Role of Rill Development in Salt Loading from Hillslopes

摘要

Field studies of salinity in runoff were conducted by applying runoff directly to the hillslope through a perforated pipe and, secondly, by rainfall simulation to produce runoff. Average electroconductivity (EC), a measure of total dissolved solids, was found to increase with increasing values of slope and after rilling of the hillslope. Rill development and flow velocities are further investigated since both are shown to be significant factors in high salt loads in runoff. Rill development is studied by computer simulation. The results show that slope has a significant effect on the rill patterns. A laboratory control situation was designed to isolate the effects of: (1) Increased flow velocities; (2) different layers of Mancos shale (unweathered and weathered); and (3) particle size of shale. Linear relationships between electroconductivity and increasing flow velocities are provided. Further laboratory results indicated that for the same flow velocity, unweathered Mancos shale yields approximately twice as much salt to the flow as weathered Mancos shale.