فهرست مطالب محمود عرب خدری

The degradation of soil structure and reduced water infiltration into the soil are indicators of soil degradation, which lead to decreased stability and production quality, as well as environmental problems. Soil conservation methods are widely used to curb soil degradation processes and improve soil structure and permeability. The effectiveness of these methods in enhancing these indicators and controlling soil degradation requires further study and evaluation. This research aims to investigate the stability of soil structure and soil infiltration rate affected by various soil management and conservation operations, and to compare them in the Razin Watershed area of Kermanshah Province.

For this purpose, eight common reclamation and conservation operations in the study area were selected and evaluated. These operations include pit-seeding and seeding, rangeland audit plan - conversion of dryfarming to rangeland, rangeland audit plan - conversion of dryfarming to forage cultivation, almond tree planting alongside digging holes, land leveling, seedling planting, conversion of dryfarming to rangeland, forage cultivation and orchard, and forest area. For evaluation, random systematic sampling points were selected within the area of each operation and their corresponding control area for study and sampling. After digging profiles and sampling the soil, the laboratory measured and calculated soil aggregate stability indices, including Mean Weight Diameter (MWD), Geometric Mean Diameter (GMD), and the proportion of stable aggregates larger than 0.25 mm (WSA>0.25). The final infiltration rate was also measured in the operation areas and their controls using a disc infiltrometer. Finally, a statistical comparison of the mean values of MWD, GMD, WSA>0.25, and final infiltration rate in soil conservation operations and their control areas was performed using the T-test for independent samples and the Duncan test for comparing the means of these indices in various operations using SPSS software.

The evaluation results showed that the lowest MWD index was related to land leveling and sapling planting at 0.15 and 0.35 mm, respectively, while the highest values at 1.9, 1.8, and 1.6 mm were related to 20-year-old almond planting, 10-year-old almond planting, and forest areas, respectively. Additionally, the highest WSA>0.25 index values were found in fodder cultivation, orchard establishment, and 10-year-old almond planting operations, indicating the formation of large and stable aggregates due to conservation operations. Among the eight operations studied, the 20-year-old almond planting operation showed the greatest improvements in MWD and WSA>0.25 indices. The results for the final infiltration rate indicated that soil conservation operations, particularly converting low-yield rain-fed lands to sapling planting and changing rangeland use to 10-year-old almond planting, led to the highest increases in final infiltration rate, at 21.8% and 16%, respectively, compared to the control.

Overall, soil conservation operations increased the relative share of larger soil aggregates. However, the soil infiltration rate index showed conflicting results, as factors other than the evaluated conservation operations also influenced water infiltration into the soil, necessitating further studies. Consequently, examining the role of management, especially land use management, is essential for sustainable soil resource utilization.

Implementation of watershed management measures in Iran to reduce the damage caused by the misuse of natural resources has begun many years ago and is still ongoing. Evaluating the performance of previous remedial work is essential for better planning of future watershed management projects. In this regard, due to the monitoring of soil loss, runoff and sedimentation at slope and watershed scales, a suitable platform has been provided to assess the effects of watershed management measures.

The Kakhk paired watershed with an area of 217 ha is located at a distance of 300 km from Mashhad City and 35 km southwest of Gonabad City.The Kakhk paired watershed consists of two sub-watershds, the control and the treatment. A series of biological and structural watershed management measures have been implemented in the treatment sub-watershed. While the control sub-watershed is exploited according to the custom of the region. In this research, the impact of different watershed management measures on the soil loss, sediment yield and hydrology in the Kakhk paired watershed were evaluated. For this purpose, the recorded data of suspended sediment and discharge at the watershed scale, as well as the data of soil loss (by standard plots and erosion pins) and runoff (standard plots) were analyzed at the hillslope scale.

The results at plot scale showed that the average annual soil loss of the two treatment and control sub-watersheds is 0.05 and 0.27 ton.ha-1.y-1, respectively. These results indicate that the soil loss in the control sub-watershed is 536% higher than the treatment sub-watershed. The amount of runoff yield in the control sub-watershed was calculated to be 138% more than the treatment sub-watershed. At watershed scale, the results showed that the total amount of suspended sediment output from the control and treatment watersheds is 379 and 85 tons, respectively, which indicates the average specific sediment of 0.4 and 0.1 ton.ha-1 in the control and treatment watersheds, respectively. The volume of runoff in the control sub-watershed is 1.3 times more than treatment sub-watershed. On the other hand, despite the difference between the treatment and control sub-watersheds in soil loss, run-off production and sediment yield, the role of maximum events in soil erosion and runoff production in both sub-watersheds is very significant. So that one to three erosive events in both studied sub-watershes are responsible for more than 80% of the soil loss in the slopes and the production of runoff and sediment yield of watersheds.

The results showed that a total of 136,000 m3 of runoff storage and 294 ton of suspended sediment control were achieved as a result of watershed operations in the treatment sub-watershed. Therefore, it can be stated that the watershed management measures carried out in the treatment sub-watershed on the one hand have reduced soil erosion and runoff production on the slopes compared to the control sub-watershed. This action has been done through increasing the vegetation, increasing the roughness of the land surface, reducing the carrying capacity of the flow and settling the materials being transported. Further, the flow from the slopes enters the waterway and is kept by watershed  management structures, and as a result, the sediment yield and volume of runoff in the treatment sub-watershed is less than the control sub-watershed.

Drylands have always been an important source of soil loss and sediment yield, so that suitable conditioner application can reduce soil erosion. This study conducted to determine the suitable rate of vinasse treatment in reducing runoff and soil loss on the loess soil of drylands in Kalaleh city, east of Golestan Province and in plots with 10 x 30 x 30 cm dimensions were done. This experiment had four treatments of vinas (0, 50, 100, and 150 ml) once at an average intensity of 70 mm per hour on three different slopes (20, 12, and 8 %) and once at three rainfall intensities (50, 70, and 90 mm/h) on a medium slope (12%) each with three repetitions for 30 minutes. Vinasse treatments were also sprayed evenly on the soil surface and given about 24 hours to balance with soil particles. Runoff was collected and volumetric measurement was done after precipitation. The remaining samples were dried. The soil losses was determined. The ANOVA results showed that differences between slope, rainfall and vinasse treatments and their effect were significant. However the treatments containing 50, and 150 ml vinasse had higher performance than the control in the component of runoff volume and soil loss. Of course, 100 ml vinasse treatment caused to reduce runoff volume and soil losses components. The effect of slope, unlike the intensity of precipitation, does not follow a specific trend, but the intensity of precipitation has a direct effect on the component of runoff volume and soil losses. In this experiment condition, the application of 100 ml vinasse could be effective in runoff volume and soil loss reduction.

Extended AbstractIntroductionAccelerated soil erosion and severe sediment production disrupt the natural balance in watersheds and have off-site impacts on river channels and downstream reservoirs. There are different estimates of soil erosion and sediment yield in Iran. However, what the researchers agree on is that it is more than tolerable erosion. Rangelands cover more than half of Iran, and poorly covered lands play a large role in flood and sediment production. Therefore, the study of hydrology and soil erosion is necessary for sustainable use of pastures. The prerequisite for these studies is long-term monitoring of sediment, runoff, vegetation, soil, etc. A careful review of previous studies on rangeland hydrology shows that most studies have focused on the effect of grazing management at the plot scale or have used simulation approaches and experimental models, as well as in a short period of time. Therefore, it is very necessary to conduct scientific research using long-term monitoring data in experimental watersheds. In this regard, the present study was proposed with the aim of evaluating the sediment yield of small watersheds in pastures with grazing exclusion vs. overgrazing. The results of this research can provide useful information to researchers, promoters, planners, and ranchers.Materials and methodsSanganeh Soil Conservation Research Station (SSCRS) with an area of 30 ha was established about 25 years ago in Kalat County (Razavi Khorasan Province, Iran). In addition to measuring erosion in plots and monitoring vegetation, by building several ponds at the outlets of six small watersheds (SWs), their runoff and sediment yields have also been recorded since 2006. The present study was conducted with the aim of evaluating the erosion and sediment production of these SWs (1200 to 17000 m2). For this purpose, the runoff and sediment of 69 events were collected at the outlets of six SWs. Also, the time series of NDVIs were calculated for SSCRS, adjacent rural and nomadic (outside the village) rangelands on a seasonal scale. To determine the time series of NDVIs, all satellite images of the study area were downloaded and after pre-processing and corrections, the images were processed. Then, the soil erosion amounts of SWs were estimated in terms of the sediment delivery ratio of the study area (Noor, 2020) based on the average sediment yields (according to their long period of 15 years). In the next step, the amounts of soil erosion obtained were compared to the amounts of tolerable soil erosion for arid climate rangelands proposed by Skouti Oskouei and Arabkhedri (2018). Finally, the soil erosion of two similar watersheds, one in the overgrazing area (E6) and the other in the grazing exclusion area (E4), were compared.Results and DiscussionThe results showed that NDVI is influenced by livestock grazing intensity. The highest value of this index was observed in the grazing exclusion area (E1 to E5 SWs), then in the Sanganeh village rangeland (E6 SW), and the lowest value was observed in the nomadic rangelands. In terms of time scale, the biggest difference in NDVIs between overgrazing and grazing exclusion areas was observed in spring. The results of the investigation of sediment production indicated an inverse and non-linear relationship between the specific sediment yield and the area of SWs. This study showed that the amount of soil erosions in E2, E3 and E6 SWs are more than tolerable erosions which suggests the need for more conservation measures. Finally, the comparison of two similar SWs (E4 vs. E6) indicate a significant reduction in annual sediment yield (582%) due to grazing exclusion in the area. Also, the results showed that the sediment productions of E6 SW in the spring and autumn seasons are significantly higher than E4 at 1% and 5% levels, respectively. Furthermore, it is remarkably (but non significant) higher than than the E4 SW in the winter season.ConclusionGrazing exclusion in SSCRS rangeland led to a significant reduction in erosion and sediment production compared to overgrazing condition outside the station. However, in some SWs, the erosion amounts were still more than the tolerable values, which indicates the difficulty of restoration of destroyed rangelands on steep slopes with sensitive formations in arid climate. Implementation of management measures including scientific grazing (especially in spring) is necessary to reducing damage caused by floods and sediments.

Considering the large extent of the country's rangelands, studying their hydrology and soil erosion is important for choosing management scenarios. Rangeland exclosure is one of the watershed management methods that is used to improve vegetation and also control soil loss. Rangeland's exclosure of the Sanganeh Soil Conservation Research Site (SSCRS) started about 25 years ago, which has led to the improvement of vegetation in most of the slopes compared to the area under livestock grazing. However, vegetation has not been established on some slopes of the exclosure region. This research site has provided suitable conditions for soil erosion studies and assessment of rangeland management measures at the scale of the plot and small watersheds by having erosion plots of different lengths located on slopes with and without vegetation. In this regard, the present research is planned with the aim of determining the effect of rangelands exclosure 1) on soil loss in plots with and without vegetation, and 2) with different lengths.

In this research, a comparison of soil erosion was made in th e area under free livestock grazing (E6) and exclosure watershed with similar conditions (E4). In this regard, six erosion plots with lengths of 5, 10, and 15 m (with areas of 10, 20, and 30 m2, respectively) in two vegetation situations (with and without vegetation cover) were selected in each study watershed. After collecting the soil erosion data under 24 natural rainfalls, the effect of plot length and vegetation situation were compared by paired t-test.

The results of data analysis indicated that the maximum intensity of 30 minutes is in the range of 2.4 to 32 mm per hour with an average of 0.9 mm per hour. It can be clearly understood from the distribution of precipitation data based on the seasons of the year that the average rainfall of three seasons, spring, autumn and winter, is almost equal. However, the average rain erosion index (EI30) in spring is 3.02 and 4.40 times higher th an the corresponding values in autumn and winter, respectively. The reason for this is the occurrence of heavy rains in spring. The comparison of two fields with cover and without cover in the areas of exclosure and under livestock grazing in terms of soil erosion showed that in both areas (with cover and with out cover) the amount of soil erosion in the plots under grazing is significantly higher than in exclosure area. So, in similar rainfalls in the region, the soil erosion in the watershed under grazing at different slopes is from a minimum of 282% to a maximum of 550% more than the exclosure watershed. By increasing the length of the plot, soil erosion per unit area decreases. The decreasing trend of specific sediment with the increase in the length of the flow path is mainly due to the decrease in the amount of specific runoff and as a result, it is not possible to move the eroded materials in the plot. In other words, due to the dominance of the surface erosion process and the lack of development of rill erosion in the investigated plots, the re-infiltration of runoff and the deposition of transported materials are the most important reasons for the decreasing relationship between the increase in the length of the plot and erosion per unit area. In both slopes (with and without vegetation), the effect of waterlogging on soil erosion has increased with the increase of the area of the plot. In other words, grazing pasture in 10 m2 plots has reduced soil erosion by 287.7 and 324.6 percent, respectively, in slopes without and with vegetation. Meanwhile, in the plots of 30 m2, the reduction of soil erosion was observed by 472.4 and 613.7 percent. On the other hand, in the slops with vegetation, grazing has a greater effect on reducing soil erosion. In this context, it can be stated that surface erosion and sheet currents are the dominant phenomena of erosion and sediment transport in the studied slopes, therefore, if the roughness and permeability of the soil increases due to the operation of pasture exclosure, it can be expected that the runoff flow in longer routes (from the slope 10 m2 to 20 and 30 m2) to increase the amount of material deposition. In this case, exclosure in the domain with a longer length has a greater effect on reducing soil erosion.

SSCRS with erosion plots in different conditions (length, vegetation conditions and pasture management) is a suitable place for scientific research in the field of pasture hydrology. In this research, the effect of plot length and vegetation status on erosion was evaluated using soil erosion data measured in two areas of exclosure and under livestock grazing. The results of this research showed that in both ranges (with and without vegetation), the amount of soil erosion in the plots under grazing is at a significant level of 1% higher than in exclosure region. So, in similar rains in the region, soil erosion in the watershed under grazing in different lengths is at least 282% more than the flooded watershed. Also, the results indicated that soil erosion per unit area decreases with increasing plot length. The decreasing trend of specific sediment with the increase in the length of the flow path is mainly due to the decrease in the amount of specific runoff and as a result, it is not possible to move the eroded materials in the plot. Finally, the results showed that in both fields with and without vegetation, the effect of waterlogging on soil erosion increased with increasing plot length. On the other hand, in the range with vegetation (compared to the range without cover), grazing has a greater effect on reducing soil erosion.The results of the surveys conducted at the SSCRS confirm the sensitivity and fragility of the dry grassland ecosystem in this region on behalf of the country's dry grasslands. In such a way that after a long period of flooding in the region, some slopes still lack vegetation. Therefore, the destruction of vegetation in some areas, especially steep slopes and sensitive formations, may not be easily returned to the original state, and great care must be taken in their management. Because these domains have high erosion and runoff production. Due to the existence of recorded information related to the ideal situation of the region (exclosure region), it is possible to create different grazing systems and evaluate its effects. Finally, it is possible to compare the information obtained from exclosure region, managed grazing and open grazing.

The present review has been compiled to monitor management practices and hydrological response in 12 representatives and paired watersheds of the country including Tangeshol (Fars), Khamesan (Kurdistan), Dehgin (Hormozgan), Zidasht (Alborz), Shush (Khuzistan), Kakhk (Khorasan Razavi), Kechik (Golestan), Kasilian (Mazandaran), Gonbad (Hamedan), Goorband (Sistan & Baluchestan), Herris (East Azarbaijan), and Tahooneh (Yazd). For this purpose, about 161 studies were used and analyzed. Only 40 sources have specifically studied and compared the control and treatment watersheds. Therefore, it can be concluded that the applicability of the practices results and studies conducted in the paired watersheds have not been adequately described or documented. The first research was carried out in 2001 in Shush and Kasilian paired watersheds and most of them were observed in Kasilian (44 studies) and Kechik (28 studies) paired watersheds. The existence of the least research in Herris, Goorband, and Tahooneh watersheds (less than four studies) can be attributed to their new establishment and lack of extracted data. Most of the studies of paired watersheds in the country were related to the years 2015, 2016, and 2021 with 18, 17, and 17 cases.

Soil erosion by water is one of the most common environmental problems worldwide and is considered a serious risk for sustainability in developing countries. Water erosion on a global scale is one of the most critical types of soil and environmental degradation due to its geographical extent and ecological effects. In this regard, effectively controlling sediment load is an important component in watershed management. In the formulation of a watershed management strategy, the estimation of sediment delivery ratio (SDR) plays a significant role. SDR is defined as the sediment yield from an area divided by the gross erosion of that same area. SDR is expressed as a percentage and represents the efficiency of the watershed in moving soil particles from areas of erosion to the point where sediment yield is measured. One of the problems in estimating the SDR in watersheds is the lack of proper information on the amount of soil erosion and sediment yield. In this context, the Sanganeh soil conservation research station, having measured soil erosion and sediment yield of small watersheds, is a suitable place to evaluate the accuracy of the RUSLE model and estimate the ratio of sediment delivery on the scale of small watersheds. The current research aims to achieve two goals: a) determining the accuracy of the RUSLE model in estimating soil erosion based on the measurements in the erosion plots, and b) estimating the SDR using the estimated soil erosion values as well as the sediment yield measured at the outlet small watershed are planned.

Considering the importance of soil erosion and the study of sediment processes in semi-arid rangeland ecosystems, the Khorasan Razavi Agricultural and Natural Resources Research Center (KANRRC) assessed some micro-watersheds for the collection of storm-wise runoff and associated sediment. The Sanganeh research micro-watershed, located 100 km from Mashhad City (northeast Iran), is one of the watersheds selected for this study. The watershed area, the longest waterways, and the mean slope of the watershed are 1.2 ha, 145.0 m, and 31.2%, respectively. The study watershed consists of semi-arid rangeland dominated by Bromus tectorum and Artemisia diffusa, with a coverage of 50%. The soil is Entisol and Aridosol, young, with a maximum depth of 30 cm. The mean electrical soil conductivity (EC), soil organic matter (OM), clay, sand, silt, and surface rock fragments of soils are 1.81, 1.57, 10.6, 54.7, 34.7, and 5%, respectively. In this research, three experimental small watersheds with areas between 4300-12000 m2 were selected along with the erosion plots in them. Then, 24 rainfall events related to two periods of 2006-2009 and 2016-2018 were recorded along with the corresponding data of runoff and sediment in watersheds and plots. In this study, water flow and sediment yield were monitored at the main outlet of the micro-watersheds and plots. The runoff volume was calculated after each storm event by multiplying the depth of collected water, measured using an iron ruler at five points in the tank (corners and central), by the surface area of the collector. The collected runoff and sediment were then mixed thoroughly and one sample was taken to determine sediment concentration and sediment yield. Then, by collecting the required information (includeing rainfall erosivity, topography, conservation practice, soil erodibility, and cover-crop management factors), the RUSLE model was run and compared with the observation data of the plots. The storm-wise soil erosion predictions were compared with observed data based on the criteria of the coefficient of determination (R2) and relative estimation error (RE). In the following, by modifying the RUSLE model and observing the sedimentation data of the studied watersheds, the value of the SDR was estimated.

After collecting the required information, the RUSLE model was implemented at the plot scale. The accuracy of the model was evaluated using erosion plot data, which was not confirmed due to huge overestimations of RUSLE. Next, to achieve more accurate results, regression types (linear, exponential, power, etc.) were used between the observed and estimated values of soil erosion (RUSLE). After applying the correction coefficient, this model was able to estimate the average erosion rate of the whole period are 12, 17, and 2% for E1, E4, and E6 watersheds, respectively, which is within the acceptable range of soil erosion modeling. Therefore, it can be said that the accuracy of the modified RUSLE model (by regression model) in estimating the average soil erosion during the period is higher than the event-based scale. Also, the prediction of maximum event estimation error for E1, E4, and E6 watersheds was 25.7, 35.8, and 21.6%, respectively. After evaluating the accuracy of the RUSLE model at the plot scale and in order to know the amount of soil erosion at the watershed scale, the values ​​of L, S, K, and C factors for the watersheds were calculated based on a weighted average and entered into the modified model. Therefore, the results of the RUSLE model were generalized to the watershed scale. In the final stage, by dividing the amount of erosion by the corresponding amounts of sediment yield measured at the outlet of watersheds, the ratio of sediment delivery was calculated. The average SDR of the entire period in the E1, E4, and E6 watersheds are 42.2, 41.5, and 39.7%, respectively, and in the maximum events, it is one or two percent higher.

Overall, the results of this research showed that using the modified RUSLE model, it is possible to estimate the average soil erosion in the Sangane soil conservation station and also estimate the SDR. Therefore, this approach can be used in executive programs in similar areas. According to the obtained results, the classification of rainfall data based on the rain erosive factor and then the evaluation of the RUSLE model can provide more accurate results. In addition, in this research, due to the small area of the watersheds, waterway processes did not play a role in the deposition and transfer of eroded soils. It is also suggested that similar research could be done in larger watersheds. Finally, considering the determination of the SDR in this area, it is recommended to evaluate the accuracy of the experimental methods for determining the SDR.

The early 20th century has been unique because of the initiation of paired watersheds (PWs) research in several world regions. So that, between 1930 and 1970, there was a significant expansion in the setting up PWs. They are currently being used for management and conservation objectives due to their special potential and appropriate research facilities. Undoubtedly, without having comparative data from the PWs approach, it is difficult to determine the cause-and-effect relationships of environmental changes and the magnitude of their impacts in some specific conditions. However, a review of experiments from PWs worldwide has been done by various researchers, unfortunately, due to the prevalence of publishing domestic articles in the Persian language, the review of studies on PWs has been neglected from the point of view of international review studies. Based on this, this article aims to express the function and introduction of representative and paired watersheds, as well as a general analysis of the studies conducted in the field of various monitoring indicators of management practices and hydrological response. The analysis of the results obtained from the study of the assessment indicators showed three main categories of hydrology, chemical, and biophysical. The hydrological and chemical indicators have the highest and lowest frequency of studies, respectively.

Identification of sediment production areas, patterns of its delivery from sources to the transport network and the location of deposition sinks are necessary to manage soil erosion. The term connectivity describes the relationship between the sources of runoff and sediment production in the upstream of the watershed and the corresponding sedimentation areas in the downstream. Based on the approach used, there are two types of structural connectivity and functional connectivity. Connectivity index (IC) is one of the most widely used indices to quantify sediment connectivity. The selection of an appropriate weighting factor is one of the challenging issues in IC calculation and it is chosen according to the conditions of each region, the characteristics of the soil surface and available data as well. Therefore, this study was conducted with the aim of reviewing, analysis and collecting past studies so far in order to have a comprehensive look at the methods of quantification of IC and introducing more appropriate approaches for future research in this field. This study reviewed 90 studies related to different dimensions of IC. The review of 25 studies on IC weighting factor published between 2008 to 2022 showed that the two frequently used variables are the C factor of USLE and surface roughness (31% and 25% respectively).It is also suggested that sediment connectivity can be investigated at different time scales, taking into account both structural and functional connectivity. As a result, with better understanding of sediment connectivity, it can be used as a tool for sustainable management of watersheds.

The purpose of this study was to compare the condition and management of rangeland before and after replacing the soil condition assessment method in the soil factor of the four-factor method in order to determine the most appropriate rangeland condition method. Rangeland status assessment was performed for both conditions in Poshtkuh rangelands of Mazandaran and then the status, rangeland management methods and their management and improvement programs were proposed and compared with each other. The results of rangeland condition assessment before replacing the soil condition assessment method in soil factor showed that rangelands had poor and very poor condition with a negative tendency and artificial rangeland management method and rehabilitation programs, mulching and seeding were proposed. The results of rangeland condition assessment after replacing the soil condition assessment method in the soil factor showed that the rangeland condition was in the middle and poor class, for which natural and artificial rangeland management methods were proposed, respectively. For the natural rangeland method, periodic-delayed and periodic-rest grazing systems were proposed based on the average status of the rangeland, and the breeding programs of the artificial rangeland method have not changed and are the same as the previous method. The results of comparative statistical analysis showed that there was a significant difference between the mean score of soil factor before and after replacement in the 95% confidence interval, . This method can be used as a method based on quantitative-qualitative evaluation to identify the functional and structural characteristics of ecosystems.

The weighting factor of the sediment connectivity index (IC) is a challenging component of this index and must be properly explicated for different situations. The aim of this study is to develop a proper weighting factor for calculating IC based on experiments on three tilled soils from dry-farming fields in Kouheen, Sararud, and Gachsaran regions under a 111 mm/h rainfall simulation using a 5.8 m2 laboratory flume with a slope of 12%. For each soil sample, two rain events (R1 and R2) were simulated with an interval of 4 hours, and the soil losses were measured. In addition, a digital elevation model with a pixel size of 2 mm was prepared by accurate photography after each rain followed by calculating the IC based on roughness coefficient (RI) as the weighting factor. Measured soil losses of two rainfalls were 4796 and 3909 g for Gachsaran soil, 3465 and 2464 g for Kouheen soil, and 2679 and 2105 g for Sararud soil, respectively. The result shows that with increasing IC based-RI, soil loss was decreased which indicates the inadequacy of RI alone as a weighting factor. To develop a new weighting factor, several physical and chemical characteristics of soils were used in combination with RI. A comparison of the results showed that the IC based on a weighting factor obtained from the combination of mean weighted aggregate diameter, penetration resistance, and RI, has the highest coefficient of correlation with soil losses (0.92, P <0.01). Examination of the new IC maps showed that the IC in R2 increased compared to R1. It is recommended to study the possibility of using the developed weighting factor in calculating the IC of hillslopes after tillage in determining critical points in the hillslope.

Iran is an arid and semi-arid country whose natural resources have a fragile balance due to unstable management under the conditions of climate change and continuous droughts. General estimates show that soil loss is 14% of the gross national income and also the annual expenditure of 4000 billion Rials for the implementation of protection and restoration projects in the country. Having accurate information about the temporal and spatial changes in the quality and quantity of these resources is a key requirement for its sustainable management. Designing a natural resource monitoring program is a key in creating the necessary information platform for many conservation and restoration projects and prioritizing watershed measures and needed research. In this article, an attempt was made to explain the current situation, the history of monitoring land resources and the data obtained from them, and their strengths and weaknesses. Following, it will be explained how to achieve a comprehensive plan and design for the global monitoring of land resources (hydrological variables, soil erosion, vegetation and carbon secosteration) at the country level. First, the design of national and regional monitoring networks is explained by describing representative basins, permanent monitoring sites and sampling systems at different scales. Then, an overview of data collection, integration and analysis, sampling protocols and required tests are presented. Finally, general data collection schedule, support structure and human resources and the main findings of meta-analysis of spatial and temporal data (in terms of conservation planning, support system and decision-making) are described.

Erosion is a selective process. And some of the clay particles that are important in fertility transmitted into small aggregates. Gradual transfer of these particles, it results in larger particles with less fertility. Therefore, it is necessary to carry out research on fertility and granolometry. This research was done to objective determine soil fertility losses due to dry-farming erosion and sediment granolometry. At first, provinces were studied for dry-farming areas and production and were selected four areas. Required soil transferred to rain and erosion simulator laboratory. Characteristics such as Particle size distribution (PSD), Nitrogen, Available Potassium and absorbable Phosphorus was measured and were determined the amount of fertility losses due to erosion and sediment granolometry. Results showed that in pishkamar and kouhin the particle size distribution of sediment was smaller than the main soil, in Sararood closer to the main soil and in Gachsaran more than the main soil. Total nitrogen of the main soil of pishkamar, Sararood, Kuhin and Gachsaran was obtained 0.08, 0.1, 0.06 and 0.09%, respectively. absorbable Phosphorus and Available Potassium in the selected areas, were calculated 4.76, 104.5 and 4.47, 359.5 and 2.02, 222.4 and 9.62, 360 mg / kg, respectively.

The SWAT model is widely used to simulate watersheds and evaluate the impact of conservation watershed management practices. In this model, the simulation of the watershed processes is based on hydrological response units (HRUs) which are created by overlaying land use /land cover, soil and slope maps. Meanwhile, in the HRUs definition steps, these units become conceptual and lose their spatial location and continuously. This approach is a useful and often inevitable way to simulate large and heterogeneous watersheds in terms of computational efficiency. However, if the aim is spatializing and evaluating the effectiveness of management methods on runoff, sediment and other pollutants in medium to small basins, it is necessary to know the exact location of HRUs. The purpose of conducting this study was present a new approach to defining spatial and independent HRUs and compare the simulation results based on this method with the standard form of the model. In the new approach, independent and spatial HRUs are defined through pre-processing procedures in GIS and uniquely named soil units. The model results of both approaches were very similar and no significant difference was observed in the model outputs in Taleghan watershed. The Nash-Sutcliffe coefficient of the simulated runoff and sediment at the outlet with the standard approach was 0.75 and 0.64, respectively. While, it was obtained 0.74 and 0.61, respectively for the new approach. The definition of spatial HRUs by applying the proposed method provides more tangible and practical outputs, which is more beneficial for identifying the critical areas as well as locating conservation practices compared to the conceptual HRUs approach.

Soil erosion is a process that is affected by surface roughness (SSR) and soil texture. The aim of this study was to investigate the relationship between roughness coefficient and detachment and deposition rate in plowed soil samples of drylands of Kouheen, Sararud and Gachsaran regions due to their susceptibility to erosion after plowing, by simulation. Two precipitations (R1 and R2) with a distance of 4 hours with an intensity of 111 mm / h were simulated in a 5.8 m2 laboratory flume with a slope of 12%. To determine soil loss, runoff was collected with sediment. Also, photographs were taken before and after each rainfall and a digital elevation model with a pixel size of 2 mm was prepared and from it, surface soil roughness was calculated and divided into three classes (rough, medium and soft). The difference of the digital elevation model (DOD) before and after each rainfall (R0, R1 and R2) was calculated to determine the amount of detachment, deposition and sediment delivery ratio (SDR) and their trend was roughly studied. Soil loss in Gachsaran soil sample were measured in 4796 and 3909 g, Kouheen, 3465 and 2464 g and Sararoud, 2679 and 2105 g, respectively. The ratio of harvest to sedimentation in the first event was 5.4, 7.3 and 1.8 in Kouheen, Sararud and Gachsaran soils and 3.2, 1.9 and 1.2 in the second event, respectively. The amount of SDR in the second rainfall in Kouheen, Sararud and Gachsaran soils has been 4.4, 6.3 and 2.3 times higher than R1, respectively. The direct regression relationship between soil loss and roughness with a coefficient of determination (R2) of 0.89 (P <0.05) was obtained. Finally, by preparing the DEM and eliminating its uncertainty, reliable amounts of detachment and deposition can be obtained.

Accelerated soil erosion and high sediment production are important issues in many parts of Iran. The identification of high erosion risk regions is necessary for the planning of soil and water conservation measures in order to reduce erosion damages. Empirical models are required for estimating soil erosion and sediment yield in the absence of gauged small watersheds. The Erosion Potential Method (EPM), originally developed in Croatia, is a popular erosion estimating model in Iran; however, its efficiency across the country has not been thoroughly assessed. Therefore, a calibration study was carried out by comparison between the model the estimated and measured sediment yields through sediment survey for 63 reservoirs at the outlet of small catchments in the Semnan, Markazi, Isfahan, Chaharmahal va Bakhtiari, West Azarbaijan, Lorestan, Fars, Golestan, and the Khorasan Razavi Provinces. All required maps and information of the study basins for estimating the EPM sediment yield were produced via field survey as well as data analysis. Comparison of the results showed that in most cases, the model estimates (0.19 to 9.71 tons per square kilometer per year) are lower than the measured sediment yields ​​at the reservoir inlets (0.44 to 459.64 tons per square kilometer per year). Thus, we calibrated the EPM by modifying its original tables and evaluated the results using the Nash‐Sutcliffe efficiency coefficient in two scenarios, a, all basins, and b, after dividing into three geographical zones, which significantly improved the estimates. The Nash ‐ Sutcliffe efficiency coefficient for scenario a was 0.66, and 0.68, 0.50 and 0.89 for the Central, Zagros, and Northeast zones, for scenario b respectively. Based on the results, it is strongly recommended to use the modified EPM instead of the original model.

The erosion data collected by plots and Cs137 methods as well as gauged river sediment yields (about 1000 places countrywide) were studied. Due to the large differences in the range of recorded data within each method and between the methods and the limited data compared to the large size and diversity of the country, it was necessary to find a suitable technique for scientific interpretation of these results. The median was selected as the most appropriate erosion/sedimentation measure of center. The median sediment yield rate of the measuring sites, which are mainly located in the mountainous areas of the country, was estimated at 336 t/km2/y. Using EPM estimates corrected by the observed sediment yield data, the country's total annual erosion is approximately 900 million tonnes (550 t/km2). Whereas, soil losses of about 300 plots in the rangelands, forests and drylands are often much less than 100 t/km2/y. In contrast, up to about 3,500 t/km2/y were measured on marl formations. Due to the large differences between erosion in plots and river sediment yields, it is likely that sensitive formations, dryfarming, gullies, landslides and streambank erosion have a greater role in sediment production. Limited sediment source studies also confirm the greater contribution of deep erosion features. Finally, by examining worldwide erosion/sediment yield maps and some global data, it was shown that despite the presence of erosion hot spots and basins with high sediment production in Iran, there are areas with much more critical conditions in Asia and the world.

Indigenous flood harvesting method for irrigation in Khorasan, which are called water-spreading weir are constructed and operated by farmers without any cost to the government. Although, the benefits of water-spreading weirs are clear for many experts and the authorities as well, this method receives a little attention by governmental soil and water conservation services. This problem and a few suggestions for the purpose of extension of this method among stakeholders were presented in this article based on the documentary method. After a short review on the historical background of water-spreading weirs, some technical and legal issues associated with water-spreading weirs and barriers to its development were discussed. First, the legal status of water-spreading weirs ownership was explained followed by the maximum total area of water-spreading weirs for an upstream watershed, developing water-spreading weirs in dry farming fields, land use change of natural resources into water-spreading weirs, and the need to adapt the watershed management and soil and water resources management programs in the upstream basin with downstream water-spreading weirs. Based on the authors' experiences, a ratio between 1:10 and 1:20 between the water-spreading weirs area to upstream basin was proposed for arid and hyper-arid climates, respectively. Also, the ability of Article 3 of the Law on Revising the Law on Protection and Utilization of Forests and Rangelands was explained in order to assigning permission to exploit national lands to construct new water-spreading weirs. Finally, some suggestions for better maintaining of existing water-spreading weirs as well as encouraging the farmers and facilitating the process of constructing new water-spreading weirs on national lands and drylands were presented.

Soil infiltration is one of the most crucial parts for designing rainwater catchment systems and has an essential role in determining the area for rainwater harvesting. Using the Kamphorst field rain simulator, the infiltration rate of the suitable sites for the rainwater catchment systems has been determined. After selecting the suitable site, the soil was saturated, and the experiments were performed a day later. Simulation experiments have been conducted in two sites. The first site was Pishkamr city in Golestan province and the second site was near Sararood research station in Kermanshah province. The constant slope was at 12%, and the rain intensities were 33, 64, and 110 mm/h for 15 minutes in four repetitions. At the end of the experiment, the total volume of runoff was collected, and the infiltration rate was calculated. The results showed that with increasing rainfall intensity from 64 to 110 mm/h, the runoff volume of Pishkamr and Sararood increased 6.1 and 13.7 times, respectively. The infiltration rate in comparison with rain intensity showed that by increasing rainfall intensity from 64 to 110 mm/h, the infiltration rate increased 16.6% and 25.3% in the Pishkamr and Sararood, respectively. The comparison of the infiltration rate in the two sites also showed that the infiltration rate in the Sararood site was higher than the Pishkamr site. Therefore, with the knowledge of soil Infiltration, suitable rainwater catchment systems can be designed to supply water for plants.

Despite their vital role in the sustainability of agriculture, the environment, and human life, the Zagros oak forests are facing severe anthropogenic deforestation and climate change. The purpose of this study was to harvest rainwater and store it in the soil to deal with drought in the Zagros forests, which is part of the forests of Southeastern Kermanshah province. The experiment was conducted as a randomized complete block design with four treatments including crescent-shaped bound with preservation (CSB+P), preservation treatment (PT), crescent-shaped bound without preservation (CSB-P), and control treatment (CT). The results showed that CSB+P treatment attributed to the re-growing of some dried trees (19 tree ha-1) and the reduction in dieback rate (36.7 tree ha-1), and in total 55.7 ha-1 trees in the Zagros forests. Therefore, both the reduction of dieback rate and re-growing of dried trees are two main positive effects demonstrated by the CSB+P treatment. There is no effect of PT treatment on the re-growing trees, while it contributes to the reduction of dieback severity (37.7 tree ha-1). Finally, the CSB-P treatment has the lowest effect among other treatments on dieback reduction (6 tree ha-1). The results also showed that after three years, the soil organic carbon (SOC) in the CSB+P, PT, CSP-P, and CT treatments were 3.25, 2.90, 2.05, and 1.90 %, respectively. In addition, the SOC increased significantly in the CSB+P and PT treatments (P <0.05). CSB+P significantly reduced bulk density (BD) from 1.46 (1st year) to 1.31 (3rd year) enhancing soil moisture content from 16.53 to 19.17%. The CSB+P and PT are significantly improved the SOC, BD, and soil moisture content. It was concluded that forest soil should be protected and in our experience, rainwater harvesting through micro-catchment was the simple and effective short-term technique for increasing soil moisture and consequently combating forest drought in the Zagros regions of Iran.

Small sediment dams are the key structures for controlling sediment flow and improving the course of waterways in watersheds. In Kermanshah province, the efficiency of these structures in sediment accumulation has been less studied and evaluated. This study aimed to investigate the efficiency of these structures in sediment retention and flood control in three watersheds of the province. For this purpose, while selecting three study basins in the East (Hajiabad basin), North (Razin basin), and South of the province (Mereg basin), the target dams for the study were identified. A total of 30, 14, and four dams were gabion, dry-stone wall, cement-masonry, respectively. Then, the accumulated sediments in the tank behind the dams were examined with the help of surveying and sampling from different sections. Examination of the results in the Hajiabad basin in the East of the province, which was the main cause of erosion showed that gabion and dry-stone wall construction have been able to reduce soil erosion and sedimentation by 13%. In the Razin watershed in the North of the province, cement-masonry and gabion dams had managed to trap about 886 tons of sediment. In the Mereg watershed, the results showed that the upstream dams with 9245 kg/ha had the highest and the downstream dams with 3575 kg/ha had the lowest sediment control performance. The results of this study showed that in basins with high sedimentation capacity, dry-stone wall dams are one of the most important low-cost structures to prevent sediment transport, especially coarse particles. However, the construction of dams with low drainage to prevent the transfer of fine particles is also effective.

Environmental challenges are increasing day by day which this is a result of the increasing human population and demand for natural resources. Mismanagement of natural resources causes instability in environmental indicators. Degradation of watersheds with soil erosion and sediment yield is one of the most important environmental issues in Iran. Therefore, it is necessary to prepare and complete the spatial information of the natural characteristics of the watersheds and their prioritization. Because it is used in comprehensive watershed management. The purpose of this study was to investigate the status of some indicators and prioritize sub- catchments in Karkheh watershed. So indices of sensitivity of rock units to erosion, modified fournier erosivity index, erosion intensity from EPM experimental model and sedimentation through logarithmic sediment delivery ratio and discharge data were extracted and analyzed. After calculating mentioned indices in the sub-cachtments of Karkheh watershed, the values of each indicator in the basin and sub basins were examined, standardized and compared and then sub- cachtments prioritization were performed. The clustering method was also used to group the sub- cachtments and the above mentioned indices and topographic indices. Investigation of the susceptibility of formations to erosion of Karkheh watershed showed that sensitive class to erosion is the most frequent in this basin (60 %). The largest similar category in sub- cachtments includes nine ones with codes2213, 2214, 2221, 2222, 2223, 2225, 2226, 2227 and 2228 and the coefficients of area and length of flow had the most similarity. The results of rainfall erosivity and average erosion also indicate that very high erosivity class and high erosion class have the largest area (49% and 52% respectively) in this basin which the average erosivity and erosion of the basin were 60.6 mm and 727 m3 / km, respectively. The results of the average ranking of the indicators of geological formation sensitivity, rainfall erosivity and erosion of each sub basin show that sub basins such as 2215 (Karkheh Bala) and 2224 (Khoramabad) are prioritized in terms of planning and practical measurments at the level of the basin at managerial levels and sub- cachtments such as 2211 (Karkheh Payab) and 2227 (Ab Aleshtar) are less priority than other sub- cachtments in the Karkheh watershed.

Sediment production at each stage of erosion and its redistribution vary at different scales in a watershed, a slope and even a plot. The preparation of sediment budgets on watershed and slope scales have been considered in the two preceding decades, and a review of this tool on a plot scale can also help to better understand the process of sediment production, redistribution and delivery. The present study was conducted to budget sediments in laboratory plots with sandy-loamy soil and under rainfall simulation with the intensities of 30, 50, 70 and 90 mm h-1. Sediment tracing was performed on the surface of the plots by measuring the changes in the density of synthetic color-contrast aggregates using image processing. The results indicated the ability of this method to prepare sediment budgets on a plot scale. The contribution of interrill erosion in sediment production was increased with an increase in the rainfall intensity; however, the proportion of sediment redistribution within the plot was decreased. The average sediment delivery ratios for the rainfall intensities of 30, 50, 70 and 90 mm h-1 were 7.30, 8.54, 11.74 and 15.64%, respectively. The insignificance of this ratio on a plot scale was emphasized due to the short period of the experiment and should be considered in laboratory research projects.

Soil quality is an essential indicator for sustainable land management that generally depends on soil physical, chemical and biological properties. Due to the multiplicity of soil properties, the number of variables is usually reduced to a minimum set by statistical methods, which reduces study time, decreases monitoring cost for sustainable use of agricultural lands. The aim of this study was to introduce the most effective soil characteristics of agricultural lands in Mohammadshahr plain, Karaj, to prevent the descending trend of soil quality.
In this study, four farms and orchards which were different in terms of crop type and irrigation system were selected and evaluated with Integrated Quality Index (IQI) and Nemero Quality Index (NQI). In both indicators, the characteristics affecting soil quality are combined in the form of a mathematical model and presented as a numerical quantity. For this purpose, first 12 soil profiles were described, followed by sampling from topsoil (surface layer) and sublayers (weighting average for the depths) and testing 17 soil characteristics affecting its quality. In the next step, both indicators were calculated using two different sets of soil properties. The first category, the Total Data Set (TDS), included all measured soil characteristics, and the second group, the Minimum Data Set (MDS), included the most important properties affecting soil quality. The Principle Component Analysis was implemented to select the MDS. Soil properties were scored to calculate IQI and NQI. For this purpose, a function was defined for each soil feature to standardize all scores between zero and one. Weighting various soil quality properties was also performed by calculating the common variance of the variables, which was obtained by factor analysis method.
Calculation of IQI and NQI indices showed that the topsoil samples were in grade III and sublayer samples belonged to grade IV with major limitations due to lack of profile development, organic carbon deficiency, salinity and high gravel. Four and six items out of 16 variables were identified effective for topsoil and sublayers, respectively. The IQI index based on TDS was more accurate and sensitive than the NQI index for soil quality assessment, as more features are considered for TDS. In the IQI index, both the weight of attributes and their scores are effective, while in the NQI index, only the attribute score is considered. On the other hand, the coefficient of determination between the TDS and MDS for topsoil and sublayer samples was 0.55 and 0.56% for IQI model, respectively, and 0.48 and 0.16% for NQI model, respectively. In other words, the determination coefficients showed the reliability of using the MDS instead of TDS in both IQI and NQI models. In the MDS, mean weight diameter (MWD) showed the highest effect on the surface layer and percentage of gravel had the greatest impact on the soil quality of the sublayer.
Although TDS took into account all soil properties and showed a slightly higher coefficient of determinations with both soil quality indicators, the MDS obtained similar results to the TDS with only about half of the properties. In the MDS, the features with an internal correlation is eliminated rendering it more cost effective. The results of this study assist decision-makers to choose better quality management and soil sustainability strategies while decreasing the monitoring cost.