اثر قرق و جهت دامنه بر مقادیر رواناب و رسوب(مطالعه موردی: حوزه‌های زوجی خامسان)

Soil  erosion  as a  one  of  the  biggest  environmental  problems  worldwide, is threatening  both ecosystem health and  food security. This case study conducted in Khamsan paired watersheds aimed to compare runoff volume and sediment yields from 51 natural rainfall events on 18 USLE’s standard plots, where they had installed on the different conditions in the term of enclosure and aspect. Factorial test used based on completely randomized designs because of two states of presence or absence of enclosure, four types of aspect (north, east, west and northwest) as well as the possibility of interactions among enclosure and aspect factors. The results showed that average runoff coefficients resulted from given events on standard plots of enclosure and control watersheds were 4.21% and 4.71% respectively, while average plot sediment yields of control watershed was about 17% more than enclosure watershed. The results of the factorial test showed that enclosure and aspects had statistically significant effects only on runoff production while the interaction of enclosure and aspect on runoff, runoff coefficient and sediment yields, were statistically significant for a confidence level of 99 %. The maximum runoff values occured in control plots installed in the North Slope. The results showed that enclosure reduce soil erosion and water losses through restoration of vegetation cover and increased permeability.