مجله پژوهش آب ایران
پیاپی 20 (بهار 1395)

In this article, effect of angle and dimension of toe drain on phreatic line have been investigated in homogenous dams. Lack of enough studies about optimal size of a toe drain and its applied standard is the main aim of this new research. That is why; applied lab model is instructed at Shahrekord University. Location of data sampling had been at behind of homogenous earth dam wall on different height water. Situation of phreatic line will be recognized by using piezometer tube in different location of toe drain. Three type of drain with constant angle (45, 60 and 90 degree) was instructed at different height and finally, phreatic line procedure recorded for variation experiment on homogenous earth dam at maximum height of water. The best formation and dimension of stony toe drain is gotten by collation of different equations on phreatic line (based on comparison by without drain test). The result shown that homogenous earth dams can be obtained highest loss in phreatic line when upward of toe drain angle and its top height had 45 degree and 0.35 maximum height of water in cistern.n this article, effect of angle and dimension of toe drain on phreatic line have been investigated in homogenous dams. Lack of enough studies about optimal size of a toe drain and its applied standard is the main aim of this new research. That is why; applied lab model is instructed at Shahrekord University. Location of data sampling had been at behind of homogenous earth dam wall on different height water. Situation of phreatic line will be recognized by using piezometer tube in different location of toe drain. Three type of drain with constant angle (45, 60 and 90 degree) was instructed at different height and finally, phreatic line procedure recorded for variation experiment on homogenous earth dam at maximum height of water. The best formation and dimension of stony toe drain is gotten by collation of different equations on phreatic line (based on comparison by without drain test). The result shown that homogenous earth dams can be obtained highest loss in phreatic line when upward of toe drain angle and its top height had 45 degree and 0.35 maximum height of water in cistern.n this article, effect of angle and dimension of toe drain on phreatic line have been investigated in homogenous dams. Lack of enough studies about optimal size of a toe drain and its applied standard is the main aim of this new research. That is why; applied lab model is instructed at Shahrekord University. Location of data sampling had been at behind of homogenous earth dam wall on different height water. Situation of phreatic line will be recognized by using piezometer tube in different location of toe drain. Three type of drain with constant angle (45, 60 and 90 degree) was instructed at different height and finally, phreatic line procedure recorded for variation experiment on homogenous earth dam at maximum height of water. The best formation and dimension of stony toe drain is gotten by collation of different equations on phreatic line (based on comparison by without drain test). The result shown that homogenous earth dams can be obtained highest loss in phreatic line when upward of toe drain angle and its top height had 45 degree and 0.35 maximum height of water in cistern.n this article, effect of angle and dimension of toe drain on phreatic line have been investigated in homogenous dams. Lack of enough studies about optimal size of a toe drain and its applied standard is the main aim of this new research. That is why; applied lab model is instructed at Shahrekord University. Location of data sampling had been at behind of homogenous earth dam wall on different height water. Situation of phreatic line will be recognized by using piezometer tube in different location of toe drain. Three type of drain with constant angle (45, 60 and 90 degree) was instructed at different height and finally, phreatic line procedure recorded for variation experiment on homogenous earth dam at maximum height of water. The best formation and dimension of stony toe drain is gotten by collation of different equations on phreatic line (based on comparison by without drain test). The result shown that homogenous earth dams can be obtained highest loss in phreatic line when upward of toe drain angle and its top height had 45 degree and 0.35 maximum height of water in cistern.

Compound channels are composed of a main channel and one or two flood plains around it that are relatively shallower than the main channel. Due to the difference between the flow velocity in the main channel and the floodplains, the flow has a complex structure in compound channels. In compound channels, a part of river discharge is carried out by floodplains, thus shear distribution and flow structure becomes complicated due to the transfer of momentum between the main channel and the shallower flow in the floodplains. In the last two decades, the attention of the researchers was devoted to the investigation of flow behavior in compound channels.
In this study, the Fluent 6.3 software was used to solve the governing equations on the open channels with compound cross section. Fluent is a powerful and flexible general-purpose computational fluid dynamics software ideally suited for simulating the flow characteristics in compound channels. In this software, the volume of fluid model (VOF) is used to solve the equations. The VOF formulation relies on the fact that two or more fluids (or phases) are not interpenetrating. The VOF method consists of three ingredients: a scheme to locate the surface, an algorithm to track the surface as a sharp interface moving through a computational grid, and a means of applying boundary conditions at the surface. To generate the mesh as well as to introduce the channel geometry, the Gambit pre-processing software was used. Gambit is an integrated preprocessor program for CFD. It can be used for geometry construction and import, mesh generation with structured and unstructured elements, mesh quality examination and definition of boundary zones. The distance among the meshes was 5 mm, albeit, it was 2.5 mm near the walls and channel bed. For simulating the flow turbulence, the Reynolds stresses model was used. The results of simulations was compared with those of experimental data. The simulated channel was a flume with 12.5 m length, and a 0.4 m * 0.4 m compound cross-section. The flow depth in the main channel was 0.08 m, and the flood plain changed from 0.02 m to 0.06 m. the width of main channel was 0.2 m.
In this study, the effect of the ratio of flow depth at the floodplain to flow depth at main channel on the velocity distribution and the location of the maximum velocity at a compound channel was investigated. In addition, the effect of flood plain roughness on the above parameters was studied. The results showed that by changing the ratio of flow depth at floodplain to flow depth at main channel, the velocity distribution in the channel changes significantly. At the junction of main channel with flood plain, two vortices were appeared, named as flood plain vortex and main channel vortex. Both of the vortices reached to the flow surface and occupied the zone limited by . At the distance of , a secondary flow was formed near the free flow surface from channel wall to the axis of the channel, named as free surface vortex. This vortex is generated because of the anisotropic turbulence. The free surface vortex and the main channel vortex meet together at the central axis of the channel . At the zone , another secondary flow is established known as bottom vortex. The simulated iso-vel curve were in good agreement with the observation of previous researchers. The dip phenomenon was observed in compound channels. As the flow depth over the floodplain decreases, the location of maximum velocity gets further away from the flow surface as well as from the junction of main channel and the flood plain. To investigate the effect of roughness on the velocity distribution at the compound channels, two cases of smooth flood plain and roughened flood plain were studied. The results showed that there are good agreement between the results of Fluent and the experimental data. In this case, the maximum velocity occurred at z/H=1.375, y/H=0.8. The roughness changed the shape of iso-vel curves at the flood plain. As the height of roughness at the floodplain increases, the velocity decreases in this zone and the iso-vel curves move to the main channel. By increasing the height of the roughness, there was no changes in the shape of iso-vel curves at the main channel.

The increase of greenhouse gasses, the so called reason of climate change, may cause global average temperature to be surged up and consequently, patterns of regional precipitation, evaporation, landuse, soil moisture and river flow rates will be altered. Based on climate change, the earth’s temperature continues to rise, it is possible to expect a significant impact on water resources. As temperatures increase, some parameters like evaporation increases, sometimes resulting in rain and droughts. Rainfall and runoff variability are important phenomenon and at times severely impacts on the water resources planning and management. It is the most studied hydro-climate variables because of its significance for sustainable water resources management, water supply, environment, agricultural activities and ecological management. In this research, prediction of outflow of Gharesu River basin, a river in the west of Iran, in current and future has been done. Gharesou River basin is one of subbasins of Karkheh basin with area of 5354 km2 and is contain of three major streams. Using climate models and under different emission scenarios, future hydrologic criteria and outflow of basin have been simulated and predicted. This study have tried to discover the effects of climate effects on hydrologic variables, rainfall and runoff variability of a river basin using a methodology combining climate models, rainfall-runoff model, GIS and predictors.
In this study, the impact of climate change on the stream flow of Gharesou River for the future period of the years 2046 to 2065 is analyzed, utilizing two climatic models, HADCM3 and MPEH5, under three emission scenarios- A1B, A2, and B1. Moreover, MapShed, a rainfall- runoff model that requires GIS layers of surface water, topography, soil type, regional climatological stations, accompanying with precipitation and maximum and minimum data produced by LARS-WG model, was used to simulate the stream flow in a given upcoming time. LARS-WG model produced future hydrological data based upon present precipitation. Major predicted data are maximum and minimum temperature and sunny hours of a day. Then, the MapShed model was calibrated and validated based on the observed stream flow, provided from the Kermanshah regional water authority, of the years 1990 to 1995 and 1996 to 1998, respectively. In order to predict the future condition, the upcoming parameters of the rainfall and the temperature were predicted by downscaling the HADCM3 and MPEH5 models’ output by means of Lars-WG statistical downscaling model. For accomplishing this goal, the past climatic parameters of the period of 1960 to 1995 are used. The output of these climatic models (for the period of 2046 to 2065) associated with GIS layers of the basin’s land use, topography, surface runoff and soil context were introduced to MapShed, a GIS-based watershed simulation model, to produce the future flow of the river basin. The goodness of fit criteria, for flow rate produced by MapShed model, including RMSE, R2 and minimum cumulative errors (CE) indicate the decent performance in calibration and validation processes for the periods of 1990 to 1995 and 1996 to 1998, respectively. In all model-scenarios except for MPEH5-A2, the future, like ling-term observation period, peak flow happens in March. Under MPEH5-A2 scenario, the peak flow was transferred to April. Additionally, model MPEH5, under the A1B scenario and in all months, predicts flow rate less than that of observation period, while this model forecasts flow rates more than the period in observation period for all months of years. Moreover, most of the model-scenarios indicate a decline of flow rate in months of February, March, April, September and October and an increase in months of June, July, August and January.
The results show that the 20-year average of future flow in the Gharesou River under four model-scenarios of MPEH5-A1B, HADCM3-B1, HADCM3-A1B, and MPEH5-B1 will increase and under two model-scenarios of MPEH5-A2 and HADCM3-A2 will decline, in comparison with the long-term mean of the observed annual flow. It is worth mentioning that most of the scenarios predict the increase of flow rate, with respect to observation period, in the late spring and during summer and the decline of flow rate in the early spring. Like observed period, in the most of scenarios, peak discharges of outflow of basin has been estimated in March, and just in MPEH5 scenario, peak discharge has been happen in April.

The aim of this study is to evaluate groundwater resources of the koohpaye-segzi Plain and its reaction rather to different parameter changes such as distance from the river of zayanderood. Then, the impacts of the input stream flow to the region, precipitation, evaporation, the mean temperature and deflation from the water table on the plain water table were assessed for the 1996 to 2010 time period. The results showed that the level of water table has been declined 3.5 meters in average during this time scale. This declination rate has spatially increased, especially in the 30 kilometers of the first part of Zayanderood river and have reached to over 14 meters. Furthermore, the results showed the water level depths of wells located within the 6 km strip width from the river are strongly influenced by discharge fluctuations during the year, and with increasing the distance from the river is reduced. A drastic reduction in input flow at the beginning of the plain has caused increasingly pressure on the groundwater resources (near the bridge Choom) for agricultural activities. At the end part of the river (near the bridge Varzaneh) by decreasing stream flow and consequently declining of water table and quality of groundwater resources, agricultural activities have been disrupted that makes less declining rather than the initial region and causing many socio-economic problems in the Koohpaye-Segzi Plain.The aim of this study is to evaluate groundwater resources of the koohpaye-segzi Plain and its reaction rather to different parameter changes such as distance from the river of zayanderood. Then, the impacts of the input stream flow to the region, precipitation, evaporation, the mean temperature and deflation from the water table on the plain water table were assessed for the 1996 to 2010 time period. The results showed that the level of water table has been declined 3.5 meters in average during this time scale. This declination rate has spatially increased, especially in the 30 kilometers of the first part of Zayanderood river and have reached to over 14 meters. Furthermore, the results showed the water level depths of wells located within the 6 km strip width from the river are strongly influenced by discharge fluctuations during the year, and with increasing the distance from the river is reduced. A drastic reduction in input flow at the beginning of the plain has caused increasingly pressure on the groundwater resources (near the bridge Choom) for agricultural activities. At the end part of the river (near the bridge Varzaneh) by decreasing stream flow and consequently declining of water table and quality of groundwater resources, agricultural activities have been disrupted that makes less declining rather than the initial region and causing many socio-economic problems in the Koohpaye-Segzi Plain.The aim of this study is to evaluate groundwater resources of the koohpaye-segzi Plain and its reaction rather to different parameter changes such as distance from the river of zayanderood. Then, the impacts of the input stream flow to the region, precipitation, evaporation, the mean temperature and deflation from the water table on the plain water table were assessed for the 1996 to 2010 time period. The results showed that the level of water table has been declined 3.5 meters in average during this time scale. This declination rate has spatially increased, especially in the 30 kilometers of the first part of Zayanderood river and have reached to over 14 meters. Furthermore, the results showed the water level depths of wells located within the 6 km strip width from the river are strongly influenced by discharge fluctuations during the year, and with increasing the distance from the river is reduced. A drastic reduction in input flow at the beginning of the plain has caused increasingly pressure on the groundwater resources (near the bridge Choom) for agricultural activities. At the end part of the river (near the bridge Varzaneh) by decreasing stream flow and consequently declining of water table and quality of groundwater resources, agricultural activities have been disrupted that makes less declining rather than the initial region and causing many socio-economic problems in the Koohpaye-Segzi Plain.The aim of this study is to evaluate groundwater resources of the koohpaye-segzi Plain and its reaction rather to different parameter changes such as distance from the river of zayanderood. Then, the impacts of the input stream flow to the region, precipitation, evaporation, the mean temperature and deflation from the water table on the plain water table were assessed for the 1996 to 2010 time period. The results showed that the level of water table has been declined 3.5 meters in average during this time scale. This declination rate has spatially increased, especially in the 30 kilometers of the first part of Zayanderood river and have reached to over 14 meters. Furthermore, the results showed the water level depths of wells located within the 6 km strip width from the river are strongly influenced by discharge fluctuations during the year, and with increasing the distance from the river is reduced. A drastic reduction in input flow at the beginning of the plain has caused increasingly pressure on the groundwater resources (near the bridge Choom) for agricultural activities. At the end part of the river (near the bridge Varzaneh) by decreasing stream flow and consequently declining of water table and quality of groundwater resources, agricultural activities have been disrupted that makes less declining rather than the initial region and causing many socio-economic problems in the Koohpaye-Segzi Plain.

The present study aimed to investigate the effects of polyacrylamide (PAM) on runoff volume (R) and soil loss (SL) subjected to freeze-thaw (FT) cycle from small experimental plots induced under rainfall simulation condition. A completely randomized design with FT cycle and none use of PAM as control were used to compare the effect of application of different rates of PAM (0.25, 0.5 and 0.75 g.m-2) on runoff generation time (TR), R and SL. The ANOVA results showed that the PAM had significant increasing effect on TR. Application rates of 0.25 and 0.50 g.m-2 decreased R and SL at tune of 49, 23 and 77 and 52, respectively, compared to those recorded for the control plot. In contrast, R and SL increased 1.62 and 4.5 times subjected to 0.75 g.m-2 application rate. It was also understood from the results that the PAM with the particle flocculation capability and increasing penetration rate could control the effects of FT cycle, with further effect on SL. Whereas, the PAM treatment of 0.75 g.m-2 had increasing effect on runoff yield and soil loss.The present study aimed to investigate the effects of polyacrylamide (PAM) on runoff volume (R) and soil loss (SL) subjected to freeze-thaw (FT) cycle from small experimental plots induced under rainfall simulation condition. A completely randomized design with FT cycle and none use of PAM as control were used to compare the effect of application of different rates of PAM (0.25, 0.5 and 0.75 g.m-2) on runoff generation time (TR), R and SL. The ANOVA results showed that the PAM had significant increasing effect on TR. Application rates of 0.25 and 0.50 g.m-2 decreased R and SL at tune of 49, 23 and 77 and 52, respectively, compared to those recorded for the control plot. In contrast, R and SL increased 1.62 and 4.5 times subjected to 0.75 g.m-2 application rate. It was also understood from the results that the PAM with the particle flocculation capability and increasing penetration rate could control the effects of FT cycle, with further effect on SL. Whereas, the PAM treatment of 0.75 g.m-2 had increasing effect on runoff yield and soil loss.The present study aimed to investigate the effects of polyacrylamide (PAM) on runoff volume (R) and soil loss (SL) subjected to freeze-thaw (FT) cycle from small experimental plots induced under rainfall simulation condition. A completely randomized design with FT cycle and none use of PAM as control were used to compare the effect of application of different rates of PAM (0.25, 0.5 and 0.75 g.m-2) on runoff generation time (TR), R and SL. The ANOVA results showed that the PAM had significant increasing effect on TR. Application rates of 0.25 and 0.50 g.m-2 decreased R and SL at tune of 49, 23 and 77 and 52, respectively, compared to those recorded for the control plot. In contrast, R and SL increased 1.62 and 4.5 times subjected to 0.75 g.m-2 application rate. It was also understood from the results that the PAM with the particle flocculation capability and increasing penetration rate could control the effects of FT cycle, with further effect on SL. Whereas, the PAM treatment of 0.75 g.m-2 had increasing effect on runoff yield and soil loss.The present study aimed to investigate the effects of polyacrylamide (PAM) on runoff volume (R) and soil loss (SL) subjected to freeze-thaw (FT) cycle from small experimental plots induced under rainfall simulation condition. A completely randomized design with FT cycle and none use of PAM as control were used to compare the effect of application of different rates of PAM (0.25, 0.5 and 0.75 g.m-2) on runoff generation time (TR), R and SL. The ANOVA results showed that the PAM had significant increasing effect on TR. Application rates of 0.25 and 0.50 g.m-2 decreased R and SL at tune of 49, 23 and 77 and 52, respectively, compared to those recorded for the control plot. In contrast, R and SL increased 1.62 and 4.5 times subjected to 0.75 g.m-2 application rate. It was also understood from the results that the PAM with the particle flocculation capability and increasing penetration rate could control the effects of FT cycle, with further effect on SL. Whereas, the PAM treatment of 0.75 g.m-2 had increasing effect on runoff yield and soil loss.

Increase of food production for growing world population makes an assessment of global agricultural water productivities and virtual water flows important. The virtual water concepts together with the water footprint links a large number of sectors and issues, thus providing an appropriate framework to support more optimal water management practices. In other word, to better understand the linkages between humanity's productive activities and this growing pressure on the freshwater resources, the water footprint was developed to measure the amount of water consumed throughout a product's value chain. In this paper, water footprint of agricultural crops was assessed with distinguishing between internal and external water footprints, blue water and green water and the amount of saving and losing water resources by virtual water trade. Agricultural crops in this study include cereal (wheat, barley, rice and maize), fruits (apple, orange, onion and potato) and pulses (chickpea). The total water footprint is calculated as the sum of the use of domestic water resources and virtual water import minus virtual water export. So the total volume of water use in these agricultural crops is calculated based on the total volume of crop produced and its corresponding virtual water content. Similarly, the volume of virtual water export or import is calculated based on the international trade of products and their virtual water content. The blue and green virtual water content of agricultural crop is the volume of blue/ green water used to produce the crop and these are calculated based on blue and green crop water requirements and yields.
The potential of green water in producing agricultural crops is different, on average 40% of these crops are produced by green water. Estimation of the amount of virtual water content can determine decision making on the production or trade of agricultural crops. Therefore, the high water-consuming products can be removed from the cropping pattern of areas with water crisis and, instead, replaced by low water-consuming products. In this case, import of high water-consuming products (having high virtual water content) lead to reduced water crisis and providing food security in these regions. As a result, the products like rice and chickpea are suggested to be removed from the crop pattern in crisis areas. On the other hand, the results show that the exported products have a lesser content of virtual water (blue and green) than the imported products. In other words, the pattern of agricultural crops imports during the investigation years has been into the importation of water-consuming products. Therefore, respect to the amount of consumed water, reconsideration in the adoption of the existing policies in the field of export and import of agricultural products is necessary. In general, virtual water import is more than virtual water export so Iran is net virtual water importer and imports 14.3 BCM in this period so it can be remedy for water crisis in Iran and that in effect it partially depend on water resources elsewhere.
The results of calculating virtual water content show that potato, onion, apple and orange need less blue water than other crops, also rice, orange and potato use less green water. In many agricultural crops, amounts of green virtual water contents are more than blue virtual water contents because of continuous water supply in irrigated lands; these crops have high crop water productivity. Furthermore, wheat and onion have great and less internal water footprint among of agricultural crops repectively so that wheat use 19168 MCM water (57.5% of green water and 42.5% of blue water) and onion 244.6 MCM (93.3% of blue water and 6.7% of green water) in this period. The results showed that average of water footprint of crops is 656 m3 cap-1 yr-1 and external water footprint is less than internal (40% of blue water footprint and 29% of green water footprint) and this means that a large amount of agricultural crops produces domestically. About 14611 MCM of water resources is saved by cereal import and 135 MCM is lost by virtual water export. Therefore, on the average, 14476 MCM of water resources is saved during 1997-2001. So we can conclude that international trade of agricultural products significantly influences the water appropriation in the country, a relation that has so far received little attention from both economists and water managers.

Construction of weirs and diversion dams in river bends has been inevitable in some cases around the world, and many examples are available to demonstrate the use of conventional types of weirs in the channel bends. The lack of design criteria for the construction of weirs on channel bends is evident. However, the operational experiences of these weirs in rivers bends indicate the non-uniformity of water surface levels, sediment distribution, and flow rates across the channel bend, hence, the poor performance of intake structures on both sides of the river. The main hypothesis for providing uniform distribution of flow across the bend is the change of the weir-crest profile from horizontal to sloping crest. Review of previous studies indicates a few researches on the performance of sloping-crested weirs in channel bends. The aim of the present study was to test the performance of horizontal and sloping Crump weirs in a channel bend, in order to achieve the most uniform distribution of the unit flow rates across the river bend. In this study, the theory of the design of a weir crest in a channel bend is presented. Flow equation was derived from mathematical and dimensional analysis. The discharge coefficient, Cd, is related to the relative curvature of the bend, the position of the weir along the bend, the geometry of the weir and the upstream head water. Flow characteristics were evaluated in a laboratory flume consisting of a 90 degree bend with a relative radius of curvature 3, with and without the standard Crump weirs. The experiments were carried out using 3 different heights of weir, 4 different weir crest slopes (3 sloping crests, and 1 horizontal crest), and at 7 different positions of the channel (2 cross sections in straight reach and 5 cross sections in curvature reach of the channel). All experiments were repeated under 3 different flow conditions. Total of 252 tests (63 with horizontal weirs and 189 experiments with sloping crested weirs) were carried out. Flow discharge, 2D velocity and water surface profiles at the control sections of weirs were measured.
The results indicated that horizontal crested weirs are appropriate for straight reaches upstream and downstream of the channel bend, and are still sufficient at the entrance and exit of the bend. The control section is parallel to the weir crest. It is located at a distance of (2-4.7)h upstream the weir at upstream and bend’s entrance sections (h is the upstream head). For the horizontal weirs at the downstream of the bend, the control section is located at (1-3.45)h, and on 2B-Downstream of the bend is at (2.1-3.5)h. In the channel bend, sloping crest weirs provide better convergence of the unit flow rates across the river. The slope of the weir crest is recommended to be in the range of 85º

Significant decrease in the quantity and quality of available water resources and arid and semiarid regions of the country lead to get more attention to modern irrigation systems to increase irrigation efficiency and water use productivity. The success of a drip irrigation system depends on its design, implementation and maintenance. In this research, citing indicators provided by the Agricultural Engineers Association of America (ASAE), the performance of a Subsurface Drip Irrigation System was evaluated. Water quality parameters, texture and quality of the soil, clogging of emitters and water distribution, installation depth, distance from each other and from the trunk of the dropper were evaluated. Uniformity coefficient and coefficient of variation and overall drippers performance were derived 74% and 25% and 20%, respectively and classified as weak. The poor performance of drippers could be due to poor design, clogging of drippers and unfamiliar technology to benefit farmers.
Significant decrease in the quantity and quality of available water resources and arid and semiarid regions of the country lead to get more attention to modern irrigation systems to increase irrigation efficiency and water use productivity. The success of a drip irrigation system depends on its design, implementation and maintenance. In this research, citing indicators provided by the Agricultural Engineers Association of America (ASAE), the performance of a Subsurface Drip Irrigation System was evaluated. Water quality parameters, texture and quality of the soil, clogging of emitters and water distribution, installation depth, distance from each other and from the trunk of the dropper were evaluated. Uniformity coefficient and coefficient of variation and overall drippers performance were derived 74% and 25% and 20%, respectively and classified as weak. The poor performance of drippers could be due to poor design, clogging of drippers and unfamiliar technology to benefit farmers.
Significant decrease in the quantity and quality of available water resources and arid and semiarid regions of the country lead to get more attention to modern irrigation systems to increase irrigation efficiency and water use productivity. The success of a drip irrigation system depends on its design, implementation and maintenance. In this research, citing indicators provided by the Agricultural Engineers Association of America (ASAE), the performance of a Subsurface Drip Irrigation System was evaluated. Water quality parameters, texture and quality of the soil, clogging of emitters and water distribution, installation depth, distance from each other and from the trunk of the dropper were evaluated. Uniformity coefficient and coefficient of variation and overall drippers performance were derived 74% and 25% and 20%, respectively and classified as weak. The poor performance of drippers could be due to poor design, clogging of drippers and unfamiliar technology to benefit farmers.
Significant decrease in the quantity and quality of available water resources and arid and semiarid regions of the country lead to get more attention to modern irrigation systems to increase irrigation efficiency and water use productivity. The success of a drip irrigation system depends on its design, implementation and maintenance. In this research, citing indicators provided by the Agricultural Engineers Association of America (ASAE), the performance of a Subsurface Drip Irrigation System was evaluated. Water quality parameters, texture and quality of the soil, clogging of emitters and water distribution, installation depth, distance from each other and from the trunk of the dropper were evaluated. Uniformity coefficient and coefficient of variation and overall drippers performance were derived 74% and 25% and 20%, respectively and classified as weak. The poor performance of drippers could be due to poor design, clogging of drippers and unfamiliar technology to benefit farmers.
Significant decrease in the quantity and quality of available water resources and arid and semiarid regions of the country lead to get more attention to modern irrigation systems to increase irrigation efficiency and water use productivity. The success of a drip irrigation system depends on its design, implementation and maintenance. In this research, citing indicators provided by the Agricultural Engineers Association of America (ASAE), the performance of a Subsurface Drip Irrigation System was evaluated. Water quality parameters, texture and quality of the soil, clogging of emitters and water distribution, installation depth, distance from each other and from the trunk of the dropper were evaluated. Uniformity coefficient and coefficient of variation and overall drippers performance were derived 74% and 25% and 20%, respectively and classified as weak. The poor performance of drippers could be due to poor design, clogging of drippers and unfamiliar technology to benefit farmers.

Introduction The majority of the world's dry lands are still farmed by small scale. In these farms, low cost simple irrigation methods are paid attention by farmers and also international development programs. Efficient traditional methods of irrigation such as buried clay pot irrigation is one of the most important methods that could be of great use on small and medium sized farms and gardens that have not been well studied in Iran. Also, the information on shape of wetted zone of soil under buried clay pot plays the great significance in design and management of this type of irrigation system for many land farms at arid and semi-arid regions on small and medium sized farms and gardens. Clay pot or porous clay capsules irrigation is able to release water in near root zone with self- regulative. Several parameters such as saturated soil hydraulic conductivity, soil porosity, water supply, pressure head and irrigation time may affect on discharging and soil wetting shape under sub-irrigation with porous clay capsule.
Materials and Methods Present research was carried out in 2014 carried out on the field of agriculture of faculty of Tarbiat Modares University, to study simulated soil wetting shape under two different type of buried porous clay capsule (GBN and GN) in calcareous soil with clay loam texture. The soil are generally deep to moderately deep with clay loam texture, ~ 17% CaCO3 (lime) , 0.44% organic matter and a moderately soil permeability. The slope in this study area is 0.5 -1.5%. The GBN and GB have different size and discharge. In this paper, wetted radius and depth of GBN (3.5 cm diameter and 12 cm height) and GN (3.5 cm diameter and 3.5 cm height) porous clay capsules as a subsurface point source were measured at 10, 25, 50, 80, 100 kPa of hydrostatic pressure by discharge-pressure automation instrument which was designed for this purpose. The soil weting shapes measured after 24 hr of irrigation with GBN and GB of buried porous clay capsule under clay loam soil texture. In order to predict the water distribution of clay capsules, several parameters such as saturated soil hydraulic conductivity, soil porosity, water supply, pressure head and irrigation time were modeled by with Buckingham theorem in dimensional analysis technique. Residual errors analysis was used to validate the simulation model.
Results Discussion According to the experimental results, the soil water distribution shape in GN and GBN clay capsules types followed a spherical trend, which is due to the low discharge of clay capsules. The analysis results of residual errors showed that the average of ME, RRMSE and R2 were 9.82, 23.78, 89.48 and 10.92, 57.97, 90.4 for GB and GBN respectively. Therefore, dimensional analysis models have good accuracy in determining the wetted radius and depth of two clay capsule types. Tese shows that developed model can be used to simulate wetting pattern under porous clay capsule irrigation system with point source of water application. Also, the results showed that wetted radius and depth of GN at 100 kPa pressure head was similar to GBN up to 50 kPa. In other hand, irrigation engineers can selected and used GN insted of GBN for places with high pressure ability. Because, the run of smaller nozzle (clay capsule of GN) is earier in related to the GBN at fileds.
Conclusion Water distribution in soil is important for the design, operation, and management of irrigation system for arid and semi-arid regions. In order to, the four equation was developed to simulate soil wetted depth and width with Buckingham theorem in dimensional analysis technique under two types of buried porous clay capsule (GBN and GN) at point source of water application. It is important to know that, The discharge of clay capsules increased with increasing pressure head and the relationship between discharge and hydrostatic pressures trend to non-linear in GB and GBN.Based on our experiment results, these equations can be used as a reliable method to predict the wetted soil shape in clay loam soil and had good accuracy for practical project to provide aids for deciding depth and intervals of porous clay capsules and designing a subsurface irrigation scheme. In othe hands, the models simulated values were following distribution not different than observed ones in two porous clay capsule types. The main conclusion drawn from the two porous clay capsule size’s is that the soil wetted shape in GN type was similar to GBN type at high pressure head. This point is important to principles of irrigation engineering and managment.

In recent years nitrate was reported as most important source of pollutant of soil and water resources because of nitrogen agricultural fertilizers leaching. On the other hand treating and reusing of drainage water is necessary because of the extreme water resource reduction. So aim of this study was reduction of nitrate from drainage water with barley straw as an organic filter. Barley straw combined with sandy clay soil in two method (layered and mixed), three volume (10, 20, and 30) percent and investigated quality of influent and effluent water from treatments through the time. On the base of results, optimum combination percent of barley straw with soil for layered and mixed treatment was 20, 30%; respectively that removed nitrate more than 81, 77%. The ammonium concentration of the drainage water was decreased with elapsed time and variation of the pH and EC were function of the influent. So application of the barley straw in layered method as a bioreactor to remove nitrate from drainage water recommended because of low price, ease availability and usage without any worry about side effect like strong variation in pH and EC.In recent years nitrate was reported as most important source of pollutant of soil and water resources because of nitrogen agricultural fertilizers leaching. On the other hand treating and reusing of drainage water is necessary because of the extreme water resource reduction. So aim of this study was reduction of nitrate from drainage water with barley straw as an organic filter. Barley straw combined with sandy clay soil in two method (layered and mixed), three volume (10, 20, and 30) percent and investigated quality of influent and effluent water from treatments through the time. On the base of results, optimum combination percent of barley straw with soil for layered and mixed treatment was 20, 30%; respectively that removed nitrate more than 81, 77%. The ammonium concentration of the drainage water was decreased with elapsed time and variation of the pH and EC were function of the influent. So application of the barley straw in layered method as a bioreactor to remove nitrate from drainage water recommended because of low price, ease availability and usage without any worry about side effect like strong variation in pH and EC.In recent years nitrate was reported as most important source of pollutant of soil and water resources because of nitrogen agricultural fertilizers leaching. On the other hand treating and reusing of drainage water is necessary because of the extreme water resource reduction. So aim of this study was reduction of nitrate from drainage water with barley straw as an organic filter. Barley straw combined with sandy clay soil in two method (layered and mixed), three volume (10, 20, and 30) percent and investigated quality of influent and effluent water from treatments through the time. On the base of results, optimum combination percent of barley straw with soil for layered and mixed treatment was 20, 30%; respectively that removed nitrate more than 81, 77%. The ammonium concentration of the drainage water was decreased with elapsed time and variation of the pH and EC were function of the influent. So application of the barley straw in layered method as a bioreactor to remove nitrate from drainage water recommended because of low price, ease availability and usage without any worry about side effect like strong variation in pH and EC.In recent years nitrate was reported as most important source of pollutant of soil and water resources because of nitrogen agricultural fertilizers leaching. On the other hand treating and reusing of drainage water is necessary because of the extreme water resource reduction. So aim of this study was reduction of nitrate from drainage water with barley straw as an organic filter. Barley straw combined with sandy clay soil in two method (layered and mixed), three volume (10, 20, and 30) percent and investigated quality of influent and effluent water from treatments through the time. On the base of results, optimum combination percent of barley straw with soil for layered and mixed treatment was 20, 30%; respectively that removed nitrate more than 81, 77%. The ammonium concentration of the drainage water was decreased with elapsed time and variation of the pH and EC were function of the influent. So application of the barley straw in layered method as a bioreactor to remove nitrate from drainage water recommended because of low price, ease availability and usage without any worry about side effect like strong variation in pH and EC.

The prediction of stream flow from a catchment has been of concern to hydrologists and water resource community since long. To this end, the unit-hydrograph approach proposed by Sherman has evolved into one of the most powerful tools in applied hydrology. A unit hydrograph is defined as the direct runoff hydrograph (DRH) resulting from 1 mm depth of effective rainfall hyetograph (ERH) falling uniformly over the drainage area at a constant rate for an effective duration. The unit hydrograph (UH) at a specific point on the stream (gauging site) in a catchment is generally determined by using effective rainfall and surface runoff data observed for the gauging site. Relationship between hydrologic and geomorphologic parameters, can lead to estimate hydrologic response of basins and is applied to the similar areas, in terms of geomorphology, that are ungauged. For ungauged watersheds and for anticipated post development conditions, synthetic unit hydrograph (SUH), based on watersheds, geomorphology and climatic characteristics, is typically used. Such conditions are common in Iran, as most watersheds lack gauging stations along its rivers and streams discharge outlets. Catchments and storm characteristics are the primary parameters that affect complex watershed responses to rainfall events. The production and behavior of runoff are functions of land use types and changes. The hydrological response of a river basin is based on the relationship between basin geomorphology (catchments area, shape of basin, topography, channel slope, stream density and channel storage) and its hydrology. In this context, several methods have been proposed. This study has been compared the consistency, accuracy and reliability of geomorphologic, geomorphoclimatic and rosso instantaneous unit hydrographs and SCS unit hydrograph, in estimating outlet runoff hydrograph characteristics in Manshad watershed. The Manshad watershed encompasses an area of about 60 km² and is located in central Iran in the western part of the Yazd province. A hydrometric station is located at the outlet of the watershed (Dare Station), and a rain recorder station (Manshad Station) is located upstream of the station .For our analysis, six single rainfall- runoff events, in which snow did not melt, were selected. Both rainfall and runoff data were recorded automatically with 1 h intervals. Then, for separation of the effective rainfall from the recorded storm for each chosen event, the CN-SCS method was applied. Flow velocity was obtained by calibrating historical data or with methods appropriate for ungauged basins. Arcview GIS software was used for extracting geomorphic informations on area, slope, length of the main river basin and Horton’s geomorphologic ratios such as area ratio (Ra), bifurcation ratio (Rb) and length ratio (Rl) in the study watershed as inputs for the models leading to the runoff simulation. The Strahler’s ordering scheme was followed for ordering of the river network. The study basin was discovered to be a fifth-order basin. Then,the GIUH, GCIUH,Rosso IUH and SCS models have been developed for estimation of the DSRO hydrographs for the catchment.
Comparisons of calculated and observed hydrographs, that have been carried out by using the Mean Relative Error, the Root Mean Square Error and the Nash-Sutcliffe indices, confirm the high potential of all the methods, in simulating the amount of flood volume (with error of less than 12%) These study's findings are in agreement with the results of Sorman. Thus, they can be used, as appropriate methods, for simulating this parameter in similar catchments. In estimating peak discharge, Geomorphologic and Rosso IUH (respectively with error of 39.03% and 42.35% ) have better performances, comparing to other methods. They have weak performances in simulating time to peak and the shape of hydrograph. Also, Geomorphoclimatic and SCS methods have weak performances in estimating peak discharge, time to peak and the shape of hydrographs.
The GCIUH and SCS models had weak performance for estimating time to peak, peak discharge and the shape of outlet DSRO hydrographs and the GIUH, Rosso IUH had weak performance for estimating time to peak and the shape of hydrographs. This may relate to exposing the watershed to Human activities in the form of urban development and land use changes which cause changes on watershed hydrographs.
The prediction of stream flow from a catchment has been of concern to hydrologists and water resource community since long. To this end, the unit-hydrograph approach proposed by Sherman has evolved into one of the most powerful tools in applied hydrology. A unit hydrograph is defined as the direct runoff hydrograph (DRH) resulting from 1 mm depth of effective rainfall hyetograph (ERH) falling uniformly over the drainage area at a constant rate for an effective duration. The unit hydrograph (UH) at a specific point on the stream (gauging site) in a catchment is generally determined by using effective rainfall and surface runoff data observed for the gauging site. Relationship between hydrologic and geomorphologic parameters, can lead to estimate hydrologic response of basins and is applied to the similar areas, in terms of geomorphology, that are ungauged. For ungauged watersheds and for anticipated post development conditions, synthetic unit hydrograph (SUH), based on watersheds, geomorphology and climatic characteristics, is typically used. Such conditions are common in Iran, as most watersheds lack gauging stations along its rivers and streams discharge outlets. Catchments and storm characteristics are the primary parameters that affect complex watershed responses to rainfall events. The production and behavior of runoff are functions of land use types and changes. The hydrological response of a river basin is based on the relationship between basin geomorphology (catchments area, shape of basin, topography, channel slope, stream density and channel storage) and its hydrology. In this context, several methods have been proposed.

Water deficit and consecutive droughts currently caused most of the world facing water critical condition. In order to saving water consumption in the agriculture sector, new technologies and several materials are used. Super absorbent polymers, as one of these materials, are capable to absorb high amounts of precipitation or irrigation and make them available for the plants. Accordingly, this study was carried out to investigate the effect of super absorbent polymer (A200) under drought conditions on some phytochemical attributes of hot pepper (Capsicum frutescence) such as: Vitamin C, Total Soluble Solids, Ion Leakage, Chlorophyll Content and Water Productivity. Mentioned research was planned in a factorial based on randomized complete design with three irrigation regimes (50, 75, and 100% water requirement) and four levels of super absorbent polymer (0, 0.1, 0.2 and 0.3% weight) in four replications. The results showed, the levels of super absorbent cause to increase the Total Soluble Solids and decrease the Ion Leakage, under stress condition. Statistical analysis showed that in order to achieve maximum Water productivity and reduce negative impacts of some of the phytochemical properties such as the Ion leakage, the most appropriate levels of the irrigation regime and the Super absorbent polymer is supply 50% water requirement and 0.3% weight Super absorbent, respectively.
Water deficit and consecutive droughts currently caused most of the world facing water critical condition. In order to saving water consumption in the agriculture sector, new technologies and several materials are used. Super absorbent polymers, as one of these materials, are capable to absorb high amounts of precipitation or irrigation and make them available for the plants. Accordingly, this study was carried out to investigate the effect of super absorbent polymer (A200) under drought conditions on some phytochemical attributes of hot pepper (Capsicum frutescence) such as: Vitamin C, Total Soluble Solids, Ion Leakage, Chlorophyll Content and Water Productivity. Mentioned research was planned in a factorial based on randomized complete design with three irrigation regimes (50, 75, and 100% water requirement) and four levels of super absorbent polymer (0, 0.1, 0.2 and 0.3% weight) in four replications. The results showed, the levels of super absorbent cause to increase the Total Soluble Solids and decrease the Ion Leakage, under stress condition. Statistical analysis showed that in order to achieve maximum Water productivity and reduce negative impacts of some of the phytochemical properties such as the Ion leakage, the most appropriate levels of the irrigation regime and the Super absorbent polymer is supply 50% water requirement and 0.3% weight Super absorbent, respectively.
Water deficit and consecutive droughts currently caused most of the world facing water critical condition. In order to saving water consumption in the agriculture sector, new technologies and several materials are used. Super absorbent polymers, as one of these materials, are capable to absorb high amounts of precipitation or irrigation and make them available for the plants. Accordingly, this study was carried out to investigate the effect of super absorbent polymer (A200) under drought conditions on some phytochemical attributes of hot pepper (Capsicum frutescence) such as: Vitamin C, Total Soluble Solids, Ion Leakage, Chlorophyll Content and Water Productivity. Mentioned research was planned in a factorial based on randomized complete design with three irrigation regimes (50, 75, and 100% water requirement) and four levels of super absorbent polymer (0, 0.1, 0.2 and 0.3% weight) in four replications. The results showed, the levels of super absorbent cause to increase the Total Soluble Solids and decrease the Ion Leakage, under stress condition. Statistical analysis showed that in order to achieve maximum Water productivity and reduce negative impacts of some of the phytochemical properties such as the Ion leakage, the most appropriate levels of the irrigation regime and the Super absorbent polymer is supply 50% water requirement and 0.3% weight Super absorbent, respectively.
Water deficit and consecutive droughts currently caused most of the world facing water critical condition. In order to saving water consumption in the agriculture sector, new technologies and several materials are used. Super absorbent polymers, as one of these materials, are capable to absorb high amounts of precipitation or irrigation and make them available for the plants. Accordingly, this study was carried out to investigate the effect of super absorbent polymer (A200) under drought conditions on some phytochemical attributes of hot pepper (Capsicum frutescence) such as: Vitamin C, Total Soluble Solids, Ion Leakage, Chlorophyll Content and Water Productivity. Mentioned research was planned in a factorial based on randomized complete design with three irrigation regimes (50, 75, and 100% water requirement) and four levels of super absorbent polymer (0, 0.1, 0.2 and 0.3% weight) in four replications. The results showed, the levels of super absorbent cause to increase the Total Soluble Solids and decrease the Ion Leakage, under stress condition. Statistical analysis showed that in order to achieve maximum Water productivity and reduce negative impacts of some of the phytochemical properties such as the Ion leakage, the most appropriate levels of the irrigation regime and the Super absorbent polymer is supply 50% water requirement and 0.3% weight Super absorbent, respectively.

The current study attempted to investigate on the water demand for Alfalfa crop computed by using parametric method in the Qorveh and Dehgolan. The data collected 100 Questionnaires by commensurate Stratified Random sampling in the 2010-11. To selection the best produce function, checked by flexible and non-flexible functions. Results indicate that production function Cobb - Douglas is better than the other functions. Also, price elasticity of water demand itself is -2/59. It is less than minus 1, which shows that pricing policy is a main factor in controlling non-optimum use of water. The economic value of this crop is 84/94 Rail but the price paid is 28/51 Rail, Thus there is difference between them. So, Could increase the water productivity with removed different price in the case study.The current study attempted to investigate on the water demand for Alfalfa crop computed by using parametric method in the Qorveh and Dehgolan. The data collected 100 Questionnaires by commensurate Stratified Random sampling in the 2010-11. To selection the best produce function, checked by flexible and non-flexible functions. Results indicate that production function Cobb - Douglas is better than the other functions. Also, price elasticity of water demand itself is -2/59. It is less than minus 1, which shows that pricing policy is a main factor in controlling non-optimum use of water. The economic value of this crop is 84/94 Rail but the price paid is 28/51 Rail, Thus there is difference between them. So, Could increase the water productivity with removed different price in the case study.The current study attempted to investigate on the water demand for Alfalfa crop computed by using parametric method in the Qorveh and Dehgolan. The data collected 100 Questionnaires by commensurate Stratified Random sampling in the 2010-11. To selection the best produce function, checked by flexible and non-flexible functions. Results indicate that production function Cobb - Douglas is better than the other functions. Also, price elasticity of water demand itself is -2/59. It is less than minus 1, which shows that pricing policy is a main factor in controlling non-optimum use of water. The economic value of this crop is 84/94 Rail but the price paid is 28/51 Rail, Thus there is difference between them. So, Could increase the water productivity with removed different price in the case study.The current study attempted to investigate on the water demand for Alfalfa crop computed by using parametric method in the Qorveh and Dehgolan. The data collected 100 Questionnaires by commensurate Stratified Random sampling in the 2010-11. To selection the best produce function, checked by flexible and non-flexible functions. Results indicate that production function Cobb - Douglas is better than the other functions. Also, price elasticity of water demand itself is -2/59. It is less than minus 1, which shows that pricing policy is a main factor in controlling non-optimum use of water. The economic value of this crop is 84/94 Rail but the price paid is 28/51 Rail, Thus there is difference between them. So, Could increase the water productivity with removed different price in the case study.The current study attempted to investigate on the water demand for Alfalfa crop computed by using parametric method in the Qorveh and Dehgolan. The data collected 100 Questionnaires by commensurate Stratified Random sampling in the 2010-11. To selection the best produce function, checked by flexible and non-flexible functions. Results indicate that production function Cobb - Douglas is better than the other functions. Also, price elasticity of water demand itself is -2/59. It is less than minus 1, which shows that pricing policy is a main factor in controlling non-optimum use of water. The economic value of this crop is 84/94 Rail but the price paid is 28/51 Rail, Thus there is difference between them. So, Could increase the water productivity with removed different price in the case study.The current study attempted to investigate on the water demand for Alfalfa crop computed by using parametric method in the Qorveh and Dehgolan. The data collected 100 Questionnaires by commensurate Stratified Random sampling in the 2010-11. To selection the best produce function, checked by flexible and non-flexible functions. Results indicate that production function Cobb - Douglas is better than the other functions. Also, price elasticity of water demand itself is -2/59. It is less than minus 1, which shows that pricing policy is a main factor in controlling non-optimum use of water. The economic value of this crop is 84/94 Rail but the price paid is 28/51 Rail, Thus there is difference between them. So, Could increase the water productivity with removed different price in the case study.

Industrial development increased concerning of heavy metals in wastewater. Heavy metals in industry have caused many problems. Heavy metals are the first hazardous materials in pollutants, which have hazard for environment and harmful for Human health. Chromium is a heavy metal could be found in industrial sewage systems like metal polish, loom, leathery, fertilizer manufactures. Chrome, often in the form of hexavalent chromium, is one of the metals in aquatic environments. Chrome is harmful to human health and has adverse effects on human and animal bodies; therefore, the use of absorbent material to remove it from the water and wastewater treatment is essential. Trivalent chromium (Cr(III)) ion is possibly required in trace amounts for sugar and lipid metabolism, although the issue remains in debate. In larger amounts and in different forms, chromium can be toxic and carcinogenic. The most prominent example of toxic chromium is hexavalent chromium (Cr(VI)). Abandoned chromium production sites often require environmental cleanup. Rice is one of the cheapest and frequent absorbent due to its cellulose and carbon fiber capacity. The aim of this study is to evaluate the effect of particle size on the amount of rice chromium removal from aqueous solution. To do so, milled rice stems were collected from rice fields of Lenjan, Isfahan. After that, the particles were sieved with 75, 300, 850 and 1200 m meshes. In this study, four level of rice amount including 1, 1.5, 2, and 3 grams with 75, 300, 850 and 1200 m were used. To prepare a solution of hexavalent chromium, potassium dichromate was used (95% purity, prepared by Merck Co., Germany). The standard solution for testing, were prepared using the dilute solution. Chromium concentration of 10 mg/lit has been selected for all experiments. In this study several non-equilibrium models, including Lagergren, Ho and colleagues and the intermolecular distribution and equilibrium models of Langmuir, Freundlich, Redlich- Peterson and Sips were used. To test results of Equilibrium and non-equilibrium models the nonlinear equations were used (Matlab ver. 7.8.).
PH of the solution is an important parameter influencing chemical reactions and biological process of sewage. Changes in pH affect the absorption of chromium. This response will affect the relationship between absorbent and absorption material. In other words, positive surface absorbent and electrostatic adsorption increases its tendency to absorb anions. Equilibrium time determines the capacity of equilibrium as well as maximum capacity of absorbent material. For a specific amount of absorbent, equilibrium time is the duration of completing absorbent capacity (unattraction of absorbent element). Absorbent particle size (specific surface area), determines absorption capacity as the most important feature of absorbent material. In general, when the absorbent material decreases the specific surface area increases exponentially, therefore, their area of irregular shapes are increased and consequently the amount of absorption capacity due to speed of the process will increase. The results showed a significant (p.≤0.05) relationship between absorbent particle size and equilibrium time as well as absorbent particle size and maximum absorption capacity.
The maximum adsorption efficiency in 1 gram of rice stem with the 75 micrometer particle size in pH=2 and 98.25 percent were occurred. Synthetic adsorption assessment shows that, none equilibrium model of Lagergren (Correlation coefficient 1) and Ho et al (Correlation coefficient 0.999) models were clarify adsorption of chromium by rice stem very good. Also, the balance time was increased logarithmic by increasing in the particle size of rice stem, to which the balance time in the particle size of 75, 300, 850 and 1200 micrometer provided 30, 90, 90, and 120 min respectively. Isotherm adsorption assessment shows that, in 75 micrometer particle size of rice stem, Langmuir (Correlation coefficient 0.993), Ferundlich (Correlation coefficient 0.989), Redlich- Peterson (Correlation coefficient 0.993) and Sips (Correlation coefficient 0.994) models were clarifying isotherm adsorption respectively. Maximum adsorption was decreased linearly by increasing in the particle size of rice stem. Adsorption capacity of chromium by Langmuir model for the rice stem particle size of 75, 300, 850 and 1200 micrometer were shown as 3.096, 2.490, 1.820 and 1.456 (mg/g) respectively. Comparing the maximum capacity of absorption of rice stem in this study with other absorbents in the other studies showed that gridded rice stem is an elegant absorption material to remove chromium of wastewater.

Scouring phenomena around bridge abutment is one of the most significant causes of bridges failure. Investigation on Erosion around bridge abutments and present a reliable method to protect them against scouring is necessary because of significant and vital rule of these structures in transportation. There have been many studies to limit the maximum depth of scouring at abutments such as using a protective collar, riprap mattress, geo bag and etc. But most of them are not economical and efficient to countermeasure the abutments with different shapes and length. Using protective collar at abutment is one of the simplest and most applicable techniques to countermeasure of abutments in comparison with other protective methods. Simple application and appropriate performance of collar lead to widespread investigations on it. To study the performance of collar, shapes and lengths (La) of the collar are the most effective parameters in reduction of maximum depth of scouring. While, the performance of collar varied for different flow intensities. For lower flow intensities, using collar may lead to diminish the scouring at tip of the abutments. But for upper flow intensities (near the threshold of the bed material), the efficient of collar reduces and flow can be able to scour below the collar and reach to tip of the abutment. As whole, there are two types of abutment (short and long abutments) in terms of length. In short abutments, the ratio of the length of the abutment to the flow depth is less than one ( ), while for long abutments this ratio is more than unit ( ). In the previous investigations, the applicability of using collar in reduction of scour depth at short abutments has not been studied widely. Also, there are no many studies on the effects of various flow conditions on efficiency of collar for both short and long abutments and no comparing between them. In this study, scouring around two kinds of rectangular abutments (short and long abutments) were investigated. All experiments were conducted in a 1 m width, 1 m depth and 14 m length rectangular flume located at the Porous Media Laboratory of Amirkabir University of Technology. The test region, where the abutments were placed in the flume, was selected in a way that a uniform flow was established and fully developed turbulent flow was reached. The bed materials are uniform with a median size of 0.91 mm and a geometric standard deviation of 1.38. The experiments were conducted under the clear water and various flow conditions (U/Ucr=0.95, 0.85, 0.75). The discharge of the flow was adjusted by an inlet valve and measured by a rectangular weir at the end of the flume. In this investigation, long duration (70 hour) tests were conducted to determine the equilibrium depth of scouring. Equilibrium depth of scour was defined as a depth with less than 1 mm change after 2 hours of experimental run. According to the conducted tests and obtained time duration data, 40 and 50 hour were adopted as the equilibrium time for short and long abutment experiments (with and without collar), respectively, in which 95% maximum depth of scouring was occurred. The experiments were continued until reach the relative equilibrium state. The experimental results for scouring of the bed materials for the various flow intensity of U/Ucr=0.95, 0.85 and 0.75 showed that the use of collar with 2La in length for short abutment and La for long abutment at bed level, causes the reduction of scouring about 46%, 57% and100% for short abutment and 26%, 24% and 60% for long abutment, respectively. The start time of scouring at tip of the long abutment in the same flow condition and using collar with the same sizes, took place 405, 490 and 760 minutes after experiments run, respectively. Also, the start time of scouring at tip of the short abutment protected by collar at bed elevation took place 300 and 255 minutes for U/Ucr=0.95, 0.85 flow intensity and no scouring on tip of abutment during 40 hour of test run. Furthermore, applying collar on abutment led to reduction of scouring volume around the abutment equal to 37%, 64% and 25% for short and 34%, 43% and 44% for long abutment in U/Ucr=0.95, 0.85 and 0.75 flow intensity, respectively.

In present study, the trend analysis of precipitation and reference evapotranspiration (ET0), as the most important input and output variables of the Lake Urmia basin were investigated. The analysis was based on monthly meteorological data at five synoptic stations located in the basin consist of Urmia, Tabriz, Khoy, Saghaz, and Mahabad during 1976-2005 data period. At first step, monthly ET0 rates at each station were estimated using a newly developed model, known as PMF56-Hybrid. Then the non-parametric Mann-Kendall and the Theil-Sen slope tests were applied. In addition, the sequential Mann-Kendall test was used to detect abrupt changes in the time series. Annual trend analysis on precipitation data showed that there is a decrease trend at all station except Mahabad. Furthermore, annual ET0 data at 5% level at the same period did not show any significant increase, The Theil-Sen test results showed the highest positive slope rate at Khoy station (3.44 mm/year). In addition, the minimum and maximum of the Sen-slope rates were 4.2 and 2.88 mm/year at Khoy and Tabriz stations, respectively. The Sequential Mann-Kendall test revealed that Khoy and Tabriz stations faced a abrupt change with decreasing trend in annual precipitation data but non-significant at 5% except at Khoy station. For the PMF56-Hybrid based ET0 time series data, abrupt changes are not significant at all stations during 1976-2005. In present study, the trend analysis of precipitation and reference evapotranspiration (ET0), as the most important input and output variables of the Lake Urmia basin were investigated. The analysis was based on monthly meteorological data at five synoptic stations located in the basin consist of Urmia, Tabriz, Khoy, Saghaz, and Mahabad during 1976-2005 data period. At first step, monthly ET0 rates at each station were estimated using a newly developed model, known as PMF56-Hybrid. Then the non-parametric Mann-Kendall and the Theil-Sen slope tests were applied. In addition, the sequential Mann-Kendall test was used to detect abrupt changes in the time series. Annual trend analysis on precipitation data showed that there is a decrease trend at all station except Mahabad. Furthermore, annual ET0 data at 5% level at the same period did not show any significant increase, The Theil-Sen test results showed the highest positive slope rate at Khoy station (3.44 mm/year). In addition, the minimum and maximum of the Sen-slope rates were 4.2 and 2.88 mm/year at Khoy and Tabriz stations, respectively. The Sequential Mann-Kendall test revealed that Khoy and Tabriz stations faced a abrupt change with decreasing trend in annual precipitation data but non-significant at 5% except at Khoy station. For the PMF56-Hybrid based ET0 time series data, abrupt changes are not significant at all stations during 1976-2005.In present study, the trend analysis of precipitation and reference evapotranspiration (ET0), as the most important input and output variables of the Lake Urmia basin were investigated. The analysis was based on monthly meteorological data at five synoptic stations located in the basin consist of Urmia, Tabriz, Khoy, Saghaz, and Mahabad during 1976-2005 data period. At first step, monthly ET0 rates at each station were estimated using a newly developed model, known as PMF56-Hybrid. Then the non-parametric Mann-Kendall and the Theil-Sen slope tests were applied. In addition, the sequential Mann-Kendall test was used to detect abrupt changes in the time series. Annual trend analysis on precipitation data showed that there is a decrease trend at all station except Mahabad. Furthermore, annual ET0 data at 5% level at the same period did not show any significant increase, The Theil-Sen test results showed the highest positive slope rate at Khoy station (3.44 mm/year). In addition, the minimum and maximum of the Sen-slope rates were 4.2 and 2.88 mm/year at Khoy and Tabriz stations, respectively. The Sequential Mann-Kendall test revealed that Khoy and Tabriz stations faced a abrupt change with decreasing trend in annual precipitation data but non-significant at 5% except at Khoy station. For the PMF56-Hybrid based ET0 time series data, abrupt changes are not significant at all stations during 1976-2005.In present study, the trend analysis of precipitation and reference evapotranspiration (ET0), as the most important input and output variables of the Lake Urmia basin were investigated. The analysis was based on monthly meteorological data at five synoptic stations located in the basin consist of Urmia, Tabriz, Khoy, Saghaz, and Mahabad during 1976-2005 data period. At first step, monthly ET0 rates at each station were estimated using a newly developed model, known as PMF56-Hybrid. Then the non-parametric Mann-Kendall and the Theil-Sen slope tests were applied. In addition, the sequential Mann-Kendall test was used to detect abrupt changes in the time series. Annual trend analysis on precipitation data showed that there is a decrease trend at all station except Mahabad. Furthermore, annual ET0 data at 5% level at the same period did not show any significant increase, The Theil-Sen test results showed the highest positive slope rate at Khoy station (3.44 mm/year). In addition, the minimum and maximum of the Sen-slope rates were 4.2 and 2.88 mm/year at Khoy and Tabriz stations, respectively. The Sequential Mann-Kendall test revealed that Khoy and Tabriz stations faced a abrupt change with decreasing trend in annual precipitation data but non-significant at 5% except at Khoy station. For the PMF56-Hybrid based ET0 time series data, abrupt changes are not significant at all stations during 1976-2005.

Sluice gates are widely used for flow control and discharge measuring in open channels. Sluice gate discharge coefficient depends on geometric and hydraulic parameters. Using experimental curves to determine discharge coefficient is subjected to error of judgment in reading this graphs. In this study, by using dimensional analysis and linear and nonlinear regression analysis, two equations are developed to determine discharge coefficient, for both free and submerged flow conditions. A total of 5200 data sets involving different effective hydraulic parameters were generated. Also, the results of the some of the preceding studies, performed by different investigators about sluice gate discharge coefficient determination were compared. The nonlinear equation got better results in comparison with the linear equation. All numerical computations in procedure of this study were performed by Wolfram Mathematica v.6 software.Sluice gates are widely used for flow control and discharge measuring in open channels. Sluice gate discharge coefficient depends on geometric and hydraulic parameters. Using experimental curves to determine discharge coefficient is subjected to error of judgment in reading this graphs. In this study, by using dimensional analysis and linear and nonlinear regression analysis, two equations are developed to determine discharge coefficient, for both free and submerged flow conditions. A total of 5200 data sets involving different effective hydraulic parameters were generated. Also, the results of the some of the preceding studies, performed by different investigators about sluice gate discharge coefficient determination were compared. The nonlinear equation got better results in comparison with the linear equation. All numerical computations in procedure of this study were performed by Wolfram Mathematica v.6 software.Sluice gates are widely used for flow control and discharge measuring in open channels. Sluice gate discharge coefficient depends on geometric and hydraulic parameters. Using experimental curves to determine discharge coefficient is subjected to error of judgment in reading this graphs. In this study, by using dimensional analysis and linear and nonlinear regression analysis, two equations are developed to determine discharge coefficient, for both free and submerged flow conditions. A total of 5200 data sets involving different effective hydraulic parameters were generated. Also, the results of the some of the preceding studies, performed by different investigators about sluice gate discharge coefficient determination were compared. The nonlinear equation got better results in comparison with the linear equation. All numerical computations in procedure of this study were performed by Wolfram Mathematica v.6 software.Sluice gates are widely used for flow control and discharge measuring in open channels. Sluice gate discharge coefficient depends on geometric and hydraulic parameters. Using experimental curves to determine discharge coefficient is subjected to error of judgment in reading this graphs. In this study, by using dimensional analysis and linear and nonlinear regression analysis, two equations are developed to determine discharge coefficient, for both free and submerged flow conditions. A total of 5200 data sets involving different effective hydraulic parameters were generated. Also, the results of the some of the preceding studies, performed by different investigators about sluice gate discharge coefficient determination were compared. The nonlinear equation got better results in comparison with the linear equation. All numerical computations in procedure of this study were performed by Wolfram Mathematica v.6 software.Sluice gates are widely used for flow control and discharge measuring in open channels. Sluice gate discharge coefficient depends on geometric and hydraulic parameters. Using experimental curves to determine discharge coefficient is subjected to error of judgment in reading this graphs. In this study, by using dimensional analysis and linear and nonlinear regression analysis, two equations are developed to determine discharge coefficient, for both free and submerged flow conditions. A total of 5200 data sets involving different effective hydraulic parameters were generated. Also, the results of the some of the preceding studies, performed by different investigators about sluice gate discharge coefficient determination were compared. The nonlinear equation got better results in comparison with the linear equation. All numerical computations in procedure of this study were performed by Wolfram Mathematica v.6 software.Sluice gates are widely used for flow control and discharge measuring in open channels. Sluice gate discharge coefficient depends on geometric and hydraulic parameters. Using experimental curves to determine discharge coefficient is subjected to error of judgment in reading this graphs. In this study, by using dimensional analysis and linear and nonlinear regression analysis, two equations are developed to determine discharge coefficient, for both free and submerged flow conditions. A total of 5200 data sets involving different effective hydraulic parameters were generated. Also, the results of the some of the preceding studies, performed by different investigators about sluice gate discharge coefficient determination were compared. The nonlinear equation got better results in comparison with the linear equation. All numerical computations in procedure of this study were performed by Wolfram Mathematica v.6 software.

Using specific capacity data are suitable method for estimating an aquifer transmissivity. specific capacity data are typically with ease available compared with time-drawdown data, therefore helping specific capacity data can increase the number of transmissivity estimates in an aquifer. Numerous researchers have tried to obtain the relationship between specific capacity with transmissivity and different methods have been Provided in which the most commonly has been the analytical approach based on the Theis formula. In this research introduce a simple approach using the Microsoft Excel software which is based on iteration algorithm, providing fast estimates of hydrodynamic coefficients in more points. This approach has been used in two different location of Qom aquifer successfully, which in each two places, hydrodynamic coefficients from this approach are logically consistent with methods of curve matching.Using specific capacity data are suitable method for estimating an aquifer transmissivity. specific capacity data are typically with ease available compared with time-drawdown data, therefore helping specific capacity data can increase the number of transmissivity estimates in an aquifer. Numerous researchers have tried to obtain the relationship between specific capacity with transmissivity and different methods have been Provided in which the most commonly has been the analytical approach based on the Theis formula. In this research introduce a simple approach using the Microsoft Excel software which is based on iteration algorithm, providing fast estimates of hydrodynamic coefficients in more points. This approach has been used in two different location of Qom aquifer successfully, which in each two places, hydrodynamic coefficients from this approach are logically consistent with methods of curve matching.Using specific capacity data are suitable method for estimating an aquifer transmissivity. specific capacity data are typically with ease available compared with time-drawdown data, therefore helping specific capacity data can increase the number of transmissivity estimates in an aquifer. Numerous researchers have tried to obtain the relationship between specific capacity with transmissivity and different methods have been Provided in which the most commonly has been the analytical approach based on the Theis formula. In this research introduce a simple approach using the Microsoft Excel software which is based on iteration algorithm, providing fast estimates of hydrodynamic coefficients in more points. This approach has been used in two different location of Qom aquifer successfully, which in each two places, hydrodynamic coefficients from this approach are logically consistent with methods of curve matching.Using specific capacity data are suitable method for estimating an aquifer transmissivity. specific capacity data are typically with ease available compared with time-drawdown data, therefore helping specific capacity data can increase the number of transmissivity estimates in an aquifer. Numerous researchers have tried to obtain the relationship between specific capacity with transmissivity and different methods have been Provided in which the most commonly has been the analytical approach based on the Theis formula. In this research introduce a simple approach using the Microsoft Excel software which is based on iteration algorithm, providing fast estimates of hydrodynamic coefficients in more points. This approach has been used in two different location of Qom aquifer successfully, which in each two places, hydrodynamic coefficients from this approach are logically consistent with methods of curve matching.Using specific capacity data are suitable method for estimating an aquifer transmissivity. specific capacity data are typically with ease available compared with time-drawdown data, therefore helping specific capacity data can increase the number of transmissivity estimates in an aquifer. Numerous researchers have tried to obtain the relationship between specific capacity with transmissivity and different methods have been Provided in which the most commonly has been the analytical approach based on the Theis formula. In this research introduce a simple approach using the Microsoft Excel software which is based on iteration algorithm, providing fast estimates of hydrodynamic coefficients in more points. This approach has been used in two different location of Qom aquifer successfully, which in each two places, hydrodynamic coefficients from this approach are logically consistent with methods of curve matching.Using specific capacity data are suitable method for estimating an aquifer transmissivity. specific capacity data are typically with ease available compared with time-drawdown data, therefore helping specific capacity data can increase the number of transmissivity estimates in an aquifer. Numerous researchers have tried to obtain the relationship between specific capacity with transmissivity and different methods have been Provided in which the most commonly has been the analytical approach based on the Theis formula. In this research introduce a simple approach using the Microsoft Excel software which is based on iteration algorithm, providing fast estimates of hydrodynamic coefficients in more points. This approach has been used in two different location of Qom aquifer successfully, which in each two places, hydrodynamic coefficients from this approach are logically consistent with methods of curve matching.

Recently, the market mechanism has been considered as an efficient method for optimal allocating of water resources and overcoming some challenge in water sector, however, there are some questions in this regard. This study investigated the economic consequences of local water markets in Ardabil county of Iran. Results show that farmers have been relied on the local water market so that they bought 23% of water input from local water markets. Water was traded at 841 Rials/m3 that is closed to the economic value of water (930 Rials/m3) during farming year of 2009-10. Results also show that after participation in water market, farmer's income was increased up to 1.8% - 23.9%. According to the results, to alleviate excessive demand for irrigation water, government expenditures on water providing and to allocate water resources optimally, local water markets should be reinforced.Recently, the market mechanism has been considered as an efficient method for optimal allocating of water resources and overcoming some challenge in water sector, however, there are some questions in this regard. This study investigated the economic consequences of local water markets in Ardabil county of Iran. Results show that farmers have been relied on the local water market so that they bought 23% of water input from local water markets. Water was traded at 841 Rials/m3 that is closed to the economic value of water (930 Rials/m3) during farming year of 2009-10. Results also show that after participation in water market, farmer's income was increased up to 1.8% - 23.9%. According to the results, to alleviate excessive demand for irrigation water, government expenditures on water providing and to allocate water resources optimally, local water markets should be reinforced.Recently, the market mechanism has been considered as an efficient method for optimal allocating of water resources and overcoming some challenge in water sector, however, there are some questions in this regard. This study investigated the economic consequences of local water markets in Ardabil county of Iran. Results show that farmers have been relied on the local water market so that they bought 23% of water input from local water markets. Water was traded at 841 Rials/m3 that is closed to the economic value of water (930 Rials/m3) during farming year of 2009-10. Results also show that after participation in water market, farmer's income was increased up to 1.8% - 23.9%. According to the results, to alleviate excessive demand for irrigation water, government expenditures on water providing and to allocate water resources optimally, local water markets should be reinforced.Recently, the market mechanism has been considered as an efficient method for optimal allocating of water resources and overcoming some challenge in water sector, however, there are some questions in this regard. This study investigated the economic consequences of local water markets in Ardabil county of Iran. Results show that farmers have been relied on the local water market so that they bought 23% of water input from local water markets. Water was traded at 841 Rials/m3 that is closed to the economic value of water (930 Rials/m3) during farming year of 2009-10. Results also show that after participation in water market, farmer's income was increased up to 1.8% - 23.9%. According to the results, to alleviate excessive demand for irrigation water, government expenditures on water providing and to allocate water resources optimally, local water markets should be reinforced.Recently, the market mechanism has been considered as an efficient method for optimal allocating of water resources and overcoming some challenge in water sector, however, there are some questions in this regard. This study investigated the economic consequences of local water markets in Ardabil county of Iran. Results show that farmers have been relied on the local water market so that they bought 23% of water input from local water markets. Water was traded at 841 Rials/m3 that is closed to the economic value of water (930 Rials/m3) during farming year of 2009-10. Results also show that after participation in water market, farmer's income was increased up to 1.8% - 23.9%. According to the results, to alleviate excessive demand for irrigation water, government expenditures on water providing and to allocate water resources optimally, local water markets should be reinforced.Recently, the market mechanism has been considered as an efficient method for optimal allocating of water resources and overcoming some challenge in water sector, however, there are some questions in this regard. This study investigated the economic consequences of local water markets in Ardabil county of Iran. Results show that farmers have been relied on the local water market so that they bought 23% of water input from local water markets. Water was traded at 841 Rials/m3 that is closed to the economic value of water (930 Rials/m3) during farming year of 2009-10. Results also show that after participation in water market, farmer's income was increased up to 1.8% - 23.9%. According to the results, to alleviate excessive demand for irrigation water, government expenditures on water providing and to allocate water resources optimally, local water markets should be reinforced.

Investigating lowflow characteristics is of vital importance for optimal water resources management and sustainable use of water resources especially in arid and semi arid regions. In this study 26 hydromerty stations in the Sefidroud basin were selected and 7-day annual minimum series were computed as low flow index. Physiographic characteristics of the basin were also gathered in GIS software. Perason type 3 (PIII) and Generalized logistic distributions (GLOG) were identified as the best regional distributions for the west and east homogeneous regions respectively based on the goodness-of-fit test. Low flow regional regression (LFRR) was then developed for each homogeneous regions. According to the established models, drainage area, land use characteristics, average basin slope and basin circularity were identified as important factors in low flows features.Investigating lowflow characteristics is of vital importance for optimal water resources management and sustainable use of water resources especially in arid and semi arid regions. In this study 26 hydromerty stations in the Sefidroud basin were selected and 7-day annual minimum series were computed as low flow index. Physiographic characteristics of the basin were also gathered in GIS software. Perason type 3 (PIII) and Generalized logistic distributions (GLOG) were identified as the best regional distributions for the west and east homogeneous regions respectively based on the goodness-of-fit test. Low flow regional regression (LFRR) was then developed for each homogeneous regions. According to the established models, drainage area, land use characteristics, average basin slope and basin circularity were identified as important factors in low flows features.Investigating lowflow characteristics is of vital importance for optimal water resources management and sustainable use of water resources especially in arid and semi arid regions. In this study 26 hydromerty stations in the Sefidroud basin were selected and 7-day annual minimum series were computed as low flow index. Physiographic characteristics of the basin were also gathered in GIS software. Perason type 3 (PIII) and Generalized logistic distributions (GLOG) were identified as the best regional distributions for the west and east homogeneous regions respectively based on the goodness-of-fit test. Low flow regional regression (LFRR) was then developed for each homogeneous regions. According to the established models, drainage area, land use characteristics, average basin slope and basin circularity were identified as important factors in low flows features.Investigating lowflow characteristics is of vital importance for optimal water resources management and sustainable use of water resources especially in arid and semi arid regions. In this study 26 hydromerty stations in the Sefidroud basin were selected and 7-day annual minimum series were computed as low flow index. Physiographic characteristics of the basin were also gathered in GIS software. Perason type 3 (PIII) and Generalized logistic distributions (GLOG) were identified as the best regional distributions for the west and east homogeneous regions respectively based on the goodness-of-fit test. Low flow regional regression (LFRR) was then developed for each homogeneous regions. According to the established models, drainage area, land use characteristics, average basin slope and basin circularity were identified as important factors in low flows features.Investigating lowflow characteristics is of vital importance for optimal water resources management and sustainable use of water resources especially in arid and semi arid regions. In this study 26 hydromerty stations in the Sefidroud basin were selected and 7-day annual minimum series were computed as low flow index. Physiographic characteristics of the basin were also gathered in GIS software. Perason type 3 (PIII) and Generalized logistic distributions (GLOG) were identified as the best regional distributions for the west and east homogeneous regions respectively based on the goodness-of-fit test. Low flow regional regression (LFRR) was then developed for each homogeneous regions. According to the established models, drainage area, land use characteristics, average basin slope and basin circularity were identified as important factors in low flows features.Investigating lowflow characteristics is of vital importance for optimal water resources management and sustainable use of water resources especially in arid and semi arid regions. In this study 26 hydromerty stations in the Sefidroud basin were selected and 7-day annual minimum series were computed as low flow index. Physiographic characteristics of the basin were also gathered in GIS software. Perason type 3 (PIII) and Generalized logistic distributions (GLOG) were identified as the best regional distributions for the west and east homogeneous regions respectively based on the goodness-of-fit test. Low flow regional regression (LFRR) was then developed for each homogeneous regions. According to the established models, drainage area, land use characteristics, average basin slope and basin circularity were identified as important factors in low flows features.Investigating lowflow characteristics is of vital importance for optimal water resources management and sustainable use of water resources especially in arid and semi arid regions. In this study 26 hydromerty stations in the Sefidroud basin were selected and 7-day annual minimum series were computed as low flow index. Physiographic characteristics of the basin were also gathered in GIS software. Perason type 3 (PIII) and Generalized logistic distributions (GLOG) were identified as the best regional distributions for the west and east homogeneous regions respectively based on the goodness-of-fit test. Low flow regional regression (LFRR) was then developed for each homogeneous regions. According to the established models, drainage area, land use characteristics, average basin slope and basin circularity were identified as important factors in low flows features.

Musa Estuary is one of the most valuable aquatic ecosystems in the in Khuzestan Province. Previous studies on sediment and organisms in this ecosystem found some indications of mercury pollution in this area and have emphasized that mercury concentrations are above global standards. The aim of this study was to evaluate the mercury concentration in the waters of Musa Estuary. For this purpose, five creeks (Zangi, Jafari, Petroshimi, Ghazaleh and Majidieh) of Musa Estuary were investigated. Water samples were collected in November 2009. The extraction of dissolved mercury from water samples were conducted according to APHA standard method and the level of Hg were determined using cold vapor atomic absorption spectrometry. Mercury concentrations in water samples ranged from 3.66 to 12.00 μg/l. The highest Hg concentrations were observed in at Ghazaleh and Majidieh and the lowest mercury contents were found in Zangi. The results of this study indicated that Hg concentration in waters of Musa Estuary exceed the maximum acceptable level (0.2 μg/l) and warning limit (2.0 μg/l) for mercury in seawater which is a critical environmental issue for this region.Musa Estuary is one of the most valuable aquatic ecosystems in the in Khuzestan Province. Previous studies on sediment and organisms in this ecosystem found some indications of mercury pollution in this area and have emphasized that mercury concentrations are above global standards. The aim of this study was to evaluate the mercury concentration in the waters of Musa Estuary. For this purpose, five creeks (Zangi, Jafari, Petroshimi, Ghazaleh and Majidieh) of Musa Estuary were investigated. Water samples were collected in November 2009. The extraction of dissolved mercury from water samples were conducted according to APHA standard method and the level of Hg were determined using cold vapor atomic absorption spectrometry. Mercury concentrations in water samples ranged from 3.66 to 12.00 μg/l. The highest Hg concentrations were observed in at Ghazaleh and Majidieh and the lowest mercury contents were found in Zangi. The results of this study indicated that Hg concentration in waters of Musa Estuary exceed the maximum acceptable level (0.2 μg/l) and warning limit (2.0 μg/l) for mercury in seawater which is a critical environmental issue for this region.Musa Estuary is one of the most valuable aquatic ecosystems in the in Khuzestan Province. Previous studies on sediment and organisms in this ecosystem found some indications of mercury pollution in this area and have emphasized that mercury concentrations are above global standards. The aim of this study was to evaluate the mercury concentration in the waters of Musa Estuary. For this purpose, five creeks (Zangi, Jafari, Petroshimi, Ghazaleh and Majidieh) of Musa Estuary were investigated. Water samples were collected in November 2009. The extraction of dissolved mercury from water samples were conducted according to APHA standard method and the level of Hg were determined using cold vapor atomic absorption spectrometry. Mercury concentrations in water samples ranged from 3.66 to 12.00 μg/l. The highest Hg concentrations were observed in at Ghazaleh and Majidieh and the lowest mercury contents were found in Zangi. The results of this study indicated that Hg concentration in waters of Musa Estuary exceed the maximum acceptable level (0.2 μg/l) and warning limit (2.0 μg/l) for mercury in seawater which is a critical environmental issue for this region.Musa Estuary is one of the most valuable aquatic ecosystems in the in Khuzestan Province. Previous studies on sediment and organisms in this ecosystem found some indications of mercury pollution in this area and have emphasized that mercury concentrations are above global standards. The aim of this study was to evaluate the mercury concentration in the waters of Musa Estuary. For this purpose, five creeks (Zangi, Jafari, Petroshimi, Ghazaleh and Majidieh) of Musa Estuary were investigated. Water samples were collected in November 2009. The extraction of dissolved mercury from water samples were conducted according to APHA standard method and the level of Hg were determined using cold vapor atomic absorption spectrometry. Mercury concentrations in water samples ranged from 3.66 to 12.00 μg/l. The highest Hg concentrations were observed in at Ghazaleh and Majidieh and the lowest mercury contents were found in Zangi. The results of this study indicated that Hg concentration in waters of Musa Estuary exceed the maximum acceptable level (0.2 μg/l) and warning limit (2.0 μg/l) for mercury in seawater which is a critical environmental issue for this region.