Click on “Download PDF” for the PDF version or on the title for the HTML version.

If you are not an ASABE member or if your employer has not arranged for access to the full-text, Click here for options.

An empirical power function model of V = kQm has been used worldwide to describe the relationship between flow velocity (V, m s-1) and discharge rate for rills and open channel flows. This study used observed data from four experimental watersheds (Figure 1) on the Loess Plateau to determine the effect of watershed size and land use management on the parameters of both the power function and an alternative logarithmic function model of V = elnQ + d. The power function model better represented the flow velocity-discharge rate relationship in the unique context of the Loess Plateau conditions. The constant parameters in both model types were impacted by watershed size and land use management. The constants k and d, which represent flow velocity for unit discharge, were negatively correlated with watershed size, and were increased by soil loss prevention practices involving land use management. The exponential constants m and e, which determine the rate of change in flow velocity, were shown to be independent of the watershed scale and land use management. The study indicated that the power function model was able to express the hydraulic relationship at outlet channels of watersheds on the Loess Plateau but needed to be calibrated with locally observed data to optimize model performance.