نشریه پژوهش های حفاظت آب و خاک
سال بیست و هفتم شماره 6 (بهمن و اسفند 1399)

Zn-Pb mine tailings of Zanjan (province of Iran) contain high concentrations of toxic metals, especially arsenic that can potentially release into the surrounding soils and water pathways. These tailings create leachate due to their connection with water, which is very dangerous to the environment and to the masses of animals and human beings. Unfortunately the geochemical and mineralogical processes that control arsenic release from tailings are not fully studded. Therefore this research aimed to assess the leaching characteristics of arsenic under different environmental conditions to recognize the parameters and factors controlling its concentration in the leachate.

Leaching of arsenic from Zn-Pb mine tailing was investigated in various environmental scenarios. In order to determine the amount of leached arsenic in different conditions, four leaching protocols, including toxicity leaching procedure test (TCLP), synthetic precipitation leaching procedure test (SPLP), field leach test (FLT) and leachate extraction procedure (LEP) were used. Also, to study the effect of various factors such as pH, contact time, particle size and solid to liquid ratio on leaching of arsenic from Zn-Pb mine tailings batch leaching experiments were carried out. Risk assessment code (RAC) based on fractionation method was also applied to evaluate the environmental risk of arsenic mobility.

The results indicated that in both samples of tailings ,the highest amount of arsenic was measured in the residual fraction that is relatively stable under natural environmental situations. According to RAC index, the tailings in term of arsenic placed in the low-risk tailings group. In TCLP, LEP, FLT and LEP test the concentrations of leached arsenic were low and the highest leaching concentration of arsenic occurred in the LEP test and sample S1. According to SPLP analysis, Zn-Pb tailings will have a high potential for contamination of surface and underground water. The mobility of arsenic in the tailings was entirely influenced by pH, contact time, particle size and solid to liquid ratio. The leaching of arsenic enhanced in acidic and alkaline condition and the amount of arsenic leached in acidic condition was much higher than that leached in alkaline condition. In fact, pH-dependent leaching behavior of arsenic from Zn-Pb mine tailing was amphoteric. Actually pH-dependent leaching behavior of arsenic from Zn-Pb mine tailings was amphoteric. In sample S1, the highest amount of arsenic was released from particles with the size of 500-600 µm, while in the sample S2 particles with the size of 150-250µm released the highest amount of arsenic.

By considering the results of leaching protocols, and arsenic fractionation and also with regards to factors affecting the concentration of arsenic in leaching water, reducing the pore water and contact time, and controlling the pH and preventing the spreading of tailings in the environment are the most important factors in preventing and managing the spread of pollution in the environment.

The trend of increasing urban-rural population and the effect of household competition in meeting the basic needs of life, has caused the consumption of various resources, including Miandorood Mazandaran, to accelerate growth. In such a competitive space, agricultural land resources have changed so that the scope of these human needs for resources has led to land use change and, consequently, increased erosion and decrease renewable resources in the target study area. In this regard, the records of global research related to land use change, have indicated approximately the same results of quantitative and qualitative reduction of arable soils and increased erosion of soil resources. So, the purpose of this strategic research is a sign of the trend of land use change commonly on the shortcomings of process effectveness and cause the stability of cultivated soils, the development of mutual employment and increase the productivity of agricultural systems in the Miandorod region.

Miandorood region, due to the structure of natural civilization and special agricultural area, this research study was conducted in this strategic area. The total area of this area is 483 square kilometers, of which the usable lands area is 30,335 hectares. This research, which is a descriptive-analytical study with a field (survey) approach, and its statistical society is the internal and external system components of the region (strengths-weaknesses and opportunities-threats), and information on important soil components. Hence, the model of choice for this strategic goal is (WOTS-UP Analysis) and its subsets. For analysis and conclusion, respectively; Excel program, quantitative strategic planning matrix table and Wensim intelligent program were used for decision making. And to rank the internal and external components, experience and strategic thinking and consulting with experts in the region (in a survey), was used.

Due to the trend of land use change and the increase of smallholders in the region, the percentage of process effectiveness 33.97%, has shown very low. As a result, with low process effectiveness, the amount of affected components such as; Reduction in soil organic carbon content from 2.7 to 0.56, usable phosphorus content of regional soils from 56.3 to 6.4 mg / kg, absorbable potassium content from 301 to 117 mg / kg, the amount of absorbable sulfur from 29.1 to 20.5 mg / kg, increasing the pH of plain soils from 6.6 to 7.9, and increasing Gradual electrical conductivity EC, from 0.9 to 3.0, (dS / m) and finally to increase the negative physical density at a depth of 25-30 cm in the arable soils of the region over the past decade Has been.

The results of this study, which were accompanied by the identification of development components (strengths and opportunities), and deterrence components (weaknesses and threat points), showed that land use change in the study area on the physical and chemical properties of soils Agriculture in the Miandorood region has a negative effect. Conversely, by implementing a strategic management system (Scenario 3 selection), it is possible to be effective in arable soils sustainability, development of bilateral employment, decrease of unemployment rate, and effectiveness in arable land productivity.

The purpose of the design of energy dissipaters is to dissipate part of the kinetic energy of the inflowing flow in order to return safely the flow to the downstream channel or river and prevent scour below spillways, chutes and sluices. However, surveys show that despite the numerous researches, there is a lack of research on the comprehensive study of hydraulic performance of stepped spillway with curve axis under downstream transition channel slope variation. Therefore, in this study, several physical models of curve axis stepped spillway with converging training walls were made and the impact of downstream transition channel slope variation on the hydraulic characteristics of this type spillway was assessed.

This study was conducted with the aim of investigating the hydraulic performance of stepped spillway with curve axis under downstream transition channel slope variation. The experiments were carried out in a rectangular flume with length of 15 m, height of 1 m and width of 2 m. The experiments were performed at different discharge rates from 0.015 to 2.1 times the design discharge and the physical model was tested under four different transition channel slopes of m=0, m=1:33, m=1:30, and m=1:27.

The results of the experiments indicate that in the converging steeped spillway with downstream transition channel slope variation, by decreasing slope of transition channel, the discharge flood in the maximum head allowed will go up. Also, it is find that in the range of H/Hd = 0.7, the discharge coefficient in the stepped physical model for all transition slopes was less than the smooth USBR model and in the range of 0.7 < H/Hd < 1. 3 there was a good consistency with the USBR model. However, with increasing the total water head, due to the spillway submergence the discharge coefficient for all transition slopes showed a descending trend and the spillway efficiency decreased in compared with the standard USBR ogee spillway. Moreover, the results showed that the models with slope of 0 and 1:33 are two models which can pass the probable maximum flood discharge in the maximum allowable height successfully But, the model dimension of physical model with downstream transition Channel slope of m=1:33 is smaller than that of m=0.Therefore, model with slope of m=1:33 can be selected as the most efficient model.

General qualitative and quantitative results of the present study are summarized as the fallowing: 1- In the converging stepped spillway by increasing total upstream head, the discharge coefficient will go up for each of the transition Channel slope (m) and until the downstream flow is at either supercritical or critical stages, the discharge coefficient is independent of variation of transition Channel slope. By contrast, at the submergence stage for the spillway, the difference in the discharge coefficient can be due to tailwater submergence occurring in the spillway. 2- Energy dissipation over converging stepped spillway decreases with increasing the discharge ratio, but model with smaller amount of transition slope (m) lead to decline more energy dissipation in higher discharge. 3- The model with slope of m=1:33 can be selected as the best model due to it’s ability to pass the probable maximum flood in the Maximum allowable head.

a significant portion of water is wasted during the conveyance and distribution process due to seepage and operational losses. To deal with the limitation of water resources, it is necessary to provide methods for reducing losses from canals. Therefore, the current study aimed to represent a method for estimating the minimum seepage and operational losses in earthen canals in order to improve water efficiency in agricultural water distribution systems using ant colony optimization algorithm.

In this research, the innovation and aim are to optimize seepage and operational losses in water distribution system using the ant colony optimization and the results of the algorithm are used to manage water resources, especially in agricultural water distribution systems. To achieve this goal, initially, basic information was collected from the Moghan plain canal and for the purpose of hydraulic flow simulation in the canal a simplified mathematical integrator-delay model was used. Then, in order to minimize seepage losses, a formula extracted from research history was applied. In addition, the seepage formula was calibrated and validated based on the measured seepage amount at each segment over the 23 km of the canal. Also, to optimize the purpose of this study, two single objectives, which they were minimizing seepage and water shortage delivered to each offtake in the main canal distribution process, respectively, were defined and adjusted in ant colony optimization algorithm model. Then, by linking the hydraulic simulator model, the estimation seepage formula and the Ant colony optimization model, it was possible to optimize the mentioned objective functions.

According to the results, optimizing the first objective function, in order to minimize seepage losses caused the reduction of total seepage amount during the 23 Km of selected research area, from 0.199 Cubic meter per second (seepage in the present condition of the studied canal) to 0.187 Cubic meter per second. Therefore, the reduction in seepage losses for the first objective function was 6 percent. However, the application of the first objective function has led to an increase in the amount of operational losses from 39.91%, which is the amount of current operational losses in the canal, to 45.55%. In other words, the operational losses from the first objective function compared to the current operational losses, increased by 5.64%. Accordingly, the total reduction of losses in the first objective function compared to the current losses in the canal was 0.39 percent. By applying the second objective function, the results show a reduction in operational losses from 39.91% to 27.91%, which indicates a 12% reduction in operational losses compared to the current situation of this type of losses. Also, seepage losses have increased from 0.199 cubic meter per second to 0.2168 cubic meter per second, which indicates an 8.9% increase in seepage losses compared to the current situation. Overall, the total losses reduction in the second objective function compared to the current situation is equal to 3.1 percent.

single objective functions of seepage and operational losses reduction results showed that optimization with the purpose of reducing seepage losses did not lead to a significant reduction in total losses in irrigation canals. On the other hand, in order to reduce operational losses, Ant colony optimization algorithm model by choosing optimum water depths could reduce the amount of operational losses to a considerable amount. According to the results, it can be generally acknowledged that modernization, renovation and rehabilitation projects of irrigation networks with the target of reducing losses and improving water use efficiency, if more focused on improving the operating process, more reduction of losses would result in agricultural water distribution system.

Interrill erosion is one of the most important types of erosion, in which various factors such as soil, runoff, and rainfall influence its process and rate. Few studies have been conducted using artificial neural networks (ANNs) to determine the factors affecting interrill erosion in Iran. Furthermore, no research has been carried out in Jiroft on this matter. Therefore, this study was conducted to evaluate the factors influencing interrill erosion using ANNs in four different regions around Jiroft in Kerman province.

For this research, 100 soil samples were collected from two pastures and two forest land uses at depths of 0-10 cm using a random sampling method. Some physical and chemical properties were determined. The amount of interrill erosion was measured using Kamphorst rainfall simulator. Modelling was performed using feedforward multi-layer perceptrons (MLP) with the error backpropagation and Levenberg-Marquardt training algorithm along with 11 soil characteristics in two scenarios. Hill sensitivity analysis was used to investigate the significance of the input variables.

The results revealed that in the study areas, clay, silt, sand (0.05-2 mm), geometric standard deviation (σg), and geometric mean diameter (dg) of particles play a crucial role in interrill erosion while cementing agents such as organic matter (OM) and calcium carbonate equivalent (CCE) were less important. According to the results, the protected forest with high contents of sand as well as low amounts of silt, organic matter and calcium carbonate equivalent showed the lowest erosion rate (2.63 tons /ha). The R2 values for the test datasets in the scenario 1 (with input variables including soil acidity (pH), electrical conductivity (EC), bulk density (BD), organic matter, calcium carbonate equivalent, particulate organic matter (POM), sand, silt, and clay) were 0.81. Whereas the R2 values in the scenario 2 (with input variables such as pH, EC, BD, OM, CCE, POM, the dg and σg) were 0.72. In addition, root-mean-square error (RMSE) for the testing dataset in scenarios 1 and 2 were 0.77 and 1.14, respectively.

Both scenarios had almost the same accuracy in interrill erosion modeling. However, according to the values of R2 and RMSE of the data in scenario 1, this scenario showed better accuracy than scenario 2. In general, the results showed that the ANNs can estimate the amount of interrill erosion using appropriate input variables with high accuracy, and therefore it might be considered as a useful technique to estimate interrill erosion.

One of the practical strategies for managing water resources is to estimate the plant's water needs and determine the amount of water used in the various stages of crop production. In order to calculate the amount of water consumed by agricultural products in the growth stages, the virtual water index and water footprint are used. Water footprint in a product is defined as the volume of fresh water used in it's production. Water footprint is defined as an indicator for the allocation of fresh water resources that provides valuable insights into the environmental impact of producing a product. Water footprint index shows actual consumption of water in three components: blue, green and gray, which is now considered in the direction of modern management of water resources with an integrated approach. In order to properly assess water consumption in the agricultural sector, it is necessary to study the water footprint index in different climates.

To conduct the research, meteorological data were first obtained from the Meteorological Organization.Then the water needs of sugar beet, potato, forage corn and tomato plants in Hamedan, Ahvaz, Shahrekord, Mashhad and Isfahan climates were calculated from the CropWat software. The yield of the crop and the amount of nitrogen fertilizer used were obtained from the agricultural jihad of each province. crop yield and the parameters required in the calculations were calculated and aggregated through agricultural statistics Then, the average volume of water consumption, virtual water, water footprint and water use efficiency of these products were calculated for the statistical period of 2011-2017. Chapagin et al. (2006) Method was used to calculate water footprint.

In the present study, water consumption for agricultural products was investigated. The results showed that among the studied products, the potato plant with 2945.4 m3/ton in Ahvaz city with hot and humid climate has the highest water footprint and sugar beet with 906.1 m3/ton in climate cold and dry of Mashhad has the least water footprint. The highest amount of virtual water used for the studied plants is potato (0.84 m3/kg), tomato (0.51 m3/kg), sugar beet (0.46 m3/kg) and forage corn (0.39 m3/kg) was respectively to the climate of Ahwaz, Shahrekord, Ahwaz and Isfahan. The lowest amount of water consumption efficiency (1.2 kg/m3) also belonged to the potato in Ahvaz climate. The lowest virtual water and the highest water consumption efficiency for the studied plants were obtained in Hamedan climate.

In the present study, water consumption for agricultural products was investigated. The results showed that the volume of water consumed in the studied products varies in different climates. According to the obtained results, it can be said that the climate of Hamedan due to the low amount of virtual water (0.29, 0.3, 0.19 and 0.14 m3/ kg) and high water consumption efficiency ( 3.43, 3.3, 5.19 and 7.46 kg/m3) for potatoes, tomatoes, sugar beets and fodder corn, respectively, compared to other climates studied for cultivation of all four the product is more suitable. Hence, according to recent droughs and water shortage, available water resources should be used accurately and decision must be made for cultivating the products with less water requirement and better performance.

Biomass plays an important role in providing energy and the global carbon cycle and monitoring the biomass is one of the most important issues in the agricultural sector. Using remote sensing techniques is an effective tool for estimating biomass. This reduces field studies and saves time and money. Today, management practices can be improved using remote sensing technology and vegetation indices. The suitability of the weather in Golestan Province for producing most agricultural products has made the province highly diversified in terms of crop and biomass production. For this purpose, in this study, satellite images of Landsat 8 and Sentinel 2 were used to estimate the residue biomass of crops in the watershed of the southwest of Golestan province (Mohammad Abad, Qaresoo, Zaringol, and Gharnabad).

For this, field surveys were carried out to sample the fields at different stages of plant growth, in the winter and spring of 2016. The number of samples for wheat, barley, canola, rice, and soybean was 90, 70, 65, 67, and 80, respectively. The biomass data were also measured from field survey using four quadrates (0. 25m2) and their moisture content was determined by weighting. The Landsat 8 and Sentinel 2 images were downloaded from the USGS site in the early and middle of the growing season for mapping sattelitesatellite-based vegetation indices including, NDVI, SAVI, RVI, DVI, and RDVI. The relation between the indices and obtained biomass was evaluated using regression analysis to produce biomass maps for five crop residues.

The results showed that the NDVI index is the best indicator to estimate the wheat, barley, and rapeseed residue biomass, in April, with a determination coefficient of 0.61, 0.65, and 0.65, respectively, according to the vegetative growth peak, and for the soybean crop in September, according to the peak of vegetative growth with a determination coefficient of 0.65, and the RVI index is the best indicator for estimating rice residue biomass in August in line with peak vegetative growth in the study area. The total amount of wheat, barley, canola, rice, and soybeans residues in the study area was estimated as 751657, 175637, 14979, 42628, and 93712 tons, respectively. The results of this study can be applied to managers and decision-makers of the agricultural sector in the province by identifying the potential for agricultural production and the amount of their residues.

The results of this study showed that the residue biomass of different products can be estimated by using the vegetation indices extracted from satellite images with acceptable accuracy in the study area. In this research, the overlaying for determining the cultivation area of wheat and soybean products was 97.74% and 97.6%, respectively. The precision of this method for peak vegetation periods was higher than the early stages of plant growth. Also, instead of a vegetation index, several vegetation indices were used and the NDVI and RVI index was the best indicator for estimating the residue biomass of different products.

Preservation of soil and prevention of occurrence and intensification of erosion are the most important functions of natural ecosystems. This issue is especially important in steep and mountainous areas. Soil conservation function, like many other ecosystem services, lacks a market to determine value. Natural ecosystems are one of the important economic resource for many developing countries that contribute to the development of regions and communities by producing goods and services. This study was conducted in 2019 with the aim of investigating the role of natural ecosystem in Kechik area in controlling soil erosion and determining the economic value of soil protection based on soil fertility maintenance function.

In order to estimate soil erosion quantitatively , the RUSLE model, which inputs include rain erosion factor, soil erodibility factor, length and degree of slope factor, vegetation factor and protective operations factor, was used in GIS environment. To calculate the economic value of soil fertility maintenance function, soil retention and soil nutrient content including nitrogen, phosphorus and potassium in the area were estimated and its economic value was calculated using the alternative cost approach.

The results of soil erosion by RUSLE method showed that the range of soil erosion in the region varied between 0 to 239.2 tons per hectare per year and its average was estimated at 7.94 tons per hectare per year. The value of the main elements preserved in the soil of the whole basin was equal to 9.21 billion Rials per year and the value of each hectare of the region's ecosystem was estimated at 2.55 million Rials per year. Also, the analysis of erosion data in IDRISI Selva software showed that the factor of length and degree of slope with a correlation coefficient of 93% and a coefficient of determination (R2) of 0.87 had the greatest effect on estimating annual soil erosion.

The result of this study states that the value obtained per hectare of forest is 3.39, rangeland 2.84 and dry land 2.16 million rials per year, which shows the more value of rangeland ecosystem than dry lands. Due to the positive effects of vegetation, the need for special attention to rangeland and forest vegetation to reduce soil erosion is felt and it is recommended that biological and soil protection programs to reduce soil erosion damage in areas with high erosion sensitivity in the region. 

Nowadays, study about the reclamation of abandoned skid trails is necessary due to the their frequency in forestry units of north of Iran especially in so-called respiration period. These skid trails turn to be bare after the primary transportation (especially within first transportation years) where resulted in erosion and damage to soil forest. The aim of this study was to determine the best conservation treatments to deal with skid trails’ water erosion.

Firstly, a skid trail with a minimum length of 500 meters was selected in Bahramnia’s forestry plan. The longitudinal slope was divided into slope classes of 20-40% and >40%. In each class a segment with a length of 126 meters was determined and treatments of ditch & embankment, ditch & slash and ditch & stone each of in length of 14 meters with 5 meters interval were implemented. A rubber bar was installed at the end of each segment to convert sediment and runoff in to collectors. Sampling was done after each rainfall during 4 months (autumn and winter 2019 and 2020). The Intensity – Duration rainfall information has been determined using Rain gauge in the location, then dry weight of sediment samples has been measured in laboratory.

Findings indicated that in both slope classes of 20-40% and >40% amount of runoff, sediment concentration and soil loss was significantly increased along with increasing intensity and duration of rainfall. In slope class of 20-40%, treatment of ditch and slash has more successfully done than other treatment in sedimentation and soil loss control than other treatments. In slope class of >40%, there wasn’t significant difference between the efficiency of treatments in sediment and soil loss control. Whereas, generally, treatments of ditch and slash as well as ditch and stone were more successful to control soil erosion than ditch & embankment treatment. In both slope classes, the rainfall intensity of 0.11 mm h-1 (2.64 mm in 24 h) was the threshold of water erosion of soil on skid trails. likewise, the interaction effect of slope and treatment type were not significant on runoff volume’s variables as well as sediment concentration and soil loss. Findings indicated that the ditch & slash treatment, in slope class of 20-40%, were the best in terms of sedimentation and soil loss control which could mitigate soil waste by 64%. In unallowable slope >40% all treatment could mitigate soil erosion by 47% which indicates the low efficiency of conservational treatments in unallowable slope tracks.

This research showed using of ditch & slash treatment cab be reduce soil erosion in skid trails, so consider to conservation the soil of skid tails this achievement has the applicability and generalizability

As the water level rises in the main channel and crosses the floodplain boundary, because of different roughness coefficient and velocity between the main channel and the floodplain, the flow in the main channel move more acceleration than the flow in the floodplains and there will be strong momentum exchange between the flows in the intersection of the main channel and the floodplain. This exchange generates vortices in the intersection of the main channel and the floodplain. Momentum exchange reduces the high velocity flow energy of the main channel and adds to the low velocity flow energy of the floodplain. Momentum exchange also reduces the discharge of the main channel, increasing the discharge of the floodplain and decreasing river transmission capacity. At intersection of the main channel and the floodplain, due to the shear layer, the potential for instability and scour are high. Understanding parameters of the bed shear stress and momentum in the compound channel especially in the intersection of the main channel and floodplain make more accurate calculations related to the protection of the riverbed and determine the protection methods. In this study, the parameters of bed shear stress and flow momentum are quantified in conditions where the compound channel, bridge abutment length in the floodplain and the type of guide-wall simultaneously affect the flow pattern.

In the present study, three-dimensional numerical analysis is performed to investigate the bed shear stress and momentum exchanging between the floodplain and the main channel in a symmetric trapezoidal compound channel by using FLOW-3D. After validating of the mentioned model, the bed shear stress and momentum exchange between the floodplain and the main channel for different bridge abutment lengths in cases with and without elliptical guide-wall have been investigated.

The bed shear stress in the case with the elliptical guide wall has increased in the main channel and decreased in the floodplain compared to without guide-wall. Shear stress in the main channel has increased to 25.5% and decreased to 36.63% in the floodplain. The momentum exchange in the elliptical guide-wall case has increased up to 78.5% compared to without guide-wall case.

One of the remarkable results is that the bed shear stress in the floodplain decreases in the case of abutment with the elliptical guide-wall which improves the conditions at the bridge abutment. But increase the shear stress in the main channel causes the conditions of the abutment located in the main channel become more critical. Also, in the case of abutment with the elliptical guide-wall, the momentum exchange between the floodplain and the main channel increases compared to in the case of abutment without the guide wall, which increases the shear stress and creates vortices at intersection of the floodplain and the main channel.

The performance of drip tape irrigation system depends on the choice of irrigation tape and its hydraulics. Numerous factors affect the discharge of the drip tape irrigation, the most important of which are the changes in pressure and temperature of the irrigation water. Changes in field topography, unsuitable design of the irrigation system, as well as the use of tapes with long length, cause a pressure difference between the drippers of the irrigation tapes. Also, the water temperature of the laterals pipes exposed to direct sunlight increases significantly. In some studies, the effect of increasing or decreasing water temperature on the discharge of tapes of drip irrigation has been studied, but in this study, the effect of water temperature in different operating pressures on the two types of drip irrigation tapes of seaming and plaque equipped has been studied and was attempted to present the results as applied equations and compared.

In this study, 10 types of drip irrigation tapes were selected from two types of seaming and plaque equipped with the codes ID, I, T1, T2, T3, T4, B, S, P, and YD. In each tape were selected 25 test sample, randomly, which every test sample included at least 3 dripper units. The length of each test sample was in the range of 100 to 120 cm. In order to investigate the simultaneous effect of pressure and irrigation water temperature on the discharge of irrigation tapes, a physical model was designed and built in the Research Laboratory of Water Science and Engineering, University of Kurdistan in 2018.4 different irrigation water temperatures, including 13, 23, 33, and 43 centigrade, were applied to the irrigation tapes at operating pressures of 1 meter to 1.2 times the maximum pressure. All tests were performed according to ISO 9261 and IRISI 6775. General Equations of discharge - Pressure and normalized discharge - Temperature, all tapes were obtained. In order to investigate the effect of temperature on the discharge of irrigation tapes, an experiment was conducted in a completely randomized design with 4 treatments and 25 replications. Experimental treatments included 4 different temperatures (13, 23, 33 and 43 ° C). Data were analyzed by SAS statistical software and the mean of treatments was compared using LSD test.

At the standard temperature of 23 ° C, the power of the discharge -pressure equation of 6 tapes was less than 0.5, 2 tapes between 0.5 to 0.6 and 2 tapes between 0.6 to 0.8. Therefore, all tapes were pressure non - compensating and their flexibility in terms of pressure changes was desirable and acceptable. At other temperatures studied, the power of discharge -pressure equation changed, which was less than 0.8 in all cases. The effect of temperature on the discharge of all irrigation tapes was significant (p < 0.05) and often increased with increasing temperature. The power of linear equation of normalized discharge -temperature of the tapes ranged from 0.02 to 0.66 and the width of their origin was between 53 and 121. The sensitivity of plaque equipped drip irrigation tapes to temperature changes was lower than seaming drip irrigation tapes and had lower discharge changes.

All of the drip irrigation tapes studied are of good quality in terms of sensitivity to pressure changes. Also, due to the fact that increasing the temperature of irrigation water increases the discharge of the tapes, it is recommended to use the plaque equipped tapes and normalized discharge equations proposed by the present study in areas where the changes in irrigation water temperature are between 13 to 43 ° C.

Aggregate stability is one the most important soil physical properties, which is estimated using easily accessible parameters. Remote sensing (RS) is a useful technique that has meaningful capabilities to monitor soil and water resources. Moreover, soil aggregate stability is an index of soil erodibility which can be used as a useful tool to manage and control the soil against destructive factors. Therefore, it is really important to model the effective factors on soil aggregate stability. The present study conducted because of importance of soil physical properties and land use effects on crop cover status and its modeling.

Methods and material:

In this research, the relation between vegetation indices and mean weight diameter (MWD) as an index of soil aggregate stability was investigated in forest and rangeland land uses. In order to evaluate the relation between land uses and vegetation indices in Dehdez watershed located in the southeast of Khuzestan Province, Iran country; the images of Landsat 8 with pass number 164 and the row of 38 provided from the Earth Explorer website with GeoTIFF format. The radiometric correction performed using ENVI 5.1 software. The evaluated vegetation indices including, RVI, VIN, TVI, YVI, SBL, DVI, NDGI, RI, NDI, NDVI, PVI, SAVI, TSAVI, ARVI ,and MSAVI. The Pearson correlation between the above vegetation indices and organic carbon, sand, silt, clay ,and mean weight diameter evaluated for 50 soil samples collected from two land uses. In this study, two type of land use, including forest and rangeland assessed. Pearson ´s correlation analysis and multivariate adaptive regression spline (MARS) applied to investigate the relation between vegetation indices and MWD.

The results illustrated that in the rangeland, MWD had a significant correlation with VIN, TVI, MSAVI, RVI, SAVI, TSAVI, NDVI, and PVI indices at the level of 0.01. However, in the forest, there was no significant relation between the studied indices. Also, MARS modeling showed that the fitted model based on vegetation indices in rangeland (Adjusted R-Sq. = 0.55, RMSE = 0.16) has much higher predictive power and accuracy than the fitted model for forest (Adjusted R-Sq. = 0.35, RMSE= 0.36).

In general, the results of this study revealed that the controlling factors of soil aggregate stability are different for rangeland and forest land uses. This has led to differences in correlation coefficient between vegetation indices and MWD, and consequently modeling results. Also, remote sensing can provide convenient technology for providing the sustainable management purposes of soil and water resources. To cover the sustainability purposes in the watershed scale, it is necessary to utilize different technologies such as remote sensing. Indeed application of various techniques helps to simplify the processes and finally preserve the soil and water resources against degradable factors.

As the occurrence of water stress in plants and agricultural crops is affected by the drought, global warming, population growth and the urban heat islands, the lack of traffic and human activities in natural environment during the Covid-19 virus pandemic can be considered as a factor reducing plants’ water stress. As water stress is typically described by physiological plant responses to water deficiency due to the lack of soil moisture or high demand for evaporation in the atmosphere, the use of remote sensing data as a rapid and economical tool in monitoring climate change during Covid-19 virus pandemic has been considered.

In this study, the efects of applying the limitations according to the Covid-19 virus is investigated on the plants water stress status in the spring of 2020 compared to three years ago. For this purpose, visible, near-infrared and short wavelenght infrared spectral bands of Sentinel-2 multispectral satellite images taken from a region in the east of Mazandaran province and in the 2017 to 2020 time interval were used. In the first step of the proposed method in this paper, by combining the normalized difference vegetation indices in near-infrared and short-wavelength infrared ranges, a vegetation map of the study area was produced. Then, three water stress indices of SRWI, NDWI and SIWSI in the vegetation map were calculated and the percentage of vegetation pixels that are under water stress was estimated in the 2017 to 2020 time interval.

The obtained results of monitoring the plants water stress status in the study area in this research indicate the fact that despite a 35% decrease in annual rainfall in the rainy year of 2019-2020 compared to the same period in the last rainy year, the percentage of pixels under water stress has decreased by about 2%. In general, the area under water stress shows a decrease of one percent compared to the total vegetation area.

The results of the analysis showed that from 2017 to 2019, the annual rainfall was an effective factor in increasing or decreasing the percentage of pixels under water stress, especially in the plant leaf water content index (NDWI). An important point in analyzing the results of 2020 is that despite a -35% reduction in annual rainfall, the results of all three spectral indicators show a decrease in water stress in the region, which is one of the main effects of limitations and restricting the entry of vehicles and passengers to Mazandaran province and as a result the temperature has decreased.

The problem of water scarcity is one of the most important agricultural problems in Iran, therefore proper and timely use of water resources is essential. One of the strategies for optimal use of water in agriculture is irrigation planning of agricultural products. Irrigation planning means specifying the irrigation time and amount of water needed at each irrigation time during the plant growth period. In this study, in order to determine the irrigation time, the color change index of pepper leaf due to the decrease in soil moisture was used. So far, some studies have been carried out to determine some of the agronomic parameters of the fruit and leaf color changes using digital image processing, but no evidence is available for the relationship between leaf color and soil moisture subject to this thesis. Therefore, it can be assumed that this research is the first research in this field.

In order to investigate the effect of water stress on leaf color of chili pepper, plastic pots and dimaz chili peppers were used. The measured parameters included plant leaf color and soil moisture. Leaves were photographed daily and finally leaf color analysis was performed using Photoshop and BAL color scheme. The experiment was conducted in a completely randomized design with five treatments including 10, 30 and 50% water stress, complete irrigation and no irrigation treatment in four replications for irrigation planning. (No irrigation treatment was considered as control treatment). Water stress was applied to the treatments for 52 days during plant growth period from transplanting (three weeks after transplanting) until harvest.

The LAB color system with a correlation coefficient higher than 94% can be used as an efficient system for investigating leaf color changes and determining irrigation time. One of the advantages of this method is its high computational volume and high accuracy of results. Increasing the accuracy of this method and examining its feasibility requires further research, and its simplicity and low cost can be a good justification for continuing its use. Certainly, by developing research on the proposed system, including the use of laboratory equipment and more accurate numerical methods, acceptable results can be obtained in estimating the exact irrigation time. On the other hand, three tree models QUEST, C5 and CHAID, which are decision tree algorithms, were used to predict soil moisture classes. The results showed that the C5 tree model had higher accuracy than other models and the accuracy of prediction of soil moisture classes by this model for the lab system was 86%.

The findings showed that as a result of soil moisture changes, there is a change in the natural reflection of the leaf color of the plant, and the lower the soil moisture, the darker the leaf color becomes and these changes affect the elements of the lab color system.