Iranian Water Research Journal

Abstract Bridge abutments cause constriction in river section and change the pattern of river flow. Due to presence of a bridge abutment in a river, velocity and bed shear stress increase, vortices are formed and finally local scouring around structure commences leading to a scour holes development. In order to reduce scouring around bridge abutments, one method is to implement collars. They mitigate scour and produce a time delay in scour holes development process by deflecting the down flow. In this research, the effect of a collar on scour reduction around vertical semicircular bridge abutments was investigated experimentally. Experiments were conducted in a flume 6 m long, 0.8 m wide under clear water condition (0.85). The results showed that collars reduced the scour depth significantly, and 63.5 to 100 percent reduction on the scour depth and delay on the time of scouring were observed using different collars. Maximum scour depth also moved downstream of the bridge abutment.

Abstract Among various approaches for mapping isohyets are regression analyses techniques that use relationship between precipitation and geographical factors. Current study was carried out to compare global regression methods (multi polynomial regression and ordinary least square methods), local regression methods (local polynomial regression, geographically weighted regression) and decision tree regression. Average of 20 years annually precipitation data of 185 meteorological observations over Gilan Province and its neighboring stations were used for modeling of spatial distribution variations of mean annual precipitation by using other variables like elevation and point locations from the sea level. Comparison between results using cross validation technique showed that geographically weighting regression method has the highest accuracy to estimate mean annual precipitation (R²=87 and RMSE=147mm) and can be used to map isohyets in Gilan province.

Abstract Drought is one of natural disasters related to prolonged decrease of humid in a region. Meteorological drought is related to prolonged decrease of precipitation and has several characteristics (severity, duration, magnitude). These characteristics are interrelated and because of this correlation, drought monitoring based on one characteristic cannot fully represent region conditions. Thereby, the best method is monitoring of drought characteristics simultaneously. In this research, meteorological drought was analyzed in Kermanshah province based on two characteristics, i.e. severity and duration using multivariate copulas function. Three families of Archimedean copulas were fitted to drought severity and duration. Gumble copula was selected as the best fit. Finally, the joint probability and return periods are determined using Gumble copula in the study area. The results showed severe drought has occurred in the western part of region with 259.3 mm severity and 18 months duration. Based on bivariate analysis, this drought has lowest probability and biggest return period than other droughts in this region.

Abstract Furrow irrigation is one of the surface irrigation methods that hereby, increase of its efficiency using optimal design and management tools were considered. In this research, a new methodology was presented to determine optimal furrow length and inlet flow rate using simulation- optimization model for three regimes including continuous, cutback, and surge regimes, and their performance were evaluated using field data of clay loam texture. To evaluate the effects of soil texture on optimization results, optimization processes were applied for sandy loam and clay soil texture. In clay loam soil, continuous regime showed longer optimal furrow length than other regimes. Surge regime needed higher inlet flow rate and shorter furrow length than other regimes to achieve maximum irrigation water efficiency and uniform distribution. Also, in continuous regime, optimal furrow length and objective function changes showed irrigation efficiency decrease by increasing inlet flow rate. According to investigation of the effect of objective functions on optimal furrow length, objective functions including combination of application efficiency and uniform distribution, or combination of tail water and deep percolation, are recommended for furrow design and management.

Abstract The drawdown of water table in the karst aquifers has occurred since 2007 due to continuous droughts. In this research, different responses of the Ilam-Sarvak (Tanush and Shavish anticlines) and Asmari (Kamarderaz and Chalkhoshk anticlines) karst aquifers in southwest of Izeh were inquired to the decrease of precipitation recharges. The precipitation, and water level data, the pumping tests in seven karst wells, and the autocorrelation analysis on hydrogeologic time series were applied to the study of the hydrodynamic behaviors of the karst aquifers. The analysis of the representative well hydrographs indicates that drawdown in Asmari and Ilam-Sarvak karst aquifers were 1 and 140 m, respectively, from 2007 to 2009. The double porosity function of Ilam-Sarvak Formation and the base flow in Asmari Formation were deduced from the autocorrelation and pumping tests interpretations.

Abstract Agricultural development has increased exploitation of groundwater resources of Mahidasht plain, Kermanshah, Iran. The increased utilization on one hand, and severe droughts conditions on the other hand, have intrigued severe drop in groundwater level in theis plain. To mitigate the crisis, artificial recharge of groundwater is a suitable alternative. Selecting feasible locations for the implication of artificial recharge is the most important step in such projects. In the present research, the Geographic Information System (GIS) was utilized for locating of flood spreading. For this purpose, six important parameters were selected in feasible artificial recharge by flood spreading method. Each of the data layers in GIS environment was developed. Layers were classified with respect to their importance in recharge feasibility selection and hence were valued by Analytical Hierarchy Process (AHP) and then integrated in Geographical information system (GIS) environment. The results of this research showed that 6 percent of Mahidsht plain positioned in five separate regions with total area 2498.75 hectares are the most suitable location for artificial groundwater recharge by application of flood spreading method. The selected regions were categorized according to areas of priority sites of runoff production according to the availability of water resources

Abstract One of the main agricultural problems in developing countries is the lack of optimal productivity due to unsuitable allocation of resources. In order to select appropriate crops for cultivation in Orzoueyeh region, this research was conducted in years 2007 and 2008 on four farms. To determine water use efficiency, regional data for major products includinge cotton, wheat, sugar beet, and maize were collected and the amount of water use efficiency for each of the products of different fields was calculated. Economic, net Benefit and water economic efficiency per unit of water volume were calculated. The results showed that maximum water use efficiency was in sugar beet cultivation (5.43 kg/m³) and the minimum was in cotton (0.19 kg/m³). Water economic efficiency was determined for the various products. The results indicated that this indicator for wheat, sugar beet, corn, and cotton were changed between 1196-2506, 1725-3294, 2694-4635 and 1734-2747, respectively. Finally, the priorities of different crops were determined from a water economic efficiency perspective in selected fields. Accordingly, the priority for fields of 1 to 4 was determined to be corn and also wheat was determined as the last priority in all fields.

Abstract Quantitative description of infiltration process is needed for both irrigated and rainfed agriculture for optimal management and designs purposes. The most difficult task in the field, however, is to determine the spatial variability of infiltration process, which is of great importance for precision agriculture. The objective of this study was to quantify spatial variability of infiltration models by using scaling in Kavar plain, east of Shiraz, Iran. A number of 161 infiltration experiments were conducted on a systematic squared grid pattern with 500*500m over the 4000 ha area, using double-ring method. The observed infiltration data from all the experimental sites were fitted to three selected infiltration models. The best-fitted model for individual sites was identified. Using the least-squares technique, the Philip model was selected as the best model to describe infiltration process. Infiltration rates of the area generally indicated low basic infiltration rates (1.11?–31.11 cm/hr) for most sites, and average amount of them was 6.69 cm/hr. The parameters of Philip model (S and A) showed a wide variation among the test sites. The sorptivity-based scaling factor ∝_S and the transmissivity-based scaling factor ∝_A were computed and the observed infiltration data were scaled. Scaling achieved through ∝_A was found better than through ∝_S. Optimum scaling factors ∝_opt were then obtained by the least-squares.

Abstract Different kinds of irrigation canal lining materials have different durability based on climatic conditions. Therefore it is necessary that in different areas, all various lining approaches be evaluated and suitable lining be selected to decrease seepage loss, and optimum usage from water resources. The aim of this research was to study the effect of concrete lining to reduce water seepage loss in the main irrigation earth canals that serves the irrigated area on Hamadan province. Total length of concrete-lined irrigation canals in this province is 500 km. 12 main lined and unlined canals with total length of 13.5 km were chosen to study in this area. Water seepage in these canals was measured by the inflow-outflow method. Water flow velocity was determined using a current-meter. The water seepage loss at unlined-canals was between 1.32 and 3.06 m³m^-2day^-1. The average seepage loss was 2.39 m³m^-2day^-1 equal to 16.4% in 1Km. The water seepage loss at concrete lined-canals was between 0.55 and 2.40 m³m^-2day^-1. The average seepage loss was 1.74 m³m^-2day^-1 equal to 8.2% in 1Km. Based on statistical analysis, there was no significant difference for seepage loss between lined and unlined canal types. It was noted that the average seepage loss of the chosen concrete lined-canals was much higher than the standard value of water seepage loss for open concrete lined-canals.

Abstract Presence of nitrogen as nutrient element in municipal effluent, and discharging it to water resources leads to increasing growth of different types of algae, finally leading to eutrophication. So, it is necessary to decrease the amount of nitrogen as much as possible before discharging effluent to water resources. The use of plants is one of the effective methods for refining polluted water. An experiment was carried out with two plants elodea (egria densa), and duck weed (lemna minor) with 4 treatments and three replicates in a completely randomized factorial design in experimental pilots with the batch. Treatments included effluent with the plant, effluent diluted with the plant and no plant (control) in two levels (initial and diluted effluents). Parameters of nitrate, ammonium, organic nitrogen and total nitrogen were measured in trend time of 8, 16 and 24 days in effluent samples and total nitrogen of plant tissue at the beginning and end of experimental period. The results showed that the concentration of nitrate, ammonium, organic nitrogen and total nitrogen in plant treatments were significantly lower than treatments without plants, so that Elodea treatment reduced the concentration of nitrate, organic nitrogen and total nitrogen by 31.56, 10 and 10.7%, respectively. The highest total N uptake was found in duck weed plant. It is concluded that duck weed is more effective in the removal of nitrogen than the elodea plant.

Abstract researches have been done on scouring, an appropriate equation to predict scour at bridges foundation has not been presented yet. In this research, an experimental study on clear water scour at pile groups under steady flow conditions at threshold velocity is presented. Experiments were conducted in a flume of 46 m length, 1.52 m width, and 1.9 m depth, and uniform bed material of median particle size of 0.8 mm. The objectives of this study were to present changes in scour at multiple piles due to the pile arrangements and present an empirical relationship to estimate the scour depth at multiple piles with different arrangements. Wide ranges of pile group arrangements were studied with pile diameters of 60 mm and 42 mm. The number of piles in line with flow (m) and normal to flow (n) were regularly increased at each successive experiment. In total, 40 experiments were carried out using possible arrangements of pile group where maximum number of n and m were 4 and 10 respectively. It was observed that the scour at pile group is affected by pile arrangements. The collected data were used to propose a new empirical equation to compute effects of the studied variables (m and n). The output of this research can be used to improve the pile group arrangement procedure to estimate local scour depth at multiple and complex piers.

Abstract Flood routing is a procedure that is used for investigation of variations of the peak, time to peak and duration of the flood hydrograph along open channels. This procedure can be performed using either hydraulics or hydrologic procedures, depending on available data of the river. In the present study, different aspects of hydrologic models that consist of the linear Muskingum, nonlinear Muskingum, Convex, modified Att-Kin and Working-Value procedures were investigated through four benchmark examples and field applications in the Karun River using eight observed flood events. Furthermore, the numerical solution of the Saint-Venant equations by considering all of the terms of the momentum equation as a hydraulics procedure was considered for comparison purposes. The criteria used for models evaluation included attenuation of peak discharge (ε), lag of peak discharge (ξ), and mean relative error (E). The results show that the relation between weighted-flow and storage volume that is based on hydraulics and hydrologic characteristics of river reach and its temporary storage is the essential criterion for investigation of the effectiveness of a hydrologic routing procedure. Also, it can be said that in the conditions of the shortage of the data of the dynamic wave model, the linear and nonlinear Muskingum models are offerable in design projects as best hydrologic models.

Abstract The main goal of this research is zoning of Dargaz plain groundwater quality for drinking purposes. Due to increasing population and demanding for new water resources, study and evaluation of water quality is very important. Based on Schoeller diagram and using Analytical Hierarchy Process and pair wise comparison matrix, the optimum weights of every hydrochemical variables are selected. To evaluate Dargaz plain groundwater quality for drinking water, data from 25 wells during 2008 to 2009 were collected. Raster maps of the study area were prepared with different methods of interpolation. Due to uniformly water quality changes in study area, we used the Inverse Distance Weighted interpolation method for preparing zoning maps of sulfate, sodium, chlorine, total hardness, electrical conductivity, and total dissolved solids. Final weights of hydrochemical variables were determined by pair wise comparison matrix and Analytical Hierarchy Process. Finally, integrating and overlaying the hydrochemical layers and applying the final weights in the GIS environment, the qualitative potential map of study area was prepared. Finally, suitable sites for drinking amenity were identified. The results showed that the southwest part of study area has the best groundwater quality for drinking purposes.

Abstract Erosion and runoff caused by rainfall in catchments are important issues in natural resources management. The Cellular Automata (CA) approach is an idealized physical system, which has capability for simple simulation of a complex process like erosion and runoff. This study was conducted with the aim of studying performance of CA method in simulation of erosion and runoff caused by rainfall. This method was used in an experimental plot located in the farm of Nuclear Agricultural Research Center in Zaferanieh (Karaj). Results of simulation showed that the size of the cells, hydraulic parameters, selection of appropriate time steps, and the number of iterations had a large effect on simulation results. In comparison between observed and simulated results, the values of correlation coefficient and root mean square error for runoff were found to be 0.98 and 0.034, respectively, and for sediment yield it was found to be equal to 0.97 and 0.045, respectively. The results showed that the CA method can be used as an accurate and applicable scheme for predicting the amount of erosion and runoff originating from rainfall.

Abstract One of the limitations of Boussinesq equation is that its parameters (e.g., hydraulic conductivity) are scale-dependent. In this work, a fractional Boussinesq equation was obtained by assuming power-law changes of flux in a control volume and using a fractional Taylor series. Unlike Boussinesq equation, the parameters of fractional Boussinesq equation are constant and scale-invariant. The linear form of fractional Boussinesq equation was solved by using spectral representation method and an analytical mathematical model was derived to calculate subsurface drains spacing. The optimal values of parameters of mathematical model developed in this study and Glover-Dumm's model were estimated from inverse modeling. In the inverse methodology, water table data between two subsurface drains and the optimisation method of Bees algorithm was used. The accuracy of obtained model was investigated using water table data between the two subsurface drains and was compared to Glover-Dumm's model. The results indicated that the mathematical derived in this study predicts the water table profile between two subsurface drains more exactly than Glover-Dumm's model.

Abstract By increasing population and fresh water deficit, the importance of water resources management increases. Agricultural, industrial and municipal activities also threat the quality of groundwater resources. Groundwater resource is the major supplier of drinking and agricultural water in the Sharekord Plain, Chaharmalal&Bakhtiari Province, Iran. Therefore, conserving the quality of this source of water is very important. The objective of this research was to evaluate DRASTIC model for mapping the vulnerability of the Shahrekord Plain groundwater. The model consisted of seven effective parameters of depth to water table, net recharges, aquifer media, soil media, topography, vados zone, and aquifer hydraulic conductivity. Thematic maps of required parameters were prepared and overlayed in GIS media by formation the databank of the plain using the relevant spatial data and attributes. The results indicated 11.5%, 79.6% and 8.9% of the area are in very low, low and medium vulnerability classes, respectively. The results also revealed the higher vulnerability of the north, south-east and west of Shahrekord Plain compared to the middle plain. The correlation coefficient between the vulnerability map and nitrate concentration of groundwater was 0.43.

Abstract Zayandehrud basin contains important water transfer projects, like transfer from Kuhrang springs to the basin and transport from basin to the Yazd and Kashan cities. Assessment of the impacts of these projects (and guidelines for alleviating these impacts) on water supply capability of Zayandehrud hydro-system, especially under long-term hydrologic uncertainties, is a very important issue for water sector decision makers and waterbasin stakeholders. In this research, the impacts of drought and future development of water transport projects is analyzed by a non-linear long-term optimization model for a 10-year horizon. Results showed that in normal (and transfer development scenario) conditions, on average 43% and 57% withdrawal from river and groundwater, respectively, leads to the least shortage in water supply to demands. Besides, Zayandehrud hydro-system operation can be managed in the case of a severe drought with 40% reduction in river flow that only 6% reduction occurs in water supply in comparison with normal condition. Analysis of the results showed the robustness of multi-period optimization model in minimizing the impacts of drought and water transfer development by making use of the spatial and temporal potentials of Zayandehrud hydro-system.

Abstract So far flood forecasting and simulation in hydrologic literature suffers from lack of explicit recognition of forcing, parameters, and model structural error. However, since any model is a simplification of reality, there remains a great deal of uncertainty even after the calibration of model parameters. Hydrologic models often contain parameters that cannot be measured directly but which can only be inferred by a trial-and-error (calibration) process that adjusts the parameter values to closely match the input-output behavior of the model to the real system it represents. This work addresses calibration of spatially physically based rainfall-runoff model (AFFDEF) implemented in FORTRAN language programming and implemented to quantify parameter uncertainty and its effect on the prediction of streamflow for Abolabbas subwatershed (??? km?) located in Khuzestan Province. This research was intended to take advantage of novel Markov chain Monte Carlo (MCMC) sampler entitled DiffeRential Evolution Adaptive Metropolis (DREAM) that is especially designed to estimate the posterior probability density function of hydrologic model parameters efficiently in complex high-dimensional sampling problems. The results for calibration period showed that observational discharge values especially peak values bracketed well within %95 confidence interval. Regarding rising and recession limb as a result of initial conditions and uncertainties originating from baseflow determination procedures have caused predictions to be out confidence interval. Updating the scale and orientation of proposed distribution during sampling is the main advantage of MCMC scheme compared

Abstract According to the studies from Hadley Center for Climate Prediction and Research (HCCPR), it is predicted that in the 21st century extreme droughts would threat millions people due to global warming. Researches have been showed that the areas affected by extreme droughts have increased in the country in the 21th. This study was performed to answer this question that "how would various climates of Iran respond to global warming in case of drought?" For this purpose, monthly precipitation and temperature data for the selected stations of the country (representing various climates of Iran including Bandar Anzali, Bushehr, Gorgan, Tehran, Mashhad, and Zahedan) were produced using statistical downscaling of CGCM? model under two scenarios A1B and A2 for 1971-2000 via change factor method. Next, a representative index of agricultural drought, i.e., the adjusted Reconnaissance Drought Index (RDI, based on precipitation and temperature data) were calculated for the base period 2011-2040and future periods (1971-2000) under two scenarios A?B and A? in stations of interest. Probabilistic analyses of drought characteristics for present and future climate conditions were done and compared. The results showed that in the period 2011-2040, the likelihood of duration and intensity of droughts will increase in all stations under investigation. Also, it was found that the sensitivity of extreme climates (very wet and very arid) to global warming is more than the other climates (arid, semi-arid and Mediterranean).

Abstract One of the aquatic structures used for protecting erodible channel beds is serial step- pools. These steps are exposed to danger of scouring similar to the vertical drops structures. The purpose of this paper is to evaluate scouring rate downstream of the step- pools. For such a task, the laboratory flume was used. The experiments were conducted providing steps with vamp slope angles of 0°, 20°, 30° and 40°, and discharges of 10, 20, 30, 40 and 50 liters per second with flume slopes of 1%, 2% and 3%. The results showed that by installing vamp segment on the steps with slope angle of 40°, the maximum depth of downstream scouring in comparison with base case (step without vamp) is decreased by 41%, 15% and 21% for flume bed slopes of 1%, 2% and 3%, respectively. Also, these results denote that installation of a vamp on the steps caused location of maximum scouring depth moving significantly toward downstream helping step stability. Based on the results of this paper, it is declared that using vamp segment on the step, increases the pool- step efficiency for protecting erodible channel beds.

Abstract Finding hydrologic criteria for regions with insufficient or no data is important in water resources studies. In basins with lack of streamflow data, it is preferred to use black-box methods to relate inputs (meteorologic and physiographic parameters) and output (river discharge) without the analysis of the process. Artificial Neural Networks model is one of the methods which can be used in such situation. In the present research, MLP artificial neural network with back-propagation algorithm is used to estimate monthly discharge of Beheshtabad watershed. The results showed that last-month's discharge and precipitation of two months ago were the main input parameters. The best model obtained for the Beheshtabad station was used for Babahaidar and Kuhe-sokhteh sub-basins and the measured and estimated discharges were compared. The results showed that the calibrated model obtained for the main hydrometry station could be applied in sub-basins.

Abstract In this study, nitrate and nitrite concentration changes in subsurface water resources Arak, during different time were investigated. Results showed that mean concentrations of nitrate and nitrite, respectively 32.43 and 0.005 mg/L^-1 is. In total nitrate concentration in % 28.3 of the wells, concentrations of nitrite in 73.6 percent of the wells were more than standard. The highest and lowest contamination, in 2004 and 2003 was respectively. Trend of nitrite and nitrate ions, was increased. For detection of precipitation relationship with nitrite and nitrate concentrations, linear regression model was used. Determination Coefficient of model for nitrate and nitrite were 0.99 and 0.78, respectively. Statistical analysis of nitrate concentration levels showed 67 % of the cases, the correlation coefficient of nitrate ions about 0.8 and its significance in 0.05 was.

Abstract Using the surface drip irrigation system tends to improve irrigation efficiency, and this system is appropriate for solving the problems of water deficit and drought. In this study in summer of year 2009 at a selected field in Marvdasht region in Fars province, the surface drip irrigation system was used for cropping corn. The experiment was done on randomized complete blocks as a strip split plot design with three replicates. The main plot was three drip spacing (60, 70 and 75 cm), and the subplot was two level of irrigation (full and alternate). At the end of the season, the crop yield and water use efficiency were measured. The results demonstrated that the treatment of 60 cm of drip spacing with full irrigation had the most crop yield (equal to 13289 kg ha^-1), and the most water use efficiency (equal to 1.78 kg m^-1), and the treatment of 75 cm of drip spacing with alternate irrigation had the least crop yield (equal to 6657.3 kg ha^-1), and the least water use efficiency (equal to 0.89 kg m^-1). Therefore, using the treatment of 60 cm of drip spacing with full irrigation can be suggested for the study area.

Abstract This paper presents numerical modeling of pressure oscillations caused by sudden closure of pipe according to the second order Godunov type finite volume scheme by solving the momentum and quantity equations of transient flows. The transient friction is applied to the model using three kinds of fiction models: quasi-steady Darcy-Wiesbach friction model and unsteady Brunone and Vardy-Brown friction models. To verify the developed model, calculated pressure oscillations considering proper boundary conditions, in a range of Reynolds number from laminar to turbulent flows, is compared with experimental Results. The quantitative and qualitative evaluation of present model will result in selecting a proper transient friction model for each initial Reynolds number.

Abstract Maroon Dam in Khuzestan province has an important role in regional water supply. Therefore, accurate estimation of inflow discharge to this dam in the coming years will have an important role in water resources planning. In the present study 41 years (1968 to 2009) of annual discharge of Idanak hydrometric station which is located on the Maroon River were used. Different models such as the autoregressive (AR), autoregressive moving average (ARMA) and contemporaneous autoregressive moving average (CARMA) were fitted to data. After performance of necessary tests, CARMA (1,1) model with the least Akaike Information Criterion (AIC) and Schwarz Information Criterion (SIC) has been known suitable. According to final selected of best model the artificial inflow discharge to Maroon Reservoir is produced, and the results are presented in this research.