مجله تحقیقات آب و خاک ایران
سال پنجاه و سوم شماره 2 (پیاپی 74، اردیبهشت 1401)

Soil salinity has sharply been increasing in recent decades due to improper use of basic resources. This issue has had severe harmful effects in different parts of Iran, especially in arid and semi-arid regions where the accumulation of soluble salts in soil surface has reduced crop yields and destroyed arable lands. Given the significance of this issue, the present research investigated the trend of temporal and spatial variations of soil salinity in Minab Plain for which the satellite images of 2001, 2011, and 2021 were used. The Envi5.1 software package was used to develop the soil salinity maps, and the hybrid CA-Markov model in the TerrSet software package was employed to study the soil salinity changes and predict it for the future period. The results showed that the land salinity would increase in these regions over time so that the area of very high salinity class has been 39.46, 45.26, and 63.09 km2 in 2001, 2011, and 2021, respectively. This increase was even greater in southern and southwestern parts of the plain. Furthermore, the prediction map showed the expansion of salinity in the studied region so that the highest area of salinity change rate in 2021 was found to be related to the very high salinity class (20.24%) and the area of very highly saline lands has increased from 12.20% to 29.62% from 2001 to 2021 whereas the area of moderately saline lands has decreased from 60.47% in 2001 to 13.88% in 2021. In general, an approach for preventing soil salinity aggravation in this region is to change the irrigation system to prevent severe water use and the loss of water quality, which would finally influence the soil to a lesser extent.

The soil particle size distribution is one of the most important of soil properties that effect on the soil hydraulic properties, including saturated hydraulic conductivity. Therefore, accurate knowledge of spatial distributon of soil particle size in the watershed is very effective on the optimal management of the watershed. In this study, the spatial distribution of sand, silt and clay particles were predicted in the Damghanrood watershed with a spatial resolution of 30 m at the depths of 0-30, 30-60 cm. For this purpose, 110 soil sampling points were determined using conditional Latin hypercube sampling (cLHS) method. Environmental variables were extracted from Landsat 8 Operational Land Imager (OLI) satellite and digital elevation model (DEM). The random forest (RF) model was used for determined the relationship between soil particles and environmental variables. The results showed that the coefficient of determination (R2) of the RF model at a depth of 0-30 cm for clay, sand and silt particles with a range of 0.6, 0.52 and 0.71, respectively, and at a depth of 30-60 cm, respectively. It was obtained with 0.69, 0.67 and 0.49. In the surface layer, the auxiliary variables extracted from the remote sensing data and in the deep layer, the variables extracted from the most part were related to the soil particle data. The results showed that the coefficient of determination (R2) of the RF model for prediction clay, sand and silt fractions at depth of 0-30 cm was of 0.6, 0.52 and 0.71, respectively, and at a depth of 30-60 cm, for prediction of these fraction the R2 value was 0.69, 0.67 and 0.49, respectively. In the surface layer, the auxiliary variables extracted from the remote sensing data were more important variables for prediction of particle fraction but in deep layer, the terrain attributes were the most important variables in prediction of particle size fractions. The values of saturated hydraulic conductivity (Ks) estimated using pedotransfer functions varied between 0.08 to 1 m / day. The lowest amount of Ks was observed in lands with rock outcrops and marl soils. The results showed that the spatial distribution of Ks derived from sand and clay data was well overly with the reality of the region. So that the lowest values of Ks were observed in areas with rock outcrops and in marly soils.

This research was conducted on lentil at Imam Khomeini international university in 2021. The treatments were included of rainfed (D) and five salinity levels of irrigation water with EC of 0.5 (S0), 2 (S1), 4 (S2), 6 (S3) and 8 (S4) dS.m-1. The experiment was performed in a randomized complete block design with three replications. In treatments of D, S0, S1, S2, S3 and S4, some parameters were measured; the biomass yields equal to 2094.66, 3621.9, 3525.6, 2771.6, 1965.62 and 1120.6 kg.h-1, the grain yield equal to 399.25, 957.53, 932.07, 639.25, 279.33 and 46.82 kg.ha-1 and the straw yield equal to 1695.41, 2664.37, 2593.53, 2132.35, 1686.29 and 1073.78 kg.ha-1,  respectively. The results showed that the use of water up to S2 salinity level was recommended for lentil cultivation. But higher salinity levels were reduced the yield relative to rainfed conditions. At the water salinity threshold of 5.5, 5.3 and 5.6 dS.m-1, the amounts of biomass, grain and straw were equal to rainfed conditions. Due to salinity stress, the relative yield (compared to rainfed) of biomass, grain and straw were decreased with a slope of 0.166, 0.325 and 0.129, respectively. As a result, the grain yield was more sensitive than the straw yield in terms of water salinity. The reason was the effect of salinity stress on plants pollination and lack of grain filling. The amount of water use efficiency (for production of lentil dry biomass) was calculated in treatments of D, S0, S1, S2, S3 and S4 which were equal to 3.55, 1.32, 1.3, 1.23, 1.11 and 0.97 kg.m-3, respectively. In general, the results showed the application feasibility of saline water (in the range of crop tolerance) for irrigation to increase the lentil yield (compared to rainfed conditions). In these conditions, the saline water resources of the region can be exploited.

The reduction of renewable and fresh water resources has resulted in a drinking water supply deficit in many parts of Iran, including Fars province. Considering that most of the water resources in Fars province and the suburbs of Shiraz city have become saline, one of the efficient solutions to supply drinking water to people living in villages with limited population is desalination. In this research, a photovoltaic reverse osmosis desalination system (PV-RO) was designed and built. Three saline water samples from; Zarghan Agricultural Research Center, Sultanabad village, and Kamalabad village were collected for evaluation of the desalination system in 2021. The results showed that it is possible to supply daily drinking water of 10 liters per capita for 146 people in the first study area, 122 people in the second area, and 50 people in the third area. The maximum flow rate of permeate water production is 61 L/h with a 41% recovery factor. Moreover, the required energy for desalination is 1.98 kWh/m3, and the permeate water production cost per cubic meter of fresh water is determined as 180,000 Rials. Therefore, it is possible to use this system in the study area to supply drinking water under drought conditions with reasonable efficiency.

Due to quantity and quality water crises in Yazd province and the necessity of precise determination of crop water need, sensitivity analysis of reference evapotranspiration to meteorological parameters is essential. For this purpose in this study, the effects of variations of each meteorological parameter on reference evapotranspiration (estimated by FAO Penman-Mantith 56) were analyzed in different weather stations of Yazd province. Meteorological parameters during 2001 to 2020 including temperature, humidity, wind speed, and sunshine hours were changed in the range of ±20%. Based on the results of this study wind speed, maximum temperature and sunshine hours were the most important parameters that affect reference evapotranspiration in three yearly, seasonal, and monthly scales. 20 percent changing of each parameter including wind speed, maximum temperature, and sunshine hours caused sensitivity coefficients of yearly evapotranspiration to be (0.32-0.46), (0.27-0.34), and (0.12-0.2) respectively. In general, on a seasonal scale, the most impact of wind speed parameter on reference evapotranspiration was in summer and the most important impact of maximum temperature parameter on reference evapotranspiration was in spring and autumn. From November until April the most sensitivity of reference evapotranspiration was observed for maximum temperature, wind speed, and sunshine hours. From April until October the most sensitivity of reference evapotranspiration was observed for wind speed, maximum temperature, and sunshine hours. According to the results of this study, for monthly scale the sensitivity of reference evapotranspiration to the wind speed is higher for the station with lower altitude. Also, the altitude variation of meteorological stations has been effective in the sensitivity of reference evapotranspiration to the wind speed for annual and seasonal scales.

Short-term prediction of heavy precipitation events is especially crucial in flood warning and mitigation. This study offered a novel concept of the regional heavy precipitation based on the probability pattern of a typical rainstorm. Daily precipitation data of 12 synoptic stations located over southwestern Iran were used for this purpose. In addition, six synoptic variables at 1000 to 200 hPa pressure levels on one to five days before heavy precipitations (covering a wide range outside the study area) were used as predictors. All data used in this study cover the period 1987- 2018. Four feature selection methods and 10 binary classifier machine-learning models were employed in this study. The results revealed that using synoptic data up to four days prior to the events best distinguishes heavy precipitation from non-heavy precipitation events. In addition, among the four feature selection methods, Chi-Square and Extra Tree methods are superior to Correlation and Random Forest. As a result of this study, it was found that the Random Forest model with the Chi-Square feature selection method has the highest efficiency in predicting regional heavy precipitation events in the study area. Relative humidity and specific humidity 1-2 days before and wind speed 2-4 days before the precipitation events are relevant synoptic variables for predicting heavy precipitation events.

Heavy metals pose a serious threat to both human and environmental health. As a result, practical and low-cost strategies to remove them are urgently needed. Biochar is such a sustainable adsorbent playing an influential role in reducing pollution caused by heavy metals. This study aimed to investigate the effects of two feedstock types (corn (Zea mays L.) residues and Conocarpus erectus L. wood) and pyrolysis temperatures (400°C and 700°C) on the removal of lead from aqueous solution and compare linear and nonlinear forms of kinetic and isotherm data of adsorption. For this purpose, characteristics affecting lead removal such as pH of the solution, biochar concentration, contact time, and pollutant concentration were evaluated. In brief, after finding the best pH of the solution, the effect of adsorbent concentration was investigated. Then, the optimum pH and adsorbent concentration were used to assess contact time. Finally, pH, adsorbent concentration, and contact time in the optimum condition were selected to assess the impact of pollutant concentration on the removal of lead by biochars. According to the results, the optimum pH affecting lead adsorption by biochars was 5. The most suitable biochar concentration regarding lead removal was 0.8 gL-1. Lead adsorption by biochars reached equilibrium after 120 minutes. Moreover, sorption capacity increased by elevating the heavy metal concentration. Corn residues biochar produced at 700°C and wood-based biochar fabricated at 400°C had the most and the least lead sorption capacity, respectively. Pseudo-second-order, intra-particle diffusion, and pseudo-first-order models in two linear and non-linear forms revealed the best to the worst description for the sorption process as kinetic models, respectively. According to the model efficiency criteria, Freundlich, Temkin, and Langmuir in non-linear form, and Freundlich, Langmuir, and Temkin in linear form showed the most to the least suitable fit. These results highlighted the importance of using models in their original type being non-linear form. According to the outcome of this study, biochars produced from corn residues had more ability to remove lead than wood-based biochars. Moreover, pyrolysis temperature of 700°C was more effective in the adsorbents' ability to eliminate lead than 400°C. Therefore, the application of low-cost adsorbents with a high capability to remove lead, such as biochars, could positively reduce pollutants from aqueous systems.

Vineyard irrigation scheduling according to actual crop water requirements in the arid and semiarid regions is crucial to improve water productivity and maintain sustainable production. This experiment was carried out to evaluate water consumption (), crop coefficient () and water productivity of grapevine in the Malekan region located in the eastern Azerbaijan province. Two different field experiments in the form of complete randomized design with three replications were carried out during the 2020 growing season in two vineyards with trellis and creeping trained systems under subsurface drip irrigation (SDI). The grape's  was determined by measuring the components of the water balance equation including variations of soil moisture at different levels of the root zone. In order to prevent water stress, the soil moisture content was kept to the range of the readily available water during the whole growing period. The grape's  was 451, 394 mm, respectively, in the trellis and creeping system. Accordingly, water productivity was 5.83 and 6.1 kg per cubic meter of . Maximal daily  was 0.8–0.9, respectively, in the trellis and creeping system, implying that the maximum daily actual water consumption was lower than the calculated corresponding reference evapotranspiration.

Acoustic Doppler Velocimeter is one of the most widely used devices in hydraulic laboratories for measuring 3D flow characteristics. The holder of these devices may be slightly deflected over time or during initial installation, and the ADV receivers may not be exactly parallel to the flume. This study investigates the effects of ADV deviation on measured values of flow characteristics. For this purpose, a technician has installed the ADV device on the flume. Partial deviations in both horizontal and vertical planes are measured accurately. Velocity profile was measured in the center of the channel. The results showed that 2 mm deviation in horizontal and vertical planes causes 240% and 67% error in measuring the transversal and vertical velocities, respectively. The effect of deviation on turbulence intensity is significant. Besides, this deviation causes 148% error in Reynolds shear stress measurements. A comparison between measured profiles and global distribution of different parameters shows big difference between them. Finally, the proposed equations to correct the instantaneous 3D velocities perform well and can be used as post-processing tool.

Today, scientific research on the types of Nexus, especially the water- energy- food Nexus as the driver of improving the welfare of society, is expanding. Since the Nexus approach is relatively new and requires the cooperation of several fields, explaining the concepts, its literature review, with a special focus on the water- energy- food Nexus is essential. This article aims to express Nexus approach simple and clear, by a detailed review of several related articles from 2011 to 2021. Articles were reviewed and categorized by year, source variety, and topic. So the outline of the formation of the Nexus approach, water- energy- food Nexus and the questions raised about this approach were codified in a way that provides a practical insight for policy making. In general, the Nexus approach, especially the water- energy- food Nexus which creates a very complex system and must be considered from a political, social and economic perspective, is difficult to implement. However, the Nexus approach is transitioning to an important component of development planning, and its success requires the guidance of strategic policies and institutional structures in multilevel governance. It seems that countries need to reform their governance structures in line with the Nexus approach. Another issue that has been considered in this article is the difference between the Water- Energy- Food Nexus approach with the approach of integrated water resources management. Due to the similarities, there are doubts about the need to move from integrated water resources management to Water- Energy- Food Nexus.