نشریه پژوهش های آبخیزداری
پیاپی 138 (بهار 1402)

One of the important and effective measures in controlling soil erosion and runoff production is the use of watershed management methods, which is currently receiving less attention. This natural phenomenon is a global environmental problem that reduces soil fertility and water quality, increases sedimentation and the possibility of floods. Therefore, using erosion plots in natural areas can play an effective role in controlling runoff and sediment production. The present study was prepared with the aim of investigating the effect of precipitation and vegetation on the production of runoff and sediment in the Noorroud watershed of Mazandaran province.

Noorroud watershed is located in Mazandaran province, the political area of Noor city, Beldeh and southwest of Amol, and the most important population center is Beldeh. This basin, with an area of 1299.78 square kilometers, is the largest sub-basin of Haraz River. To calculate the runoff from individual showers on a plot scale and two different land use types of hand-planted forest (Pine, Pinus halepensis) with seven and eight years old and rangeland lands, using test plots with a size of two by ten square meters with two treatments. And three repetitions were used in the months of April, April, June, October, November and December of 2016 and 2017 and Anova statistical analysis was used to check the relationship between the parameters.

The results of precipitation from 2017.04.17 to 2018.06.07 showed that the maximum amount of runoff occurred on May 31, 2018 and caused the production of 0.35 mg of sediment per plot unit. The results of the Kolmogorov-Smirnov test also showed that the eastern domain has a normal distribution at the level of 0.95 for the two dominant types. The results of the correlation between the canopy and litter percentage of each land use showed that the presence of natural factors such as litter and vegetation canopy has a strong relationship with the weight of sediment produced in two treatments. The highest value of the runoff coefficient is for rangeland use (33%) and the lowest for hand-planted forest (31%).

Conclusion and Suggestions :

According to the obtained results, it was found that in general, the amount of runoff and sediment produced in forest areas is more than rangeland. On the other hand, there was less relationship with production sediment in the rangeland areas with the eastern slope. One of the main cases in the destruction of national lands is grazing beyond the capacity of rangelands and forests. This factor causes the destruction of the rangeland, and with not very intense rains, the resulting runoff moves some of the soil. Various factors are involved in the occurrence and aggravation of runoff and sediment, and considering the conditions of each region, one or two factors may play a greater role. The role of its use and vegetation under different rainfall conditions has an important role in the amount of runoff. Therefore, it can be seen that the presence of vegetation has a direct effect on reducing the amount of runoff and sediment. According to the obtained results, in order to improve the results, it is better to use artificial rainmakers in the natural field so that the role of vegetation can be better understood.

Iran is one of the countries that soil erodibility is becoming one of the acute environmental problems and every year millions of tons of fertile soil are left unusable due to lack of proper management.  In order to effectively protect and prevent the adverse effects of soil erosion, it is necessary to identify the factors affecting soil erosion and provide an appropriate estimate of their amount in the country. In this regard, the present study was conducted to estimate soil erodibility (K-factor) for a soil depth of 0-30 cm in Iran.

For this purpose, two database were used, including the Harmonized World Soil Database (HWSD) and global gridded soil information (SoilGrids), as well as RStudio and ArcGIS software. First, SoilGrids data was prepared at four depths of 0, 5, 15 and 30 cm and averaging was done. Also, the HWSD database was received in vector format for a depth of 0 to 30 cm. Finally, these data have been used to estimate the erodibility factor based on the soil content of organic carbon, clay, sand and silt using the EPIC equation. Finally, Relative Error (RE), Median Absolute Deviation (MAD) and Root Mean Square Error (RMSE) were calculated to compare two databases.

Assessments indicate that the average percentage of clay particles in the sub-basins of Iran varies between 15 and 32% and the average for the whole country is 23%. On the other hand, the average percentage of silt particles in the sub-basins of Iran varies between 19 and 45%, and the average for the whole country is 32%, among which the maximum and minimum percentage of silt particles are in the sub-basins of Qarasu-GorganRoud and Kavir Lut, respectively. Also, the average percentage of sand particles in the sub-basins of Iran varies between 28 and 65, and on the other hand, the average for the whole country is 44%, the minimum of which is related to the sub-basin of Karkheh and the maximum is related to the sub-basin of Kavir Lut. In Gavkhouni and Kavir Lut sub-basins, the reason the low soil erodibility factor is the high percentage of sand in these sub-basins, so that the percentage of sand in the Lut and Gavkhouni basins is 65 and 47% of the total soil particles, respectively. Considering that the average percentage of organic carbon in the sub-basins of Iran varies between 0.3 and 3.9, respectively, these values are related to the sub-basins of Hamun-e-Hirmand and Sefidroud-Haraz, so it can be said that the majority of the country's sub-basins are in poor conditions in terms of the percentage of organic matter. The results show that the southwestern, western and northeastern parts of the country have the maximum amount of soil erodibility factor, and the central Iran and desert parts of Iran have lower erodibility due to having a higher percentage of sand particles. Also, the results show that the lowest average amount of soil erodibility at the sub-basin scale using SoilGrids data with a value of 0.033 (ton*h/Mj*mm) is related to Lut Desert and also its maximum value is 0.045 (ton*h/ Mj*mm) related to it is the sub-basin of Haleh. In addition, the maximum and minimum values of the erodibility index with the HWSD data as an average of the basins of Iran are corresponding to the Mand and Gavkhouni sub-basins, respectively, with values of 0.042 and 0.033 (ton*h/ Mj*mm). So, the results showed that the average soil erodibility factor in Iran using two the HWSD and SoilGrids databases was 0.036 and 0.038 (ton*h/ Mj*mm) respectively.

Conclusion and Suggestions:

The study of soil erodibility with the data of SoilGrids and HWSD at the sub-basins scale showed that the maximum and minimum RE in Atrak and South Balochestan sub-basins are 21 and 1 percent, respectively, and the amount of RE is about 5% for the country average; Therefore, it can be concluded that although the RE between the two databases is not high, SoilGrids data is a more suitable source for soil and water resource modeling due to its continuity and better spatial resolution. Finally, it should be said that although this database is modeled using a larger number of profiles (about 150,000 soil profiles in the world), so they have appropriate accuracy. However, it is necessary to state that investigating the uncertainty of these data in order to improve the results of this database in order to improve the results of that in different parts of the country is recommended to researchers and researchers. Also, it is noteworthy that the EPIC model was used to estimate soil erodibility in this study, while its evaluation and comparison with other soil erodibility estimation models in the country is suggested to other researchers and experts.

Assessing the socio-economic effectiveness of natural resources and watershed management projects on the conservation and principled use of forests and pastures is an important executive tool for managers and implementers of such projects. Therefore, by evaluating the performance of watershed projects from the perspective of experts, while determining the effects of the project and the factors affecting it, the necessary guidelines for the optimal implementation of these projects in the future can be provided to officials and planners.

The current research is defined in two stages: in the first stage, the researcher conducts interviews with specialists, experts and experts to identify the criteria and indicators for evaluating the socio-economic effects of watershed management projects, in the next stage, in order to prioritize and rank indicators for evaluating the socio-economic effects of watershed projects, quantitative data was collected through the design and distribution of paired comparison questionnaires. The purpose of this study is to evaluate the socio-economic effects of watershed management projects implemented in the Rimeleh Watershed of Lorestan province based on the opinions of experts. For this purpose, after preparing the initial list of indicators and criteria, the final list of criteria and indicators was evaluated using the Delphi method and a survey of experts. Then, a pairwise comparison questionnaire was designed and distributed using the analytic hierarchy process (AHP) method. Finally, in order to prioritize the indicators, multi-criteria decision-making methods were used.

According to the results obtained based on the analytical hierarchy process (AHP) method and pairwise comparisons, among the six evaluation criteria, the economic criterion - added value has the most weight and the social criterion - increasing the level of knowledge and awareness has the least weight. The results of weighting the evaluation criteria showed that the economic criterion-value added (0.246) had the highest weight and the social criterion-increased level of knowledge and awareness (0.078) had the lowest weight. The results of prioritizing the indicators showed that "increasing the price of land in the region", "increasing the yield of horticultural products", "increasing the participation of watersheds in decision-making and decision-making" and "converting low-yield rainforests into sloping orchards" Respectively, they are one of the most important indicators in evaluating the effects of watershed management projects. The indicators of "activating the private sector to invest in production", "developing local markets and market access for watersheds" and "strengthening the role of women and low-income groups in society" are also high priority.

Conclusion and Suggestions :

The results of the social evaluation from the experts' point of view showed that increasing the participation of watershed residents in decision-making and decision-making took the largest role in human and financial participation. It is suggested that the participation of stakeholders in future decisions and the use of participatory measures in this basin and other basins are of importance. Therefore, in order to evaluate the socio-economic effects of the implementation of watershed management projects, it is suggested that attention to the mentioned priorities be included in the agenda of managers and planners.

One of the important natural hazards is land subsidence. This phenomenon has also been observed in Iran due to the indiscriminate extraction of underground water resources, and unfortunately, more areas are exposed to it. The DPSIR tool or Driving Force, Pressure, State, Impact, Response framework is a tool that describes environmental problems through cause and effect relationships between human activities and the environment. This framework provides a background to combine different types of indicators and considers not only the environmental effects but also the economic and social effects resulting from changes in the status of ecosystems. The purpose of this research is to present the cause and effect relationships for the most important issues and problems of the risk of land subsidence in one of the important and critical plains of Fars province (Seydan-Farooq) and the most appropriate management responses using the DPSIR tool. and provide non-management to improve the current situation.

First, the problems of Seydan-Farooq Plain were determined based on library studies, asking experts and referring to the region, and based on this, possible strategies were determined. Then, the DPSIR tool was used to identify the cause and effect relationship analysis between the factors that determine the characteristics affecting land subsidence in the plain, and the DPSIR table was prepared for the risk of land subsidence in this plain. In order to prioritize and determine the importance of the problems, pressures and management strategies of the plain, a Likert scale questionnaire was used as a measurement tool and 40 experts were surveyed. Friedman's test was used to rank the items and Cronbach's alpha method was used to check the reliability of the questionnaire using SPSS version 22 software. Then Friedman's test was used for two-way analysis of variance by ranking and also comparing the average ranking of different groups using SPSS software.

The ranking of the items of the driving force component in Seydan-Farooq plain of Fars province showed that the range of the average values of the ratings varies from 1.86 to 4.45. The ranking of the items shows a significant difference in the items of the driving force component, so that the item "Population" with an average rating of 4.45 and also the item "Development of Industries" with an average rating of 1/86, it has been ranked first and fifth respectively. Therefore, in the "driving force" component, according to the factors: population, agricultural development, garden development, climate change and industrial development, the highest priority in intensifying the risk of land subsidence in this plain. assigned Regarding the ranking of the pressure component items, the range of the difference in the average values of the ratings in the pressure component varies from 1.25 to 5.40. The ranking of the items showed a significant difference in the items of the pressure component, so that the item "withdrawal from the underground water table in the agricultural sector" with an average rating of 5.40 and also the item "withdrawal from "Underground water table in the domestic sector" with an average rating of 1.25 has been ranked first and sixth respectively. Therefore, in the "pressure" component, according to the factors: withdrawal from the underground water table in the agricultural sector, failure to comply with the environmental rights of the aquifer, decrease in rainfall, withdrawal from the underground water table in the garden sector, From the underground water table in the industrial sector and the withdrawal from the underground water table in the domestic sector, they have assigned the highest priority in intensifying the risk of land subsidence in this plain. The average values of the ranks in the response component vary from 2.35 to 5.75. The ranking in the items of the response component also shows a significant difference, so that the item "increasing irrigation efficiency" with an average rating of 5.75 and also the item "nutrition" Point of water in the plain" with an average rating of 2.35 has taken the first and sixth place, respectively. Therefore, in the "response" component, in the order of the factors: increasing irrigation efficiency, changing the cultivation pattern, controlling the harvesting of authorized wells, aquifer operations, blocking unauthorized wells, cultural measures and spot nutrition. Water in the plain has the highest priority in reducing the risk of land subsidence in this plain.

Conclusion and Suggestions :

Five driving forces (D) have caused six pressures (P) on the water resources of this plain, the most important of which are "withdrawal from the underground water table in the agricultural sector" and "not respecting the environmental rights of the aquifer". are The pressures, in turn, have created a disordered (S) situation (dropping of the water table) in this plain. This situation has two adverse effects (I) "land destruction" and "aquifer destruction". In order to improve the situation, seven management responses (R) were presented, the most important of which are "increasing irrigation efficiency" and "changing the cultivation pattern". In the current situation, it is not possible to stop the pressures; However, their adjustment and modification should be specially considered by planners and managers. It is worth mentioning that if these cases are not corrected, there will still be pressures (P) and will lead to more critical conditions than the existing situation (S) and finally, its effect (I), destruction of lands, aquifers. and the destruction of water and soil resources of this plain will be more. Due to the fact that the executive structure of the country's natural resources management is more in line with the components of pressure (P) and situation (S); It is suggested to develop suitable, practical and operational answers (R). It is also necessary to pay serious attention to the preventive approach in reducing the risk of land subsidence; Because, unfortunately, this matter has not been paid attention to in the country. Therefore, it is suggested to consider and implement a preventive approach that both understands the driving forces (D) and prevents the implementation of policies that cause pressure.

More than other biological and environmental factors, the water crisis reduces the production of plant ecosystems, especially in dry climates. For this reason, the evaluation and measurement of rain becomes more important, especially in arid and semi-arid regions where soil moisture is a limiting and effective factor on plant production (Sadeghi and Attard 2014). The proportion of precipitation which is converted to precipitation depends on three major parameters. It includes: plant characteristics, precipitation characteristics and evaporation conditions (Grits et al. 2010). The aim of the current research is the effect of the amount and intensity of precipitation and the percentage of the canopy density of the Calligonum comosum and Haloxylon persicum leaves in the climatic conditions of Birjand in the period (October 2018 to June 2019).

This research was conducted from October 2018 to June 2019 in Faculty of Agriculture and Natural Resources, University of Birjand. This area is located at 59' 63' 21 º East and 21' 43 º 32 North. The average annual rainfall of this area in the 50-year period was 170.8 mm (Derakhshan et al., 2014). In this research, the rate of canopy rainfall interception of H. persicum and C. comosum were measured. For this purpose, four replications with low to high crown cover density were selected. Taking into account the large and small diameter of the shrub, the percentage of the mass of the crown were measured. To collect rainwater under each species, tray-shaped containers with dimensions of 30 × 30 cm were used. Also, in order to calculate the effective area of the canopy of the species during autumn to spring, the surface of their canopy was photographed vertically. In order to analyze the data, correlation tests, analysis of variance and one-way analysis of variance (ANOVA) were used. All statistical tests were performed by SPSS software and graphs were drawn by Excel software.

comosum is a drought resistant species and it is spread in sandy hills in deserts. The results show that the highest amount of canopy rainfall interception belongs to spring season with the amount of 15.6 mm. Also, based on the Pearson correlation coefficient, there is a significant positive correlation between the amount of precipitation and the amount of rain at the level of 0.01 (R2=0.93). There is a significant positive correlation between the intensity of precipitation and the amount of interception at the level of 0.05 (R2=0.79) and there is a significant positive correlation between the intensity of precipitation and the percentage of interception at the level of 0.01 (R2=0.87). H. persicum has a high ability to absorb soil moisture due to its low osmotic potential. The results revealed that there is a significant positive correlation between the amount of precipitation and the amount of interception and the percentage of canopy mass with the amount of interception at the level of 0.05 (R=0.78 and R=0.71, respectively). Also, there is no significant relationship between the percentage of interception and any of the precipitation characteristics.

Conclusion and Suggestions :

 The highest amount of interception belongs to C. comosum with a value of 15.6 mm and the lowest amount of interception is related to the H. persicum with 1.2 mm. The highest percentage of H. persicum is in February with 46% and the lowest percentage is 10% in December (p ≤ 0.05). Due to the density of leaves, H. persicum is more suitable for preventing floods and soil erosion, since more water is absorbed by the canopy and less water reaches the ground.

Gully erosion affected by many factors causes the destruction and loss of large volumes of soil along with great economic and social damage. The variability of diversity, the number and size of the influence of different factors from one point to another and the difference of their participation in the formation and expansion of gullies is based on the conditions of the land. Such conditions have caused more researches to be carried out to identify as many factors as possible in the phenomenon of gully erosion and the extent of their participation in the formation and expansion of this phenomenon. In this regard, the present study has been planned with the aim of monitoring and evaluating the effective factors in the development of gullies in the Haddam and Sharif watersheds of Khuzestan province. Modares Shushtar watershed, having Sharif and Hadam subwatersheds, as one of the important and typical basins of the province, every year a large area of its agricultural land is threatened by gully erosion.

In order to carry out this research, first, the parts with gullies in the study area were identified on the topography map with a scale of 1:250,000 during the 20-year period (1993-2012). Then, 15 gullies have been identified and investigated from each climate class of hot-dry desert and hot-semi-arid. Features such as the slope of the initial point of creating a gully and the slope of the front of the gully were calculated by the field method and using a tape measure, level and inclinometer measuring device and the mirage area of the gully front in the Google Earth softwave. Also, the physical and chemical characteristics of the soil of each gully were tested.

The results showed that the average percentage of bare soil above the head cut of selected gullies in Haddam and Sharif watersheds is 99.8% and 97.26%, respectively. Based on soil characteristics, the main cause of soil instability and erosion in gullies in both watersheds is EC. The morphometric characteristics of the gullies showed that in the Haddam watershed, all gullies are V-shaped in terms of cross section, and in the Sharif watershed, only gullies are B12, V-shaped and the rest are U-shaped. The Haddam watershed has the highest depth, width, and top of the gully compared to the Sharif watershed. The total volume of soil loss in Sharif and Haddam watersheds is 23000 and 51579 m3, respectively. Gullies A18 and B1 in Haddam watershed have the highest and lowest soil loss volume, at 11599 and 1612 m3, respectively. In the Sharif watershed, the maximum and minimum soil loss volume of gullies related to gullies A2 and B4 are 5282 and 369 m2, respectively.

Conclusion and Suggestions  :

The most important factors in the volume of soil loss and expansion of gulies are the characteristics of the watershed located upstream of the gully front (such as the extent and slope of the watershed) as well as the fineness of the geological formation (silt) and high soil salinity. Due to the excessive bareness of the soil, increasing the roughness of the soil surface with the establishment of vegetation is one of the compatible and low-cost methods in protecting soil resources. In order to control the spread of gully erosion, it is necessary to increase soil organic matter, modify saline and sodium soils with the use of modifiers, and also divert the runoff from the gully front.

Biochemical activities of soil have been proposed as one of the most well-known indicators of soil quality and health, which are considered in evaluating the effect of afforested species on soil characteristics. This research was conducted with the aim of investigating the long-term effect of flood spreading operation and type of vegetation on the activity of acid and alkaline phosphatase, urease and dehydrogenase enzymes and soil microbial activity, including basal respiration and stimulated respiration, in 2019.

Sampling the soil around the roots of Acacia salicina Lindl., Eucalyptus camaldulensis Dehnh., Atriplex lentiformis (Torr.) Wats. (0-20 cm depth) was carried out with 6 treatments in three replications. Statistical analyzes were performed using SPSS software as a factorial test in the form of a randomized complete block design and the means were compared with Tukey test at P<0.05.

The results showed that the interaction between flood spreading and vegetation type on the activity of acid phosphatase, alkaline phosphatase, urease, dehydrogenase, stimulated respiration and organic carbon was significant at P<0.01. The activity of acid phosphatase and alkaline phosphatase enzymes in the soil under cover of Acacia and Eucalyptus plantations was higher than the activity of these enzymes in the soil under cover of Atriplex, especially in the situation with flood spreading. The activity of urease enzyme showed the highest value in the soil under the Atriplex with flood spreading and the lowest value in the soil under the Atriplex without flood spreading, and this difference is statistically significant with Tukey's level test at P<0.05. The activity of dehydrogenase enzyme showed the highest value in the soil under the Atriplex with flood spreading and the lowest value in the soil under the Atriplex without flood spreading, and this difference is statistically significant with Tukey's test at P<0.05. Dehydrogenase activity in the soil of Atriplex with flood spreading compared to the activity of this enzyme in the soil of Acacia with flood spreading and also the activity of dehydrogenase in the soil of Acacia and Eucalyptus in the situation with flood spreading, statistically with the test Tukey did not show a difference at P<0.05. In the conditions of flood spreading, the basic respiration rate in the understory soil of Acacia, Eucalyptus and Atriplex was higher than the basic respiration in the soil under the cover of these plants without flood spreading, although the difference in the basic respiration in the two situations with flood spreading and without flooding were not statistically significant at P<0.05. The amount of stimulated respiration in the soil of Atriplex with flood spreading was higher compared to the amount of stimulated respiration in the soil of Eucalyptus with flood spreading, but it was not statistically different from the amount of stimulated respiration in the soil of Acacia with flood spreading and Acacia without flood spreading. The highest and lowest amount of stimulated respiration was observed in the soil under the cover of Acacia and Eucalyptus, respectively, in the condition without flood spreading, and these differences were statistically significant at P<0.05.

Conclusion and Recommendations:

The results of this study showed that the activity of soil enzymes can potentially predict the amount of nutrient deficiency. In addition, afforestation in arid areas, improves soil quality indices. Considering the important role of organic matter in improving the biological properties, quality and health of the soil, in order to increase the amount of organic matter in the soil, rehabilitating flooded rangelands with native and compatible trees and bushes, managing grazing and increasing non-grazing periods are recommended.

Floods and earthquakes are the most common and unpredictable natural events that harm communities by affecting life and property and affect the landforms of the basin. Therefore, in ways to reduce the effects of natural events, The main goal has changed to public awareness and emphasis on informing the people in line with preventive measures before the occurrence of abnormal events. Considering these explanations and the need to compare and evaluate the effectiveness of probabilistic statistical methods, The main goal of this research is to investigate the morphological, hydrological and climatic factors affecting the occurrence of floods, Modeling and evaluation of land sensitivity potential in Gorganrood watershed to flood occurrence. Also, the most important innovation of the current research compared with to the previous researches related to risk zonation in the country, the comparison of two probabilistic methods of Shannon entropy and weight of evidence in order to determine the most efficient model and increase the accuracy of flood prediction maps.

1- Selection of the study area, Collecting and preparing maps of effective factors as independent variables, 15 factors were considered in this research. 2- The flood event distribution map was prepared using the information received from the Ministry of Energy and field observations as a dependent variable, and it was divided into two groups of test points (30%) and training points (70%). 3- Quantifying the effective factors with the help of the frequency ratio index and also performing the multilinear test (independence of the effective factors). 4- Implementation of entropy and weight of evidence models, Preparation of flood sensitivity zoning maps and classifying them into five categories: very low, low, medium, high and very high. 5- Assessing the accuracy of classification and validation of zoning maps and predicting sensitivity to flood events. 6- Determining the importance of effective factors and choosing the most suitable model.

In total, based on the calculated weights of both entropy index and weight of evidence models, in the order of factors land use, altitude, Normalized difference vegetation index (NDVI), soil, Topographic Wetness Index (TWI), Drainage density, Stream power index, slope (SPI), Topographic position index (TPI), lithology, average annual precipitation, Infiltration number, Profile curvature, Stream frequency and Intensity of daily rainfall are effective in flood occurrence. In this research, the land use factor and then the vegetation cover factor have a high priority in the occurrence of floods due to land use changes. The intensity of rainfall is in the last rank, but its importance and influence should not be ignored along with other factors. The maps resulting from flood risk zonation by both models indicate the high accuracy of zone classification and proper distribution of flood points in high and very high zone. Also, based on the receiver operator characteristic (ROC) curve and accuracy classification levels, the efficiency of both models is in the very good category (0.8-0.9) In terms of comparing the models to each other, the results of the area under the curve (AUC) values of the Shannon entropy model show a higher score accuracy in both testing and training situations (0.94 and 0.98) than the Bayesian weighting method (83.83). 0 and 0.88) which indicates a high correlation between the prepared flood sensitivity map and the distribution map of the number of flood events.

Conclusion and Suggestions:

In this research, in order to prepare a map of flood event zoning, 368 flood zones with a repetition number of 782 flood events and 15 factors affecting flood events were used. Based on the fitting of both models and the prioritization of the factors affecting the occurrence of floods, it was determined altogether that land use, altitude and vegetation factors have importance and priority in the occurrence of floods in the study area and Profile curvature, Stream power index and Intensity of daily rainfall factors were placed in the last priorities. The results showed that Shannon's entropy model has the appropriate class threshold in classification, and by using 30% of flood occurrence zones, it has more priority for zonation and flood occurrence prediction. But in general, both models are effective in zoning and predicting flood occurrences.