paper This was peer-reviewed for scientific content. Pages 710-716. In: D.E. Stott, R.H. Mohtar and G.C. Steinhardt (eds). 2001. Sustaining the Global Farm. Selected papers from the 10th International Soil Conservation Organization Meeting held May 24-29, 1999 at Purdue University and the USDA-ARS National Soil Erosion Research Laboratory.
Sediment Transport in Irrigation Furrows
Thomas J. Trout*
ABSTRACT
Sediment data were collected in southern Idaho irrigation furrows. Irrigation furrows allow detailed study of sediment transport relationships because of gradually decreasing flow rates in long, uniform, preformed rills. The measured trends of rapidly increasing sediment transport (load) with distance at the inflow ends of furrows (due to high erosion rates), maximum load near mid-furrow, and then decreasing load (due to net deposition) follows the expected basic processes. However, the measured high rates of sediment deposition are not predicted by transport relationships of the type used in the WEPP model. Also, the measured wide variation in sediment load over time on a field cannot be explained by sediment transport capacity concepts. An alternative sediment transport theory, not based on transport capacity, fit the furrow transport data better with fewer parameters and more consistent coefficients.
the controlled inflows and relatively low slopes, in some areas with highly erodible soils, there is significant furrow irrigation-caused erosion damage (Koluvec et al. 1993).
Sediment Transport Processes
Most models of sediment transport assume that a flow has a capacity to carry sediment at a steady-state rate, termed the transport capacity, in which particle settling and deposition on the bed and detachment and entrainment from the bed are in equilibrium, resulting in no net change in load. The transport capacity is a function of the hydraulics of the flow - commonly represented by shear or shear velocity, and the characteristics of the sediment - primarily particle sizes and densities. Most of the transport theory was developed to predict erosion and sedimentation in large streams with coarse, non-cohesive bed materials. Scientists trying to model rill and interrill erosion and deposition on agricultural fields have adopted similar methodologies based on a transport capacity (Foster, 1982; Alonso et al. 1991), even though flow and so...
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