Spatial and temporal coefficient of variations of soil loss under concentrated flow in furrows of dryland wheat

In the past decades، the study of soil erosion has gained considerable attention by many researchers. This was thorough understanding of soil erosion processes and variable factors affecting it which is essential for making land management decisions. The aim of this study was to investigate the spatial-temporal coefficient of variation of soil erosion and flow hydraulic parameters in top-down conventional ploughing rills with 20 percent average slope. The artificial rills were produced with a length of 10، 20 and 30 meters. Hydraulic parameters and sediment concentration were measured at three equal time and distance intervals after applying 10، 15 and 20 Lmin-1 inflow rates for 10 minutes. Consequently، sediment detachment and transport rates were calculated. In addition، relative errors (RE) of these parameters were calculated in order to investigate the coefficient of variations. The results showed that there was a significant difference (P<0. 01) between sediment (soil detachment rate، transport rate and sediment concentration) and hydraulic parameters. Stream power was significantly different with sediment detachment and transport rates (P<0. 05). Temporal evaluation revealed that coefficient of variations in the first and final time intervals of RE values of detachment and transport rates were more than middle time slot. This is perhaps due to stochastically movement of available sediment in the first step and undercutting and bank failure of rills in final stage. Spatial variability showed that the RE in the primary section is significantly (P<0. 01) greater than following sections، whereas there was no significant difference between second and third sections.