نشریه پژوهش های حفاظت آب و خاک
سال بیست و هشتم شماره 2 (خرداد و تیر 1400)

The construction of aprons and diversion dams on alluvial beds have important role in rivers protection. Design of such hydraulic structures on permeable foundations is required to determine hydraulic gradients and seepage discharge after the downstream end of the structure. This important issue is well done by seepage flow analysis. The seepage flow may occur in or beneath hydraulic structures and also from the bed of open channels. One of the existing methods for analyzing seepage flow and solving Laplace’s equation is the application of analytical solution which is usually based on the theory of conformal mapping. The hydraulic gradients at the end of downstream and seepage discharge passing beneath diversion dams could be controlled by cutoff walls. In the present paper, analytical closed-form equations for the variations of hydraulic gradients and seepage discharge are presented as a function of the distance from downstream end for various arrangements of cutoff walls. The porous media beneath the structure is assumed to have infinite depth. The problem is solved for four scenarios: cutoff wall at downstream end, cutoff wall at upstream end, double cutoff walls at both ends and the structure with depressed floor.

In this paper, hydraulic gradients and seepage discharge have been obtained with respect to the distance from downstream end by the use of conformal mapping and an approach based on Darcy’s equation. Indeed, this method is the extension of Pavlovsky’s solution. The Schwarz-Christoffel transformation is used in conformal mapping.

Based on the resulting equations, non-dimensional charts have been produced for the variations of hydraulic gradients and seepage discharge with respect to the distance from downstream end and the length of structure. Assuming b is the length of structure, s is the depth of cutoff wall, x is the distance from downstream end, and d is the depth of depressing floor, at constant ratios of b/s or b/d , the hydraulic gradients values are decreased with increasing the distance from the end and also at constant ratios of x/s or x/d , the hydraulic gradients values are decreased with increasing the b/s or b/d ratios. For limiting the seepage discharge in a determined value which is passed from the downstream end of the structure, the value of b/s in the case of cutoff at upstream end is greater than double cutoffs, cutoff at downstream end and, depressed floor, respectively.

Based on the obtaining charts, the results show that the cutoff wall at the downstream end is more effective than the others and the hydraulic gradients in the case of depressed floor is less than the other cases

In drip irrigation systems, the low surface reactivity of the sand filter for physical-chemical treatment led to the use of other filter media that increase the retention capacity of wastewater contaminants along with the sand. The purpose of this study was firstly to compare the application of sand and geotextile with zeolite in filters to reduce nitrate pollution in wastewater and secondly to compare the quality parameters of Shahrekord University effluent with international standards.

This research was conducted at Shahrekord University in 2014-2015. The wastewater used in this project was prepared from an observation well located near the east door of Shahrekord University. In order to investigate the nitrate status, a factorial experiment was performed in a completely randomized design with three replications. Treatments include control treatment Ctrl (sand without application of zeolite), geotextile without application of zeolite J, sand-geotextile without application of zeolite SJ, sand with zeolite SZ, geotextile with zeolite JZ, and geotextile sand with zeolite. The treatments were poured into cylindrical columns made of PVC tubes. Inlet effluent nitrate and wastewater were measured with a spectrophotometer. The total suspended solid, EC, pH, sodium, calcium and magnesium in the effluent were determined and compared with the standards. Statistical analysis was performed using SAS software.

The results showed that the filters had a significant effect on the effluent nitrate passed from the columns (P<0.01). JZ, SJZ, and SZ treatments showed the highest nitrate reduction with 57, 55, and 52%, respectively. Sand treatment did not affect nitrate as expected. Measurements showed that the amount of nitrate in Shahrekord University effluent for irrigation was less than the allowable amount of some organizations, but was not suitable for irrigation according to the FAO standard. Also, the amount of EC (1.02 dS/m) and suspended solid (109.6 mg/L) was too much for irrigation according to most standards, but the pH and SAR of the effluent were sufficient to be used for irrigation. The minimum and maximum pH values were 7.2 and 8.03, respectively, which were lower than the maximum value of all standards. The measured SAR of the effluent entering the filters was 2.14, which was allowed according to the standards in terms of application in irrigation.

This study showed that sand filters alone did not affect the amount of suspended load in the effluent, but using geotextiles and zeolite in sand filters can reduce nitrate pollution from effluent. The amount of sodium, and total calcium and magnesium in the effluent was higher than the allowable amount for use in irrigation according to the standards of the US Environmental Protection Agency. But the amount of sodium absorption ratio was less than the allowable amount for use in irrigation according to all standards.

The excessive use of water resources, particularly in areas where water resources are scarce and demand is much higher, has led to clashes between the various stakeholders that benefit from water extraction and water allocation. Most decision problems in natural resources management involve opposing objectives such as maximizing economic profit and minimizing negative environmental effects. Current research aims to find a compromise solution between economic and environmental objectives in Qarehsou reservoir basin.

Qarehsou basin is an important agricultural center in Golestan Province. Assessment of changes in water levels indicates an increase in water extraction, especially groundwater in such basin. In order to achieve economic and environmental goals, five scenarios were analyzed, including 10%, 20%, 30%, 40%, and the maximum withdrawal of water. Then, optimal cropping pattern and optimum amount of water extraction were determined, using positive mathematical programming model and asymmetric Nash solution, respectively. In this research, the two primary stakeholders, or players, are economic benefit, whose payoff goes to the local farmers (player 1), and the reduction of water resources, whose payoff goes to the community residents (player 2). The total water extraction volume is the decision variable.

The result of applying positive mathematical programming indicate that the cropping pattern has changed toward more profitable crops. According to our results from a game theory application, we observe that the optimal decision will depend on the relative importance weights assigned to the conflicting objectives. When economic benefit is considered as the only objective, the optimal groundwater withdrawal is at its maximum level. On the opposite extreme, when only the environment is considered, the optimal groundwater withdrawal decision is to extract the minimum volume of groundwater. Given the equal weights for economics and environmental goals, the optimal extraction of water resources is 175 million cubic meters. Accordingly, the amount of water extraction can be reduced by 27% to achieve environmental goals.

This study illustrates how game theory can be used to obtain tradeoffs in a straightforward and understandable manner to facilitate an objective assessment of benefits to the various stakeholders and decision makers. Based on the results from our game theory application, in a case of equal weights which are given to both economic and environmental impacts, the optimal withdrawal of water resources is less than the current withdrawal. Therefore, the economic benefits should be balanced with associated negative environmental impact of water withdrawal.

Quinoa (Chenopodium quinoa Willd.) is a species belonging to the family Amaranthaceae s.l., domesticated at least 5000 years ago in the Bolivian-Peruvian highlands. Quinoa is a nutritious herb with favorable nutrition and potential for growth and production in adverse environmental conditions that can withstand salinity. Use of sea water in agriculture will increase farmers' income, sustainable production and food security. Therefore, this study was conducted to investigate the effect of mixed management of seawater with freshwater on the growth properties of quinoa Sajama cultivar.

To investigate the reduction of seawater salinity on growth and yield of quinoa Sajama cultivar, this study was conducted in a completely randomized design with three replications and based on potted cultivation in greenhouse conditions at Gorgan University of Agricultural Sciences and Natural Resources in 2016. At sixth-leaf stage, plants were exposed to 5 saline irrigation treatments, i.e., the control treatment (S1: 0.5 dS.m-1), 15 (S2: 4.3 dS.m-1), 30 (S3: 8.0 dS.m-1), 45 (S4: 11.8 dS.m-1), and 60 percent mixture of seawater and tap water (S5: 15.5 dS.m-1). Salinity stress was initially applied by irrigating the pots with saline water resulting from a mixture of 15% of the sea and tap water, and gradually the salinity of irrigation water increased until reaching the treatments being studied. After eighty-five days of germination, plants were harvested and plant height stem, leaf, and panicle fresh weights, no.of branches and inflorescence, grain and panicle yield, and 1000-kernel weight/plant. Shoot were oven dry for 48 h at 70 C and shoot biomass was recorded. Grains were collected from panicle to record 1000-grains weight and grain yield/plant.

The results inducted the effect of different moderation of irrigation regimes on the stem, leaf, and panicle fresh weights, grain and panicle yield, 1000-kernel weights, and plant height were highly significant (P<0.01), but branches and panicle number were significant at the 5 percent levels (P<0.05). The highest amount of 1000 kernel weights, grain, and panicle yield (4.8, 15.93, and 18.52 gr) were measured at irrigation by freshwater The results showed that increasing the salinity of irrigation water decreased some traits of growth and yield (stem, leaf, and panicle fresh weights, no.of branches and inflorescence, grain and panicle yield, 1000-kernel weight/plant, and plant height). Because in most irrigation traits mixing 15 and 30% of seawater and freshwater has resulted in less decline compared to other treatments, this treatment is recommended to irrigate quinoa in irrigation conditions with saline water of the Caspian Sea. Fifteen and 30 percent mixture of seawater and freshwater has resulted in decreasing 1000-kernel weights 22.9 and 27.1 percent, respectively.

In conclusion, saline irrigation provoked a decrease in quinoa plant growth and yield compared with non-saline irrigation; meaning that the morphological properties and yield of quinoa plants will be decreased due to salt stress. In conclusion, the highest values in most of the morphological traits were observed when using salinity irrigation water at a rate of 4.3 dS m-1 to irrigate quinoa plant under greenhouse conditions, which proves the high resistance of quinoa to salinity stress.

Water scarcity is the most important problem in agricultural development, especially in arid areas. Therefore, the study of strategies to increase water use efficiency must be considered. Providing methods to control and reduce soil evaporation can be a suitable way to increase water use efficiency. Soil surface Evaporation can be considered as the main part of water balance components in arid areas that cause water wastage. One of the ways to control and reduce evaporation from the soil is to use natural amendments. Therefore, this study was conducted to investigate the effect of three minerals including bentonite, vermiculite and zeolite on the amount and intensity of evaporation from the soil surface in a period of 4 months from Tir (July) to Mehr (October).

This study was conducted as a completely randomized design (CRD) with 10 treatments and three replications at Shahrekord University. The studied treatments in this research include 3 types of natural amendments (bentonite, vermiculite and zeolite) at three levels of 0.5, 1 and 2% with a control treatment (soil without any amendment). These natural minerals were mixed in soil of whole pots. The amount of evaporation was measured by measuring the amount of irrigation water of each pot and outlet water of them and based on the water balance equation. Moisture content was measured with a hygrometer at two depths of 5 and 15 cm. Finally, the soil moisture characteristic curve for each treatment by using of pressure plate was obtained and compared.

The results showed that among the three studied minerals, the highest reduction in soil evaporation was related to bentonite. The two minerals vermiculite and zeolite also significantly reduced evaporation compared to the control treatment, but the difference between them was not significant. Among the studied treatments, the highest reduction effect on evaporation was observed in 2% bentonite mixed with soil and the lowest effect was observed in 0.5% zeolite treatment. This treatment did not show a significant difference with the control, but 2% bentonite treatment significantly reduced the rate of evaporation compared to the control by 6.4%. The results the soil moisture in the treatments was the opposite of the evaporation results. In the treatments where the evaporation rate was lower, the moisture content increased. Due to the significant effect of the three minerals on the soil moisture, the soil moisture curve in the studied treatments has also changed compared to the control.

The use of natural soil amendment in addition to preventing soil contamination, helps to improve soil structure to reduce evaporation. Overall, due to the highest effect of using 2% bentonite on significant decreasing of soil evaporation therefore, this soil amendment can be recommended to control of evaporation from soil.

Management practices such as land use change is one of the main components of global change that affects the process, structure and function of ecosystems by changing microbial communities (due to their role in the decomposition of organic matter and food mineralization(.Changes in soil biological characteristics due to land use change and management practices may lead to significant changes in soil organic carbon dynamics, soil microbial respiration and affect nutrient cycle and plant growth. Therefore, to better understand human management on carbon cycle, it seems necessary to understand the correlation between soil microbial properties during land use change.

The aim of this study was to investigate the temporal dynamics of soil microbial characteristics during land use change in rangelands around Kiasar Chahardangeh city of Mazandaran. For this purpose, in this basin, the studied habitats were including Erost village with pastures turned into agricultural lands (barley) and orchards (apples and walnuts) with an age of more than 30 years, with a control pasture, Vavsar village with pastures turned into lands. Agriculture (barley) and orchard (apple and walnut) with an age of more than 20 years and also rangelands converted to garden use (apple and walnut) less than 10 years, with a control rangeland and Ara village with rangelands converted into agricultural land (Barley) less than 10 years old with a pasture. Soil sampling in each land use was done systematically randomly from two depths of 0-15 and 15-30 cm.In total, nine soil samples from landuses were transferred to the laboratory for analysis of soil physico-chemical characteristics including texture, bulk density, moisture content, organic carbon, total nitrogen, pH and microbial characteristics including Basal respiration, Substrate induced respiration, Microbial biomass carbon, Microbial biomass nitrogen and Microbial biomass phosphorus, qCO2, microbial ratio and carbon capability index.

The results showed that the highest amount of physicochemical characteristics (except sand and silt percentage and bulk density, pH and C/N) and soil microbial characteristics (qCO2, microbial ratio and carbon capability index and MBC/MBN) at both depths and mean depths belonged to orchard land uses older than 20 and 30 years. Principal Component Analysis (PCA) indicates that over time, higher values of microbial activity and soil fertility in the orchard uses are older than 20 and 30 years with a completely different location on the axis. In general, the results of this study showed that the variability of organic carbon, total nitrogen, acidity and soil moisture content in the long run caused an increase in microbial respiration rate (Basal respiration and Substrate induced respiration), While the qCO2 in the orchard less than 10 years old and control rangeland for lands older than 20 years, also the microbial ratio in the control rangeland for lands less than ten years old had the highest value, while the carbon capability index showed no significant difference between users of different ages.

In general, the results of this study showed that soil characteristics in orchard uses with older ages were in a better condition. Also, variability in soil physicochemical properties changed the microbial characteristics of the soil over time. Therefore, it is suggested that long-term studies and management strategies to reduce uncertainty and estimate the rate of organic carbon pool of ecosystems, which are not unrelated to soil microbial characteristics, are considered necessary during land use change.

The opening and closing of the miter gates in the river direction have a special complexity that makes it necessary to study its effect on the bed scouring pattern. The present study was performed on miter gate gates (in the single gate opening position) and investigated the effect of a single miter gate opening on the scouring volume of the river bed (case study; Bahmanshir shipping gate). Timothy Loved (2012) used a physical model to investigate the condition of the upstream scour of the Dam of Mississippi River. The results showed that several holes were formed, the deepest of which is about 1.22 meters deep.

Based on the available laboratory facilities and conditions and the principle of similarity, a physical model with a scale of 20 (LR = 20) was constructed. The present study tests were performed on the experimental flume in the hydraulic laboratory of Khuzestan Water and Power Industry Research Institute. In this study, the physical model of the miter gate was placed inside a rectangular flume 6 m long, 1.30 m wide, and 0.5 m deep. The depth of sediment from the half-flume to the end (approximately 3 m in length) was 20 cm and no sediment was considered upstream of the miter gate. Sediment particles used in the present study were supplied from Bahmanshir River, their average diameter (D50) was 0.25 mm (D50 = 0.25 mm) and determined by the Geotechnical Laboratory; Sedimentary particles were silt. In the direction of flow conveyance, the volume and amount of discharge were controlled by a valve and a digital flow meter. The flow slowly and with low discharge entered the flume and the desired hydraulic head was checked and recorded on both sides of the miter gate (upstream and downstream of the miter gate) and finally, the flow enters the pumping tank through the downstream channel after passing through the miter gate and the navigation lock area and returns to the cycle. The Miter gate was tested with different discharge ratios as well as different opening speeds when one of the miter gate gates was opened. The miter gate in this study was made of Teflon; Using a laser meter, the data of the flume bed elevation (erosion and sedimentation) were read, the values of which were calculated by volume.

According to the results of Buckingham's dimensional analysis, several experiments were performed to determine the effect of parameters such as miter gate opening velocity ratio (2, 2.4, 3) and different discharge ratios (0.5, 0.75, and 1) on the scouring volume was done along the flume.

The results of the study of the effect of miter gate opening rate ratio on volume and scour depth showed that in general, with increasing valve opening speed, scour volume increased and decreased, which was due to flow concentration for a longer time at lower opening speed and caused erosion. The depth was greater than the opening speed of the valve. The results showed that with increasing the opening speed of the valve, the erosion volume increased up to 17.3%, and also with increasing the opening speed of the valve, the erosion depth decreased to 23%. It should be noted that with increasing flow, both the depth and the volume of the erosion hole increased, the depth of erosion increased to 18% and the volume of the hole increased to 17%. Regarding the hydraulic head, the results showed that with increasing the hydraulic head, the erosion depth increased to 42% and the scour volume increased to 85%.

The concept of water footprint is used to know the volume of water used in the production of various crops. Considering that the two potato and tomato crops on a Country scale, have the highest amount of waste compared to other crops, Therefore, in this study, the harvest stage losses of these two crops were studied in four fields located in Isfahan and in two irrigation methods. Finally, using water footprint, the volume of water lost due to waste of the mentioned products was calculated.

In the present study, first, the inflow of water to each field was measured and the gross irrigation volume of the crops was estimated using the irrigation program of the relevant fields. Then, using CROPWAT software and Climate data of stations close to the study area (east of Isfahan and Kabutarabad), the net irrigation requirement of crops was determined. Then, using the weighing method, the yield of products and the weight of lost crops were determined. Finally, water footprint was calculated for each crop and the volume of water lost due to their waste was estimated.

According to the results of this study, the average losses of potato and tomato crops in the harvest stage are estimated to be 4.8 ± 1.3 and 8.5 ± 0.8 percent of their total harvest, respectively. The total water footprint of potato crop in furrow and drip irrigation method is equal to 277.8 and 129.7 (m3 ton-1), respectively, while the amount of total water footprint for tomato crop is equal to 145.1 and 175.2 (m3 ton-1).

Based on the percentage of losses of potato and tomato crops and the average use of their total water footprint and also, according to the annual production of these crops in Isfahan and the country, the average volume of water lost due to waste of these two crops and only in Harvest stage is estimated to be 4.2 (minimum 2.9 and maximum 5.7) and 128 (minimum 102 and 152.9) Mm3 year-1 in Isfahan and the country, respectively. However, based on the total waste of these two crops from harvest to consumption, the average volume of water lost due to them is equal to 17.4 (minimum 11.5 and maximum 23.2) and 482 (minimum 380.3 and maximum 583.6) Mm3 year-1 is estimated, so the management of waste water from crop waste is important in the management of water resources allocated to the agricultural sector.

The transverse dike has many applications for River bank erodibility stabilization and consolidation. Water flow pattern, erosion and sedimentation around the transverse dike are dependent of various factors, Such as transverse dike type, geometry sections, sediment transport capacity and etc. In This study With regard to the significance role of the flow velocity and shear stress forces on river bank erosion, two-dimensional numerical modeling as CCHE2D was performed to Numerical Simulation of the Transverse Dike and Islands effect over Water Flow Pattern in Natural Meandering of the Tajan River (in the north of Sarakhs and downstream of Noruzababd village- Razavi Khorasan Province, Iran).

In the first step of this study, a large topographic scale map was prepared with scale 1: 2000. And in three sections of the surveyed sections, the flow parameters were measured. Using topographic data obtained from field surveys and then the geometry model and the computational mesh (grid) with different dimension and also field measurements of flow characteristics such as velocity and depth, the two-dimensional hydrodynamic model was run. Simulated data were compared with observed ones in order to assess the velocity horizontal profile gradients, the distribution of shear stress and the flow depth condition in curved parts of the river channel and around the transverse dike and islands.Furthermore, two statistical criteria (RMSE and MAPE) were used to evaluate the performance of the model.

The results indicated that the simulated values are in good agreement with the field measurements. In the study area, water flow pattern around the transverse dike and islands is dependent of hydraulic conditions and at various discharges has different impact on the flow pattern. due to transverse dike and islands, cross-sections reduce, reason increasing the depth, speed and shear stress, sediment transport capacity and bed load.

The results of this study show that for Observation discharge (47 m3/s) and discharge with a return period of less than 25 years, transverse dike have local effects on the deviation of the flow, and they cannot lead to the diversion of floods with a return period of less than 25 years to the eastern banks. Because the high density of vegetation and high roughness on the east coast, prevents the distribution of flow to the two natural canals. Key words: Transverse Dike (Epi), Island, CCHE2D, Meandering, Tajan riverKey words: Transverse Dike (Epi), Island, CCHE2D, Meandering, Tajan river

Soil nutrient deficiency is one of the main problems of arid and semi-arid rangeland soils in Iran. The use of soil conditioners can be one of the available solutions to improve soil quality of these lands. Application of biochar due to stability of this soil conditioner against microbial decomposition and its long durability causes an increase in soil organic matter, improves soil properties and increases forage quality of rangeland plants. Studies on the effects of biochar application on soil properties and plant growth have often been performed in tropical farms and acidic soils. In the present study, the effects of biochar produced at different temperatures from peach trees pruned foliage on silty-loam alkaline rangeland soil properties, which is an indicator of winter rangelands in Golestan province, are investigated.

Peach trees pruned foliage was prepared from gardens around Gorgan city and in the laboratory using a electric furnace at temperatures of 200, 300, 400 and 500 degrees centigrade, within one hour, various biochars were produced. Then, properties of produced biochars including pH, EC, organic carbon, total nitrogen, adsorbable phosphorus, exchangeable sodium, potassium, calcium and magnesium were measured. Soil used in the present study was collected from the topsoil 0–15 cm at Mangali educational-research station located in the northwest of Aqqala city in Golestan province and some of its physical, chemical and biological properties were measured before being treated with biochar. The soil was treated with biochars produced at different temperatures (200, 300, 400 and 500 ° C) in four replications and incubated for 56 days. At the end of the incubation period, the soil of the pots was sampled and their chemical and biological properties were measured.

The results demonstrated that the soil treated with biochar produced at 200°C had the lowest pH (8.1) and the soil treated with biochar produced at 500°C had the highest one (8.79). The highest and the lowest increase in the value of soil CEC, organic carbon, total nitrogen, microbial biomass and respiration was observed in the soil treated with biochar produced at 400°C and 200°C, respectively.

The use of peach trees pruned foliage biochar, which is produced at a temperature of 400 ° C, is recommended to improve the properties of alkaline soils in arid and semi-arid rangelands. Based our obtained results, the use of biochars produced at temperatures of 500 and 200 ° C is not recommended.

Rain flat sprinkler irrigation system is a new irrigation system that can be evaluated for its efficiency in crop yield. Due to the fact that a significant area of land in Markazi province is dedicated to bean cultivation and on the other hand, the effect of irrigation on beans by Tape drip and Rain flat sprinkler method in this area is unknown, so the purpose of this study is to determine the appropriate irrigation system with the aim of increasing productivity and reducing water consumption. Also in this study, furrow irrigation will be investigated as a control treatment.

In order to compare water use efficiency and nitrogen fertilizer distribution in dry bean cultivation under the furrow, Rain flat and drip irrigation systems, an experiment was conducted in a randomized complete block design with three replications in Arak. Urea fertilizer was used three times, including the appearance of the third three leaflets, the beginning of flowering and the stage of filling the seeds. The TDR device was used to measure soil moisture. Crop biological yield, grain yield, harvest index and water use efficiency were determined in experimental treatments. Finally, to investigate the amount of soil nitrogen changes before and after planting, soil sampling was done from zero to 120 cm depth and it was determined by automatic Kjeldahl machine.

The results showed that the effect of different irrigation methods on the number of pods per plant and number of seeds per plant was significant at the level of 5% probability and on the amount of water consumed at the level of 1%. The Rain flat irrigation method increases the grain yield by a maximum of 29.5 and increases the biological yield to a maximum of 27.8 compared to the tape and furrow irrigation methods; however, this increase was not significant. Differences in water use in Rain flat and drip methods were not significant, but differences were significant in other cases with the furrow system. The highest physical water efficiency with an average of 360 grams of dry matter per cubic meter of water consumption belonged to the Tape irrigation method; but this advantage was only 2.8% compared to the Rain flat irrigation method. The rate of nitrogen leaching at the depths of 0 to 30 cm and 30 to 60 cm in the Rain flat irrigation method was higher than the drip Type irrigation method; However, no significant leaching of this element was observed at depths of more than 60 cm. Considering the ratio of the costs of implementing each irrigation method in comparison with the crop yield, it was found that the cost of implementing the drip Type irrigation system for each kilogram of beans produced was about 2.7 times more than the Rain flat irrigation system.

Physical efficiency of water in Rain flat irrigation is not significantly different from Tape drip irrigation, but it is significantly different from Furrow irrigation. However, bean cultivation using Rain flat sprinkler irrigation method is recommended due to better economic efficiency compared to Tape drip irrigation systems and Furrow surface irrigation.