comparison of suspended load in two sub-catchments grazed and ungrazed in the kakhk area of gonabad

the management of sedimentation problems in rivers and reservoirs depend greatly on the sediment yield from the catchment land surface. in this research the effects of biological measures and ranges enclose on suspended load in two sub-catchments of kakhk experimentalwatershed in gonabad has been studied. this catchment contains both control and experimental sub-catchments. these sub-catchments are similar in all aspects and differ only based on watershed management operations. experimental sub-catchment has been under rangeland enclosures and operation of biological, biomechanical and mechanical measurements since 1998 whereas control sub-catchment is under normal operation. to determine the biological impact of management and biological measurements on sediment production, the yield suspended load on hillslopes in 18 experimental erosion plots during 4 rainfall events occurred in 2011-2012 has been analyzed in both control and experimental sub-catchments. analysis was performed in spss software using independent-sample t test and anovawith repeated measure test. based on these comparisons, difference between the amount of suspended load in two sub-catchments was significant at 1 percent level, while runoff depth was significant at 5 percent level. also results showed that correlation between the runoff depth and suspended load has been 94 percent in control sub-catchment and 62 percent in sample sub-catchment. slope of the line changes between the runoff depth and suspended load in control sub-catchment has been 5.3 times of the sample sub-catchment. the research clearly showed the effect of the biological measures and ranges enclose on reduction of suspended load and runoff depth in experimental sub-catchment.