بررسی فرسایش خاک و تولید رسوب با استفاده از مدل WEPP مطالعه موردی: حوضه آبریز قنبرلو

Extended Abstract

Introduction
Soil erosion is a natural process that causes soil loss due to various environmental factors such as climate, soil, topography and vegetation (Abedini et al., 1402: 115). This phenomenon is one of the most critical problems that cause the destruction of land on the earth's surface all over the world. This phenomenon occurs as a result of complex interactions between natural and human-caused factors (Elson et al., 2022). Erosion is the movement of materials from one point to another, after the destruction of rock or soil, the resulting materials due to the loss of adhesion and density by various factors such as water, wind and snow, and depending on the strength It acts as a transport and deposition agent (Ahmadi, 212: 1386). Soil erosion is one of the most important factors of destruction and reduction of soil fertility, which is increasing throughout the year and leads to the loss of high-quality agricultural soil (Bayziz et al., 2011:238). The ever-increasing increase in world population, especially since the last half century, severe interference in water and soil resources (pressure on the land), has caused the study of soil erosion as one of the most important issues in its various dimensions, such as environmental effects, sustainable development of agriculture and food production. and so on, the more attention is paid to it (Abdini, 1400 and 1401(.
Ghanbarlu watershed with an area of 34.50 square kilometers and 3450 hectares is one of the sub-basins of Dareh-Rood in Pars-Abad, Moghan city.

Methodology
The WEPP model is a new technology for predicting erosion, which was established for the first time in 1985 by the US Soil Protection Organization (Refahi, 2016). This model has three methods of watershed, range and flow paths. The amount of soil erosion and sediment production is estimated in the watershed method, in slopes and waterways, in the slope method, in the slope and in the flow path method. In the recent method, the amount of erosion and deposition in waterways is not estimated and the waterway is the only transporter of incoming sediment. The required factors of the WEPP model are: topography, soil, climate, management and waterways. Two factors of slope and direction of slope are considered for the topography factor and GeoWEPP software is used to enter their information into the model. The slope factor was entered in two files: one in the slope file where the slope of the domain and the other in the waterway file where the slope of the waterway was entered. Slope information was entered into the software by means of a digital elevation model map (in GISASCII format) and as a longitudinal profile. Therefore, for this purpose, first the route of waterways was determined and a suitable cross-section for each domain was selected on the topographic map, and then the relevant profile was drawn with the help of ArcGIS software.
The main goal of this research is to estimate the soil erosion and sedimentation rate of Ghanbarlo watershed with the WEPP model. In this research, according to the topic, various books, articles, official publications, theses and websites related to the topic have been used. Meteorological and regional water organization of Ardabil province was used to collect meteorological data and discharge and sediment statistics of the basin. Then, in order to directly observe and investigate erosion issues and identify existing phenomena in the area and take soil samples, several stages of field visit to the area have been carried out. Also, the soil laboratory of the Faculty of Agriculture and the laboratory of Moghan Soil Testing Company have been used to obtain the parameters of the WEPP process model in estimating the amount of erosion and sedimentation. WEPP model has three modes of watershed, flow paths and range. In the case of a watershed, the amount of sediment in the slopes and waterways is estimated. In the case of slopes, the amount of sediment is estimated in the slopes, and in the case of stream paths, the amount of sediment in the slopes is also estimated, and waterways are the only transporters of incoming sediment (Abadini and Toulabi, 2016). In this research, the amount of sediment was estimated with the above three modes. Estimating the sediment produced using the WEPP model was done in two steps: calculating the factors required by the model and entering the data into the software and calculating the sediment.

Conclusion
So far, many experimental and process models have been used to estimate erosion and sedimentation, each of which has strengths and weaknesses in prediction. As a process model, the WEPP model is able to estimate the amount of soil loss on the slopes and on the surface of a watershed based on each rainfall event or for consecutive years. The information required to implement the WEPP model is entered into the relevant software in 5 files: climate file, management file, soil file, slope slope and waterway. Finally, after preparing all the data and implementing the WEPP model, the model identified 5 types of management, 2 types of soil, and 5 types of waterways for the Canberra basin. Based on this, the amount of specific sediment was obtained with 3 methods of watershed, flow paths and range with 0.73, 0.168 and 0.119 tons per hectare per year and the range method of WEPP model was obtained with 0.119 tons per hectare per year. . The results show that the WEPP domain method provides better results in mountain basins (Figure 10).
A similar scientific work done by Ahmadi al (2016) in Cherdavel basin, Ilam province, and its results also showed that the WEPP model is more accurate in estimating the amount of soil erosion and sediment production in the watershed compared to the hydrophysical method. In this model, the flow path method to estimate the amount of soil erosion and sediment production is close to the observed number in the hydrometric station, but because the range method is suitable with the natural conditions of the studied basin, it provides correct results and the results show this problem. That the domain method of the WEPP model has a suitable efficiency in the hilly and mountainous areas.

Keywords: Soil erosion; sediment yieldusing; Ghanbarlo basim; WEPP model