Iranian Water Research Journal

Abstract Knowing the effects of various environmental stresses on plant's physiology is necessary to get information about the plant's resistance and survival mechanisms. Drought stress is one of the most common stresses that always threatening agricultural products in widespread parts of the world. Therefore, considering the shortage of water resources, improving water use efficiency in agricultural fields and paying more attention to usage and development of water saving strategies are necessary. As freshwater resources have declined, irrigating crops to meet their full demands are difficult. To reduce the irrigation volume, irrigation techniques such as Deficit irrigation (DI) have been developed meeting the minimum crop water requirement without any significant reduction in crop yield and quality. During the last decade, a novel deficit irrigation strategy named Partial rootzone drying (PRD) has been developed. In PRD one half of the root zone is irrigated while the other half falls dry out. Irrigated and dry sides are periodically switched. PRD irrigation has been tested for different field crops, fruit trees and vegetables. In most cases, PRD irrigation has shown a great potential to increase water use efficiency and to maintain yield. It has been shown that PRD can greatly induce the initiation and growth of secondary roots, which improved the ability of the plant to absorb both water and nutrients from the soil matrix. It seems the combination of irrigation techniques and mechanized irrigation systems such as drip irrigation can significantly improve agricultural water use efficiency.
For this purpose, the effects of deficit irrigation and partial rootzone drying techniques on potato (Solanumtuberosum L. cv. Agria) yield and some components of yield has been studied. This research was done in a field at Shahrekord University in spring, 2012.
The soil texture's field was clay and soil moisture contents at field capacity (FC) and wilting point (PWP) were 37.33% and 15.49%, respectively. A completely randomized block design with seven treatments and three replications was used. Each block (23m × 2.5m) was divided into seven plots. Each plot consisted of three rows of 2.5 m in length. Blocks were bordered by a 1.5m wide protection area.
The tubers were planted on June in rows (75cm between rows and 25cm between tubers). Potatoes were subjected to water treatments Full Irrigation (FI), Deficit irrigation (DI) and Partial rootzone drying (PRD) in three level of soil matric potential (-60, -80, -120 kPa) after tuber initiation. Drip irrigation was used in field and time domain reflectometry (TDR) sensors were used to monitor soil moisture. In FI and DI treatments, one drip line was placed in the center of each ridge. The distance between emitters was 25cm and they were placed near plants. Their discharge rate was 2 (L h-1). In PRD treatment, two drip lines were placed in the center of the ridge. The two drip lines were placed in parallel and emitters distance were 50cm. Some of the physiological and morphological characteristics of the plant were measured in final crop harvest and analyzed by SAS v.9 software. Analysis of variance showed that the difference between irrigation treatments was significant in 1% probability level in most of plants characteristics. Also, with increasing the stress severity, the difference between PRD and DI irrigation was increased. PRD was able to maintain higher biomass production plant under water stress. The results showed that highest and lowest dry biomass was observed in FI (226.49 gr/plant) and DI-120 (187.45 gr/plant), respectively. The maximum and minimum dry weight of root were observed in PRD-120 (8.98 gr/plant) and FI (7.69 gr/plant), respectively. Tubers from each treatment were graded into various size classes and weighed. Among the tuber sizes, the categories of 40-60mm diameter were considered as marketable. Results showed PRD technique increased the marketable yield more than DI.
The maximum and minimum dry matter tuber were seen in PRD-120 (113.03 gr/plant) and DI-120 (98.169 gr/plant), respectively. The maximum and minimum fresh weight of tubers were observed in FI treatment (0.570 kg/plant) and DI-120 (0.430 kg/plant) .the maximum and minimum water use efficiency (WUE) was observed in PRD-120 (5.11 kg/m3) and DI-60 (4.268 kg/m3), respectively. This treatment increased WUE by 14.33%. Also, the obtained results showed that water stress induced in level of soil matric potential (-60, -80 and -120 kPa), reduced water used by 9.85, 16 and 22.45% in field, respectively.
These results showed in comparison to the traditional deficit irrigation strategy (DI) in which the crop is subjected to some degree of water stress, PRD is a successful alternative to FI for saving irrigation water.

Abstract Considering the complexity of water resource systems, nowadays managers have widely
accepted optimization models as efficient tools to reach to a useful decision in this case. The
existing optimization models provide new opportunities for better decision making in field of
water resources development and planning. Using optimization methods allows decision
makers to make the most appropriate decisions among the solutions available for water and
soil resources. Optimization is a method which the best possible answer for a problem is
determined according to the target and the existing conjugations, which are specified by
functions and mathematical relations. The optimal problem has a target function and several
constraints. Math planning is suggested as a useful and efficient way to solve resource
allocation problems, especially when decision variables, constraints and various parameters
are examined. Linear programming is one of the simplest and most practical optimization
models. This type of planning can be used for issues with simple relationships such as direct
resource allocation to complex operational and management issues. Since all the
mathematical relations contained in this model are of the first order type, it is called the linear
model. Hamedan -Bahar plain has faced many problems such as lack of water resources,
decline of underground resources and the negative balance of groundwater in the in recent
years, a part of agricultural land in Hamadan-Bahar Basin is located in Bahar city and other
part in Hamedan city. The water needed by the agricultural sector in the Bahar city is
completely extracted from underground resources and in Hamedan, about 80% extracts from
underground resources and the rest from the surface resources. In this region, the first priority
is the allocation of water resources to the drinking sector and the second priority belongs to
the industrial sector, and agriculture sector is in the third priority. Due to this priority as well
as lack of water resources in the region, the water need of crop pattern is not fully ensured. In
this research, it has been tried to compare the different methods of planning, with considering
the priorities of water resources allocation and percentage of water supply needs in
agricultural sector. So linear programming model with the goal of 1- determining the optimal
cultivation pattern, 2- determining the optimal allocation of surface water and underground
water sources, and 3- maximizing the benefit from crop production were created. This model,
based on available water resources and also with considering limitations, determines the
pattern of crop and the amount of water allocated, so the most benefit from crop production
will be obtained. So to study the cultivation pattern on this plain and water resources
management scenarios, linear program and LINGO software have been used. Objective of this model was maximization of benefit and optimized allocation of water and cultivation pattern.
Evaluating three Scenarios of optimization of cultivation pattern in current situation,
optimization of cultivation pattern in changing irrigation method and optimization of
cultivation pattern by limitation of ground water utilization, showed that, optimization of
cultivation pattern in changing irrigation method is better than two other ones and have more
benefits. Water consumption of cultivation pattern shows 23.8 % decrease and production,
area of cultivation and advantage show in order. 13.1%, 12.7% and 15.8% increase. The
results of this research consider the necessity of changing the pattern of water consumption in
agriculture as an optimal solution to overcome the problems of dehydration and reduce the
reservoirs of aquifers. Meanwhile, providing social and cultural backgrounds for modifying
the pattern of crops by replacing less-water-based products with more economic costs,
instead of high water requirements products, can reduce water use and improve conditions
and Sustainable use of water resources in the region. Due to the proper allocation of water,
demand management and water consumption patterns, especially in the agricultural sector,
can create a better and more stable economic situation. Finally, it can be said that with the
help of planning and optimization models, it is possible to examine and compare different
methods in the field of water resources management and to make the best decision. Finally, it
is suggested that other models such as nonlinear planning and more limitation and scenario,
especially changes in cultivation pattern be used, and compared with the results of this study.

Abstract Desertification is one of the global phenomena affecting natural resources which occurs not only in arid and semi-arid regions but also in some of the areas in semi-wet regions. Evaluating desertification in a region with vulnerable climate faces unpredictable and damaged conditions plays a significant role in evaluation of the environmental capabilities, prevention of desertification, and restoration and rehabilitation of degraded areas.Destroying the water resources, both their quality and quantity, can lead to decrease in biomass and resulted in desertification. The decreasing levels of ground water resources and deteriorating water quality are considered among desertification processes.
Nowadays, groundwater exploitation in arid and semi-arid regions for agricultural lands has increased and subsequently over-exploitation of these sources has degraded groundwater quality. Therefore, investigating the groundwater quality and its effects on the increasing rate of desertification intensity is a necessary task. In this research, the effects of groundwater quality on the desertification in Mehran plain have been investigated by employing water quality parameters including electrical conductivity, total dissolved solids, sodium adsorption ratio, and chloride using the Iranian model of IMDPA.
In the IMDPA model, a weight ranging from 1 to 4 was assigned to each layer based on its influence on desertification according to literature renews and researches performed by other researchers and geographical condition of the Mehran plain. Value 1 and value 4 indicate the best and the worse conditions of desertification, respectively. Numerical value of produced indices were transformed to thematic maps in ArcGIS Desktop 9.3. In order to determine the current quality of water in Mehran Plain, the data obtained from 9 quality wells located in the area have been used and analyzed over three time periods (2001-2004, 2005-2008, and 2009-2012). Then, to investigate the desertification intensity of Mehran Plains based on the IMDPA model, the criterion of water quality was used. After determining the numeral value of each parameter, the standard numerical value is determined based on the geometrical average of the selected criteria.
The information layers related to each index and criterion for all the three periods were prepared using interpolation and weighting methods in GIS. After preparing the related layers for the criterion of water quality in selected wells, the measures were combined in Arc GIS 9.3 software application to obtain the final map for the desertification status of the region for all the three selected time periods. Finally, they were classified in desertification classes of low, medium, intense, and severe intensification.
The results show that the indices of chloride and sodium absorption ratio duo to their locations in the low desertification class and quantitative value of less than 1.5 are not very effective on the intensity of desertification in the region. Based on the results, the amount of chloride and the sodium absorption ratio over the entire study region during the recent years have not fluctuated significantly, so that many of the areas are classified as low desertification and the effects of this index are not readily visible in this region. The total dissolved solids show a greater change compared to chlorine and sodium absorption ratios in the last period in so that based on this index, during the two first periods, the region is classified as low desertification while in the last period, due to higher concentration of these substances, the region is classified as mild desertification. The desertification intensity map of Mehran Plain based on the index of electrical conductivity shows that the intensity of desertification from the beginning of the period has been increased towards the end of the period in a way that 8.95 percent of the region in the first period is classified as intense desertification and in the last period, the extent of this area reaches 14.47 percent of the entire region. Moreover, the desertification map based on the indices of ground water quality during these periods shows that almost 72 percent of the region is classified as low and negligible desertification.
Decreasing of ground water levels caused by digging multiple wells has led to an increased electrical conductivity of the water from these wells as well as their salinity. Intense decline of water level due to uncontrolled withdrawal and other factors such as climate change, drought, and irrigation methods have increased the water salinity, which in turn increases the salinity of the soil in the study area.
The results obtained from evaluating the average weight of the quantitative values of the selected indices for the water quality showed that in the studied region, the average weight of the criterion of water quality is in negligible and low desertification class. Among the indices assessed for water quality, the obtained value (the score) for the electrical conductivity is higher than those for other measures, so, it has more effects on increasing the desertification intensity in the region regarding the quality of water criterion (i.e. it has caused a rise in the final amount of desertification since the value of each criterion is obtained from the geometric average of the numerical values and the value of the total desertification score is obtained based on the geometric average of the numerical value of the criteria). Hence, the electrical conductivity index is the most important index in the desertification of the region.
Considering the fact that one of the reasons behind higher electrical conductivity is the low level of water, it is recommended that uncontrolled withdrawal be avoided in this region as well as similar regions all over the country by making the wells smart using devices such as electronic cards for water withdrawal. In other words, after withdrawing a predefined quantity, there must be a power outage so that nobody can withdraw any more water. At the moment, unfortunately there are several unauthorized wells withdrawing water in all regions in the country which lead to decrease in levels of ground water and caused aquifers go dry. Hence, it is recommended that these unauthorized wells must be closed since preventing uncontrolled withdrawal is one of the effective ways to solve the water crisis.

Abstract Many of heavy metals discharge to water resources through wastewater. One of these heavy metals is Chromium. Two types of Chromium remain stable in the environment. Chromium(III) is a necessary ingredient for human body. But Chromium(VI) is toxic and even causes lung cancer. Industrial activities like plating, cement, steel, cannery and etc. produce large amount of contaminated sewage, so make the wastewater infected. The amount of Chromium(VI) allowed for agricultural water is 0.1 mg/lit. Many experiments include electrochemical deposition, ultrafiltration, ion exchange, reverse osmosis and natural biopolymers have been used to remove Chromium(VI) from sewage. Chitosan has the highest capacity to remove various metal ions. In this study, adsorption of Chromium(VI) ions from aqueous solution using chitosan biological adsorbent was investigated. In these experiments different doses of chitosan 1, 2, 3, 4, 5, 10, 15 and 20 gr/lit were mixed with the different concentration of Chromium(VI) 12.5, 20, 30 and 40 mgr/lit and were shaken for two hours with 450 rpm. The top layer of the solution was transferred to another container and every 20 minutes, concentration of metal ions was measured by an atomic absorption device. Experiments were performed 5 times and then average of the results was used in calculations.
All experiments were carried out at room temperature. The effect of different doses of chitosan at pH 4, 6, 8 at different concentration of Chromium(VI) is 150 minutes has been investigated. After this amount of absorption, no significant effect on removal efficiency of Chromium(VI) ions has been observed. This is due to the coincidence of the active sites in higher concentrations. Hence, some of the ions are affected by adsorbents and some other substances remain in the solution even if more adsorbent is added. There are more ion exchange locations at the higher concentrations of chitosan. The NH3+ chitosan group is primarily responsible for the interaction of the onions and negative charge levels. Therefore according to the above texts, 10 mg/lit is determined as the optimum concentration of chitosan. The pH of solution, because of the metal ions potential, has a significant effect on absorption of heavy metal. Also, the pH affects the concentration of opposite ions in the adsorbent group and ionization degree during the adsorption reaction. The pH of 4-8 was investigated for studying the effect of pH on adsorption of Chromium(VI) ions. The result of experiments showed while the maximum removal occurred at pH 4,the minimum removal of Chromium(VI) ions with chitosan happened at pH 8 . The absorption of Chromium(VI) and other metals, such as Arsenic known as anion, depend on pH. At pH less than 4, the amino group protonated chitosan in varying degrees. The NH3+ group on chitosan is mainly responsible for the removal of Chromium(VI). At higher pH, oxygen functional groups negatively affect the absorbent surface; therefore an electrostatic interaction is produced between the adsorbent and the onions. The effect of contact time on the removal of metal ions with water-soluble chitosan powder was investigated. The removal efficiency reached its maximum value at 140 minutes and thereafter no further deletion occurs until 150 minutes. This may be due to the fact that at the beginning, all occupied areas and the gradient of Chromium(VI) concentration were high, therefore based on these results, 140 minutes were selected for isotherm studies. Quickly removing of Chromium(VI) was increasing from 20-140 minutes. Because at first steps most of sites are potentially empty, as soon as the contact time increase, most of the ions absorb to empty sites. Therefore, finding rest of empty sites is difficult for metal ions. For this reason, the ratio of absorption is decreasing. The presence of most functional group on the surface of chitosan, which requires the interaction between the anions and cations, significantly improves with the bonding capacity, and this process proceeds rapidly. So, contact time is an important parameter treatment system that is cost-effective, therefore, an optimal time of 140 minutes was considered for purification. Absorption isotherms are obtained by plotting the absorbed metal graph versus the equilibrium concentration in the solution. Three model of Temkin, Langmuir and Freundlich were investigated in this paper by chitosan for removing Chromium(VI). Freundlich isotherm is used to absorb the single layer absorbing chemical and the absorption of several layers of physical absorption is based on the assumption of absorbent adsorption on homogeneous surface. According to the result of experiments, the absorption data with Freundlich isotherm was the better fitted with higher correlation coefficient than the other isotherms. This means that the metal has also penetrated the underlying layers and absorption takes place uniformly, therefore, the Freundlich isotherm is a suitable model for describing this absorption behavior. The process to remove Chromium(VI) ions from the liquid phase by absorbing the kinetic models and test speed control mechanism of adsorption, such as chemical reaction, mass transfer and playback controls are explained. Kinetic studies were carried out on various kinetic models such as pseudo-first order, pseudo-second order and intraparticle diffusion model. Pseudo-second order model describes the absorption rate based on the square of the number of occupied spaces on the adsorbent. This kinetic has a higher correlation coefficient than the previous two preceding ones; therefore the absorption rate follows the pseudo-second-order.
In this study, it was concluded that this method is possible to investigate the possibility of using chitosan in water purification and heavy metal removal of Chromium(VI). However, for practical use in the process of water and wastewater treatment for irrigation, performing a technical and economic assessment is necessary and comparing this method with others is recommended.

Abstract Surface fertigation in furrow irrigation has potential to decrease water and fertilizer losses. Fertigation is as a technique having more advantages than conventional fertilizer application methods such as flexibility, potential for improving fertilizer distribution uniformity and high application efficiency. Due to time restriction and experimental field implementation cost, fertigation simulation models have been developed to achieve the desired management conditions. Research has been performed in the last decades to out for simulate surface water and solute flow under surface fertigation. These researches reported that simulation could be effectively applied to improve surface fertigation design and management, reducing water and fertilizer losses. Playan and Faci (1997) stated that a short duration of the fertilizer injection resulted in low fertilizer distribution uniformity in border fertigation. However, Sabill?n and Merkley (2004) advocated relatively short injection times and relatively high injection rates in furrow fertigation. Abbasi et al. (2003) conducted a blocked-end furrow fertigation experiment and simulated overland water flow and solute (bromide) transport. These authors reported that high solute uniformity was obtained when the solute was applied during the entire irrigation event or during the second half of the irrigation event. Burguete et al. (2009) presented a fertigation model, named SURCOS, for furrow (and level furrow) irrigation. Model simulations succeeded in predicting fertilizer concentration in irrigation water at different times and distances along the furrow for different fertilizer application strategies. The objective of this study was to simulate nitrate concentration in runoff in conventional, variable alternate and fixed alternate furrow irrigation regimes by SURCOS fertigation model and Abbasi et al. model and comparison of these two models. For this purpose, experimental field data were used in the two fertigation events during maize growing season.
A field experiment was conducted in the experimental station of College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran. This zone has a semi-Mediterranean climate with an average annual rainfall of 265 mm and an average annual temperature of 16 ?C. Three furrow irrigation methods; conventional, variable alternate, and fixed alternate furrow irrigation (CFI, AFI and FFI, respectively) were investigated in this work. Inflow and outflow (runoff) rates were measured by WSC flume installed at the inlet and outlet of the experimental furrows. The experimental furrows were marked for measuring the water advance times. The average basic infiltration rate (f_0) was determined by the inflow-outflow method (Elliot and Walker 1987). The two-point method (Elliott and Walker 1982) was also used to determine the Kostiakov-Lewis parameters, coefficients a and k. The Manning’s n was assumed to be 0.04. Two different numerical models (Abbasi and SURCOS) were used and assessed for the simulation of the surface fertigation which both are capable of simulating overland water flow and solute transport. The governing equations for water flow were solved in the form of a zero-inertia model of the Saint-Venant’s equations. Also, Solute transport was modeled with the advection-dispersion equation.
Both models were run for the first and second fertigation events regarding the input data. The runoff nitrate concentrations were predicted and compared with the measured data. The predicted nitrate concentrations were almost constant whereas the measured values were relatively fluctuating. These variations could be related to spatial variability in soil infiltration and roughness properties and small changes in water and fertilizer rates in the field. Having high solubility and mobility, nitrate could easily move with water. There were good agreements between the measured and predicted nitrate concentrations. The R2, RMSE and NRMSE values for simulation of nitrate concentration in runoff were obtained 0.989, 13.5 mg/L, 4.3 % for the Abbasi et al. model and 0.913, 17 mg/L, 5.45 % for the SURCOS model, respectively. The results indicated that both models were able to successfully simulate nitrate concentration in runoff.
Although the water and fertilizer movements in furrow irrigation are bi-dimensional, both 1D surface fertigation models could successfully simulate the fertigation process. However, the Abbasi model had relatively better performance than the SURCOS model due to the less error in predicting nitrate concentration while the SURCOS model could better distinguished differences of the irrigation treatments. The results indicated that the simulation models can be used to get better design and management of the fertigation in alternate and conventional furrow irrigation for alleviating the water crisis and environmental risks

Abstract The most important factor in improving the environmental planning and hydrological management decisions is introduced as the modeling and exact simulation of rainfall and runoff processes. The accurate and exact modeling of hydrological processes such as rainfall-runoff can give impressive information for urban planning, land use, flood and water resources management for a given watershed. Also, in order to mitigate drought impacts on water resource systems, the management attempts are based on hydrological process modeling. So, the need for accurate modeling of the rainfall-runoff process has grown rapidly in the past decades. Recently, new techniques in Artificial Intelligence (AI) like Support Vector Machine (SVM) have been used by hydrologists.
New techniques on AI, with a great variety of applications, have been recognized over the past decade. One of them is the SVM which is used in the classification and regression algorithms assortment. Support Vector Machines (SVMs) are kernel machines useful for classification and regression problems. The SVM model is based on the statistical learning theory. This model is a supervised learning technique that provides the input-output mapping functions with respect to a set of training data. The advantage of SVM modeling in comparison with the other methods is that this modeling works with less training data and variables. Compared to a traditional neural network, the SVM method replaces traditional empirical risk with structure risk minimization and solves a quadratic optimization problem which can get the optimal global solution in theory. In this paper, the wavelet analysis was linked to the SVM model concept for modeling Aghchai watershed rainfall–runoff process. To do this, the main time series of two variables, rainfall and runoff were decomposed to some multi-scale time series by wavelet theory. On the other hand, the annual or seasonal data were decomposed into large-scale approximation sub–signals and daily data in small periods were decomposed into the detailed sub-signals; then, these decomposed rainfall and runoff data act as the inputs of SVM to predict the daily runoff discharge. As a result, the runoff discharge was forecasted about 1 day ahead. To reach this aim, the classical SVM was first used for data modeling. The Kernel function was employed for data classification in the SVM. There were various kinds of Kernel functions. In this paper, the SVM modeling was done by three kinds of Kernel functions with respect to rainfall and runoff data concerning Aghchai watershed. Afterwards, some input combinations (combs. 1-5) were used as the inputs of SVM model; then, the performance of each combination was measured. The most significant part of the study occurred when the wavelet transform was combined with the SVM. So, the single SVM modeling gets promoted by the wavelet transform. In this step, the time series of each watershed were calibrated and verified by the Wavelet-Support Vector Machine (WSVM) model with the different kinds of mother wavelet types including Haar, db2, sym1 and coife1 and different decomposition levels (1-4).
The obtained results indicated that the RBF-Kernel function has the highest efficiency as compared to Poly and MLP Kernel functions for both watersheds. So, the RBF-Kernel function was employed in next steps. The comparison results of data combinations showed that the combination (2) has a better compatibility as the SVM input for both watersheds. Finally, in the WSVM model, the db2 mother wavelet and the decomposition level 3 were selected as high-efficiency ones for both watersheds and their calibration and verification results were illustrated in the given figures. So the maximum value of determination coefficient (R2) and the minimum value of root mean square error (RMSE) in verification for the SVM model was 0.69 and 0.79, respectively and for the WSVM model was 0.92 and 0.35, respectively. As a result, the proposed hybrid model was relatively more appropriate because the WSVM model uses some multi-scale processed time series with different resolution levels as inputs to model instead of using raw rainfall-runoff data time series. Also, the WSVM model had a high performance to predict the peak values of runoff discharges by considering seasonality and multi-scale time series. Finally, studying compatibility of the model with other rivers' data, the hybrid WSVM model caused accurate results for the watershed of Eel-River, located in California State. Also, WSVM model showed better performance in comparison with the other hybrid model such as Wavelet-Artificial Neural Network (WANN).

Abstract Soil erosion is a global problem that seriously threatening natural resources, human welfare and even life human. Globally, there are many methods for soil conservation including biological, mechanical and bio-mechanical methods, which these methods are expensive and they are not environmental friendly. Mulching is one of the management practices to reduce the impact of raindrops on soil erosion and control surface runoff. From these, organic mulches improve soil texture and infiltration capacity and avoid from environmental pollution. Mulching also decreases crusting of the soil due to rainfall impact also reduces erosion by absorbing the kinetic energy of the raindrops. Wood mulches have been developed from wood manufacturing waste (e.g., wood strands such as Wood Straw, wood shreds or wood chips) made from burned trees or forest thinning operations, and shredded forest floor material from nearby eroded areas. Although these wood-based mulches are unlikely to harbor non-native seeds, their greater density can increase the cost of transportation to the site and aerial application as compared to straw mulch. Laboratory studies established that wood strands have greater resistance to wind displacement as compared to agricultural straw, and both wood strands and wood shreds provide equal or greater protection from erosion as compared to agricultural straw mulch at equal areal coverage rates. Foltz and Wagenbrenner (2010) reported that a 50% cover of wood shred mulch, with small (

Abstract Using deficit irrigation management has an important role in increasing water use efficiency in areas that are faced with water shortage. Alternate furrow irrigation is one of the deficit irrigation strategies which improve water use efficiency without significant effect on crop production. Results of different research demonstrated that alternate furrow irrigation has been widely used to reduce water use up to 50%. Application of integrated management of irrigation as alternate furrow irrigation at the critical growth stages of maize can be used both to save water and increase water use efficiency. So, this management with regard to the critical stages of maize development in different regions (with different soil textures, including loam, clay loam and silty clay)was studied, Also, combined effects of reducing water consumption and increase water use efficiency were investigated.
This research was conducted in Soil and Water Research stations (Karaj, Darab and Isfahan) for 2 years. The randomized complete block design with three replications was considered in this research project. Irrigation timing was determined based on allowable depletion of soil moisture (50% deficit) and irrigation water depth was considered based on refilling soil moisture content till field capacity in rootzone for all treatments. In this regard, irrigation management was conducted in six treatments, included: (T1) full irrigation in total period (Control); (T2) alternate furrow irrigation in total period; (T3) full irrigation in development stage and irrigation during an alternating among other stage; (T4) full irrigation in flowering stage and alternating irrigation in other stage; (T5) full irrigation in development and flowering stage and alternating irrigation among other stage; (T6) full irrigation in flowering and getting stage and alternating irrigation among other stages. The treatments were done in different areas with different soil textures (The soil textures of Karaj, Darab and Isfahan were Loam, Clay loam and Silty Clay, respectively). Water use efficiency index expresses the relation between obtained yield and total amount of water applied. In this research, variation between irrigation treatments on maize production including dry biomass, grain yield and water use efficiency has been demonstrated.
Results in all locations showed that irrigation treatments have significant effect on dry biomass, grain yield and water use efficiency of maize. Using alternate furrow irrigation management in other growth stages with full irrigation in flowering stage (T4) for Clay, Clay loam and Silty clay soil textures, respectively decreased water consumption by 38, 25 and 37%. Grain maize production in full irrigation treatment (T1) was about 9510 kg/h in loam soil (Karaj). Statistical analysis showed that T2 (with 5850 kg/h of grain yield) and T3 (with 6090 kg/h of grain yield) treatment were in the same group but T4, T5 and T6 (with respectively 7563, 8040 and 7770 kg/h of grain yield) were located in another group that produced higher grain yield than T2 and T3 in Karaj site with loamy soil. Also, results in Darab with Clay loam soil showed that grain yield of control treatment (T1) was 9412 kg/h. Grain yield reduction in T4 treatment (full irrigation in flowering stage and alternating irrigation in other stage) was about 10% comparing to the control treatment in Darab site. While, application of alternate furrow irrigation in all stages of maize, decreased the grain yield about 19 %, comparing to T1. In Isfahan, results showed the significance difference between irrigation treatments on grain yield. The maximum grain yield was about 8690.3 kg/h in control treatment and the minimum of grain yield was related to T2 treatment (alternate furrow irrigation in total period), which was about 6848.8 kg/h. In this site with silty clay soil texture, the grain yield of T2, T3, T4, T5 and T6 were decreased about 21,18,16,14 and 12%, respectively. Considering T4 in all sites, water use efficiency increased as 25, 21 and 30% in the soil textures of Loam, Clay loam and Silty Clay, respectively. Using alternate furrow irrigation management in other stages with full irrigation in flowering stage (T4) decreased water application about 35% and increased water use efficiency about 25%, in average, comparing to the full irrigation treatment. The most critical stage of maize, that is better to be fully irrigated, is flowering so we can use alternate furrow irrigation in the other growth stages except flowering (Full irrigation in flowering stage for more water saving and achieving higher water use efficiencies). This reflects the importance of full irrigation at critical stages of flowering and ripening. Hence, with this irrigation management, we can increase cultivated area and achieve more total yield with higher water use efficiency. Therefore, alternate furrow irrigation is a valuable strategy for dry region, where water is the limiting factor in crop cultivation.

Abstract sasa

Abstract One of the hazards which almost always threaten dam spillways is the cavitation phenomenon which is caused by high-velocity flow hydrodynamic effects on the structure. Presence of air in high-velocity flow can prevent the dangers of cavitation or at least reduce them. Stepped spillways with considerable applications have been economically justified the downstream of RCC weight dams. Superiorities over smooth spillways include high rate of energy dissipation along the spillway and reduction in stilling basin dimensions.
The most important indexes of the flow passing the stepped spillways are the high level of turbulence and the way air enters the flow. Turbulence fluctuations near the water-air free surface (two-phase flow) create air bubbles. Generally, turbulent flow is present in the vicinity of boundary layer which begins from the crest, develops downstream and crosses the water surface. When outer edge of the boundary layer reaches the free surface, turbulence occurs and causes a natural aeration of the flow. Air entrance location is called the inception point. In the downstream, the flow is fully developed and there is accelerated aeration in the free surface.
In these spillways, aeration length which is defined as the distance between the crest to the inception point can be exposed to cavitation. The boundary layer thickness has been estimated by different researchers for spillways without any step but it is not accurately determined for stepped ones. The reason is due to the complexity of flow conditions in these kinds of spillways.
Inception point location in most cases is obtained by observation. Therefore, the specifications and coordinates presented for this point by different researches have a wide range of discrepancy. Classically, this point conforms to a cross section of the step in which the water flow has a white or milky color. In this experimental study, three models were used at Water Research Institute of Ministry of Power. Plexiglas was applied in the models for stepped spillways with 18.44, 38.81 and 50.2 degrees tangents. The step numbers were 59, 61 and 65 and they had 1.33, 1.5 and 2.12 meters width, respectively.
The objective was to investigate the distance between the crest and the inception point along the spillway tangent, so the inception point was determined by passing different amount of mass flow rates on different experimental models. It is worth mentioning that the minimum and maximum amount of mass flow rate, required to record the flow inception point, are not the same for the three models since they are based on model width and its tangent. By increasing the tangent and its width, the mass flow rate will be higher for a continuous flow to be established.
According to the results obtained, increasing the spillway tangent would bring the inception point closer to the crest. In other words, it would delay the flow. Considering the model specifications of this study, an equation is extracted which is applicable for a wide range of angles. To do this, taking the Froud number (F_*) and spillway tangent as variables, the following relation is obtained:
l_i/k_s =11.08 ?F_*?^0.675 ?(tan???)??^(-0.2114) R^2=0.87 (1)
This equation is valid for the range of ?18?^°????52?^°.
A comparison between above equation with the Wood’s relation for ogee spillways in model number 2 with mass flow rates in the experiments showed that the length without air in stepped spillways was less than the length in ogee spillways. Consequently, the inception point was closer to the crest. Also, a comparison was performed between the recommended relation and Chanson and Boes relations. The reason of selecting these two relations was the wide range of angles they conclude. Results showed that the presented equation had the smaller standard error with respect to the abovementioned relations.
Generally, the results show that a stepped spillway will bring the inception point closer to the crest in comparison with smooth and ogee spillways i.e. l_i will be smaller in these kinds of spillways. Implementing a quantitative comparison between the Wood's relation and the equation obtained in this study shows that l_i can be reduced up to 5-10%, depending on the mass flow rate. Increasing the mass flow rate in these spillways which promotes the Froud number (F_*), will increase the aeration length and cause a delay in aeration process. This means that F_* has a direct relationship with l_i. Results also show that increasing the spillway tangent will reduce l_i and bring the inception point closer to the crest. Consequently, equation 1 which verifies the abovementioned discussion was derived with an acceptable correlation coefficient.