مجله پژوهش آب ایران
پیاپی 9 (پاییز و زمستان 1390)

Flow separation from the upstream corner of the intakes is one of the major problems. This phenomenon produces a flow rotation zone in the intake, hence decreasing the flow passage and intake efficiency as a result of accumulation of sediment at the intake. During the past decades, several methods have been conducted to reduce the area of separation zone and increasing the intake efficiency. One of the methods used to increase intake efficiency is to change the hydraulic conditions by altering the intake geometry. Any method that creates a uniform velocity distribution at the intake, reduces the secondary flow, separation zone, sedimentation leading to increases in the intake efficiency. In this study, the effect of intake geometry on the sedimentation and flow pattern was investigated using the dimensions and shape of the flow separation zone. Results for three discharge ratios of 0/2, 0/4 and 0/6 showed that an optimized intake wall curvature reduced the entrance sediment by 58, 50 and 33 percents, respectively.

Transverse mixing coefficient is one of the hydraulic parameters of flow by which the amount of self-refinement and dilution of river water can be estimated. In this research, the effect of variations of width to depth ratio on the transverse mixing coefficient was studied. Experiments were carried out in a straight rectangular flume of 7 m length, 0.32m width and 0.35m height. The maximum flow rate was 16.4 lit/s. Water was circulated in the channel, the flow was uniform and the depth of water was controlled with a gate way. A tracer was continuously injected with a constant head into the center of the flume. Dye concentration was measured at 4 different downstream locations from the injection point; Twenty seven points were measured and dimensionless transverse mixing coefficient was determined. The results showed that increasing the width to depth ratio from 2.8 to 5.69, the transition by secondary flow increased. Accordingly, in constant velocity of 0.33m2/s, transverse mixing coefficient decreased from 0.049 to 0.012 by increasing the depth from 5.6 to 11.4 cm.

Drought forecasting plays an important role in the planning and management of natural and water resources. In this study, multiplicative seasonal autoregressive integrated moving average (SARIMA) models as the linear stochastic models were used to forecast droughts. The models were applied to forecast droughts using standardized precipitation index (SPI) time series. The SPI values for time scales of 3, 6, 12 and 24 months for Abadeh, Shiraz and Fasa synoptic stations in Fars province were calculated. The SARIMA model with the minimum of Akaike's information criterion bias corrected (AICc) was selected as the best model. The auto-correlation function plots of the residuals for the selected models indicated that the residuals were uncorrelated. The SPI values from January 2004 to December 2005 as the test data have forecasted using fitted models. For example, model was identified for 12 months SPI time series in Shiraz station. The results of this model indicated that the correlation coefficient between the observed and predicted values of SPI is 0.74 which is significant at 0.01 level and 22 months of drought category was correctly forecasted.

Rainfall-runoff models are one of the best models for flood hydrograph simulation and flood management, especially in regions with no flood data. In this study, the capability of HEC-HMS model was investigated and the magnitude of peak flood, time to peak and runoff volume parameters were compared by the Snyder, Clark and SCS methods for flood simulation in Chelgazi basin. For this purpose, seven rainfall events were selected. The model parameters were calibrated based on five observed events. Another two events were used for model verification. Then the model capability was used to estimate runoff through comparison with real data. The simulated and observed hydrographs were compared using R2 and RMSE statistics. The results showed that the SCS method is more appropriate than Clark and Snyder methods. The RMSE values of simulated and observed peak flow were 1.1, 1.4, and 1.5 for SCS, Clark and Snyder models, respectively.

In rainfall- runoff simulation of a basin under climate change, various uncertainties affect final results which would reduce reliability of the results if neglected. Also, overlooking uncertainties relating to climate change could exert unreal results for decision makers. In this research, we are trying to investigate the influence of uncertainty of rainfall-runoff and AOGCM models on Gharesu basin in 2020-2069 periods under A2 emission scenario. Nine AOGCM-AR4 models including; CCSM3، CGCM3، CSIRO Mk3، GFDL، GISS E-R، ECHAM5، HadCM3، MIROC-med، PCM and two conceptual rainfall-runoff models; SIMHYD, IHACRES were applied. At first, two rainfall-runoff models were calibrated for 1971-2000 periods. Downscaling the data of nine AGCOM-AR4 models for study area and introducing them to the rainfall-runoff models, changes of basin temperature, precipitation and runoff in 2040-2069 relative to the 1971-2000 was highlighted under A2 scenario. Results of this research showed that regarding uncertainties related to AOGCM and Hydrology models result in more accurate nomination in runoff modification in the area of study.

Knowledge of source of sediment and determination of relative contributions of sediment sources are required for watershed management strategies as soil and sediment erosion control methods that have important effect on soil and water quality and quantity. Uncertainty confidence levels ascertaining is needed in sediment fingerprinting mixing models but it has not yet been fully incorporated in these models. The objective of this study is to apply a Bayesian-mixing model to assess the uncertainty estimation in sediment fingerprinting in the Zidasht catchment, Iran. In view of this, 28 tracers were measured in 42 different sampling sites from four sediment sources and 14 sediment samples. Backward discriminant analysis provided an optimum composite of seven tracers viz. B, C, K, Mo, P, Pb and Tl that afforded more than 97% correct assignations in discriminating between the sediment sources in the study area. Sediment source fingerprinting was used to explore the uncertainty in the contributions of sediment from the four sources. In the study area, the relative contributions associated with Bayesian uncertainty from rangeland/sheet erosion, crop field/sheet erosion, stream bank and dry-land farming/sheet erosion sources ranged between 13 (8-20), 7.5 (0-10), 59 (45-75) and 20.5 (10-30) percent, respectively. These results can be useful as a scientific basis for selecting proper soil conservation and sediment control methods and integrated watershed management.

Identification of drought and wet periods has an important role in water resources management. In this paper, climatic and hydrologic droughts were evaluated using SPI and SWI indices in Chghalvandi Watershed. The Data used in this study included 18-year climatic and hydrometric data obtained from 8 climatic and 2 hydrometric stations and also groundwater level data. Drought area delineation was made by ArcGIS kriging method, while the linear trend of the phenomena was assessed using Minitab and Makesen softwares. The results showed that magnitude and duration of drought have been considerable in recent years. Comparison of the climatic and hydrologic droughts represented a lag time between these two types of droughts. Drought area delineation maps revealed more severity of the hydrologic and climatic droughts in the southern and central parts of the study area.

Using riprap is one of the common and economical methods for bridge abutment protection against scouring. Literature review showed that no study could be found for designing riprap size for protection of bed at bridge abutments which are located at the bends of rivers. For this purpose, physical model experiments were conducted with three types of ripraps of specific gravities of 1.51, 2.05 and 2.65, and sizes of 4.75, 9.52, 12.7 and 19.05 millimeters. Tests were conducted under various discharges of 17, 20, 23 and 28 lit/s(corresponding to the Froude number ranging from 0.19 to 0.58). The wing wall abutment was located at 75o of 90o of the river bend. The suitable size of riprap diameter at the bridge abutment located on the river bend was suggested in the form of a formula with error percent of 5.8, and correlation coefficient of 0.97. The formula developed in this research was compared with formulas of earlier studies on riprap around abutments in straight channels, and suitable correction coefficient was suggested for corresponding straight channel relations to be applicable for river bends.

Operators usually follow the rule curves for operation of a reservoirs system in actual conditions. Rule curve indicates desired release or target storage volume for a reservoir in the specified period of year. In the present study, combination of a simple genetic algorithm with the simulation model (ARSP) was used for multiple reservoir systems to find optimum rule curves. In this hybrid model, a linear programming was used for water allocation per single period. In addition, the genetic algorithm through a nonlinear programming was utilized for searching the rule curves. Capability of the developed model was evaluated by defining and analyzing of the three dam water resources systems in Zohre River. Calculations showed that the above combination improved the limitation modeling greatly, increased optimization convergence rate and made considerable flexibility for total process of planning and management in complex systems.

In this study, the effect of bed roughness and adverse slope on the characteristics of hydraulic jump in a rectangular channel was experimentally investigated. Experiments were conducted in a laboratory flume with a rectangular cross-section of 0.7 m wide, 0.6 m deep and 15 m long. Initial Froude numbers, adverse slope and roughness factor in the range of 3-6 were considered. Experiments were conducted in five adverse slopes in the range of 0-0.02 with four different roughness factors in the range of 0.0114-0.0191. Characteristics of hydraulic jump including sequent depth ratio, length of jump and the energy dissipation were studied. The results showed that the sequent depth ratio and length of jump decrease by increasing the adverse slope and roughness factor. The main reasons for these changes are effects of the weight as a result of increasing the slope and increase in bed shear stress as a result of bed roughness. Also, results showed that the the energy loss of the hydraulic jump increaseed by increasing adverse slope and roughness factor.

Fluctuations in soil moisture and salinity would often result in variation of root water uptake. In this study, separate and conjunctive effects of water and salinity stress were investigated for water uptake from two separate layers. Two levels of salinity (ECe) namely 1.0 and 3.8 dS/m and two levels of depletion of 30 and 60% for the available water were selected for this study. Each layer combined of a salinity level and a level of depletion of available water. Experiments were conducted in corn under open field conditions. For this reason, 16 treatments with 3 replications, and total of 48 lysimeters were selected. Soil profile was divided into two layers of 32 (up) and 48 cm (down). The uppermost layer layer was irrigated from surface irrigation method while the lower layer with a subsurface irrigation technique. Results showed that, the maximum water uptake appeared in layers with higher moisture contents and lower salinity levels. Lowering of water uptake in the upper layer could be compensated by lower layer to some degrees. In some treatments, even though water uptake was not compensated, however an increase in water stress in one layer resulted in higher water uptake in the other one. Adjustment of crops to new stress conditions resulted in the maximum uptake to be from the layer with minimum stress. This study revealed that compensation of water uptake occurs when adjacent layer would experience no stresses.

Scaling methods have been developed to describe the spatial variability of soils. Among them, physically based methods are more desirable in which the scaling factors can be estimated from the soil physical properties. Assuming that the pore size distribution of soils is lognormally distributed, Kosugi and Hopmans developed a physically based method to scale the water retention curve. However, similar to the previous methods, application of this method is limited to the similar soils. To alleviate this limitation, in this paper, a physically based method is proposed for dissimilar soils. Using this method, data of a wide textural range of soils can be scaled without the similarity condition and can be represented by a unique exponential reference curve. This method was validated using 487 sets of soil retention curves taken from UNSODA database including all the textural classes from sand to clay. The results showed that the proposed method had a better performance in scaling the retention curves than that of Kosugi and Hopmans. The criteria defined here for scaling error was obtained equal to 0.074 and 0.105 for the proposed and Kosugi-Hopmans method, respectively. In addition, it was shown that, in contrast to the previous methods, the scaling error of the proposed method does not depend on the soil texture and all the soils have an equal chance for being scaled.

To reduce the constructional costs of stilling basins, changes in geometries of cross section and plan of basin are sometimes used to adopt the basin with the upstream and downstream sections to eliminate transition structures. Any changes in the geometry of the basin would cause changes in the conditions and characteristics of the hydraulic jump. Hence, in this research, the effects of variation in both the adverse bed slope and the diverging angle of a gradually expanding stilling basin with rectangular section on the jump conditions were investigated both experimentally and theoretically. The experimental tests were conducted in a specially designed model for a wide range of bed slopes and longitudinal divergences of the basin walls. The important parameters of the jump, such as the length, sequent depth and the energy loss, were computed and compared to those in the classic jumps. Experiments was performed for 4 diverging angle (3, 5, 7 and 10°) and adverse bed slopes (2.27, 4.1, 5.61 and 8 percent) in addition to classic jump at wide range of Froude numbers (2.5-9). There is a good agreement between experimental and theoretical values of sequent depths of jump. The results show that for each diverging angle, increase in adverse bed slope from horizontal bed to 8 percent, caused approximately a decrease of the sequent depth and relative length of jump 47 and 35 percent respectively, and also an increase of the relative energy loss by 20 percents.

Buried porous clay capsule irrigation is one of the most important traditional methods that could be of great use on small and medium sized farms and gardens. Hydraulic characteristics of porous clay capsules are affected by clay type, clay percent, sand percent, T.N.V. %, wall thickness, soaking time, firing temperature and hydrostatic pressure. The present paper has attempted to evaluate the hydraulic characteristics of porous clay capsules based on firing temperature, soaking time, and hydrostatic pressure. Raw materials used for making porous clay capsules were obtained from calcareous soil of Nasr-Abad village of Gorgan city. The amount of sand added for improving hydraulic properties was 0, 200, 400, 600, and 800g into 1000g of Nasr Abad of Gorgan soils respectively. These produced clay capsules were named Gorgan-0, Gorgan-200, Gorgan-400, Gorgan-600, and Gorgan-800 respectively. Results showed that with increasing firing temperature, the soaking time of porous clay capsules decreased. Also the discharge of porous clay capsules, with increasing firing temperature increased. The relationship between discharge of Gorgan-0 and Gorgan-200 with hydrostatic pressures is linear and with increasing fine sand in Gorgan-400, Gorgan-600 and Gorgan-800, the relationship became non-linear. Meanwhile soil wetting shape with clay capsules followed a spherical trend, which is due to the low discharge of clay capsules.

Lining of irrigation canals with suitable materials is imperative for sustainable agriculture in water scarce areas. Durability and seepage losses of different linings are related to three technical characteristics i.e. external factors, meteorological conditions and kind of flow. Therefore, it is necessary that in different areas, all various linings be evaluated and suitable lining chosen for decrease seepage loss and optimum usage from water resource. Total length of lined irrigation canals in Hamadan province of Iran is 800 km. More than 60% of them are concrete-lined canals and the rest have stone linings. The aim of this research was to determine water seepage loss in the main stone-lined canals irrigation network that serves the irrigated area on Hamadan plain. Six main canals with total length of 15.25 km were chosen to study in this area. Water seepage in these canals was measured by the inflow-outflow method. While water velocity was determined using a current-meter. The water seepage loss at canals was between 0.24 and 0.65 m3m-2day-1. The average seepage loss was 0.34 m3m-2day-1. It was noted that the average seepage loss of the chosen canals was much smaller than the value of water seepage loss for open concrete-lined canals in this area (20%). With reviewing or replacing of this lining instead of the concrete lining, the loss of water can be reduced and planning for optimal use yearly more than 6.4 M.C.M. in the entire province, equivalent to 20% of Ekbatan dam volume. It’s because of durability and longer-lasting of stony lining in such cold climate conditions.

Kinematic wave equation is a simplification of the fully dynamic wave equation of the fluid flow in open channels. In this equation, the inertia and pressure forces are neglected compared to the gravity force and the friction. Due to the simplicity of kinematic wave, many researchers are still interested in this model in its range of applicability.Until now, various numerical methods such as Finite Difference (FD) and Finite Element (FE) have been used for solution of kinematic wave equation. Differential Quadrature Method (DQM) as an alternative numerical method has attracted the attention of some researchers because of its stability, accuracy and efficiency. In this study, the applicability of DQM for solution of the kinematic wave equation is investigated. For evaluation of this method, the results were compared with analytical solution and observed data.Results of this study show that the type of grid distribution affects the results significantly. The cosine grid distribution is better than uniform grid distribution as it was suggested by previous applications in the literature. DQM for simulating kinematic wave model is not sensitive to choice of the test functions. In general, DQM can be considered as another numerical method for kinematic wave equation using less number of grid points to achieve accurate results. It is also unconditionally stable. The main disadvantage of the kinematic wave equation is its failure to predict wave attenuation. This can be resolved by using diffusion wave model and the same numerical technique.

This research was carried out to study the effect of water and salinity stresses on yield and yield components of maize (KSC-260) during different growth stages in farming years 2009-2010. The research consists of three levels of irrigation water (100, 75 and 50 % treatments I1 to I3) and three levels of salinity irrigation water (salinity of water river (S1), S1+ 1.5 and S1+3 dS/m treatments S1 to S3) during three growth stages as vegetative (Experiment 1), flowering (Experiment 2) and after flowering (Experiment 3). The experiments were arranged according to a randomized complete block design with split plot layout. The results of this study showed that the interaction of water and salinity stresses had not any significant effect on factors (number of seeds per ear, 100-grains weight, grain yield, biological yield and harvest index) during all experiments. I3 and S3 treatments showed respectively 20, 23, 27.5 and 20.5, 26.4, 13.2 % reduction with respect to I1 and S1 treatments in experiment 1, experiment 2 and experiment 3, respectively. Flowering stage was the most sensitive growth stage to water and salinity stresses.

Growth of industry and agriculture in the plain of Nayshabur on one hand, and drawdown of groundwater levels and reduced water quality on the other hand, has stressed the necessity of locating potential groundwater sources to put to use in this plain. The purpose of this study is to present Fuzzy Analytic Hierarchy Process as a tool for determining suitable locations according to the qualitative and quantitative characteristics of aquifers. For this purpose, the qualitative and quantitative characteristics of aquifer such as transmission coefficient of aquifer, isodrawdown and isosalinity of the aquifer, were analyzed using available data. First, fuzzy membership function was determined for each parameters, and Index map was computed using AHP method with 0.05 Inconsistency Rate. The results showed that 55.77% of plain area has high operation capability, 8.52% of plain area has very high operation capability, 3.85% of plain area has low operation capability, and 0.42% of plain area is in the unsuitable zone. Zoning Index map indicates that south-east areas have very high and East Plains have high capabilities in pumping groundwater and can be considered as the most suitable areas for this purpose.

Recognizing climatic parameters impacting on crop yield is so necessary for yielding maximization policies. The main purpose of this study is to estimate crop performance under the effect of three climatic factors of temperature, rainfall, and SOI index in Hamedan, iran region in periods of 1978-1979 to 2002-2003 years. Results showed the number of yield significant correlations with three above mentioned climate factors are 18 for dry farming, and 12 for water farming. Also, results indicated that most of the monthly correlations corresponded with The March temperature and SOI, and annual rainfall and temperature. The Highest March temperature correlation with dry wheat yield was 0.532 while it was -0.456 for March SOI for dry barley. Also, it was seen that the highest correlation for spring and annual precipitation were -.549 and. 604 for dry Wheat respectively, and -.404 and. 456 for spring and annual SOI for watered Barley. Predicting the performance using stepwise regression method showed that multivariate regression models were able to justify about 66, 74, 86 and 72 % of the change in the yielding of wheat, barley, dry wheat and dry barley respectively. Furthermore, a Normal Root mean Square Error of 0.17 and a coefficient of determination of 0.86 represented a successful of the fitted model.

The objective of this study was to compare the performance of multiple linear regression and regression tree for deriving pedotransfer functions (PTFs) to predict soil saturated hydraulic conductivity (Kfs) and inverse of macroscopic capillary length parameter (*). Therefore, Kfs and * of 60 points of Azadegan plain in Shahrekord region were measured by multiple constant head method using single ring apparatus. Using some of the readily available soil data of two first pedogenic layers of the soils as inputs, multiple linear regression and regression tree were then applied to derive the PTFs. The accuracy and reliability of the derived PTFs were evaluated using root mean square error (RMSE), mean error (ME), relative error (RE) and Pearson correlation coefficient (r). Results indicated that regression tree predicted the parameters better than multiple linear regressions. Values of relative error (RE) and the mean square error (RMSE) for * estimated by regression tree was 0.24 and 0.019 (cm/min), respectively, that was 0.03 and 0.023 (cm/min) lower than those of multiple linear regression. Furthermore, results showed that bulk density, geometric mean and weight mean of peds diameter had the most major effects on saturated hydraulic conductivity and macroscopic capillary length. Regression tree and multiple linear regressions overestimated and underestimated the soil saturated hydraulic conductivity, respectively.

World population growth is reaching the point where available fresh water is insufficient for basic needs of mankind. The municipal wastewater account common revival the sources for amends water deficit, since long for irrigation had used in agriculture section. For purpose of assessment of municipal wastewater of Khorasgan University (KHUW) on soil quality, four treatments in three replications were designed at 2007. The treatments were included furrow irrigation with normal water (check), furrow irrigation with KHUW (FW), surface drip irrigation with KHUW (DI), subsurface drip irrigation with KHUW (SDI). The soil samples were collected from 0-15, 15-30, 30-45 and 45-60 cm in two stages (beginning and end of research period). In this research, some parameters of soil quality were estimated. The (EC, pH, OM, Cl-,, SO2-4) parameters were measured. The results show that the wastewater increases salinity soil but there is significant difference between DI and SDI only at surface(0-15cm). Also, using wastewater does not affect soil PH. Wastewater leads to increase of OM% soil at surface (0-15 cm) with significant different between DI, SDI and FW. SO2-4 show significant difference between DI with SDI, FW at 0-15 cm of depth and there was same condition for Cl- on (0-15 cm) depth. The results indicates that wastewater reuse causes to increase EC, OM, SO2-4, Cl-. In conclusion, it was found that better condition based on EC and other salt solution in comparison with other treatments.

Stochastic weather generators are used in a wide range of studies, such as hydrological, environmental applications and agricultural risk assessments and can produce time series of synthetic daily weather data of proper duration. In the present study, the performance of the LARS-WG model was analyzed in four northern and eight southern coastal stations of Iran, in relation to the simulation of wet/dry series, precipitation, temperature, solar radiation and the simulation of temperature extreme events. The results showed that the model performance was very acceptable in relation to daily distribution, monthly, and seasonal mean of almost every series. However, its performance in estimating the values of total monthly precipitation standard deviation, mean monthly temperature standard deviation and mean monthly solar radiation standard deviation was not tolerable. In the whole, the LARS-WG model had a better performance in northern stations in comparison with southern stations.

Stochastic weather generators are used in a wide range of studies, such as hydrological, environmental applications and agricultural risk assessments and can produce time series of synthetic daily weather data of proper duration. In the present study, the performance of the LARS-WG model was analyzed in four northern and eight southern coastal stations of Iran, in relation to the simulation of wet/dry series, precipitation, temperature, solar radiation and the simulation of temperature extreme events. The results showed that the model performance was very acceptable in relation to daily distribution, monthly, and seasonal mean of almost every series. However, its performance in estimating the values of total monthly precipitation standard deviation, mean monthly temperature standard deviation and mean monthly solar radiation standard deviation was not tolerable. In the whole, the LARS-WG model had a better performance in northern stations in comparison with southern stations.

Design of different types of hydraulic structures, flood plain zoning, and economic evaluation of flood protection projects require information on flood magnitudes and their frequencies. Regional flood frequency analysis resolves the problem of estimation of the extreme flood events for the catchments having short data records or ungauged catchments. One of the most common methods which are applied for frequency analysis is L-moment method. Superiority of this method to other ones is its less sensitivity to outlaying data. In this research, the L-Moments method is used to analyze the regional flood frequency of Kashafrood basin. Two kinds of homogeneity statistics, discordancy measure and heterogeneity measure, are used for studying the station matching and regional homogeneity. Based on the L-moment ratio diagram and statistic criteria, general extreme value (GEV) distribution is identified as the robust distribution for the study area. On the other hand, both the Log Pearson-III and the three-parameter lognormal distributions are acceptable at the at-site level.

The effectiveness of check dams on the morphology of ephemeral channels and their impact on sediment deposition was investigated in a semiarid catchment. According to results, dams located in downstream were more effective in deposition of fine sediment than upstream dams. The results showed that dams influenced the width/depth ratios. The stream channel became wider and flatter in downstream, resulting in an increase of the volume of sediment and present of fine sediments from upstream to downstream.