مجله تحقیقات آب و خاک ایران
سال پنجاه و سوم شماره 4 (پیاپی 76، تیر 1401)

One of the issues that researchers have always considered in the design of storage dams is reducing the kinetic energy of flow passing through the spillways to control the velocity, reduce the destructive energy, and scour depth downstream of spillways. Stepped chutes and flip buckets are the most common energy dissipator structures in emergency spillways at dams. Regarding the effect of scour depth at downstream of these structures on their stability and safety, in the present study, the effect of hydraulic and geometric parameters on variations of scour characteristics downstream of smooth and stepped chutes was investigated experimentally. Experiments were conducted at a hydraulic lab at the University of Guilan in 2020-2021 with a ratio of critical flow depth and step height (yc/h) of 0.53-0.97, bucket exit angles of 15° and 30°, the ratio of tailwater and critical flow depth (ht/yc) ranging from 1.5–2, the ratio of height falling and step height (HF/h) varied in the range of 2-4, and a spillway slope of 1:2 (V: H). The comparison of results demonstrated that implementing steps over a smooth chute profile reduced maximum downstream scour depth of the flip bucket by 15° and 30° exit angles in comparison with a smooth chute for the minimum relative critical flow depth by 22 and 41 percent, respectively, and for the maximum relative critical flow depth, by 14 and 20 percent, respectively. Also, with an increase in the exit angle from 15° to 30°, the maximum scour depth decreases for the minimum and maximum tailwater depths by an average of 18 and 11 percent, respectively, for a smooth chute and by an average of 19 and 17 percent, respectively, for a stepped chute. Furthermore, a regression relationship was derived for predicting the scour depth at downstream of stepped chutes with the flip bucket.

Gypsum is spread in soils of arid and semi-arid regions and controls the soil physiochemical properties when it exists as the main soil component. Due to the undesired effects of gypsum in agriculture and plant growth, the accurate determination of its concentration is very important for soil classification and land use management. In this study, the parameters affecting the gypsum determination by the acetone method, namely contact time, extractant to soil ratio, and different extractants were investigated. Results revealed that the gypsum dissolution reaction was fast and most of the gypsum was dissolved in less than 0.5 h. Gypsum extracting with high extractant to soil ratios (1:200) had led to underestimation in the gypsum concentration. So that, the measured gypsum at 0.5 h extraction in soils with 10, 20, 30, 40, 50, 60, 70, 80, and 100% gypsum was underestimated by -1, 3.5, 9.6, 11.0, 22.4, 29.3, 39.6, 47.5, and 87.8% (according to the actual content) respectively. Decreasing the extractant to soil ratio to 1:400, overestimated (10 to 50%) the gypsum in the samples containing less than 50% gypsum. NaCl, KCl and MgCl2 solutions increased the gypsum solubility eliminated the underestimation in gypsum determination especially in 1:200 ratio. However, the use of salt solutions as extractants in the natural soils had led to overestimate at the higher extractant to soil ratios (1:400). The critical electrical conductivity (EC) in the measuring of gypsum by the Acetone method was 1000 µS/cm. According to the results, use of deionized water as the extractant, 0.5 h contact time, and variable soil to water ratio according to the soil gypsum content and to reach the EC of lower than 1000 µS/cm were the optimum condition for determination of soil gypsum by the acetone method which is recommended.

In recent decades, the increasing development of satellite technologies has provided access to climate data around the world with different spatial and temporal resolution. Therefore, in the present study, the goal of evaluating ECMWF datasets models is to predict climate data and drought monitoring in Qarechai basin of Markazi province. To this end, first monthly precipitation and temperature data of synoptic stations of Hamedan, Qom and Shazand in three provinces during the period of 1987-2018 were collected. Then, the mentioned data with spatial resolution of 0.125 * 0.125 degrees during 1979-2020 were extracted from the reanalysis models including ERA-Interim and ERA5 of ECMWF datasets. Statistics criteria's such as coefficient of determination (R2), nash-sutcliffe (NS), normalized square root mean square error (NRMSE) and mean oblique error (MBE) and contingency table indices consisting of POD, FAR and CSI were used to compare the data of reanalysis models with observational data. The results showed that ERA5 data were more consistent with observational data than ERA-Interim data. As the values of correlation coefficient in most areas above 0.5, mean square error in 70% of areas is very low and mean oblique error in most areas is positive and small. The values of the agreement table indices also confirm the greater compatibility of the ERA5 model.   Afterward, based on data of the selected model and observational, SPEI and SPI drought indices in selected stations were calculated. The results showed that SPEI index had higher correlation and less error with SPI than SPI. Finally, the trend based on the selected index showed that the severity of drought in the western region compared to other regions, has an increasing trend at the level of 5%.

Hydraulic jump phenomenon is a rapid variation in flow conditions that occurs for dissipation of the kinetic energy of the flow in downstream of the hydraulic structures in stilling basins. The aim of this study is to investigate flow characteristics of stepped and smooth chute and the effects of block geometry on the hydraulic jump characteristics in the stilling basin USBR III. Experiments were conducted on the stepped chute and they were compared with smooth chute as well as stilling basin and baffle blocks and end sill in different geometry shapes to test the hydraulic behavior of different hydraulic conditions. The results were compared with stilling basin without block. The results of comparing the two types of chutes showed that in stepped chute, the air entrainment inception locations a positioning further upstream than the smooth chute due to the turbulence of the flow on the steps. The energy dissipation and Darcy roughness coefficient in stepped chute increases by 10% and 15.6% on average compared to smooth chute, respectively, which indicates the appropriate hydraulic performance of stepped chute compared to smooth type. Results showed that increasing the Froude number and height of the baffle blocks caused decreasing sequent depths ratio and the jump length by 22.12 and 36 percent, respectively, compared to classical jump. It is believed that the main reason was raising the rate of secondary flows and flow resistance due to the baffle blocks in stilling basin. The energy dissipation increased by 24 percent, compared to the classical jump and further increase in high Froude number.

Wind erosion is one of the most dominant soil degradation factors in semi-arid and arid regions. Mulching is a management scenario to protect the soil surface. The present research accomplished to assess the efficacy of some organic and inorganic mulch on soil physical and hydraulic properties in the Kupal region of Khuzestan province. These mulches consist of organic mulch (O) at three levels O1, O2 and O3 at combined ratios of sugarcane bagasse, gelatin and gum arabic, mineral mulch (M) at two levels M1 and M2 from MNF mulch and Nanosilica hydrogel (H) mulch was made of nanosilica hydrogel at two levels H1 and H2, which were applied to the erosional plots with the size of 50 × 30 cm in May 2020, profile meters installed in each plot. After four months, applying the mulches had significant effects to improve the physical and hydraulic properties of the soil. The O3 and O2 treatments demonstrated the highest effect on soil MWD, by the value of 2.49 mm, and 2.45 mm, respectively. Soil organic carbon (SOC) increased from 0.2% in the control treatment to 0.92% in the O3 treatment. The H1 treatment depicted the lowest effect on SOC by the value of 0.50%. The biggest amount of soil water content in all moisture points was related to the O3 treatment. The lowest amount of soil loss was observed in O3 treatment (1490 ton / km.year) and the highest value was related to the control treatment (6028 ton / km.year). The organic matter in the mulches due to its binding effect was able to improve aggregation process. To conclude the binding and armoring effect are the main effects of organic mulch. Organic matter in mulches, due to its binding effect, is able to improve and increase the agglomeration process and reduce soil losses.

Compared to the other micronutrient fertilizers, chelated amino acid can significantly improve rice growth, increase grain yield, and macro and micronutrient contents of rice aerial tissues due to better uptake, higher efficiency and nitrogen content. In this study, the effect of glycine amino acid chelated zinc and iron on yield, grain biofortification, and macro and micronutrient contents of rice aerial tissues was compared to zinc sulfate. The experimental treatments were conducted in a randomized complete block design with three replications on the most common Iranian local rice cultivar (Hashemi). The experimental treatments were the foliar application of 0.5, 1, and 1.5 kg ha-1 of Zn and Fe glycine amino acid chelates and ZnSO4 under recommended and 50% of the recommended NPK application. The highest increase in the grain yield was recorded at 0.5 kgha-1 Fe-glycine amino acid chelate by about 29.2%. The maximum increase percentage of Fe, Zn, N, P, and K content of rice grain was observed through foliar application of glycine amino acid chelated zinc and iron by about 32, 22,23,17 and 7%, respectively. This trend also was recorded for white rice and rice straw, but milling processes through removing of rice husk significantly reduced head rice iron, zinc, nitrogen, phosphorus and potassium content by about 10 to 15.5, 0.5, 6.5, 3.8 to 8, and 8 to 12 times compared to rice grain.

Mashhad-Chenaran aquifer catchment covered by various geological formations (igneous, metamorphic, carbonate, non-carbonate and alluvium) which effects on the quality and the type of groundwater. Statistical analysis of water quality of more than 1000 samples of selected water resources (springs, qanats and wells) from 1987 to 2020 and the application of hydrogeochemical techniques shows that the dominant type of water discharge from igneous, metamorphic, carbonate, non-carbonate, non-carbonate and alluvial are CaNaHCO3, CaHCO3, CaMgCl and NaCl, respectively. In igneous and metamorphic rocksm the dissolution of silicate and plagioclase (albite and anorthite) minerals and feldspars increases the Ca+2 and Na+ in water. However, in carbonate and non-carbonate sedimentary formations, Ca+2, Mg+2 and Cl- ions are dominant in water due to the dissolution of calcite, dolomite and evaporation. Investigation of the average of long-term quality data and 14 piezometric in the plain shows that, although groundwater due to recharging from surrounding mountains has varius water types, but along the flow direction, except the northwest region which is affected by evaporation (Jks) and has sodium chloride, the dominant type of water is sodium sulfate. In the alluvial aquifer, the calcite, dolomite and aragonite minerals are supersaturated and the gypsum, anhydrite and halite minerals are saturated. The inverse hydrogeochemical model results in Phreeqc software, indicate that the dissolved materials in water in the second group results from the dissolution of calcite, dolomite and albite minerals in the first group.

In the past few decades, accumulation of heavy metals in soils has increased as a result of human activities. The objective of this study was to evaluate the effect of common reed nano-biochar and Fe-modified nano-biochar on cadmium (Cd) mobility and fractionation in a Cd-contaminated soil. This study was carried out in 1399-1400 as a factorial experiment based on a completely randomized design (CRD) with two factors including absorbent type (at four levels including biochar, modified biochar, nano-biochar and modified nano-biochar), and biochar application levels (0, 0.5 and 1% w/w) in three replications under laboratory conditions. After treatments’ application, the soil samples were incubated for 90 days. At the end of incubation period, Cd availability and fractionation were measured and Cd mobility factor was determined. The results indicated that with the application of all absorbents (especially at 1% w/w level), concentration of available Cd, exchangeable and Cd bound to carbonate fraction were significantly decreased, while Cd bound to Fe-Mn oxides, Cd bound to organic matter and residue fraction of Cd significantly (P<0.05) increased. The Cd availability in modified nano-biochar treatment (1%) decreased by 26.37 % compared to the control. Results also indicated that nano-biochar had a more significant impact than raw biochar on the immobilization of Cd and decrease its mobility in the soil. In addition, modified-biochar and nano-biochar had more efficiency than raw biochars on the Cd stabilization in the soil. In general, the results revealed that common reed nano-biochar and modified nano-biochar with FeCl2 can be suitable absorbent for stabilization of Cd in contaminated soils.

Biochar is a carbon-rich organic compound that has recently been recommended for use as a soil conditioner. Little research has been done on the effect of biochar amount and elapsed time after biochar addition on soil physical properties. This research performed at Shahrekord University, in 2018. The aim of this study was to evaluate the long-term effects of different amount of rice straw biochar on soil bulk density (ρb), total porosity (n), mean weight diameter of dry (MWDdry) and wet (MWDwet) aggregates, air filled porosity (AFP) and capillary porosity (CP) of clay loam soil. This experiment was performed as a factorial experiment based on completely randomized design with three replications in a greenhouse. Biochar have four levels of zero as control (B0), 0.5 (B1), 1 (B2) and 2 (B3) weight percentage and the time have four levels of 2 (T1), 3 (T2), 6 (T3) and 9 (T4) months after biochar adding to the soil. The results indicated that two months after adding rice straw to the soil, ρb decreased by 6% compared to the control. At the same time, ‘n’, ‘MWDdry’ and ‘MWDwet’ increased by 3, 11 and 13%, respectively, compared to the control. Means comparison showed that the lowest ρb was obtained in B1T2, the highest ‘n’, ‘AFP’ and ‘CP’ were obtained in B1T2, B0T1 and B1T3, respectively, and the highest ‘MWDdry’ and ‘MWDwet’ were obtained in B3T4 and B0T4 respectively. Different times are needed for the effect of biochar on soil physical properties improvement. Based on the findings of this study, 1% of rice straw biochar can be used to durabil improvement of the physical properties of clay loam soil.

Accurate estimation of runoff plays an important role in water resources and hydrological studies. Due to simple structure and minimum data requirements, the conceptual hydrologic models are the best way to estimate runoff. The main objective of this study is to investigate the performance of Sacramento model in runoff simulation and determining the best reanalyzed evapotranspiration dataset for using in the model. In this study, four different datasets including HBV, ORCHIDEE, PCR-GLOBW, WATERGAP3 and W3RA are used in Sacramento model. Also, for estimation of basin-averaged rainfall time seri, the Thiessen method was used based on ground gage observations. Results indicate that using most of the reanalyzed datasets in Sacramento model lead to reliable outputs and the performance of model in simulation of daily stream flow is relatively high. However, the performance of model in the case of using W3RA and WATERGAP3 is better than the other data sources, and in both calibration and verification phases the Nash-Sutcliffe efficiency (NSE) is higher than 0.60 and 0.87, respectively. Moreover, findings show that the W3RA dataset is the best one for estimation of runoff volume, high flows (peak floods) and the time to peak flows. Overall, based on the outputs of this research, the reanalyzed datasets can be considered as an alternative or complementary in data-limited regions for water resources and hydrological studies.

Chromium is one of the heavy and toxic metals for microorganisms, animals, and plants, which the use of the sources that contain them may lead to serious environmental pollutants. High concentrations of chromium are considered a stress factor for plants that can affect plants' physiological and biochemical properties as a growth-limiting factor. Due to an active chromite mine in the Forumad area of ​​Mayamey city, Semnan province, this research is to determine the status of chromium contamination in water resources, the soil of the region, and plant samples. Regarding the mentioned issue and for the identification, simultaneously sampling of all water resources in the region, including wells, springs, and aqueducts, are implemented. Besides the qualitative analysis and determination of ions (anions and cations), the total chromium concentration is investigated in the Soil and Water Research Institute. The results indicate pollution centers in the areas of Forumad, Pole Abrisham, Estarband, Kalateh-ye Sadat. A sampling of crops, horticulture, and medicinal plants in the region showed that the amount of chromium adsorption in pepper as a national index product of the region was less than the allowable limitation (less than 1 mg/kg), and the initial concerns were largely resolved. The absorption of total chromium in pistachio and pear crops is also within the allowable range, considered in the region's cultivation program. Since the absorption of chromium in sesame seeds, wheat, alfalfa, figs, and some crops is higher than the allowable level, incentive policies should be implemented to improve the cultivation pattern and replace it with contaminated crops. Contamination of soil sources in the region with chromium was investigated at 32 points. The results showed that almost all soil samples are more contaminated with chromium (range 386-142 mg/kg). The results showed that the concentration of total chromium in the four samples sent from Forumad and the Pole Abrisham before treatment was 123.5, 107.2, 127, and 110.6 μg / l after treatment of zero, 6.7, zero, and 4.2 μg / l, which indicates the use of reverse osmosis in drinking water.

The area of an embayment and its characteristics, which are located along a river, are the most important factor for the maintenance of different species of Flora and fauna. To study the hydraulic characteristics of the flow in the embayment, a three-dimensional simulation model is needed to detect the exact location of the size and shape of the vortices. In this study, the data obtained from experiments, performed at Shahroud University of Technology, have been used (2019 - 2020). Measurements were performed on a continuous and homogeneous cavity flow with free surface in a square embayment with dimensions of 0.3 * 0.3 cm in 4 discharges (0.017, 0.024, 0.028, 033 / 0 cubic meters per second). Gyre formation observed in the embayment. In order to identify and analyze the flow pattern, numerical modeling was performed using physical model data and Flow3D numerical model. The RNG turbulence model, which was more consistent with the actual data, was selected and used by calibration. The flow pattern in the bay area showed that the created rotational cycle is a circular gyre. The speed at the entrance to the square embayment has a downward trend to half, and after reaching the zero point in the middle of the embayment, it finds an upward trend again. The longitudinal velocity, which is greater than the transverse and deep velocities, is also symmetrical in the embayment. Also, the transverse velocity has a negative direction in the first half of the embayment and a positive direction in the last half, which indicates the counter-clockwise movement of the gyre.

The economic benefits of dams have been outweighing the costs of this artificial handmade construction by human being, so it has been providing a rational reason for building them. However, it has been found that the construction of these handmade structures has had a strong effect on the residents along the river, in which have been settling along with. To do so, the present study was conducted to investigate the effects of Shirin Dareh Dam construction on the agricultural status of lands covered by pumping stations along the Atrak River. To achieve this goal, field and library studies were conducted. This research was a survey and the data collection tool was a questionnaire including closed and open questions. The content validity of the research tool was confirmed in consultation with prominent professors of the Department of Agricultural Management and Development, University of Tehran and the Department of Geography, Payame Noor University, Gonbad Center. The statistical population of the present study was two groups of villagers and guards of pumping stations located along the river. Cronbach's alpha coefficient for different parts of the study was higher than 0.7, which indicated that the reliability measurement tool was appropriate. The statistical population of the present study was two groups of villagers and custodians of pumping stations located along the river. The sample size for the statistical population of the villagers using the Cochran's formula was 136 people and to increase the reliability of the data was increased to 160 residents, besides 14 custodians of pumping stations water pumping stations were studied. The results indicated a significant difference between the agricultural situation of the villagers and those in charge of pumping stations before and after the construction of the dam. Factor analysis of positive effects showed that five factors of social, agricultural, environmental, economic and mechanization effects explained a total of 62.21% of the variance. Factor analysis of the negative effects of Shirin Darreh Dam also showed that four factors of physical, chemical, social and environmental effects explained 65.95% of the total variance.

The behavior of many complex natural phenomena, such as rivers, can be analyzed by fractal tree geometry. Zarrineh Rud sub-basin in Kurdistan province is one of the most watery basins of Urmia basin, which hydrological condition has a great impact on runoff management and downstream flows. Therefore, it is necessary to study the characteristics of this basin using fractal geometry. In the present study, the fractal behavior of Zarrineh rud basin in Kurdistan province has been investigated using GIS layers of stream, DEM map, and application of Strahler, Hack, Horton and fractal tree geometry by Richardson method. According to Hack's law, the slope of the basin trend line is high and this indicates a relatively high erosion in the Zarrineh Rud basin. According to Horton's law, the form factor decreases between stream order 1 and 2 and is almost the same for stream order 3 and higher. In addition, the fractal structure indicates that there is a fractal behavior in the range of stream order 2 and higher. Finally, based on the Richardson method, the fractal dimension of the basin was calculated in the range of 1.695- 1.837, which includes a significant part of the basin space. In addition, the results indicated that the fractal dimension obtained for the stream order 4 by the Horton method was 1.67, which is consistent with the results obtained by the Richardson method. Finally, it can be mentioned that, considering the special topography, climate, and hydrologic conditions of Zarrineh rud sub-basin, it is possible to help the country's planners and decision-makers to better manage this basin by identifying the hydrological behavior of the river.

Recently, there has been significant research into Microbial Fuel Cell (MFC) technology due to its potential for simultaneous bioenergy generation and wastewater treatment. The fundamental physical processes within CW and MFC are highly complementary, and combining them offers a number of tantalising possibilities for greatly improving wastewater treatment methods. Recent findings have demonstrated a number of beneficial symbiotic interactions that improve overall system performance within an integrated CW-MFC system. Notably, CW operation is enhanced by improvements in the electrochemically active bacteria population at the electrode surfaces, consequently boosting wastewater treatment efficiency. Similarly, the MFC can utilise the natural redox gradient present within CW to assist bioelectricity generation. In this review article, the performance of integrated CW-MFC systems was discussed in comparison with both standalone MFC and CW systems based on criteria that the review identified as significant. The review shows that the combination of CW and MFC increases wastewater treatment efficiency by phytoremediation, MFC power generation is enhanced by the action of the wetland plants, and wetland greenhouse gas emissions are reduced due to the dominance of electrogenic bacteria. Consequently, a CW-MFC can achieve higher efficiency for contaminant removal and bioelectricity generation compared to standalone CWs and MFCs. However, in view of the physical size and operational life span of wastewater treatment systems required for domestic or metropolitan applications, the CW-MFCs presented within the literature are small and have only been studied over short periods of time. Large-scale controlled trials and long-term studies are urgently needed to provide more definitive evidence that can enable CW-MFC technology to advance to the point of successful implementation.