چكيده لاتين :
Introduction
The Zal watershed is located in the south of Khalkhal town and the south of Ardabil Province. It is one of the Khazar (Casbian Sea) and Ghezel Ozane river sub-basins. It is located in 37? 11? 08? to 37? 27? 43? northern latitudes and 48? 28? 59? to 48? 39? 43? eastern longitudes in north western of Iran. Zal watershed area is 299 Km2, mean height is 1889m, highest point of basin is Aq Daq (3322m), lowest point is 600m and main derange is 47 Km. In this watershed the factors such as weakened formations, roughness of topography, excessive difference between high mountain and low heights area, excessive grazing and vegetation decrease, destruction of forest for creation of farmland, construction of roads, unsuitable and incorrect plugging in slope direction and excessive exploit of soil was caused to soil erosion. Therefore estimating of soil erosion and sediment yield in the Zal watershed is very important. Attentive to above problems the purpose of this study is assess to soil erosion and sediment yield in Zal basin using PSIAC and MPSIAC Models and comparing them.
Methodology
In this study, we used the observation and field method for seeing kind of erosions and topographic, geologic, vegetation cover and land use maps coincidence. The library method used for study research history and literature. Also the PASIC and MPASIC model is used to estimating of soil erosion and sediment yield in The Zal basin and its sub basins. In this model 9 effective factors such as: geologic condition, soil, climatic condition, runoff, topography, land cover, land use, erosion condition and river erosion are surveyed. Implement of this research were: topographic maps (1:50000), geologic maps (1:100000), soil maps, Arial photograph, satellite images and Arc GIS.
Results and Discussion
For estimating of soil erosion and sediment yield, first the basin was divided into four sub-basins with names of the Lord, Zal, Klbndrud and Darechai, then erosion rates and sediment production were investigated using PSIAC and MPSIAC methods and draw maps. Geologic prominence is 5.9 for whole basin and 6.1, 5.3, 5.8and 6.5 for Klbndrud, Lord, Darechai and Zal sub basins in orderly. Soil concesion is 9.4 for whole watershed and 9.7, 8.8, 9.3 and 9.9 for Klbndrud, Lord, Darechai and Zal sub basins in orderly. Cliamatic distinction in Klbndrud sub basin is more than others sub basins (table 3). Runoff advantage is 4.1 for whole watershed and 5.2, 4.7, 5.4 and 4.9 for Klbndrud, Lord, Darechai and Zal sub basins in orderly. Topographic prominence is 9.7 for whole watershed and 10.8, 9.2, 7.4 and 10.8 for Klbndrud, Lord, Darechai and Zal sub basins according. Land cover concesion is 4.1 for whole basin and 3.8, 3, 4.3 and 5.4 for Klbndrud, Lord, Darechai and Zal sub basins in orderly. Erosion distinctions are 9, 8.2, 9.8, 12.5 and 9.8 for Klbndrud, Lord, Darechai, Zal sub basins and whole basin in orderly. Land use prominence is 4.5 for all basin and 4, 4.2, 5.4 and 4.6 for Klbndrud, Lord, Darechai and Zal sub basins accordingly. Finlay River distinction is 10.8 for whole watershed and 11.6, 8.3, 10 and 13.3 for Klbndrud, Lord, Darechai, Zal sub basins and whole basin in orderly.
Conclusion
The results showed that whole watershed and Kalbandrud, Darechai and Lord Sub-basins are located in average class of erosion and Zal sub-basin is exposed high erosion class base of PSIAC model. The special sediment was estimated 388.6 m3/km2/yr in the whole basin, 520.9m3/km2/yr in Zal sub-basin, 409.8m3/km2/yr in Kalbandrud sub-basin, 357.1m3/km2/yr in Darechai sub-basin and 311.1 m3/km2/yr in Lord Sub basin, base of PSIAC mothod. But in MPSIAC model, whole watershed, Kalbandrud sub basin, Darechai sub-basin and Lord Sub-basin were located in low erosion class while Zal sub-basin was exposed to average erosion class. The special sediment was estimated 195.1m3/km2/yr in the whole basin, 263.1 m3/km2/yr in Zal sub-basin, 206 m3/km2/yr in Kalbandrud sub-basin, 179 m3/km2/year in Darechai sub-basin and 155.5 m3/km2/yr in Lord Sub basin.
