مجله تحقیقات آب و خاک ایران
سال پنجاه و یکم شماره 2 (پیاپی 50، اردیبهشت 1399)

One of the ways to improve the food security of a growing population of the world is to increase the amount of production per unit area. Some of the nutrient elements such as silicon not only increase nutrient use efficiency but also increment product quality. In this research, the effects of various sources of silicon included Potassium silicate, Calcium silicate, Humistar Si in two levels 200 and 400 mg/kg and Nano-silicon in two levels 50 and 100 mg/kg and Control treatment on morphophysiological responses of the herb of the stevia plant were examined. After three months, the plants were harvested and fresh and dry weight of shoot and root, height and diameter of the shoot, root volume and leaf area as morphophysiological indices of the plant, and leaf chlorophyll, the concentration of silicon, phosphorus, potassium in the shoots, and Glycosides in the stevia leaf, including Stevioside, Rebaudioside A and B were measured. The results showed the effects of silicon sources on the fresh and dry weight of shoot and root, height of shoot, root volume, stem diameter, leaf area and leaf chlorophyll index were significant. The treatments of calcium silicate-200, Nanosilicon-100, and Humistar silicon-200 yielded the highest fresh weight of the shoot compared to the control samples and Nanosilicon-100 led to an increase of 55, 64, and 35% of mentioned elements compared to the control treatment. The treatment of Humistar silicon-400 showed the highest amounts of Stevioside (5.23%), Rebaudioside A (0.67%). Considering the effectiveness of the use of silicon element on morpho-physiological and nutritional responses, and improving the quality of Stevioside and Rebaudioside sugars, it is recommended that along with the optimal use of nutrients, more attention should be paid to the role of this valuable element.

Application of drainage water with appropriate management for saline soil reclamation is one of the suggested methods for reuse of drainage water. This research was carried out with the aim of investigating the effect of water and drainage water applying method (mixing before applying or applying in turn) and also the effect of leaching method (intermittent or continuous) on desalinization and desodification of Heavy textured soils of southern Khuzestan province. Leaching experiments were carried out applying 120 cm of water in 1.5 m × 1.5 m plots. Five leaching treatments were D1F1 and D2F2, which respectively consisted of 1-2 times applying of “Salman Farsi sugar cane agro-industry “drainage water with a salinity of 9.0 dS/m, and then, in the same manner, Karoun river water with a  salinity of 2.61 dS/m was applied to the plots. Also, M1, M2, and M4 treatments, in which respectively a mixture of water and drainage water with a salinity of 6.0 dS/m, were applied to the plots by continuous leaching and intermittent leaching with two breaks and intermittent leaching with four breaks. The remaining salts in the soil in M1 and M2 treatments in 0-30 cm soil top layer were 17% and 24%, respectively, and the sodium absorption ratio in these treatments was 57.5% and 24.7% higher than the M4 treatment, which indicates a positive effect of increasing the number of discontinuities in the desalinization and desodification processes.

Since many parts of Iran are located in arid and semi-arid regions of the world, groundwater recharge is an important component of the water cycle in these areas. In this paper, groundwater recharge under different irrigation scenarios for thirty logs lied in Neishabour plain was investigated. Daily data, including precipitation, evapotranspiration and leaf area index were used to run HYDRUS-1D software. Thirty observation logs with different depths of water table were selected at different locations in the plain. Analysis of the recharge rate in the wheat-fallow scenario showed that for different soil textures, groundwater recharge is dependent on the number of irrigation applications. For the logs with sandy soil textures, the maximum amount of recharge was obtained in five irrigation events scenario by an average of 325.23 mm year-1. For the logs with sandy clay loam soil texture, the highest recharge rate was obtained in the seven irrigation events scenario by an average of 67.43 mm per year-1. In the logs dug in loamy soil texture, due to the high depth of the soil block, the same recharge rate was obtained at different scenarios. In the case of a double-cropping scenario, groundwater recharge increased due to irrigation of tomato in summer. In this scenario, the highest recharge rate was obtained in observation log drilled in sandy soil texture with a depth of 15 m which was equal to 440.47 mm year-1.

In the present study, a nonlinear hybrid model, based on multivariate adaptive regression splines (MARS), artificial neural networks (ANN) and K-nearest neighbor (KNN) has been presented for downscaling the precipitation of Shahrekord, Barez, and Yasuj under climate change conditions. This model, similar to SDSM, is composed of two steps; classification and regression. The MARS model is employed for classification of precipitation occurrence and the ANN and KNN are employed for determination of the amount of precipitation. The results of MARS showed that the mentioned model is more accurate than the SDSM model. Comparing the results of downscaled precipitation showed that the ANN model is more accurate than the SDSM and KNN in prediction of average annual and monthly precipitation. So that the R value for ANN was 54% more than the one in SDSM model, in Shahrekord. Also, according to the highest accuracy, standard deviation and skewness coefficient, the ANN, KNN and SDSM model ranked first, second, and third, respectively, for prediction of monthly average precipitation in three investigated stations. Eventually, the precipitation changes in the near future (2020-2040) and far future (2070-2100) periods were investigated under the A2 and B2 scenarios of the HADCM3 model. Results revealed that the lowest precipitation reduction is corresponded to ANN (in Shahrekord) and A2 scenario in the near future period and the highest precipitation reduction is corresponded to SDSM (in Yasuj) and A2 scenario in the far future period. Finally, it can be concluded that the proposed model is more accurate than the SDSM model and can be used as an alternative to the SDSM model.

Salt accumulation in the soil profile and root zone has significant effect on quality and quantity of agricultural products. Vetiver grass is one of the most important plants which is resistant to salinity and compatible to different situations. The solute transport models in salinity studies plays an important role in time and cost saving. This research was performed to find out the effects of different irrigation salinities on vetiver grass and also to investigate the effect of Vetiver grass in controlling soil salinity and sodicity. In addition, the distribution of salinity and sodium in the soil profile was measured and simulated by HYDRUS-1D model. In this research five salinity irrigation levels including 0.68, 2, 4, 6, 8 and 10 dS/m were applied and soil samples were taken from depth of 0-90 cm. The HYDRUS-1D model was calibrated using 6 dS/m irrigation saline water data and validated using the other salinity levels data. The results showed that the model simulates the soil salinity (ECe) values properly in 4, 6, 8 and 10 dS/m treatments. The prediction of soil salinity in treatments 0.68 and 2 dS/m was close to the reality, with the exception of surface layer. The results of sodium concentration in the soil profile showed that this model didn't simulate the soil sodium with good accuracy, especially in the soil surface and the predicted valued were underestimated. The reason, such as salinity, is the lack of proper prediction of sodium in the top layer.

Nitrate is a major contaminant that is extensively found in water resources in many countries, leading to environmental problems. In this study, a batch system was used to study the removal of nitrate from aqueous solutions by micro and nanoparticles of beech leaves. After the preparation and modification of adsorbents, the effect of soluble pH, contact time, and dosage of adsorbent on nitrate adsorption were investigated. Kinetic and isotherm adsorption models were used to study the adsorption process. The results showed that the optimum pH and adsorbent dosage for nitrate removal by micro and nanoadsorbent of beech leaves were 3 and 10 g/L, respectively. Equilibrium time for micro and nanoadsorbent beech leaves was obtained 120 and 90 minutes, respectively. Among the kinetic models, Ho ̓s pseudo-second-order for the micro adsorbent and the Lagergren ̓s pseudo-first-order kinetic model for the nanoadsorbent had the best fit to the experimental data. According to the Langmuir model, the maximum adsorption capacity for nanoadsorbent beech leaves (16.69 mg/l) was higher than the micro adsorbent beech leaves (10.68 mg/l). The results showed that the nanoadsorbent of beech leaves are more capable for nitrate removal from aqueous solutions than the microadsorbrnt.

In most cases, advance data is used for evaluating border irrigation. Due to soil variability, as well as initial and boundary conditions in border irrigation, water advance rate varies considerably in different borders. Scaling techniques helped to reduce the required measurements in soil and water issues. The aim of this study was to scale the volume balance equation and provide a simple equation to determine water advance in border irrigation. For this purpose, 21 borders, including cultivated and uncultivated borders with slope of 0.001 to 0.005, roughness of 0.017 to 0.211, length of 91.4 to 100 m, and discharge rate of  0.08 to 0.16 m3/m/min were used. Scale factors were defined such that the volume balance equation remained independent from soil and initial conditions. The scaled advance curves showed certain patterns. As a result, empirical equations were fitted to the scaled solutions. The empirical equation was evaluated for prediction of water advance in the border. The root mean square error obtained from the observed and calculated values by the experimental equation for the different borders, in most cases, was less than 5 minutes, and the mean absolute error value was less than 10%. The determination coefficient of the final advance from observed and calculated values by the experimental equation was 0.93. In general, simple form and independent to the soil type equations presented are advantages of this method.

Knowledge about the spatial distribution of particle-size fractions in different areas is required for various land management applications and resources, modeling, and monitoring practices. In recent years, with the advancement of data mining methods and the availability of cheap data from satellite imagery, digital soil mapping methods have been developed to predict the spatial distribution of primary soil particles. The objective of this study was to conduct a spatial prediction of particle-size fractionssuch as clay, sand and silt using digital soil mapping in agricultural lands in Semnan. To achieve these goals, a total of 84 soil samples were collected from 0 to 20 cm of soil surface. Also, the environmental variables were obtained from OLI Satellite Landsat to make dependence with soil particles. In this study a linear model such as Partial Least Squares (PLS) and two non-linear models, including Random Forest (RF) and Stochastic Gradient Boosting Machin (GBM) were used for spatial prediction of particle-size fractions. The models were calibrated and validated by the 10-fold cross-validation methods. Three statistics, such as Root Mean Squared Error (RMSE), Coefficient of determination (R2), and Mean Absolute Error (MAE) were used to determine the performance of the investigated models. Values of RMSE, R2, and MAE statics of RF model for prediction of sand, silt and clay were (15.6, 0.35, 12.62), (11.49, 0.33, and 9.34), and (8.42, 0.28, and 5.9), respectively. These results indicated that the most accurate model for the prediction of particle-size fractions was the RF model. Also, the results showed that the most important environmental covariates for predicting particle-size fractions were band 10 (B10), band 5 (B5), and the gypsum index (GI). This indicated that the variables containing the near-infrared and infrared thermal waves had a major contribution to explaining the spatial patterns of particle-size fractions.

Greenhouse gas emissions cause warming and impacting climate components and consequently affecting water demand in agricultural sector. This study aimed to identify the impact of climate change on reference evapotranspiration in Mazandaran province. For this purpose, climatic data of Gharakheil, Babolsar, Noshahr, and Ramsar weather stations were used during 1985-2005. Meteorological data for a future period (2006-2081) were estimated using the CanEMS2 model under RCP2.6, RCP4.5, and RCP8.5 scenarios and the reference evapotranspiration was calculated using climatic data for future periods. The SVM model was used for downscaling the climatic parameters. The results showed that the maximum and minimum temperatures would increase over the coming period and the annual maximum temperatures in the selected meteorological stations under RCP2.6, RCP4.5, and RCP8.5 scenarios will be increased by 1.5, 2, and 3° C, respectively. Minimum temperatures in the selected stations under RCP2.6, RCP4.5, and RCP8.5 scenarios will be increased by 3.8, 5.7, and 5.7° C, respectively. Precipitation will also be reduced between 8 to 29 percent over the selected weather stations. The results show that the reference evapotranspiration will be increased or decrease in some months in all meteorological stations compared with the base period. The highest increase in maximum temperature under different climatic scenarios will be occured in March between 1.4 to 6.4° C at Babolsar Meteorological Station, and the highest increase in minimum temperature under different climatic scenarios will be occured between 3.8 to 5.7° C in February at the Gharakheil Meteorological Station. The results showed that the highest and lowest percentages of reference evapotranspiration changes would occur in October and March, respectively. Evaluation of the reference evapotranspiration at the selected stations shows that the percentage of evapotranspiration variations in different months varies between -16.1 to 25.7% and the highest increase and decrease in reference evapotranspiration will occur in Ramsar and Gharakheil stations, respectively.

The flow analysis in rockfill materials is often fulfilled by solving differential equations that combine non-linear equation [i=mvn] and continuity equation. This differential equation has first been developed by Parkin. It's solution by finite difference method is massive and time consuming, proportion to boundary conditions at this particular case. These calculations would end up with more significant problems where the water table profile is not specified inside the rockfill material. For flow analysis in rockfill material, another method can be used which is based on the gradually varied flow theory. This method is very simple and less massive. Literature review shows a significant error in parts of flow in which the curvature of the streamlines is high, if drag force is not considered in the gradually varied flow theory. In the current study for the first time, using experimental data of different rockfill materials, the effect of drag force on water profile calculation accuracy was investigated considering gradually varied flow theory. The results show by considering drag force, the calculation accuracy of water profile at permanent flow, especially in high flow curve, would significantly increase and a promising results could be obtained.

In this research, the effect of submergence on the discharge of flow over the sharp-crested weir with an arc in the plan and toward upstream is investigated. This research was conducted on the physical model with twenty different samples of the sharp-crested circular weirs including four different arc lengths (or arc angle), each with five different heights. In these experiments, flow analysis has been carried out for the submergence conditions of the weir. The effect of submergence magnitude on discharge rate of circular weir to find a relationship for determination of this effect was the effort of this study. Examining the submergence conditions for these types of weirs proved that the general equation derived from previous research (Villemont equation, 1947), is not valid to the circular weir.  Villemont Eq. produce an error between zero to 50% and an average of 14% for various laboratory experiments. Therefore, a modified equation for submergence conditions of this type of weir was proposed. This equation in different experiments yields an error between zero and 17% and an average of 4%.

The main problem in surface irrigation systems is the low irrigation efficiency due to poor management, inaccurate estimation of design parameters and inadequate design. Losses in surface irrigation include deep infiltration and runoff, which is one of the ways to increase the efficiency of border irrigation, using closed-end mode in irrigation systems. This research was conducted to evaluate the effects of geometrical variables (slope and length of border) and flow control (inlet flow rate and cut-off time) on application efficiency and uniformity of water distribution in closed-end border irrigation system. The length, slope, inflow rate, and cut-off time are considered as the decision-making variables for developing the multi-objective genetic algorithm based on the non-dominated sorting. For this purpose, three irrigation borders with closed-end system were considered in the Ramshir network. The optimization algorithm for calculating the objective functions involves maximizing the minimum water depth and minimizing the infiltration depth in a modeling loop. The optimization algorithm was linked to WinSRFR 4.1.3 software to calculate the objective functions. The results showed that the best combination of inflow rate and the cut-off time for 75 mm of required water depth was 1.9 lit/s/m and 150 min, respectively, which increased application efficiency and distribution uniformity to 79 and 78 percent. Furthermore, the application efficiency in the closed-end border irrigation system is higher (30% to 50%) than the open end method in different scenarios.

In the present study, horizontal screens at brink of inclined drop were used as an energy dissipater structure to increase the downstream energy dissipation. The experiments were carried out in three angles of drop, two drop heights, and two porosity ratios of horizontal screen. In total, 108 experiments were performed in discharge range of 200–700 L/min. The results showed that the energy dissipation increases with increasing relative wetting length of the screen, such a way that the highest energy dissipation occurs in the horizontal screen with a porosity of 40%. Inclined drop equipped with horizontal screen reduced downstream Froude numbers in three angles of drop and two porosity ratios from a range of 4.49 - 8.35 to a range of 1.48 - 5.78. Also, increasing the angle of drop increases the relative depth of downstream, so that the drop angle of 45 ° and screen porosity of 40% had the best performance in increasing the relative depth of downstream. Increasing the drop angle and screen porosity also reduces the average efficiency of energy dissipation.

The seawater greenhouse system is a new technology that utilizes a desalination approach using saltwater to provide fresh water production and crop growth in arid areas. By controlling the atmospheric factors, this system increases relative humidity nearly up to saturation point and the amount of evapotranspiration in these conditions greatly decreases. Despite the capabilities of this system, there are limitations, such as the eclipse of evaporator and salt collection make it difficult to operate. Therefore, in this study, a new idea under the name of "Novel Integrated System of Greenhouse and Saltwater Evaporative Pond" is proposed for the first time in which the evaporator in saltwater greenhouse system has been replaced by the saltwater evaporative pond. In this study, after implementing the pilot project of this integrated systemin in south east of Tehran, the atmospheric factors variations, reference crop evapotranspiration, plant water requirement, crop yield, and water use efficiency in basil cultivation were studied in this system. The results were compared to the results of open field as a control. Based on the obtained results, the priority impact of the open field atmospheric factors on atmospheric factors variations in integrated system were temperature, relative humidity, and sunshine parameters. According to the measured amounts of water requirements and crop yield in this study, the amount of water use efficiency in basil cultivation in the open field and greenhouse media of the proposed integrated system were 1.14 and 2.89 kg/m3, respectively.

For safe pass of flood flow from upstream to downstream of dams, the spillways are used. Among the various spillways, in stepped spillways, the flow is dissipated when passing through the structure. This will reduce the cost of downstream energy-dissipaters structures such as stilling basin. In addition to energy dissipation, the volume and cost of stepped spillways can affect its design. The best design of the stepped spillway is that the remaining energy and the volume and cost of the spillway will be minimized. Therefore, the stepped spillway design is a multi-objective optimization problem. In the present study, a two-objective simulation-optimization model based on the NSGA-II algorithm was used to minimize the possible remaining energy and spillway volume. The results showed with increasing the relative height of spillway stairs, the amount of remaining energy is increased initially and after reaching a peak point, it would be reduced to a constant value. From the perspective of volume and cost of spillway, by increasing the relative height of the spillway stairs, its volume is increased linearly and by increasing the spillway angle, its volume decreased. The results of multi-objective optimization model showed that in the current plan of Siah-Bisheh Dam spillway, the remaining energy and the volume of spillway criteria were considered well. So that 83.7 percent of the flow energy is dissipated.

Several factors affecting pollutant transport in rivers. Among those, vegetation is less studied by researchers. Due to the appropriate conditions in floodplains, such as adequate moisture and fertile sediments, it is possible to develop and grow different types of vegetation in these areas. Depending on the type of vegetation, their effect on the flow and subsequently on mass transfer is different. In this paper, the effects of flow depth, vegetation arrangement, and the interaction between the floodplain and the main channel on the longitudinal dispersion coefficient, K, in a compound channel has been studied. The results show that K is greater in the main channel rather than the floodplain. In addition, the interaction of the main channel and floodplain increases the K values up to 30 and 88% for non-vegetated and vegetated conditions, respectively, which are statistically significant. Similarly, the effect of vegetation arrangement on the K values are statistically significant, and K /U*iHi is greater for the staggered arrangement rather than tandem arrangement.

In this study, the impact of operation of the study/construction inter-basin water transfer and agricultural development projects in Big Karun Basin has been investigated. In this regard, the Big Karun Basin including six under operating dams, five under operating inter-basin water transfer projects, 12 drinking and industrial consumers, seven fish farmers, 34 agricultural consumers has been simulated using a dynamic system approach. In addition to quantitative investigation, water quality has been also modeled. Then the behavior of the system was investigated under operation condition of seven under study/construction inter-basin water transfer and nine agricultural development projects. In both conditions, the capability of Big Karun Basin in terms of power generation and water supply for downstream demand was assessed in a different sector based on reliability, resiliency, and vulnerability performance indices. The results indicate 28% reduction in firm hydropower energy generated by the Big Karun Basin system in the condition of operating under study/construction inter-basin water transfer project compared to the present condition. This is very important due to the key role of the Big Karun Basin in hydropower generation throughout the country, especially during the peak consumption hours. Also, the results indicate that the amount of reliability, resiliency, and vulnerability in south Karun will be 70.9, 60.67, and 36.33 for present condition and 51.3, 49.4, and 72.66 for operating under study/construction inter-basin water transfer and agricultural development projects. Quantitative and qualitative zoning figures at each consumer site show although the impact of operating under study/construction inter-basin water transfer and agricultural development projects in northern Karun and Dez rivers is less than the one in southern Karun River basin, however, ignoring integrated water management and continuing system operation process based on the present condition results not only reduction in hydropower generation, but also the inability of Big Karun Basin in terms of quantitative and qualitative supplying of consumers demands in southern Karun Basin and especially in the end parts.

Cadmium (Cd) is one of the most toxic and non-biodegradable heavy metals which can be emitted into the aquatic ecosystem, accumulated in the food chain and posing a serious threat to the aquatic organism and human health. In this study, the effect of peanut shell (PN), pristine biochar (PBc), and modified biochar by potassium permanganate (PPBc) on cadmium removal from aqueous media was examined. Some characteristics of absorbents such as pH, cation exchange capacity (CEC), surface functional groups, and values of C, N, H and surface area were investigated. Adsorption isotherms (Langmuir, Freundlich, and Temkin) and Kinetic models (pseudo-first-order, pseudo-second-order, and Elovich) were used to explain the adsorption process. Results showed pH, cation exchange capacity and the oxygen containing functional groups such as COOH and Mn-O increased after the chemical treatment of biochar. Maximum sorption capacity obtained at the equilibrium time 120 min, adsorbent dosage of 0.25 g, and pH=6. Langmuir isotherm and the pseudo-second-order kinetic model have the best fitness on cadmium biosorption data. The RL values for adsorbents were calculated to be 0.02 to 0.37 with initial concentration ranging from 10 to 60 mg/L, which indicated the Langmuir isotherm of Cd (II) was a favorable isotherm in the adsorption process. Results showed that the Langmuir maximum Cd adsorption capacities of the modified biochar (28.24 mg/g) is higher than the one in pristine biochar (13.40 mg/g). PN did not show a significant effect on the Cd sorption. This work shows that the modified biochar by potassium permanganate may be an effective, low-cost, and environmentally-friendly adsorbent to remediate Cd contamination in the environment.

Date is one of the most important horticultural products in Iran, which plays an important role in added value of the agriculture, economy and food security. Water resources restriction is one of the main challenges of date product in different areas. Thus, consumption management and optimal use of water resources for production is essential. A practical approach to water resources management is estimation of crop water requirements and determination of water volume consumed in the process of crop production. Virtual water is a measure to estimate actual water use by different crops. Therefore in this research, date water requirement was firstly estimated by CROPWAT in Sistan and Baluchestan Province. Afterward, the volume of virtual water, water footprint, blue and Green water were calculated for growing seasons of 2011-2017. The results showed that the average date water requirement is 21976.52 m3 ha-1 in this province. However, the amount of applied water was measured to be 46659.58 m3 ha-1. This indicates a low water productivity for date production in this province, as the water productivity of date was calculated to be 0.29 kg/m3. The average application of water for date production was estimated to be 399.67 million Cubic meters. Iranshahr, Saravan, Sarbaz and Nikshahr had the highest exploitation of water resources. The average virtual water for date production was found to be 3.82 m3 kg-1. The results of estimated footprint showed that this province has a low potential for using rainwater to irrigate date palm.

Soil salinity and shallow and saline groundwater have been made subsurface drainage and drainage effluents to be inevitable in irrigated lands of south of Khuzestan. Due to the development of irrigation and drainage networks (IDN) in the southwest of Khuzestan (with an area of 340,000 hectares), it is necessary to study integrated agricultural drainage management in all area. Drainage management is depending on its quality and quantity (Q & Q), which are changing continuously. Therefore, a model for predicting drainage water Q & Q in the operation period of IDNs was developed and validated using 25 hectares' research field. Predicted drainage water salinity of the IDNs was used to make the decision for reusing or disposing options. Based on the predictions made by this model, the quality of drainage water from the plans of the southern Karkheh basin and western Karoon, with the exception of sugarcane cultivations, is not suitable for at least 10 years to cultivate salt-tolerant plants and their disposal is inevitable. In case of drainage water with better quality, it could be reused for irrigation of salt-tolerant crops and forestation to prevent dust storms. Drainage transportation to the Persian Gulf is proposed to have the least hazard to the environment. In the present study, the content of phosphorus and nitrogen in drainage water was measured to be 0.043-0.70 and 2.2-22 mg/L respectively, which showed a much higher amount of nitrogen than Mahshahr bay (discharge point). Although drainage disposal into the Persian Gulf seems to release high levels of nitrogen, however, due to low phosphorus content in these drainage waters, additional nitrogen cannot be entered in the production cycle and does not result utrification.