نشریه آب و خاک
سال سی و دوم شماره 3 (پیاپی 59، امرداد و شهریور 1397)

Determining the amount of watershed sedimentation and its spatial distribution by using field measurements in practice faces a serious challenge. In recent decades, hydrological models have been widely used by hydrologists and water resource managers as a tool for analysing water resource management systems. The SWAT model is one of the semi-physical and semi-distributed hydrological models that have been widely used in recent years. Despite the wide use of the SWAT, simulation of the sediment has been associated with a large error in comparison to flow. These errors may come from using empirical methods such as the sediment rating curve for estimating sediment based on measured data. Therefore, in this research, the capabilities of the genetic algorithm (GA) were used to optimize the relationship between discharge and sediment and further optimal equation used for calibration and validation of the model.

The studied area is Fariman dam watershed with an area of 278.8 km2 which is located at latitude of 35 ˚ 33' to 35˚ 41' and longitude of 59 ˚ 34' to 59 ˚ 44' in Razavi Khorasan province. In this study, SWAT model was used to simulate runoff and sediment yield of Fariman dam watershed. In order to run the model, meteorological and hydrometric data including daily rainfall and maximum and minimum temperatures and sediment yield and discharge data, soil and land use maps of the watershed were achieved from relevant resources. The capabilities of the genetic algorithm were used to optimize the discharge -sediment relationship and were compared with sediment rating curve. For this purpose, optimization problem was defined for the genetic algorithm in MATLAB software as a search space of continuous values of the discharge –sediment coefficients. After that, sediment yield was extracted based on discharge data and calculated monthly sediment for SWAT calibration and validation. Sensitivity analysis, calibration and validation of the model were performed using the SUFI-2 algorithm using SWAT-CUP software. For this purpose using high sensitive parameters, the model was calibrated and validated for the period of 1991 to 2000.

Optimal coefficients extracted by GA indicate a better performance of the genetic algorithm in estimating the sediment yield. The comparative results of the sediment estimation models, revealed better performance of the genetic algorithm with RMSE = 70.9, NSE =0.46 and R2= 0.72 than the sediment rating curve. According to senetivity analysis of SWAT model, twelve parameters for stream flow and seven parameters for sediment yield were found to be sensitive. The most sensitive parameters for stream flow were SCS runoff curve number (CN2), effective hydraulic conductivity in tributary channel (CH_K1) and base flow alpha factor for bank storage (ALPHA_BNK) and the most sensitive parameters for sediment yield were peak rate adjustment factor for sediment routing, USLE equation soil erodibility factor (USLE_K), sediment concentration in lateral flow and groundwater flow (LAT_SED) and exponent parameter for calculating sediment reentrained in channel sediment routing (SPEXP). The SWAT calibration and validation results showed that the Nash-Sutcliffe efficiency index for monthly sediment and discharge for calibration period was 0.75 and 0.73, respectively and in the validation period was 0.85 and 0.76, respectively. Calibration and validation of the SWAT model was done with genetic algorithm model as an optimal method for deriving sediment data from measured daily discharge. The Nash-Sutcliffe efficiency coefficient for monthly discharge was 0.75 and 0.85 in the calibration and validation periods. Nash-Sutcliffe efficiency coefficients for monthly sediment yield were 0.86 and 0.81 for the same periods. SWAT evaluation results indicate that the model simulation is acceptable for predicting sediment yield and river flow. The performance of SWAT model in predicting of sediment in low flow is poor, which can be due to the effect of the parameters and model simplifications in the simulation of the sediment load.

In this research, simulation of runoff and sediment flow for Fariman dam watershed was performed using SWAT model. For this purpose, the capabilities of the genetic algorithm were used to optimize the relationship between discharge and sediment yields; then the results were used to calibrate and validate the SWAT model. The results indicate that genetics algorithm can be used for optimizing coefficient of sediment discharge equation and the result is better than sediment rating curve. Simulation of watershed hydrology using SWAT shows that the capability of the model in prediction of sediment yield and water flow is good. Using genetic algorithm to optimize the relationship between discharge and sediment has an important role in extracting daily sediment yield and simulation accuracy of the model. Also, the use of evolutionary algorithms can have a significant role in extracting the discharge -sediment relations, which usually is accompanied with a large error in experimental models such as a sediment rating curve.

Simulation models have been used for decades to analyse crop responses to environmental stresses. AquaCrop is a crop water productivity model developed by the Land and Water Division of FAO. It simulates yield response to water of herbaceous crops, and is particularly suited to address conditions where water is a key limiting factor in crop production. It is designed to balance simplicity, accuracy and robustness, and is particularly suited to address conditions where water is a key limiting factor in crop production. AquaCrop is a companion tool for a wide range of users and applications including yield prediction. Aquacrop has high accuracy and performance for yield prediction than other models regarding to irrigation and fertilizer management base foundation. Using Aquacrop model for crop yield simulation in different soil and water managements has high accuracy and its use requires calibration and validation. The use of models saves time and cost and, if calibrated and validated, acceptable results are expected.
Material and This research was carried out in order to calibrate and validate the Aquacrop model for simulating wheat grain yield in the three selected pilots in Hamidiyeh province of Khuzestan province in two years of cultivation.In this regard, three different plots with a total area of about 10 hectares were selected in Hamidyeh region. Sampling, measuring and determining the parameters of soil, water, plant, irrigation management (information required for the Aquacrop model) and the existing conditions of the area were carried out.The climatic data required in Aquacrop model was collected from synoptic meteorological weather station of Ahvaz. Irrigation water quality with mean water salinity of 1.9 dS/m has a good quality for irrigation. In the first year, 5 irrigation events (with a total volume of 9500 cubic meters per hectare) are available to the wheat plant at different stages. In this regard, based on meteorological data and field and vegetation data that was taken from the field level in the first year, the Aquacrop model calibration and performance variations were carried out at different times of irrigation using a simulation model. In order to validate the results simulated by the model, the best scenario provided by the model in the second year was implemented at selected farm level and its results were compared with the simulation results by the model.
Aquacrop model calibrated for the first year and then compared for different scenarios of irrigation timing (3-6 irrigation event).The amount of grain yield and total in 4 irrigation intervals are not different with the corresponding values in 5 irrigation intervals. Irrigation rotations were considered in accordance with routine irrigation rotations of the region during planting, tillering, stemming, flowering and seed filling (5 turns) for 4 steps of irrigation step and for 3 irrigation stages, the tiller and stem elongation was deleted. The model showed that, using four irrigation timing is the most appropriate irrigation scenario. Using the results of the model with considering 4 irrigation times, wheat was planted in the second year for model validation. In the second year, the average of measured and simulated wheat grain yield was 3.8 and 4.4 t/h (with 14% error).Average values of total yield and simulated wheat seeds in 4 and 5 irrigation intervals were not different, while the amount of water consumed in 4 irrigation intervals decreased by 20% compared to 5 irrigation intervals. On the other hand, water use efficiency increased by up to 21% in 4 irrigation intervals compared to 5 irrigation intervals. Also, according to the simulation, it was observed that increasing the irrigation interval at the arrival stage, while not significantly increasing the grain yield and the total, did not increase the water use efficiency in order to increase the water consumption (one irrigation interval) Reduced. Considering 3 irrigation timing, the grain yield decreased by 15%. Due to the reduced yield in three irrigation intervals than the more irrigation intervals, this scenario is not recommended for performance reasons. So, according to the simulation, at least 4 irrigation intervals (during planting, stemming, flowering and seed filling) are recommended to maintain proper production level in existing conditions. Comparison of statistical indices between measured and simulation values of wheat grain yield in both years showed that the coefficient of correlation, normalized root mean square error (RMSE) and agreement index were 0.9, 0.14, and 0.89 respectively, which indicates the proper performance of the model for simulating yield of wheat for two consecutive years. The average grain yield of simulated wheat has been estimated at 3.8 ton / ha, which estimates 14% of grain yield less than actual experimental conditions compared to its measured value, indicating the accuracy and efficiency of this model in simulating wheat yield in the present situation. With considering 4 irrigation events, the water use efficiency of wheat grain yield increased by 0.7 kg/m3, which confirms the ability and accuracy of the Aquacrop model for simulating grain yield of wheat and also improving water use efficiency.
The results of this study showed that the simulation of wheat yield in the first year (2.6 t/ha) has a close proximity to the measured values of yield (3 t/ha). Also, validation of the model with changing conditions in the second year showed that the simulated yield of wheat (4.4 t/ha) also had a good agreement with its measured value (3.8 t/ha), which indicates the high accuracy of this model in simulating wheat grain yields every two years. Therefore, this model has the efficiency and accuracy in simulating wheat yield in research conditions.

Regarding population growth rate and drought challenges, one of the effective strategies for sustainable development in agricultural sector is irrigation. In this regard, in recent years, the use of tape irrigation method has been considered in crop plants, but the use of this system will be successful if it is to evaluate the system performance in terms of soil sustainability before it is implemented and its problems are solved. Problems in the field of sustainable agriculture are saltinification of soil resources that the tape irrigation over time and due to the continuity of its use in cultivated land, especially in warm and dry areas due to global warming, climate change and decline of the atmospheric precipitation leads to salinity accumulation in the soil.

In order to investigate the distribution and changes of salinity of soil profile in the root development zone of wheat, maize, barley and tomatoes grown in Qazvin Plain with initial salinity of 1/5 dS/m and salinity of irrigation water 1 dS/m In hot and dry climate, a type of irrigation was used (strip drip) and during the 20 years of cultivation, the AquaCrop version 5 was used. The results of simulation output were analyzed by Minitab 17 and Excel 2007 softwares.

The results showed that in all previous stuides, the amount of salinity accumulated through the tape irrigation in the soil surface is greater, but in this study, due to the time effect on salt accumulation in the soil profile in the root development area, The maximum salt accumulation below the soil surface and at depths (0/5, 1/5, 0/5 and 0/16) meter of the total root development depth of each plant, respectively, for tomato, maize, barley and Wheat has occurred. It can be said that over time, accumulated salt on the surface of the soil evaporated, re-moved with irrigation and redistributed under the soil profile. Simulation results were obtained after statistical analysis with Minitab 17 and Excel 2007 software showed that in tomato and corn products, tape irrigation with irrigation water salinity of 1 dS/m resulted in significant increase in average salinity of The root development zone from 1/5 is 4 and 4/4 dS/m over the course of 20 years (correlation significance at 5% level) and sustainable utilization of soil resources is questioned, While the increase in average salinity of root development zone in wheat and barley products due to tape irrigation over the course of 20 years has risen from 1.5 to 2/03 and 2/02 dS/m, which is not noticeable and at the level of 5% is not significance. This can be attributed to rainfall during the growing season of wheat and barley, which led to salt salting from the root zone. The correctness of this theory was tested by the significance of the correlation between rainfall and salinity in the 5% level and proved to be. Therefore, it is recommended to wheat and barley with the ability to tolerate high soil salinity are placed in the top priority for local irrigation in hot and dry areas with limited atmospheric rainfall and limited water resources.

From the above results, it was observed that, in products such as maize and tomatoes, tape irrigation resulted in a significant increase in the mean salinity of the root development zone over time. However, the increase in average salinity of root development in wheat and barley products due to the tape irrigation is negligible and canceled over time. In other words, the cultivation of crops such as barley and wheat in areas with scarcity of water resources and soil salinity ensures sustainable land management. These results, while using water with salinity of about 1 dS/m, and soil cultivation with an average salinity of 1/5 dS/m, have been taken. Since comprehensive and practical research has not been done on long-term salinity changes and the use of tape irrigation, after the cultivation of important crops such as wheat, barley, corn, tomato, the results of this research can be used in conducting managerial guidelines, The selection and prioritization of the appropriate cropping pattern in the warm and dry areas will be beneficial with few atmospheric precipitations.

The largest share of water consumption in Iran is related to the agricultural sector. Therefore, in order to save water resources, priority is given to reducing irrigation water consumption. On the other hand, reducing of water quality and salinization are the main problems which are commonly found in the areas with limited water resources. One of the most important effects of salinity is the reduction of yield and its inhibitory effects on plant growth and metabolism. Also, increasing salinity can reduce potassium, calcium and magnesium ions. One of the significant points regarding the effects of salinity stress is a significant decrease in the hydraulic conductivity of the roots, which leads to a decrease in the water use efficiency index. According to the food and agriculture organization (FAO), more than 40 percent of Iran's irrigated lands are affected by salinity stress, which is generally found in dry and semi-arid areas. Therefore, studying the combined effect of stress caused by salinity and water stress can be used to provide management solutions for irrigation and crop production.

This study was conducted in greenhouse laboratory at University of Mohaghegh Ardabili, Ardabil, Iran during August to November 2016. In this research, the effects of saline water on cherry tomato yield under water stress conditions were investigated. The applied treatments included irrigation with saline water (in two levels: S1=4ds/m and S2=7ds/m) and water stress (in three levels, irrigation at 40, 50 and 65% field capacity, respectively, I1, I2,I3). The experimental design used in this research was a completely randomized block design with four replications. On the other hand, in order to compare the plant yield under water stress and salinity conditions with non-stress conditions, control treatment with salinity characteristics less than 1ds/m and irrigation without water stress were used in three replications. In this experiment, cherry tomatoes were cultivated in the pots with diameter and height of 26 and 27 centimeters, respectively. The moisture meter (Model: PMS-714) was also used to measure soil moisture and determine the irrigation time. The most important parameters included cherry tomato yield, total evapotranspiration and water use efficiency index. It should be mentioned that analyses of the results were done by MSTATC software (Version: 2.10).

The results of this study showed that the interaction between two factors of water and salinity stress on the parameters was not significant, but the effects of salinity stress on yield, total evapotranspiration and water use efficiency (in two levels: 2% and 5%) are significant. Also, the greatest effect of salinity stress on cherry tomato yield was observed, so that by increasing the amount of irrigation water salinity from 4 to 7 ds/m, the yield was decreased by 27%. Also, the performance in salinity treatments of S1 and S2 decreased by 27.2% and 46.7%, respectively, compared to the controled treatment. Probably the reason for the yield reduction caused by decreasing in plant evapotranspiration and plant growth and metabolism. In addition, water use efficiency index in treatments of S1 and S2 decreased by 3.4% and 22.3%, respectively, compared to the controlled treatment. As it can be seen, the differences in water use efficiency between the control and S1 treatments were not significant. In this study, the average values of Ky (plant response coefficient to salinity and water stresses) were achieved 1.39, which was higher than the value that was reported by FAO for tomato plant under water stress conditions (equal to 1.05). This can be due to the significant effect of saline irrigation water on the yield of the tomato plants. Finally, based on the results of this research, it can be said that although salinity decreased yield significantly at 1% confidence level, in the coming years, with severe water resource constraints and increased costs for its preparation, this yield loss can be economical and feasible.

In this research, the effect of saline water on cherry tomato yield under water stress conditions was investigated. According to the results of this study, with increasing salinity of irrigation water from 4 to 7 ds /m, total evapotranspiration decreased by 10%. On the other hand, due to salinity stress, tomato yield was decreased to 27% in the most salinity levels of irrigation water compared to control treatment; one of the main reasons of which could be the reduction of total evapotranspiration in the growing season. In the end, the important point to note is that although, based on the results of this study, utilization of irrigation saline water decreased the yield, total evapotranspiration and water use efficiency by 27%, 8.9% and 19.2%, respectively compared to the control treatment, but in the near future, by increasing the water production costs and the quantitative reduction of water resources, even use of saline water is economically feasible and justifiable.

According to the Statistical Center of Iran, the country's population between 1957 and 2017, has increased approximately from 19 people to 80 million. With population growth, the water demand is increased and water resources are threatened cumulatively. Agriculture is recognized as the main water consumer in the country. Due to the arid and semi-arid climate of the country, it is essential to use water reduction strategies such as deficit irrigation (DI) and partial root zone drying (PRD) deficit irrigation in agriculture. In case of water shortages, DI is an optimal solution for production, which is usually accompanied by a reduction in product per unit area. The base of PRD is keeping dry the half of root while irrigating the other half. The plant root in the wet area absorbs enough water. The other part of the root in dry soil, with a reaction to dryness and sending symptoms to the stomata, affects their opening size and reduces water losses. Sunflower is one of the four major oil producing plants in the world. The high volume of this product's import causes the country's strong dependence on oil import and the currency's outflow from the country. Although all living and non-living stresses are considered to be major factors in reducing production, water deficit stress is one of the main factors limiting the production of sunflower; Therefore, studying the reaction of this plant to different drought stress conditions and providing a solution to reduce the negative effects of dryness would be essential.

The present study was conducted on sunflower plant (Hysun 25) in a research farm of Sari Agricultural Sciences and Natural Resources University (SANRU) in 27 plots (5 × 5 square meters). Each plot consisted of 6 rows of planting at a distance of 75 cm from each other and 5 meters long. Sunflower seeds were planted at a depth of 4 cm from the soil and at a distance of 20 cm from each other. The experiment was conducted by using split-plot design, with three main factor (irrigation interval) and three sub-factor (irrigation water amount) in randomized complete block design in three replication. The irrigation intervals were irrigation after 20, 35 and 50 mm evaporation from class-A evaporation pan (F-20, F-35 and F-50 respectively). The sub-factor was irrigation water in levels of 100%, 75% and 55% of water demand (FI, PRD-75 and PRD-55 respectively). Controlling the volume of water delivered to each treatment was carried out using a volumetric flow meter. The application of irrigation treatments was carried out six weeks after planting. The irrigation for FI was conducted regularly at both sides of the root and for PRD it alternatively changed at the right and left sides of the root. The studied traits were irrigation water use efficiency (IWUE, kg/m3), height (H, cm), the flower diameter (D, cm), the seeds number per flower (SN), the 1000 seeds weight (W, gr) and the chlorophyll index (SPAD). Statistical analysis of data conducted by SAS software using Duncan test (1% level). Diagrams extracted by Microsoft Excel software.

Evaluation of irrigation interval factor based on the experiment two years data, indicated that the best results for plant growth parameters was for F-20. Also, the best results for sunflower plant growth parameters was for FI. According to the significant difference between FI and PRD-55 at most of the growth parameters, it’s suggested to conduct PRD-75 for PRD. For the irrigation interval factor, there was significant difference for most of the plant growth parameters between F-20 and F-50. Therefore, considering this case as well as the problem of increasing the operating cost by reducing the irrigation interval, F-35 is recommended for irrigation interval. It’s concluded that there was significant difference between all of the irrigation interval treatments by analyzing the IWUE trait. The highest amounts was for F-50 and the lowest was for F-20. Despite the increase in the value of IWUE in PRD-75 in comparison with other treatments for each two years of the experiment, this difference was not significant. According to the non-significant difference between F-35 and F-50 for IWUE at the second year of the experiment and this trait relative increase at PRD-75 in comparison with two other treatments, it’s suggested to conduct PRD-75 with F-35 to have higher IWUE.

Simultaneous analysis of sunflower’s IWUE and its growth parameters showed that it could be possible to save in irrigation water use and increase the IWUE with the lowest decrease in the sunflower plant growth parameters by applying PRD-75 and F-35.

Among wide variety of soil pollutants including heavy metals, acidic precipitation and other toxicants, the importance of heavy metals due to their pollution capacity has received growing attention in recent years. Heavy metals are important environmental pollutants and their toxicity is a problem of increasing significance for ecological, evolutionary, nutritional, and environmental reasons. Of all non-essential heavy metals, cadmium (Cd) is perhaps the metal that has attracted the most attention in soil science and plant nutrition due to its potential toxicity to humans, and also its relative mobility in the soil–plant system. The uptake of ions takes place in competition with that of elements such as Zn, P, Cl–, Ca, and Cu. Soil, environmental, and management factors impact the amount of Cd accumulated in plants (Hart et al., 1998). Much of the Cd taken up by plants is retained in the roots, but a portion is translocated to the aerial portions of the plant and into the seed. The amount of Cd accumulated and translocated in plants varies with species and with cultivars within species. Cd toxicity causes inhibition and abnormalities of general growth in many plant species. After long-term exposure to Cd, roots are mucilaginous, browning, and decomposing; reduction of shoots and root elongation, rolling of leaves, and chlorosis can occur. Cd was found to inhibit lateral root formation while the main root became brown, rigid, and twisted. The changes in the leaf included alterations in chloroplast ultrastructure, low contents of chlorophylls, which caused chlorosis, and restricted activity of photosynthesis. Radish (Raphanus sativus) is a root vegetable grown and consumed all over the world and is considered as a part of the human diet, even though it is not common among some populations. Usually, people eat radishes raw as a crunchy vegetable, mainly in salad, while it also appears in many European dishes. Some people, at least in the Middle East, prefer to drink its juice in pursuit of certain health benefits. Radishes have different skin colors (red, purple, black, yellow, and white through pink), while its flesh is typically white. In addition, the edible root of radish varies in its flavor, size, and length throughout the world.

In this study, we investigated the influence of Cd application rates on vegetative parameters, and physiological and biological indexes of radish. The experimental design was a factorial with randomized block with two treatments and three replications carried out at the Research Farm of College of Agriculture, Shahid Chamran University. Treatments included three rates of Cd application of 0 (control), 30 and 60 mg kg-1, and two harvesting dates of commercial maturity (CM) and a week after CM, hereafter referred to as 1st and 2nd harvesting dates. Measurements included vegetative parameters such as wet and dry weights, leaf area, length and width of leaves, leaf numbers and root length. Physiological indexes of electrolyte leakage and relative humidity, and biochemical indexes of chlorophyll a, b and total, Cartonoeid, Proline and vitamin C were also determined.

The results indicated that the Cd application reduced all of the vegetative parameters. Application of 60 mg kg-1 of Cd increased the electrolyte leakage by 28.2% and Proline concentration by 48.8 mg g-1. Cd application increased the relative humidity. All biochemical indexes decreased as the Cd application rates increased. The maximum concentration of Cd in plant was observed at 60 mg kg-1 Cd contamination. It seems that decrease of physiological indices due to increased Cd concentration reduced the growth properties.

Application of different Cd concentrations affected the vegetative, physiological and biochemical properties. By increasing Cd concentration of soil, the Cd accumulation in the plant increased. Increasing the Cd concentration increased the electrolyte leakage and proline concentration and reduced the content of relative humidity, chlorophyll, vitamin C in radish. In addition, it decreased yield including fresh and dry weights, root length, leaf area, leaf length and width, and number of radish leaves. Further, the effects of degradation on vegetative, physiological and biochemical characteristics of radish were one week after commercial maturity more than the first time (commercial maturity). Therefore, the phosphorus-containing Cd for the cultivation of vegetables, especially tubers, such as radishes, as well as harvest management, should be carefully applied.

In recent years, concern over the long-term effects of heavy metals has been increased as environmental pollutants. Environmental pollution of heavy metals is one of the major environmental issues. Unfortunately, due to the uncontrolled entry of various types of industrial waste, their input is increasing into air, water and soil sharply. Heavy metals are irresolvable and tend to accumulate in the organs and tissues of living organisms that cause a variety of diseases and disorders for humans and other living organisms. Recently, biological methods and technologies such as biosorbent and bio-accumulation have been used to help researchers to confront the problem of removing heavy metals from sewage. In bio-accumulation technology is used living biota to remove metals. However, in the second method, or biological absorption is used of dead or inactive biologically is this purpose. The main objective of this research is to determine the capability of the storage of cadmium as heavy metal by modified Ceratophyllum demersum biomass. In addition, the effect of pH on adsorption rate, contact time on adsorption rate, adsorbent adsorption, initial concentration of adsorbant (cadmium) were evaluated on adsorption. Also, kinetic and isotherm models of absorption were determined.

In the present study, the effect of modification of Ceratophyllum demersum on the removal of Cadmium from aqueous solution was investigated. Ceratophyllum demersum or blue fork is a submerged plant that is commonly found in aqueous humorous streams containing moderate to high levels of nutrients. One of the suitable environments for growth of Ceratophyllum demersum is low depth and laminar flow of water channels. In this regard, a search was conducted on irrigation channels inside Shahid Chamran University of Ahvaz and large quantities of this plant were observed in many parts of these channels. The plant was collected from the entrance channel of the Karoon River to the university. After collecting the plant and washing it with urban water and distilled water and drying it in free air was dried at 70 ° C. After that the dry matter was milled and it passed through the standard No. 50 sieve. In this study, alkaline solutions (0.5M NaOH solution) were used to modify biomass. This method has been shown to be effective in similar studies, and has greatly increased the absorption capacity of adsorbents. Preparation of cadmium storage solution was performed based on the methods presented in the standard reference for water and wastewater testing.

The morphology characteristics of biosorbent surface by Scanning Electron Microscope (SEM) were studied and desirable effects of modification on characteristics of biosorbent surface were proved. The result of study showed that by increasing pH from 3 to 8, the removal efficiency increased from 93% to 97% at pH 7, and then decreased to 85% at pH 8. In addition, adsorption capacity, in similar way, increased from 7.04 to 7.35 and then decreased to 6.44 mg/g. Therefore, pH 7 was determined as optimum pH. Increasing contact time, from 5 to 240 minute, caused changes in removal efficiency from 67% to 98% after 180 minute, and then decreased slightly. Adsorption capacity, in similar way, increased from 6.25 to 9.13 mg/g and then decreased slightly and contact time of 60 minute was determined as equilibrium time. Increasing dose of biosorbent from 0.02 to 4 g/L, causing increase of removal efficiency from 37% to 99% and decrease of adsorption capacity from 169.5 to 2.35 mg/g and finally dose of 10 mg/L was determined as proper dose of biosobent. Increasing of initial concentration of Cadmium solution from 10 to 200 mg/L led to decrease in removal efficiency from 96% to 31%, and increase in adsorption capacity from 9.18 to 59.7 mg/g, and concentration of 10 mg/L was determined as optimum initial concentration of Cadmium. Finally, kinetic and isotherm adsorption models were studied. In kinetic models, pseudo-second order kinetic model, with correlation coefficient of 0.99 described biosorption better than pseudo-first order. In isotherm models, the Langmuir isotherm with correlation coefficient of 0.99 described biosorption process such better than other models. Based on results obtained in this study, the high capability of modified Ceratophyllum demersum, as a favorable biosorbent for cadmium removal from aqueous solution was proved.

The images from the SEM device showed that adsorption modification increased the absorption capacity to absorb cadmium ions. The highest efficiency was achieved in pH equal to seven. According to the economic considerations and optimum consumption of the energy 60 minutes was determined as the time of equilibrium. Kinetic modeling shows that Pseudo second order has the best matching with experimental data.

In calcareous soils of Iran, using fertilizers that reduce soil pH over long periods are prioritized. Reducing pH in calcareous soils increases the concentration of essential nutrients such as phosphorus, iron, zinc, copper and manganese in the soil solution. The use of organic and inorganic acids in calcareous soils may also have other advantages in addition to gradually decreasing the soil solution pH. The effect of organic and minerals acids on plant growth and uptake of essential nutrients has not been studied. The aim of this study was to evaluate the effect of organic acids like acetic, citric and oxalic acid and mineral acids like sulfuric on the growth of forage corn.

The experiment was based on randomized complete block design and carried out in pots in a greenhouse. A calcareous soil with electrical conductivity of 0.86 dS m-1 and organic matter of 4.3 g kg-1 was collected from research farm of University of Zanjan. Treatments were T1 & T2: citric acid with concentration of 5 and 10 mM (C5 & C10), T3 & T4: acetic acid at a concentration of 5 and 10 mM (A5 & A10), T5 & T6: oxalic acid at a concentration of 5 and 10 mM (O5 & O10), T7: mixture of citric, acetic and oxalic acid each at a concentration of 3.33 mM (mix):, T8: sulfuric acid at a concentration of 5 mM (S), and T9: control. Treatments were applied in three stages: immediately after sowing, four-leaf and eight-leaf stages. Irrigation of pots was done with water with EC value of 400 μS /cm. Considering the possible effect of acids on increasing the availability of phosphorus, potassium, iron, zinc, copper and manganese, fertilization was done only based on nitrogen demand and 0.55 g urea was added to each pot (equivalent to 200 kg ha-1) with irrigation water in three steps. The shoots of plant samples were harvested after 50 days and the roots were carefully removed from the soil. Some growth related characteristics such as stem height, fresh weight, dry weight, and moisture content of vegetable tissue were also measured. Concentration of nitrogen, potassium, phosphorous, iron, zinc, manganese and copper in roots and shoots was measured. Translocation factor (TF) indicating the transfer rate of the elements from root to shoot was obtained by dividing the concentration of the element in the shoot by that in the root.

The results showed the significant effects of the treatments on the growth factor (fresh weight, dry weight and plant height). The percentage of moisture content was the same in all treatments. Citric acid treatment (T2) significantly increased fresh weight of shoot (18.3 percent) and dry weight (20.9 percent) of the plant. Organic acids also increased the concentration of nitrogen in shoots and roots. The concentration of nitrogen in the shoots was roughly twice as compared with that in the plant root. As for the potassium treatments, except for A10 treatment (T4) (the lowest concentration), other treatments did not show a significant difference with control. The highest concentration of potassium in roots was observed in sulfuric acid treatment (T8). The highest translocation factor of potassium (3.34) was observed in O10 treatment (T6). The results indicated a positive effect of 5 mM citric acid, acetic acid, mix treatment and sulfuric acid on shoot phosphorus and the positive effect of acetic acid and mix treatment on the phosphorus root. Citric acid treatments (T1 and T2) were the most effective treatments in increasing the concentration of iron (289 mg kg-1) in shoots. For roots, C10 treatment (T2) and Mix treatment (T7) showed the highest iron concentration. The highest TF for iron was observed in A10 treatment (T4). Acetic acid treatments (both concentrations), and sulfuric acid were more effective than other treatments and significantly increased the manganese concentration of the shoots. Sulfuric acid also caused a significant increase in the manganese concentration of the root. Acetic acid treatment (T5) showed the highest amount of TF for manganese. The amount of zinc element in shoots and roots was significantly affected by the mix treatment (T7). There was no significant difference between all Cu treatments.

In general, application of citric acid in both concentrations is useful to increase the biological yield and product quantity in maize farms. These treatments increased fresh and dry weight of shoots and roots. Acetic acid seems to improve translocation of elements in plants. The use of other acids is likely to enhance concentration of nutritional elements in roots and shoots.

Potassium is one of essential elements for plants and it is the most abundant nutrient on soil surface which is important factor on plant growth and development. Factors such as potassium fixation, erosion, run-off and leaching cause reduction in available potassium of soil. Microorganisms especially bacteria play important role in changing unavailable potassium to available form. Hence, such bacteria can be used for increasing available potassium in soil and consequently production and quality of crops. The K- releasing bacteria can be employed as a biofertilizer to provide plant nutrients in a sustainable approach.
In this study, 10 bacterial isolates including Enterobacter sp. S16-3, Azotobacter chroococcum 14SP2-1, Pseudomonas sp. 34A-2, Pseudomonas Az-48, Psudomonas Az-8, S11-2 and 36A-2L provided from soil biology laboratory, department of soil science, University of Tabriz, Bacillus sp. 44-1 provided from soil biology laboratory of Gorgan University of Agricultural Sciences and Natural Resources, and S19-1 S14-3 isolated from Potabarvar biofertilizer produced by Green Biotech Company were used as a potassium biofertilizer. For this purpose, bacterial inoculant prepared in bagasse and perlite carrier was used to inoculate the disinfected seeds of corn (single cross 704). In this research, bacterial treatments were compared with chemical fertilizer treatments including K50 and K100, in these treatments based on soil test, 50% and 100% of fertilizer recommendation were used (equal to 0.115 g and 0.23 g potassium sulfate per pot, respectively). The experiment was conducted based on completely randomized design with three replications. Duration of this study was about 2 months. Parameters measured during growth were stem diameter, height, chlorophyll index and stomatal conductance and after harvesting, wet and dry weight of root, shoot wet and dry weight, total wet and dry weight.
The results showed that expect root dry weight, total wet weight and stem diameter, all parameters were significantly affected by the treatments. The highest plant height was observed for fertilizer treatment 50% (100.8 cm) with an increase of 3.5% compared to the negative control. As to bacterial isolates, highest height was measured in Bacillus sp. 44-1 (98.6 cm). Plant height and stem diameters are indicators of vegetative growth, these parameters can thus increase when plant can use soil nutrients more than others. Enterobacter sp. S16-3 had the maximum stem diameter and the lowest height. It can be due to decreased potassium nutrition and auxin and gibberellin transferred from root. The chlorophyll index and stomatal conductance were equal to 9.567 and 0.097, respectively, which were related to A. chroococcum 14SP2-1. These are the factors of photosynthesis parameters. Increase of these factors may be attributed to the hormone balance effects such as cytokinin which can expand root growth and absorbance of nutrients. A. chroococcum is one of plant growth promoting rhizobacteria which can provide more phytohormones and cause improved plant growth. Therefore, photosynthesis activities can be better. The highest wet weight (265.6 g) and shoot dry weight (44.4 g) were found at fertilizer treatments 50% and then 100% fertilizer recommendation, but in regards to bacterial isolates, A. chroococcum 14SP2-1 and Pseudomonas Az-8 had higher values as compared with the control. The maximum root dry weight was observed in Pseudomonas Az-48 (187.2 g). However, the lowest root weight was obtained at 50% fertilizer recommendation. Hence, this can be explained by the root developing types. The highest total dry weight was measured in Enterobacter sp. S16-3 (63.68 g) and Pseudomonas Az-8 and after these bacterial isolates, fertilizer treatments had better condition. Consequently, these bacteria had another effects on plants such phytohormones productions and enzymatic activities that chemical fertilizer did not have such influences. The highest average of shoot potassium content was observed at 100% fertilizer recommendation (1077.3 mg/plant).
The results showed that fertilizer treatments K50 and K100 had better conditions and pots with chemical fertilizer grew more than others in most plants. But some bacterial isolates showed comparable results relative to K50 and K100. These bacteria can affect plants with directly and indirectly mechanisms. Bacterial treatments such as A. chroococcum 14SP2-1 and Pseudomonas Az-8 improved growth parameters through solubilizing potassium and producing phytohormones. Hence, these isolates can be considered for further studies particularly under field condition.

Over the past decades, due to climate change and water scarcity, the recovery and use of urban wastewater, especially in arid and semi-arid climates, has increased. But since wastewater is considered as an unconventional source of water, its use in agriculture requires special management which, while benefiting from it, does not have environmental and health hazards in soil, plant and surface water and underground water resources. On the other hand, sewage systems often have significant amounts of heavy and toxic metals, the type and amount of which varies from place to place, and even in the specific location, over time. The soil also has a limited capacity to absorb and maintain these elements, and if their concentration exceeds the permitted range, they can cause pollution of the water, soil, plant and human cycle. Therefore, the present study was conducted to investigate the effect of irrigation with treated wastewater in Urmia city on concentrations, distribution and contamination of Zn, Cu, Cd, Pb and Ni elements.

In field work, 6 soil profiles (5 profiles from the wastewater-irrigated soils and a profile from the well-irrigated soil as control soil) were dug, described, and sampled. At around each profile, composite soil samples were also obtained in the root depth of the area (Ap horizon, the depth of 30 cm). Soil samples were first air-dried and passed through a 2-mm sieve and then analyzed for the determination of heavy metals. The available and total fraction of zinc (Zn), copper (Cu), cadmium (Cd), leads (Pb), and nickel (Ni) were extracted by DTPA method and concentrated acid (HNO3) procedure, respectively. The content of Zn, Cu, Cd, Pb and Ni were determined by an atomic absorption spectrophotometer (Shimadzu AA-6300). Descriptive statistics were conducted using SPSS 16 for Windows. In order to study the effect of irrigation with treated wastewater on the extent of contamination of heavy metals, the AP (availability percentage), PI (Single-factor pollution index), NPI (Nemerows pollution index), and PLI (Pollution load index) in the affected soils with this wastewater was calculated. Also, all soil and water experiments were performed in 3 replicates and then, using the excel data software category, tables and charts were plotted.

The soils were alkaline and calcareous as characterized by high pH, ranging from 7.6 to 8, and calcium carbonate equivalent, ranging from 30 to 42%. On average, the value of the available fraction of the examined metals in the wastewater-irrigated soils ranged from 1.9 to 3.5 mg kg-1for Zn, 2.5- to 3.5 mg kg-1for Cu, 0.4 to 0.62 mg kg-1for Cd, 2 to 2.9 mg kg-1for Pb, and 1.34 to 1.75 mg kg-1for Ni. Comparing to the control, irrigation with wastewater resulted in a considerable build-up in the available fraction of the metals in the rank of Ni (79-142%)> Cd (54-125%)> Zn (35-73%)> Cu (13-87%)>Pb (6-32%). These patterns can be due to the quality and quantity of the used wastewater and impact of the used wastewater with its receiving soils. Similar to the available fraction, there was an increasing trend in the total fraction of metals in the order of Cd> Zn>Pb> Ni> Cu following wastewater irrigation. In this context, the mean content of total Zn, Cu, Cd, Pb, and Ni in wastewater-irrigated soils was as 51-157%, 10-32%, 243-310, 11-203%, and 13-126% higher than those of control soil, respectively. In spite of such enrichment, only the Cd values exceeded the maximum acceptable limits. The AP index is an appropriate index to compare the mobility potential and the toxicity of heavy metals in soil. In this study, the highest rate of this index among the heavy metals was related to Cd and its lowest level was related to Pb, which showed more toxicity and more mobility of Cd compared with other elements. The average of single-factor pollution index of five elements was observed in sequence Cd> Zn> Ni>Pb> Cu that the element of Cd had the highest class of PI (class 4). The highest and lowest of NPI values of five elements were observed in profiles 4 and 2, respectively. Also, the greatest effect of the five elements of this study is on the elements of Cd and Zn in the generation of this level of contamination. The pollution index of the five studied elements in irrigated soils with treated wastewater was similar to the NPI, its maximum was observed in profile 4 and Cd showed the highest effect on increasing the value of this index.

The results of this study showed that irrigation with sewage significantly increased the available fraction of the metals in the order of Ni (78.9-141.8%)> Cd (54.4-125%)> Zn (35.7-73.3%>Cu (13-87%)>Pb (6-32.3%) compared to the control. However, with the exception of cadmium, the available fraction of other elements was within the permissible limit. Compared to the control, in the majority of studied soils, the total fraction of the metals (with the exception of copper) was significantly increased and the lowest and highest increase associated with Cu (10-32%) and Cd (2 - 3 times). Also, the results of pollutant indices showed that the majority of the studied soils were in the low to high contamination and Cd was known as the major metal affecting the indices yield.

Land use changes such as conversion of forest to cultivated lands, significantly affect soil properties and modify soil forming processes. Land use changes can drastically affect the soil environment, which in turn markedly affect soils and soil processes. Human activities that are not associated with proper planning have undesirable effects on natural resources such as soil, including land use change. The results of the investigations in different parts of the world show that changing the use of natural ecosystems to managed ecosystems has destructive effects on soil properties. Cutting off the forest trees and converting pastures into agricultural lands will destroy or disrupt natural ecosystems and reduce the current or future production capacity of the soil. One of the important issues in the world is the destructive effects of agriculture on soil quality. These destructive effects can include a wide range of soil changes including physical properties such as soil compaction, soil water depletion, soil structure destruction and soil texture change, chemical properties such as accumulation of some elements such as N, P, K, and soil salinity, and soil biological properties such as soil microbial population and soil fauna activity changes, soil organic matter reduction and also effect on useful soil enzymes. Land use change from forest to agriculture does not necessarily lead to soil degradation. Land use changes and forest destruction in Yasouj region has increased in last decades. In this study, we investigated the effects of land use change on some soil characteristics in Servak plain, Yasouj region.

Servak region is located in 4 km south of Yasouj city. Three main land uses of dense forest, degraded forest, and dry farming were chosen to study the role of land use change on some soil properties.. The elevation of the region varies from 1833 to 1869 m above sea level. Five soil samples (0-20 cm) were taken from each land use. Samples from each land use were taken from almost similar elevation and slope to minimize the effect of topography. Soil samples were transferred to the laboratory, air dried and passed through a 2mm sieve. The chemical and biological analyses were carried out. The determination of soil organic carbon was carried out based on the Walkley-Black chromic acid wet oxidation method. Available K was extracted with 1N ammonium acetate at pH=7 and was determined by flame photometry. The Olsen method was used for the determination of available phosphorus. Total nitrogen was measured using the Kjeldahl method. Soil bacterial communities were counted using culture medium (Nutrient agar. The basal respiration rate was estimated by back-titration of the unreacted NaOH to determine CO2 evolved over 10 h. The substrate-induced respiration was measured by adding 2 ml of 1% glucose to soil samples over 6 h. Soil suspensions were prepared by 10-fold serial dilutions with 1g soil. Counting the soil fungal community was done using a culture medium (Potato dextrose agar) and was prepared by 10-fold serial dilutions. The activity of alkaline and acid phosphate enzymes was measured based on a colorimetric method using p-nitrophenol.

The land use change from a dense forest to dry farming has modified many chemical and biological soil properties. The results of analysis of variance and comparison of the means of data obtained from this study showed that as a result of land use change from dense forest to dry farming, Organic matter, total nitrogen, exchangeable potassium, basal and substrate-induced respiration, fungal community, acid phosphatase and alkaline phosphatase enzymes contents were decreased. Also, soil bacterial communities were increased at 1% level in dry farming land use. The amounts of phosphorus did not show any significant difference. In general, it can be concluded that following the degradation of the forest and land use change, the soil organic matter and relevant properties, especially biological indices, are more affected compared to the other properties. Soil organic matter plays a key role in ensuring agroecosystem productivity and the long-term conservation of soil resources.

Large-scale conversion of indigenous forests to cultivated land, driven by long-term agricultural development in the Servak region, has greatly affected the physicochemical and biological properties of the soils. Generally, the conversion of the natural ecosystem to agroecosystems decreased organic carbon content and relevant indices such as basal and substrate-induced respiration, fungal community, acid phosphatase and alkaline phosphatase enzymes contents in the top-soils at depth of 0 to 20 cm. The decrease of organic carbon in cropped farms could be attributed to the enhanced oxidation of soil organic C caused by cultivation. The results of this study showed that any management and type of land use that decreases soil capabilities can reduce soil quality and increase the susceptibility to degradation. So, in order to maintain soil quality, appropriate management practices should be done.

Climate change (CC) is one of the most important concerns for mankind in the current century. Increasing CO2 concentration and the proof of the greenhouse effect theory in which the type and composition of atmospheric gases which influence the earth temperature, are among undeniable facts makes the future climate change more possible. Impacts of Global warming on hydrological cycles and precipitation patterns would be more prominent in arid and semi-arid regions of the earth. For the arid and semi-arid nature and the poverty more fraction of Afghanistan suffer from, it is likely that the impacts of CC on the country will be more intense. This is while there is no credible and reliant research addressing the impacts of CC on agriculture and food security sector of Afghanistan. Studying the impacts of CC on agriculture, future changes in agroclimatic indices and application of crop growth simulation models intensively require a precise and adequate sets of meteorological data. Because of many reasons, Afghanistan's historical meteorological data coverage is really weak. In this research the applicability of AgMERRA as a gauge-satellite based dataset for filling the Afghanistan in-situ meteorological gaps is evaluated via goodness of fit measures, patterns of seasonal changes and the probability distribution functions.

This study is conducted on four major stations of Afghanistan (Kabul, Herat, Mazar Sharif and Qandahar in the east, west, north and south of the country, respectively) (Fig. 1 and table 1) which had the best in-situ meteorological data coverage. Observed Maximum (Tmax) and Minimum temperature (Tmin) and precipitation (PRCP) data is collected via Afghanistan Meteorological Authority (AMA) or other sources. AgMERRA database downloaded with .nc4 format and extracted with R statistical software or Panoply ver. 4.8.4, dependently. Then five goodness of fit (GOF) measures (RMSE, NRMSE, MBE, R2 and d) are calculated according to the equations 1 to 5. There are different norms and indices to measure the validity of a models, some based on Pearson correlation coefficient (R and R2) which indicate the degree of correlation between observed and predicted data but have some amounts of sensitivity to extreme values (outliers). Although, many other measures are considered to overcome the weaknesses but it is hard to distinguish the best.

The results of this research indicated the good potency, effectiveness and ability of AgMERRA for gap-filling of in-situ meteorological data and producing spatiotemporal data series. Several studies in this area have almost the same results. It is reported that AgMERRA is the most applicable dataset for reflecting precipitation data comparing with ERA-Interim, ERA-Interim/Land and JRA-55 datasets. Comparisons via NRMSE shows great (>10%) and good (>20%) amounts in all stations and temporal scales. Among other stations, Mazar Shrif showed the best conformity between AgMERRA and observed data, while Kabul station had the weakest, probably due to complex topographic situation of the Kabul airport station. The amounts of R2 for predicting temperature (Tmax and Tmin) were more than 0.86 in daily, 14-days and monthly temporal scales. The lowest amount of the coefficient of determination was obtained at Qandahar station for Tmean in daily temporal scale (R2=0.8) and the highest amount obtained for daily Tmax at Mazar Sharif station (R2=0.947). R2 for daily PRCP were inadequate, but increasing to adequate amounts in 14-days and monthly temporal scales. The highest spatiotemporal amount of Tmax,Tmin and Tmean was obtained in daily scale and the lowest amount was obtained for Tmean (1.8 and 0.9, respectively). The Index of agreement (d), also had adequate amounts for 14-days and monthly PRCP (>0.87). The amount of MBE for precipitation in Herat, Mazar Sharif and Kabul stations were negative, while it was positive in Qandahar station with a hot and dry climate. AgMERRA could show a good compliance with changes of observed seasonal patterns, however, some amount of over and under-estimates are obvious especially for Kabul station. This compliance with in-situ observed patterns was acceptable for daily temporal scale, although AgMERRA was unable to predict some of the fluctuations in probability distribution composition (with the range of 1 °C), especially fot Tmax and Tmin, but fot Tmean the fluctuations simulated well.

According to the results of the study, AgMERRA showed an acceptable potency to simulate the in-situ meteorological data in four major studied stations of Afghanistan. According to the stochastic nature of PRCP, the variable showed the weakest results in daily temporal scale but acceptable in 14-days and monthly. Given the weak coverage of in-situ meteorological data of Afghanistan, AgMERRA could be a valid dataset for producing well scaled spatiotemporal data series to be used in agroclimatic, CC and crop growth modeling studies.

Evapotranspiration is one of the key elements of hydrological cycle. This parameter plays a crucial role in different water related studies such as agricultural water management, environmental energy budget, water balance of watersheds, water reservoirs and water conveyance structures (such as channels, dams, barriers and so on). Increasing greenhouse gases has led to increased atmosphere temperature. Such changes in air temperature and other atmospheric parameters caused some natural hazards in many regions. One of the important parameter impacted by climate change is potential evapotranspiration. Different studies conducted in the recent decade to detect the monotonic trends and abrupt changes in meteorological parameters. Most of them are on trend analysis of meteorological and hydrological parameters. In the recent years, monotonic trend analysis of reference crop evapotranspiration (ET0) has interested many investigators around the globe. Many investigators attempted to find the possible reasons of trends in ET0. In many cases, this is accomplished by sensitivity analysis of ET0 to different meteorological parameters. Other investigators attempted to model ET0 using the hydrologic time series modeling. Detection of sudden change point in different time series including ET0 is very important in changing climate. However, in spite of tremendous studies on monotonic trend analysis, it seems that no serious work has been conducted to detect abrupt changes in ET0 in Iran, especially in west and northwest of Iran. This region has fertile soils and produce an important portion of cereal yields of Iran, thus providing water to agricultural section is crucial under climate change. Therefore, the main objectives of this study were i) estimation of ET0 values in the selected stations in west and northwest of Iran using the FAO-Penman Monteith method, and ii) detection of significant change points in ET0 time series using the nonparametric Pettit test.
The 32 synoptic stations were selected in this area for analysis. Data needed for this study were gathered from IRIMO. Meteorological parameters were daily records of maximum air temperature, minimum air temperature, sunshine hour duration, wind speed, and relative humidity. The ET0 values were estimated using FAO-56 Penman-Monteith model. In order to detect the significant change point the non-parametric, Pettitt test was used. Both monthly and annual time scales were used in analysis. The null hypothesis of test is there is no sudden change point in the time series. We calculated the p-values for time series under test and compared it with significance level (5%). If the calculated p-value was less than the significance level (0.05), then the null hypothesis is rejected, and the alternate hypothesis (i.e. there is a significant sudden change point in the time series) will be accepted.
The results showed that around 60% of the monthly time series had significant sudden change points. For instance, Urmia showed significant abrupt changes in ET0 for all months. Specifically, more than 86 and 78 % of the stations experienced sudden change in ET0 in March and August, respectively. The strongest abrupt change observed at Maragheh, in which the difference in monthly ET0 before and after the change point date reached to about 45 mm. It is worth to mention that all detected sudden changes had upward direction. In annual time scale, more than 80 % of the stations showed significant abrupt changes in ET0. Among all stations, Sararoud- Kermanshah showed a large difference in mean annual ET0 for the subseries of before and after the change point date which was approximately 235 mm. In annual scale, all sites (except Sahand and Parsabad) experienced upward ET0 abrupt changes. In order to inspect the reason this change, we plotted different meteorological parameters time series. The results indicated that the wind speed showed negative trends (except for two stations) leading to ET0 increase. Furthermore, it was found that almost all stations exhibited increasing trends in air temperature. These changes caused an increase in ET0. The most prominent abrupt change date in ET0 time series was found for the years from 1995 to 1998. For example, in February, April, May, and June, monthly ET0 time series suddenly increased in 1998, which were statistically significant (p The sudden change in ET0 was confirmed in west and northwest of Iran. According to the results, ET0 time series (in monthly or annual time scales) exhibited upward sudden changes. Such changes in ET0 time series ring the alarms and decision makers should be, therefore, cautious in management of water resources.

During the last decades, runoff decreasing is observed in our country as many dam reservoirs face water supply crisis even in normal periods. This decreasing trend is mainly due to the uncontrolled withdrawals, lack of supply and demand management as well as droughts. Using different flow prediction methods for surface water resources state analysis is important in water resources planning aspects. These methods can provide the possibility of planning for proper operation by using different factors to meet the needs of the region. Due to the stochastic nature of the hydrological processes, various models are used for prediction. Among these models, Bayesian Networks (BNs) probabilistic model has been considered by many researchers in recent years and it has shown the efficiency on these issues. Due to the growth of demand in different sectors and crises caused by drought of the water supply system that has put the basin under water stress, the water shortage has appeared in different sectors. Regarding to the strategic situation of Zayandeh Rood Dam in providing water resources for tap water, industry, agriculture and environmental water rights in Gavkhooni basin, this research presents the development of a model for prediction of Zayandeh Rood Dam annual inflow and hydrological wet and dry periods. Since the uncertainty of the predictions increase when the prediction horizon increases, this factor is the most important challenge of long-term prediction. Using Bayesian Network with reducing this uncertainty, provides the possibility of planning for water resources management, especially for optimal water allocation.

In this study for prediction of zayandeh Rood dam inflow five scenarios were defined by applying Bayesian Network Probabilistic approach. According to this, prediction of numerical annual dam inflow (scenario1), annual wet and dry hydrological periods (scenario 2, 3, 4) and range of annual inflow (scenario 5) were performed. For this purpose rainfall, runoff, snow, and discharge of transferred water to the basin from the first and the second tunnel of koohrang and Cheshmeh Langan tunnel were considered as predictor variables and the amount of Zayandeh Rood Dam inflow was selected as predictant for modeling and different conditions of input variable’s learning have been analyzed considering different patterns. Calibration and validation of the model have been done based on observed annual inflow data and the relevant predictors in scenario 1, by using SDI Hydrological drought index and long-term average of inflow to classify the runoff and clustering the other parameters in scenario 2, 3 and 4 and with classification of annual inflow data and other parameters by using clustering in scenario 5. To achieve this target, K-means method has been used for clustering and Davies-Bouldin and Silhouette Width has been used to determine optimal number of clusters.

The results of Bayesian Network modeling showed that the scenario 1 has a good potential to predict the dam inflow so that the best pattern of this scenario (considering discharge of first tunnel of Koohrang and Cheshmeh Langan tunnel, Zayandeh Rood natural inflow and rainfall with two years lag time as predictor variables), has had a correlation coefficient of 0.78 between observed and predicted dam inflow and relative error of 0.21 which shows an acceptable accuracy in prediction. Among scenarios 2, 3 and 4 for prediction of wet and dry hydrological periods, scenario 2 in which classification of runoff has been based on the long-term average, in the best pattern (with dam inflow with one-year lag predictor), is able to be predicted up to 75% accuracy. The analysis of the results showed that the scenario 5 is not very accurate in prediction of dam inflow’s range.

The results showed that the Bayesian Network model has a good efficiency to predict annual dam inflow numerically as well as hydrological dry and wet periods. Obtained results from prediction of hydrological dry and wet periods will be effective in better planning of water resources in order to considering possible ways of drought effect reduction. The overall results provide the possibility of water resources planning for the water authorities of this region. Systematic planning leads to optimal use of water and soil resources and helps considerably to analyze and modify the policy or rule curve of this dam for allocating water to downstream especially for agriculture and environment and industry sectors.