نشریه مرتع و آبخیزداری
سال هفتاد و هفتم شماره 1 (بهار 1403)

Flood is one of the most devastating natural disasters, causing financial and human losses each year. At the same time, many rivers in Iran's watersheds lack complete and accurate statistics and information. On the other hand, estimating the flow of floods is one of the most important factors for the design and implementation of water structures. In such cases, one of the appropriate solutions to estimate the maximum flow rate with different return periods is flood analysis. In order to conduct the present study, 55 hydrometric stations with a common statistical period of 20 years were considered to perform the work after the statistical deficiencies were eliminated. Then, based on the distribution of the third type of Pearson logo with the lowest error rate and the highest number of first rank as the most suitable fit function, the amount of discharge in different return periods was estimated. The following information was collected on the types of physiography, land use, climate and geology variables. After collecting information about all independent variables using Gamma test, the most important variables affecting the maximum instantaneous flow, including area, drainage density, maximum 24-hour rainfall and watershed environment, were selected and modeled using methods. Random forest modeling and support vector modeling were performed and their efficiency was determined based on statistical indicators With an efficiency coefficient of 74 to 83%, the error of 3.05 to 32.11 m3 and the coefficient of explanation of 76 to 91 are more accurate than the random forest model.

Awareness of human about the existence of environmental pollution crisis and its effects on his own destiny can have a positive effect on changing the course of these crises. Sangan mines release dust particles and pollutants into the soil and air, which will have huge consequences for environmental pollution and even endanger human Health, including the spread of skin and respiratory diseases. Environmental assessment is considered as one of the most efficient methods to evaluate and predict plans and projects on environmental components, so the present study aims to Environmental impact assessment of Mine Utilization Using Iranian Leopold Matrix (Study area: Sangan Khaf Mines). The main tool for collecting research data for the study area is a library and a field survey based on a questionnaire that was completed among the community of experts. The statistical sample population is 30 experts who were familiar with environmental issues. The results showed that the number of negative algebraic mean effects in the column is equal to 10 and the number of negative algebraic mean consequences in the row is equal to 14, among which the number of negative consequences less than -3.1 in the column is only related to the effects of dust diffusion. The most important negative effects among the environmental components are related to dust diffusion activity with an average classification of -3.1 with an algebraic sum of -50.

The aim of this study is to propose an approach for modeling spatiotemporal changes in rainfall that can be used as input for rainfall-runoff models.

To achieve this, rainfall data from four rain gauge stations in the Paskouhak catchment were used. Five parameters, including elevation, slope, aspect, longitude, and latitude, were identified. The different combinations of these five parameters were prioritized using the gamma test in WinGammaTM software. After the use of different regression models, the best model was selected based on evaluation criteria such as R2, RMSE, and the Taylor diagram. A raster map of a selected rainfall event was drawn in the Arc GIS environment. Finally, using the proposed approach of relative equations, the spatiotemporal changes in rainfall were modeled.

The results showed that using a second-degree nonlinear model and parameters of elevation and latitude, it is possible to accurately obtain the spatial distribution of rainfall in the form of a regular pixel grid (100 square meters) with high precision (R2=0.917 and RMSE=0.2277).

In different rainfall events in small catchment areas, the variation in rainfall in each pixel is almost constant relative to other pixels, including the rain gauge station, the proposed approach in this study can model the spatiotemporal changes of each rainfall event as a three-dimensional matrix in the study area. The approach can be valuable in predicting potential flood events and in water resource management and planning. However, further research is required to validate the results and test the approach in other areas.

In this research, the nutrient value of Zygophyllum eurypterum, Salsola orientalis, and Sanguisorba minor during different growing periods in the winter rangelands of Gachsaran County was considered. For this purpose, sampling was done randomly and with 4 repetitions from the species in different periods of growth. To determine the quality, crude protein percentage (CP), acid detergent insoluble fiber (ADF), dry matter digestibility (DMD) and metabolizable energy (ME) were evaluated. The results showed that the quality indices in the studied species have significant differences (p<0.05). The highest values of crude protein percentage, dry matter digestibility percentage and metabolic energy (MJ/kg) are 16.91, 60.88 and 8.35, respectively, was observed in S. minor and the lowest values of the indices 7.39, 49.05 and 6.33, respectively, were detected in S. orientalis. Also, the highest amount of ADF was obtained in S. orientalis (45.66%) and the lowest in S. minor (36.16%). The nutrient value of the plants in different growth periods has significant differences (p<0.05). In the growth period, the highest percentage of crude protein (20.87) belongs to the Z. eurypterum, the highest percentage of digestibility (65.92) and the amount of metabolic energy (9.2 Mj/kg) was belonged to the S. minor and the lowest percentage of crude protein (8.65), dry matter digestibility percentage (57.34), and metabolic energy (7.74 Mj/kg) was belonged to the S. orientalis. The highest (36.25%) and the lowest percentage of ADF (31.50%) at this stage belong to S. orientalis and S. minor. In the flowering period, the highest amount of crude protein percentage (17.50), dry matter digestibility percentage (62.50) and metabolic energy (8.62) belong to the S. minor.

In the comprehensive and integrated watershed management approach, watershed management has progressed from a mechanical and biological program to a comprehensive and integrated management system, through which we can guarantee human needs for the present and future generations in a reasonable way. Despite the fact that there is no doubt about the effectiveness of most watershed projects, the alignment of these projects with the goals of sustainable development needs to be evaluated.

We used IUCN method to assess sustainability of the watershed management plans in Sistan and Tol Heidari watershed of Jahrom County from 2005 to 2021. The most important strength of this method is simultaneous consideration of human and ecosystem factors. For this purpose, using opinion of experts, we determined criteria and indices in two main categories including ecosystem and human welfare. Finally, we selected three criteria and 15 indices for ecosystem section and four criteria and 13 indices for human section to assess watershed sustainability condition. The sustainability assessment of the watershed was performed with and without weighting the indicators and criteria.

The final score, according to the stability barometer respectively in the first method, was 66.30 before implementation and 71.33 after implementation. In the second method, the final score of 60.64 and 66.66 which indicates an upward trend in the level of stability and increase in the state of stability.

The results of the present study show that the watershed projects carried out in the region have been able to bring about a relative improvement in the ecological and economic-social conditions of the region.

The response of water balance components as indicators of hydrological performance to stimuli such as land use change is of strategic importance. In this study, the effect of land use change on water balance components was evaluated, focusing on the relationships and change of the main indicators of water yield and sediment yield. Based on this, the Markov chain model was used to predict land use in 2040. Also, the American soil and water assessment tool was developed as a base model for evaluating and estimating hydrological indicators in the Taleghan Watershed as a mountainous watershed with structural heterogeneity. The results of model showed that the increase of settlements and urban development in Taleghan watershed will result in increased runoff, increased water yield and sediment yield indicators, and more sedimentation. Land use change leads to an increase of sediment yield by 11 times until 2040. The conversion of pastures to barren lands is the most important land use change that can increase sediment yield. Also, the increase of barren lands will be the reason for the reduction of evapotranspiration in some sub-basins of this watershed. Increasing rainfall and decreasing soil permeability will increase surface runoff, and as a result, soil erosion and sediment yield will increase. In this study, exactly the sub-basins that had the highest quantitative amount of predicted water yield index also had the highest quantitative amount of sediment yield index and increased sedimentation. In this research, it was determined that land use change as a type of structural change in the land will have visible effects on the functions and hydrological responses of the watershed.