Ravanbakhsh Raisian; Amir Hossein Charkhabi; Mohammad Nekoueimehr
Abstract
One of the main factors accelerating soil erosion in the watersheds in Iran is improper management including overgrazing and improper land use changes of pastures into agriculture. This problem is true in the whole Karoon watershed. Therefore, the objective was to study the effects of land use changes ...
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One of the main factors accelerating soil erosion in the watersheds in Iran is improper management including overgrazing and improper land use changes of pastures into agriculture. This problem is true in the whole Karoon watershed. Therefore, the objective was to study the effects of land use changes on soil loss in Gorgak sub-watershed. The statistical design was split plot design with pasture and rain fed agriculture as main factors. A drop maker rainfall simulator with 40 mm/hr intensity and 30-minute rainfall period was used on five field locationsunder two soil moisture conditions of air-dry and field capacity and three slope classes of 10-20, 20-30, and 30-40%. A total of 180 sediment and runoff measurements were made using the above rainfall simulator under field conditions for two land use systems of rain fed cereal and overgrazed pastures. All the measurements were done in triplicates (5 fields x 2 land uses×2 moisture content×3 slope classes×3 replicates = 180 plots). The results showed the soil loss under overgrazed and air-dry soil condition was 45.6 times more than the rain fed agricultureunder the similar soil moisture condition. However, the results showed the soil loss under overgrazed and field capacity soil moisture condition was 2.33 times more than the rain fed agriculture under similar soil moisture condition. Once the soil loss was compared for different slope classes of 10-20, 20-30, and 30-40 slope percent, the results indicated the soil loss under overgrazed and air-dry soil condition were 4.77, 5.19, and 2.34 times more than the rain fed agriculture under similar soil moisture condition. Overall, soil loss under overgrazed conditionwas 3.38 times more than rain fed agriculture. Therefore, although most soil conservationists generally believe that the rain fed agriculture in Iran is very improper managed and it has high soil erosion rates but the results of this study showed the overgrazed pastures in the north Karoon watershed need much more priority for any soil loss measures and controls.
Mohammad Nekouiemehr; Said Naim Emami; Ravanbakhsh Raisian; Majid Soufi; Msoud Goodarzi
Abstract
Applied research about preventing gully initiation and expansion, needs basic knowledge about the types and morphometric characteristics of gullies. The purpose of current research is the classification of gullied regions based on morpho-climatic characteristics in Chaharmahal and Bakhtiary province. ...
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Applied research about preventing gully initiation and expansion, needs basic knowledge about the types and morphometric characteristics of gullies. The purpose of current research is the classification of gullied regions based on morpho-climatic characteristics in Chaharmahal and Bakhtiary province. In this research, two gullied regions covering an area about 500 ha were selected in each climate zone and three representative gullies were chosen in each region. The morphometric characteristics were measured in each studied area. Classification of gullied regions was done using cluster analysis based on quantitative characteristics. The results indicate that gullied regions in Chaharmahal and Bakhtiary province can be divided to three groups base on morpho-climatic characteristics. Maximum similarity level was 94.12 percent. A comparison of variance analysis and mean value of variables in groups shows that, annual rainfall, elevation above sea level, gully length, gullied region area and top width of gullies were the most important variables in separating of the groups. Generally, we can emphasize that among all morphometric characteristics; only gully length and top width have the main role in morpho-climatic classification.
