil of UNSODA database. Regardless texture soil, all predicted and measured volumetric soil moisture were compared with a one-to-one. The result showed no significant difference between the predicted moisture content (q p) and measured (q m) with a one-to-one. So it seems that the empirical simple model is able to estimate soil water retention curve with reasonable accuracy.

The SCS model is one of most important proposed models for estimation of flood hydrograph in ungauged basins and need to land cover, land use, physiographical properties and antecedent moisture data but using this model is limited for basins with no access to these data. In this study, the lag time based on proposed relation between lag time and time of concentration and estimation of time of concentration based on velocity of flood peak is investigated to overcome to this limitation. The results of proposed model are compared with traditional SCS model in four rainfall-runoff events in Amameh basin using percentage error in volume (PEV), percentage error in peak (PEP), percentage error in time to peak (PETP), and root mean square error (RMSE). The results show the mean of PEV, PEP, PETP and RMSE for SCS-Proposed models are (-6.35) - (-6.45), (0.97) - (-48.31), (27.38) - (56.08) and (1.4) - (2.55) respectively. Both models tend to overestimation of runoff volume and underestimation of time to peak while conventional SCS tend to underestimate and proposed model tend to overestimate flood peak. Also, comparisons of RMSE beside other criteria indicate that with lack of required data for SCS model, the proposed model can present relatively estimation of runoff hydrograph acceptable.

Wave attack is the main source of irreparable damages to the sea coast line. The coastal protection techniques are now improved from structural protection to biological ones. This includes plantation of trees and development of vegetation canopy (called green belt) along the shorelines and protection of coastal structures against the waves created by tsunami. For this, the application of green belt has been studied and effect of vegetation density and wave height on wave force is evaluated for waves in broken condition. Experiments were conducted in a flume with 8.3m length, 0.8m width, and 0.55m height. Experimental variables include four bed slopes, four vegetation densities, and 110 wave heights. The results show that absorption of wave force increase with increase of wave height and density of vegetation. At the highest vegetation density the wave force effect was reduced by about 75% compared to the case without vegetation.

Soil is not only a medium for plant growth but also a transmitter of contaminants to atmosphere, surface water and ground water. Therefore, studying the movement of substances in soil is important. In this study, the effects of soil slope and rainfall intensity on solute transport in soil were investigated under laboratory conditions. The experiments were conducted in two sloping and not-sloping soil bulk and included injection of a conservative solute (NaCl) with two different intensities. The results showed that the soil slope increases the solute transport in the lateral direction, and the increase of injection intensity accelerates the solute movement towards the depths and increases the peak concentration. Solute movement was well simulated using Hydrus-2D model with the coefficient of determination (R2) between 0.848-0.907, the Nash–Sutcliffe efficiency coefficient (EF) between 0.805-0.907 and the low values of the root mean square error (RMSE).

Tomato is one of the major agricultural products in Fars Province with a cultivation area of 20000 ha. Previous studies show that the tomato farms under traditional surface irrigation systems lose a large volume of water with low water productivity. In the present research, the influence of different irrigation regimes on tomato yield and water productivity was studied. The farm under study located in Marvdasht plain with a heavy soil texture. The irrigation water was applied under drip irrigation system, base on 60, 80, 100, and 120 percent of Penmann Montieth water requitement method. Another treatment was considered and irrigated by the farmer management. Water stress indicators were measured and evaluated. These indicators were soil moisture and difference between leaf and air temperature. Different statistical test such as t and Duncan test were used for the evaluations. Results show that the obtained yield increased with irrigation water while the water productivity decreased. The irrigation volumes of water used for the treatments were about 3900 to 7800 cubic meters per hectare. However, only the differences between the treatments 60 and 120% were statistically significant. Differences between the two treatments 80 and 100%, and the critical values were not significant in most cases. The treatments with higher irrigation water than the 80% treatment, shows no signifant effects on tomato production. The irrigation water volume in this study and the traditional surface irrigation systems was 5200 and 23000 cubic meter per hectare, respectively, which shows a decrease more than 75 percent in irrigation water.

Design and implementation correct drip irrigation plays an important role in increasing the productivity of agricultural land and help to using water low-quality. Attention to the problem of soil salinity, is determine the distribution pattern of soil salt is an effective tool for the proper management of soil. This study was done with goal to assess the two surfaces and subsurface drip irrigation system in olive trees in Tarom. In this regard, was discussed the pattern of distribution of mineral in soil, especially soil salinity and sodium adsorption ratio at various depths. Also distribution of soil salts were compared at in levels 50, 75 and 100% irrigation treatments. However, generally were obtained the concentrations of salt and sodium in different depths in this study in subsurface drip irrigation less than surface drip irrigation. Accumulation of Salinity and sodium in surface of soil in the top emitter in subsurface irrigation was greater than subsurface drip irrigation. Investigation different irrigation levels showed that in Spite of minerals reduction and leaching in irrigation level 100 percent, there isn’t significant difference in distribution of salinity and sodium between irrigation level 100 percent and 50 and 75.

According to the reduction in the quantity and quality of water resources, the use of high efficiency drip irrigation system is inevitable. A limitation of this method is the use of unusual water. For example, in surface drip irrigation, remaining salt after evaporation is caused the eclipse. While in subsurface drip irrigation, because of less evaporation from the soil, eclipse is minimized. In the subsurface irrigation methods, due to reducing water evaporation, plant water needs can be reduced. To investigate irrigation system in pistachio garden, pistachio gardens in Koshkooyieh village (Rafsanjan city) was selected and plan design that consists of two tube insertion depth (50 and 70 cm) and three consumption Water level (50% I1=, 75% I2=100 % I3=water requirement) with three replications were assembled. To feed Pistachio trees, fertilization was done simultaneous with subsurface irrigation pipe installation. The type and amount of needed fertilizers were calculated according soil test and added to each treatment with organic materials using placement in-depth approach. Four years results of the study indicated that the average irrigation water were calculated 2050, 3065 and 4010 cubic meters per hectare per year for treatments I1, I2 and I3 respectively. Each year, the performance of the each treatment during test was measured using scales with an accuracy of 1kg. In years that tests were done, samples of the leaves were gathered and the nutrients nitrogen, phosphorus and potassium in these samples were determined. During of the project, there was no significant difference between the performances of each tree under treatment in none of years. Nutrients concentrations in the leaves of trees indicated that any significant changes did not accrued. in nutrient concentrations in leaf samples.

Babolroud watershed in Mazandaran province in recent years experienced different climate events. On this basis, emphasize necessity to investigate further on impact of climate change on watershed runoff. This work is done by climate change models that able to simulate climatic variables. Due to the forecast lack of meteorological parameters in the point scale by climate change models, weather generator tool interface was developed by which it can be evaluated climate change in point scale and the desired station. In this study, using this method, the data model HadCM3 general circulation of the atmosphere with the use of LARS-WG software according to A2, B1 and A1B three scenarios for first time periods (2046-2065) and second (2080-2099) were. The results revealed that change in rainfall in Babul-rod watershed varies between -43% to+32%. This variation ranges accompany with rainfall increase in rainy months and severe decrease in months with low rain, respectively. Also, Increase in annual temperature in average was 1.4o to 3.6o, especially in warm months. After this step the values of temperature and precipitation predicted by the HadCm3 climate model introduced to IHACRES rainfall-runoff model and changes in discharge determined in both the first and second periods, respectively. Average monthly flow (m3/s) in the base period (17.42) was higher than the average of the first period (14.82) and the average of the second period (14.20) which it refers to reduction of 15 to 18.5 percent the average monthly runoff. According to the study, rising temperatures and reduced rainfall throughout the coming years lead to reduce runoff and water resources due to more evaporation and aridity will watershed that consequently affects the climate of the region in the near future, the number and intensity of floods and droughts will increase.

Drought is a hydrologic and climatic phenomenon, this phenomenon can occur in different watersheds and climatic conditions. Water resources management, design of water transmission and distribution systems and determination of agriculture water demands depend to applied methods for management and controlling of drought considerably. In this study for distinguishing of occurred droughts in upstream of the Dez Dam, annual precipitation data of Tangpanj and Telezang stations have been applied in a 17 years period (1994-2010).Occurred droughts have been determined using of these data and drought indexes as Percent of Normal (PN), Deciles Index (DI), Standard of Precipitation Index (SPI), Chinese Z Index (CZI), Modified Chinese Z Index (MCZI) and Z-Score index (ZSI). Results illustrated that most of severe droughts were observed in Telezang station. PNI, MCZI, ZSI indexes showed them (these indexes showed one drought in 2007-2008, 1995-1996 and 2007-2008 respectively). Also DI and SPI indexes illustrated an occurred severe drought in Telezang (2007-2008) and Tangpanj stations (1999-2000) respectively. But CZI index did not show occurrence any drought in these stations. RAI index distinguished that three (1999, 2008 & 2011) and four (1994, 1999, 2008 & 2011) severe droughts occurred in the Tangpanj and Telezang stations respectively. These indexes showed that most of droughts have occurred from 2007 till 2009.